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83627

THE BIOLOGY OF
SPIDERS

83627

THEODORE H. SAVORY, M.A.

LATE EXHIBITIONER OF ST. JOHN'S COLLEGE, -CAMBRIDGE

LONDON

SIDGWICK & JACKSON, LTD.
1928

" Man wants to know, and when he ceases
to do so he is no longer man."

F. Nansen

PRINTED IN GREAT BRITAIN BY
WILLIAM CLOWES AND SONS, LIMITED, LONDON AND BECCLES.

DEDICATED

MY CHILDREN,

WHOSE INTEREST IN THE PROGRESS OF THIS BOOK
IS GRATEFULLY ACKNOWLEDGED TO HAVE
BEEN A VERY REAL ENCOURAGEMENT
TO THEIR AFFECTIONATE

FATHER.

PREFACE

Every writer, it has been said, sees in imagination a desert
island where he would be free to work undisturbed. I
myself periodically visit one such solitude when each year
I receive and read the precious blue paper-covered booklet
which constitutes the Arachnida section of the Zoological
Record. That invaluable annual (how could we get on
without it ?) always inspires me to dream of my island, yet
shared peradventure with certain other persons, where I
should be able to write two books which seem to me to be
wanted.

One of these is a complete work on British Spiders —
a Blackwall, a Pickard- Cambridge up-to-date. It is, indeed,
not impossible that such a book may one day appear.

The second is suggested by the very obvious fact that the
papers published on spiders fall into two categories. One
consists of faunal lists, reports on collections made by expedi-
tions and descriptions of new species ; the other of records
of observations on the structure, habits and behaviour of
spiders. It has always seemed to me that the second
category ought to be used as material for a synthetic work,
dealing with every aspect of spider-study other than
systematic diagnosis of families, genera and species. The
ideal for such a book would be that its reader should have no
need to refer to any other work for information about any
topic pertinent to the biology of spiders.

That, at least, is the ideal with which one might set about
the writing of such a book as this. In practice it is very
difficult to attain, as is common with ideals. When one has

vii

viii

PREFACE

only devoted half of one's life to the study of spiders, there
is bound to be much that one has never read, much that one
has forgotten, much of which one has never heard of, and it
is seldom possible to make the acquaintance of every one
of the several hundred papers which one feels that one
ought to know. But an effort may be made, and no one
who is at all familiar with the literature of spiders will
fail to realise how much I owe to the work of my pre-
decessors.

In the nature of things, therefore, such a book as this
does not lay claim to complete originality. Much of it is
necessarily but an integration of the work of others, previously
scattered in several languages all over zoological literature,
correlating their results and opinions into one accessible and
more or less homogeneous whole. " That is the worst of
erudition," says Dr. A. C. Benson, " that the next scholar
sucks the few drops of honey that you have accumulated,
sets right your blunders and you are superseded. You
have handed on the torch, perhaps, and even trimmed it.
Your errors, your patient explanations, were a necessary
step in the progress of knowledge ; but even now the pro-
cession has turned the corner and is out of sight." I do not
presume to set right or to supersede any of my predecessors
and I can but express the hope that they will not regard my
borrowings as " the worst of erudition," but as studied
compliments to themselves.

At the same time certain interpretations of the behaviour
of spiders, much of the earlier parts of Chapter VII and
of Chapter IX and the major part of Chapter XV may
lay claims to originality as the work of the present writer.

The book owes much to the suggestions and careful
reading of Prof. J. Arthur Thomson. I am glad to take this
opportunity of expressing my thanks to him for all that he
has done.

PREFACE

It gives me very great pleasure to acknowledge the help
I have received from my own pupils. Their enthusiasm
has not only been an encouragement to myself, but has had
practical results which are incorporated in the following
pages. I owe Fig. 34 to the dissections of G. T. Pitt3
and M. L. Meade-King, and Fig. 48 to a dissection made
by L. W. Spratt. Fig. 15 was drawn by G. T. Pitts.
Help was also given by C. M. Adcock and R. D. McKelvie.

To Mr. H. Main and Mr. E. A. Robins I am indebted
for the photographs from which the Plates have been made ;
and finally I owe acknowledgments to the following pub-
lishers, who have permitted me to make use of figures
published by them :

Messrs. L. Mulo, of Paris, and Mme. Simon for
Figs. 7, 8, 14, 21, 71, 72, 104.

Messrs. Doubleday Page & Co., of New York, for
Fig. 30.

Messrs. Gustav Fischer, of Jena, for Figs. 43, 55, 100.
Messrs. Sime & Co., of Dorchester, for Fig. 113.
Messrs. Watson & Sons, Ltd., of London, for Figs. 117
and 120.

Messrs. Hodges, Figgis & Co., and The Royal Irish
Academy of Dublin, for Fig. 112.

Messrs. Taylor & Francis, of London, for Figs. 57,
80, 82.

The Cambridge University Press for Figs. 93 and 94.
The Zoological Society of London, for Figs. 66-9, 83,
90. 95.

T. H. Savory.

Wentworth House,
Great Malvern,
May, 1928.

a 2

CONTENTS

CHAPTER PA 3B

Preface vii

Contents xi

List of Plates xv

List of Drawings in the Text xvii

I. General Characteristics of the Class Arachnida . i

II. The External Structure of Spiders . . . 14
The cephalothorax, 16. The pedicle, 17. The abdomen,
18. The reproductive orifices, 22. The sternum, 24.
The chelicerae, 25. The palpi, 28. The legs, 33. The
setae, 36. The claws, 39. The spinnerets, 40. The
cribellum, 43.

III. The Internal Structure of Spiders . . . .45

The body- wall, 46. The endoskeleton, 47. The ali-
mentary canal, 51. Fat, 56. The vascular system, 56.
The blood, 59. The respiratory system, 60. The excre-
tory system, 62. The reproductive system, 65. The
nervous system, 66. The glands of the cephalothorax,
68. The silk glands, 71.

IV. The Senses and Sense Organs 77

The eyes, 77. Vision, 83. The spines, 86. Touch, 88.
Hearing, 89. Stridulation, 93. Scent, 98. The lyri-
form organs, 99. Taste, 102.

V. The Behaviour of Spiders 104

0 Reflex actions, 105. Tropisms, 106. Simple instincts, 108.
Chain-instincts, 111. Intelligence, 114.

VI. The Quest for Food 116

The choice of food, 116. The treatment of captives,
118. Specialised webs, 119. Hunting-spiders, 122.
Crab-spiders, 123. The spider's bite, 124. Other kinds
of food, 125. The venom of spiders, 125 Drink,, 130.
Fasting, 132.

xii

CONTENTS

VII. The Spider's Web 134

Spiders' silk, 134. The origin of the web, 137. The
evolution of webs, 137. The making of a web, 142.
Spinning the orb-web, 143. Geometry of the orb-web,
145. Webs of young spiders, 148. Divergences from
pattern, 149. Protection for the web-spider, 150.

VIII. The Spider and its Environment . . . .157
The colours of spiders, 158. The shapes of spiders, 161.
Mimicry in spiders, 163. Protective habits, 169. Preen-
ing, 169. Catalepsy, 171. Autotomy, 173. Myrme-
cophilous spiders, 174. Social spiders, 175. The
enemies of spiders, 176. Longevity, 180.

IX. The Distribution of Spiders 181

Gossamer, 181. Spiders' stations, 184. Choice of
environment, 186. Influence of temperature, 187.
Response to physical change, 188. Geographical distri-
bution, 191. The distribution of Liphistiomorphae, 192.
The distribution of Arachnomorphae, 192. Spiders on
mountains, 193. Spiders of the Polar regions, 195.
Spiders of oceanic islands, 196. Spiders of the sea-
shore, 197.

X. The Courtship of Spiders 201

The courtship of jumping-spiders, 201 . Of wolf-spiders,
204. Of crab-spiders, 206. Of web-spiders, Agelenidae,
208. Of web-spiders, Linyphiidae, 209. Of web-
spiders, Theridiidae, 210. Of orb-spiders, Epeiridae,
211. Earlier theories of courtship, 212. Behaviour of
the male, 214. Behaviour of the female, 215. Relation
between male and female, 217. The significance of
spider courtship, 217.

XI. The Mating and Parenthood of Spiders . . . 222

Sperm-induction, 222. Copulation, 224. The cannibal
female, 227. Egg-laying and cocoon-making, 229. The
cocooning instinct, 232. Forms of cocoon, 233. Care
of the cocoon, 234. Hatching: care of young, 238.
Fertility, 240.

XII. The Development of Spiders 241

Cell-division, 241. Oogenesis, 243. Spermatogenesis,
244. Fertilisation, 246. Parthenogenesis in spiders, 246.
Development, 248. Hatching, 252. Thespiderling, 253.
Recapitulation, 255. Moulting or ecdysis, 256. Re-
generation, 258. Size, 258. Alternatives in develop-
ment— dimorphism, 260. Abnormalities in develop-
ment— gynandry, 262.

CONTENTS

Xlll

CHAPTER

PAGE

XIII. Fossil and Primitive Spiders 265

The geological record, 265. Paleozoic spiders, 267.
Mesozoic spiders, 269. Cainozoic spiders, 270. Primi-
tive spiders, 271. History of the Liphistiidae, 273.
Characters of the Liphistiidae, 274. Internal structure
of the Liphistiidae, 278. Habits of the Liphistiidae, 279.

XIV. The Trap-Door Spiders 284

Features of the Mygalomorphae, 284. Habits of the
Mygalomorphae, 286. The makers of trap-doors, 288.
The Migidae, 291. The Atypidae, 292. The bird-eating
spiders, 296. The Barychelidae and Dipluridae, 298.

XV. The Evolution of Spiders 300

The Evolution Theory, 300. Spiders as evidence of
Evolution, 302. Ancestral spiders, 304. Methods of
respiration, 306. The cribellum, 308. The tarsal claws,
309. House-spiders and wolf-spiders, 310. The classi-
fication of spiders, 314.

XVI. Some Other Arachnida 321

The King-crab, 321. Scorpions, 325. Solifugae, 328-
False-scorpions, 330. Harvesters, 335. Mites, 339.

Bibliography

349

Index

37i

LIST OF PLATES

I. Trap-door Spider in Nest
II. A. Feet of Jumping-Spider
B. Foot of Epeira

III. A. Male Jumping-Spider .

B. Jaws of Tegenaria

C, D. Prominent Epigynes

IV. Sections of a Spider
V. A. A Linyphiid Spider

B. House- Spider
VI. Wolf-spider with Young .
VII. Spider with eggs in cocoon
VIII. Banana Spider with Eggs and Young
IX. Cocoon of Epeira fasciata
X. A. Eggs of Epeira

B. Nest of Agelena .
XI. Tube of Atypus affinis at Hastings
XII. A Trap-door open and closed

XIII. A. British Trap-door Spider
B. Bird-eating Spider

XIV. A. Crab-Spiders
B. Zebra-Spider

XV. A. Scorpion
B. Harvester
XVI. A. False- Scorpion

B. Scorpion

C. Tick .

TO FACE PAGE

Frontispiece

DRAWINGS IN THE TEXT

FIG. PACE

1. Prosthomeres .3

2. A Spider's Cephalothorax . . . . . .16

3. Spiders' Eyes 17

4. lorum and plagula 1 8

5. Abdominal Patterns 19

6. Tetrablemma 19

7. Spiked Abdomens 20

8. Remarkable Shapes 21

9. Underside of Abdomen 22

10. Types of Epigyne 23

1 1 . A Spider's Sternum 24

12. A Spider's Chelicera 25

13. Chelicera of Pholcus , 27

14. Chelicerae of Archaeidae and Landana ... 27

15. A Spider's Lip and Maxillae 28

16. Female Palp and Simple Male Palp . . . .30

17. Palp of Sipalolasma 31

18. Palp of Pachygnatha 31

19. Palp of Centromerus 32

20. Leg of Xysticus 33

21. Elaborated First Legs . . . . . . 35

22. A Spider's Tarsus 37

23. Arrangement of Leg-spines 38

24. Tarsal Comb of Theridiidae 38

25. Spiders' Claws ......... 39

26. Spinnerets of Hahnia ....... 40

27. Spinning Tubes or Spigots 42

28. The Cribellum 43

29. The Calamistrum 44

xvii

xviii DRAWINGS IN THE TEXT

FIG. PAGE

30. Section of Body-wall 46

31. Section of Seta-producing Cell 47

32. Endosternite ......... 48

33. Vertical Section through Cephalothorax ... 49

34. Leg-muscles 50

35. Abdominal Apodemes 50

36. Dissection of Fore-gut 52

37. Fore-gut from above 54

38. A Spider's Heart 56

39. Side View of Blood System 57

40. Dorsal View of Blood System 58

41. Section through Lung-book . . . . • .61

42. Coxal Glands 64

43. The Nervous System 67

44. Poison Gland and Duct 68

45. Maxillary Glands . . 70

46. A Pyriform Gland 72

47. An Ampullaceal Gland 73

48. A Cylindrical Gland 74

49. The Indirect Eyes ... . ... 79

50. Sixteen Eyes 81

si. a postbacillar eye 82

52. A Prebacillar Eye 82

53. Palp of Leptyphantes minutus 86

54. Palpal Spines 87

55. An Acoustic Seta 88

56. Stridulating apparatus of Steatoda . . . 93

57. Stridulating apparatus of Leptyphantes ... 94

58. Lyra 95

59. Pecten 95

60. Stridulating apparatus 98

61. Lyriform Organs 100

62. A Lyriform Organ 100

63. Web of Hyptiotes 120

64. Web of Menneus 120

65. Making an Orb-web 147

66. Web of Uloborus I5I

DRAWINGS IN THE TEXT xix

FIG. PAGE

67. Web with Dispersing Bands 153

68. Web with Dispersing Zigzags iS4

69. Web of Argiope iSS

70. Ariamnes simulans . 164

71. Beetle-mimicry 165

72. Myrmecium rufum 166

73. Metatarsal Preening Comb . . . . 171

74. Cocoon of Ichneumon 178

75. Web of Zilla 185

76. Epeira pyramidata 189

77. Antarctic Eye-pattern 195

78. Courtship of Icius mitratus 202

79. Courtship of Astia vittata 203

80. Courtship of Lycosa amentata 205

81. Courtship of Tarentula barbipes 206

82. Sperm-web of Xysticus cristatus 223

83. Sperm-web of Linyphia clathrata .... 223

84. Sexual Organs of Micrommata virescens . . . 226

85. Spiders' Cocoons 233

86. Developing Spider's egg 250

87. Developing Spider's egg 250

88. Developing Spider's egg 250

89. Developing Spider's egg 251

90. Ogulnius obtectus 259

91. Pattern variation in Phyllonethis .... 260

92. Dimorphism in Maevia vittata 262

93. Gynandromorph Oedothorax fuscus .... 263

94. Gynandromorph Lophomma herbigradum . . . 263

95. Eyes of Liphistius 276

96. Sternum of Dolichosternum 277

97. Abdomen of Heptathela ...... 277

98. Palp of male Heptathela 278

99. Profile of Heptathela 280

100. Chelicera of a Mygalomorph Spider .... 285

101. The Rastellus 288

102. Types of trap-door nests . . ... 290

103. Cage for Atypus 294

xx DRAWINGS IN THE TEXT

FIG. PAGE

104. Spinnerets of Diplothele 299

105. The Archearanead 304

106. Tarsus of Spiderling . . . . . . .309

107. Spiders' Genealogical Tree 312

108. The King-Crab 322

109. Gill-book of King-Crab 323

no. A Scorpion 325

111. galeodes arabs 328

112. Obisium muscorum 331

113. Body of a Harvester 336

114. Chelicera of a Harvester ...... 336

115. Leg of a Harvester 337

116. Mouth of a Harvester 337

117. Linopodes 340

118. Mouth Parts of Tick 342

119. Ixodes ricinus 344

120. Spincturnix 345

121. Demodex 347

THE

BIOLOGY OF SPIDERS

CHAPTER I

GENERAL CHARACTERISTICS OF THE CLASS ARACHNIDA

Among the wonders of Natural History, few things are
more remarkable than is the multitude of small many-
legged animals, often of beautiful structure, striking habits
and complex life-histories, yet seldom obtruding themselves
upon our notice. Down among the grass roots, under the
drifted leaves and amid the fallen pine-needles lives a
Lilliputian populace, fighting and slaying, mating and
bringing forth young, pursuing a life vivid, intense and
! fierce, of which the Brobdingnagian mammal is in most
cases quite unaware. Well represented among these small
Arthropods are the Arachnids, such as spiders, which form
the subject of this volume. Elusive creatures they are,
unversed in the arts of self-advertisement, or taught by age-
long experience to refrain from testing its doubtful advan-
I tages. Save for a few spiders, a scorpion or two, and here
I and there a mite that has long been unsuccessfullypersecuted,
mankind neither sees them nor gives them heed. He has
paid, and he yet will pay, a heavy price for this neglect, as
now he is beginning to discern. It is here our purpose to
look more closely at these little creatures, to read in the book
of their lives stories more wonderful than the imagination
of man has conceived ; to find, too, that in their little
domain the same principles hold as in our larger world, for

i B

2 THE BIOLOGY OF SPIDERS

the same laws hold throughout the length and breadth, the
height and depth of the continued miracle that we call Life.

The name Arachnida (apdxv?), a spider ; elSos, shape)
was created by Lamarck when in 1815 he separated Scor-
pions, Spiders and Mites from the order Aptera of the
Linnean Insecta. The Class Insecta of Linneus was almost
co- extensive with the Entoma of Aristotle, as well as with the
modern phylum Arthropoda founded by von Sievold and
Stannius. The phylum includes an enormous number of
segmented Invertebrates, whose most characteristic feature
is the specialisation of one or more pairs of the appendages
in the vicinity of the mouth into jaw-like structures or
gnathites. This specialisation has been accompanied by a
shunting backwards of the mouth, which thus comes to have
more in front of it than the simple pre-oral lobe or pro-
stomium, familiar in the earthworm and characteristic of
all the Annelida. This backward shunting of the mouth
implied simultaneously an advance in cephalisation, that is
to say, the formation of a definite head from a number of
segments, rings or somites which have become pre-oral,
the " prosthomeres " of Lankester. Among the Arthropoda,
three different types of head are recognisable, according to
the number of prosthomeres which go to its composition.
Peripatus, a primitive type of Arthropod, has but a single
pre-oral segment. The Arachnida represent a stage of
progress intermediate between Peripatus and the Crustacea
or the Insecta in that they have two prosthomeres, while
both Crustaceans and Insects possess three. This gives
us some idea of the position of the Arachnida in relation to
the other Arthropod classes. The gnathites which are
accessory to the Arachnid mouth are borne by the third
somite ; these animals are describable as tritognathous,
Peripatus being deuterognathous and the Crustacea and
Insecta tetartognathous.

The diprosthomerous condition of the Arachnida is
seen only in the adult. In the embryo the second somite
and its appendages are not yet actually in front of the mouth
(Fig. 1). The existence of two prosthomeres is indicated

GENERAL CHARACTERISTICS

both by their coelomic cavities and by two nerve-masses or
neuromeres. Appendages do not exist on the first somite,
though it is possible that they are represented by the eyes.
The chelicerae are the appendages of the second somite.
The five conspicuous limbs which follow, namely, the palps
and the four pairs of legs, indicate a coalescence of five
further somites, the result being the construction of a
cephalothorax, i.e. a head or cephalon and breast or thorax
fused together. The reason for being patient with technical
terms like " prosthomeres " is that they are less misleading

Fig. i. — Diagram of Embryo Arachnid Head. In embryo, somite ii
is not yet in front of mouth. From Lankester. E, eye ; CH, chelicerae ;
M, mouth ; i-iv, coelom of somites, 1-4.

than easy-going popular words like " head " and even
" thorax," which are too suggestive of man or mammal.

The region behind the cephalothorax, the opisthosoma,
generally called the abdomen, is composed of twelve seg-
ments or somites. The first of these is the so-called pre-
genital segment of scorpions and is represented by the
" waist " of the spider. The second and third somites of
at least some of the terrestrial forms bear the lung-books.
The fourth and fifth somites are of interest because in
spiders they retain their appendages in the form of spinnerets,
of which primitively there are eight, four (two endopodites
and two exopodites) to each segment. The last seven
somites are devoid of appendages in all living forms. The

4 THE BIOLOGY OF SPIDERS

last may carry a post-anal telson, represented by the spine
of the King-Crab, Limulus, and by the sting of the scorpion.

The alimentary canal of Arachnida has the stomodeal
and proctodeal invaginations of the external chitin possessed
by most Arthropoda. It is a more or less straight tube,
provided as a rule with blind glandular outgrowths from the
mesenteron which increase its absorbtive action. Excretory
Malpighian tubes discharge waste products into the hinder
part of the canal in all the terrestrial forms. True nephridia
are not found in Arachnida ; other ducts from the body-
cavity to the exterior are represented by gonoducts and by
coxal glands. The latter are the only excretory organs of
Limulus and are found in other Arachnida also.

The blood system is of the lacunar type common to
Arthropoda. The heart, a simple tube with valved ostia,
is situated dorsally in the opisthosoma. The arteries are
better defined than the veins, which tend to expand into
sinuses. The blood is colourless and contains numerous
corpuscles.

Respiration is effected by three different methods. The
marine Merostomata breathe by gills, which are borne
externally as appendages of the segments of the opisthosoma.
In the terrestrial forms these are replaced by lung-books,
within the body, but still to be regarded as appendages,
extremely modified. In addition, respiratory tracheae are
also found, and may co-exist with lung-books or may
altogether replace them.

The " brain " is a supra-oesophageal ganglion which
supplies the two prosthomeres : the posterior ganglia are
more or less fused so that five separate ganglia are never
found in the prosoma of the adult. Of the sense organs,
two are predominant, the eyes and the organs of touch.
The eyes are simple and of the characteristic Arthropod
type, never more than eight in number. Several blind forms
are known. The sense of touch is acutely developed in
connection with an elaborate system of complex sensory
hairs. Some of these hairs probably function as auditory
organs.

GENERAL CHARACTERISTICS

Asexual reproduction is unknown in Arachnida and
parthenogenesis is extremely rare. The sexes are separate
although gynandrous forms are sometimes found as freaks.
Sexual dimorphism is not great and may be totally lacking
as far as external appearance is concerned. In spiders,
however, the male is distinguishable by its smaller size
and by the modification of its palpi into sexual organs.
Both viviparous and oviparous forms are found. Develop-
ment of the young is usually direct, but metamorphosis
occurs among the Mites.

Arachnida are generally carnivorous and attack and eat
living prey, but some will eat dead flesh and among the Mites
the diet is more varied. Mites alone include parasitic forms,
the hosts attacked being both animals and plants. Few
examples of organised communal or society life are known ;
activities are solitary and generally nocturnal.

The habit of producing quantities of silk and of spinning
this either into a snare for prey or into a protective cocoon
for eggs is one of the most striking peculiarities of the
Arachnida, inasmuch as, though a thoroughly successful
device, it is almost unknown outside this Class.

The Arachnida as a group provide an interesting com-
parison with the Crustacea. Whereas the numerous living
and fossil members of the Crustacean class give us good
evidence of its racial history from primitive to specialised
forms, the primitive Arachnida are not so readily discernible.
Limulus and the scorpions, the nearest living approach
to such creatures, are not primitive animals in the biological
sense and the many small and simplified Arachnida alive
to-day are degenerate types, and not survivals of an early
ancestor.

Sir Ray Lankester has suggested a solution of the problem
by the following argument. If we may expect a reasonable
parallelism between the Crustacea and the Arachnida, then
we must be prepared to find differences between the
scorpions and the primitive Arachnida at least as great as
and probably comparable to the differences between a higher
Crustacean such as a crab and a primitive one like Apus.

6 THE BIOLOGY OF SPIDERS

The higher Crustacea, like the higher Arachnida, are
characterised both by a definite typical number of segments
to the body and by an obvious grouping of these segments
into divisions or tagmata. The lower Crustacea have a very
variable number of segments and they show less inclination
to group these segments into sharply defined regions. We
are therefore led to expect of the primitive Arachnida less
exactitude of segments in respect of both numbers and
arrangement. With these considerations in mind, Lankester
has pointed out that it is not unreasonable to regard the
Trilobites as representatives of the distant past of Arachnid
history. They are monoprosthomerous, which differentiates
them from living Crustacea : they have lateral eyes which
resemble nothing so closely as the lateral eyes of Limulus,
and a superficially similar trilobation of head and body is
seen in the larva of Limulus. There are other features in
the structure of these interesting fossils which seem to
confirm them in such a position. For instance, they show
a varying tendency to unite the posterior segments into a
pygidial shield comparable to the metasomatic carapace of
Limulus, and some of them carry a large posterior spine
like that of scorpions. Some other zoologists, however,
maintain that the Trilobites are really more nearly allied
to the Crustacea and they will not, in this book, be considered
as members of the Arachnida. Primitive Arachnida may
have been similar in structure and habits to Limulus ; or
we may seek to conceal our ignorance by saying that the
relation between the primitive Arachnida and Limulus is
comparable to that between the Trilobites and the lower
living Crustacea.

The Arachnida are, then, taken to be a class of eleven
orders, one of which is represented only by fossil forms.
The classification is as follows :

Class ARACHNIDA
Sub-class DELOBRANCHIATA (= Merostomata)
Arachnida with exposed gills, breathing dissolved
oxygen.

GENERAL CHARACTERISTICS 7

Order XIPHOSURA

Marine Arachnida with prosoma of horseshoe-like
outline ; opisthosoma unsegmented ; telson in the form of
a spine.

Order EURYPTERIDA (=Gigantostraca)

Fossil Arachnida, nearly all marine, found in Palaeozoic
formations.

Sub-class EMBOLOBRANCHIATA

Arachnida with lung-books or tracheae or both, breathing
free oxygen.

Order SCORPIONIDEA

Segmented Arachnida with chelate chelicerae and palpi ;
opisthosoma divided into a mesosoma and a tail-like meta-
soma, each of six segments ; telson in the form of a sting ;
four pairs of lung-books ; a pair of pectines on the second
mesosomatic segment.

Order PEDIPALPI

Arachnida with two-jointed non- chelate chelicerae and
strong palpi ; first pair of legs used as tactile organs ; the
prosoma unsegmented, the opisthosoma segmented ; one
pair of lung-books.

Order ARANEAE (== Araneida)

Arachnida with two-jointed non-chelate chelicerae
carrying the orifice of a poison duct ; palpus of male bears
a sexual organ ; the prosoma always, the opisthosoma
usually unsegmented ; the appendages of the latter function
as spinnerets ; respiration by both lung-books and tracheae.

Order PALPIGRADI (= Microthelyphonida)

Arachnida with three-jointed chelate chelicerae ; pro-
soma consisting of an anterior portion unsegmented, and a

8 THE BIOLOGY OF SPIDERS

posterior portion of two segments ; opisthosoma of eleven
segments, bearing a flagellum of fifteen joints.

Order SOLIFUGAE (= Solpugae)

Arachnida with two-jointed chelate chelicerae and
sensory palpi ; prosoma has the last three segments free ;
opisthosoma segmented.

Order CHERNETIDEA (= Pseudoscorpiones)

Arachnida with chelate chelicerae, bearing the opening
of the spinning organ ; palpi large and chelate ; opisthosoma
segmented ; respiration by tracheae.

Order PODOGONA (= Ricinulei)

Arachnida with prehensile palpi ; tarsus of third leg of
male bears a sexual organ ; respiration by tracheae.

Order OPILIONES (= Phalangidea)

Arachnida with three-jointed chelate chelicerae ; pro-
soma contains odoriferous glands ; opisthosoma segmented ;
no spinning organ ; respiration by tracheae.

Order ACARINA (= Acari)

Arachnida with suctorial and biting or piercing mouth-
parts ; opisthosoma nearly always segmented ; respiration
by tracheae ; life-history includes metamorphosis.

The fifth of these orders, that of the spiders, is the one
with which the bulk of this book is concerned, and it may
be as well at this point to clear up the unfortunate uncertainty
as to how it may best be named.

C. Clerck, who wrote a book on Swedish spiders,
" Svenska Spindlar," in 1757, used Araneus as Linneus
had done for every spider, recognising no generic divisions.
Subdivisions were first made by Latreille in 1804, when he

GENERAL CHARACTERISTICS

used Aranens for the common garden spider, Epeira dia-
demata. At the same time he suggested Araneides as a
family name and Leach changed this in 1817 to Araneidea.
Araneida was a form subsequently used solely for the sake
of uniformity with the names of other arachnid orders.
However, in 1827 Latreille, somewhat casually, transferred
Araneus to the house spider, Tegenaria domestica, whereon
Walckenaer, realising the disadvantages attaching to the
name as a generic term, set up Epeira and restored Tegenaria.
With the disappearance of Araneus, Araneida, which signifies
" like the genus Araneus ," became meaningless, and Sunde-
vall, in 1833, proposed Araneae, to which there is no such
objection.

The final complication was due to the revival by Simon in
the first volume of his Histoirie Naturelle des Araignees, of
Araneus as an immense genus, embracing Epeira and many
of its allies. His subdivision of the genus into several
artificial groups was no more satisfactory than the older
system of separate genera, with the result that most authors
have not followed him and. Araneus has not gained general
acceptance. In the form Aranea it is used in America, but
on the whole it seems wisest to use Araneae as the name of
the order.

It is not too much to say that of the eleven Arachnid
orders, spiders are the dominant group, dominant both by
virtue of their numbers and their world-wide distribution.
Mites alone seriously challenge them in these respects ; all
the others are limited in range and inconspicuous in
activities.

In taking a view of the order of spiders as a whole it is
soon clear that they stand for several reasons detached from
all other groups.

The first feature of this isolation is their copious use
of silk. Some insect larvae and some of the other Arachnida
can produce silk, but other spinners make of it only an
occasional or a particular use, whereas the whole of the
spiders' life shows an entire dependence on this invaluable
material. " The young spider is born into a silk nursery,

io THE BIOLOGY OF SPIDERS

and on a silk monoplane it flies away ; with a silk web it
catches its food, binding up with silk threads and ribbons its
struggling prey or its bitter enemies. It drops from peril
on a silk rope, of a silk sheet it makes its cocoon, its eggs
wrapped round with silk cushions. In a silk chamber the
old spider sleeps through the cold of winter, and even
in death it is sometimes wrapped in a silk shroud." So
complete a reliance on a single material is altogether
unique.

Secondly, the spider is alone or nearly alone in spinning
a web or snare for its prey. Few of us, coming by chance
upon a spider's web, realise this aspect of its nature. Birds
build nests, beavers dams, bees combs, termites cities, but
the spider builds a trap. The only other instance of such a
structure is the web made by the larva of the caddis
Hy dropsy che.

Thirdly, spiders have an anatomical peculiarity which it
is hard to match elsewhere in the animal kingdom. The
palpi of the mature male become modified at the final moult
into complex intromittent organs, but they have no direct
connection with either the testes or the vasa deferentia. The
spermatozoa produced by these organs, which are situated
in the abdomen, must therefore be transferred to the palpi
before they can be passed in mating to the female. This
picking up of the semen by the palpi (the " sperm-induction,' '
as it is called) is one of the spider's most extraordinary actions,
and incidentally one of the hardest to witness. Such a
separation of testis and penis is all but unheard-of — one had
almost said impossible.

That a group of animals should possess three peculiarities
like these is not a little remarkable, and no one would be
surprised if they were among the most popular subjects
for study by zoologists throughout the world. And yet the
striking fact is their neglect by naturalists in all times and
countries. It is not as though spiders were rare or few in
kind or difficult to catch, for they are none of these, and long
before we have become aware of the peculiarities described
above, they have advertised themselves, thrust themselves

GENERAL CHARACTERISTICS n

upon our notice with their orb-webs — one of the most
wonderful structures in the animal world.

It seems possible that the spider's very isolation is partly
responsible for their neglect. The spider does not illustrate,
better than any other " type," any principle of zoology,
except, perhaps, evolution ; and the spider's contribution
to the evolution theory (see Chapter XV) is of very recent
recognition. Thus the spider is immediately relegated, or
shall we say promoted, from the domain of the student to
that of the specialist. This is the more understandable
because it is a very difficult animal to dissect, and under
the scalpel of the inexperienced generally becomes a most
lamentable-looking object.

Again, modern zoology is almost wholly organised in
terms of evolution, and the spider's isolation places it in
an evolutionary backwater which, successful though it may
have been, takes it out of the main stream of past history.
The phylogenist can pass it by unheeded and suffer nothing
for his neglect.

Lastly, the spider has no economic importance. It
does not attack the food, the clothing, or the houses of man ;
a few attempts to use its silk have been pathetic disappoint-
ments ; and its occasional captures of noxious insects are
counterbalanced by its catholic taste and readiness to eat
without discrimination man's entomological allies.

When one leaves the ranks of zoologists for inquiry
among other persons, one finds not neglect so much as
active dislike, and this too is not a little remarkable. Such
an attitude towards the spider seems to be a universal human
trait, more widely spread than claustrophobia, and much
more difficult to explain. A natural dislike by a careful
housewife of a creature whose propensity for filling her
rooms with cobwebs adds to her work, is understandable, but
in a different category altogether is the intensity of the feelings
from which some people suffer. Every one of us must have
many such persons among our acquaintances. In other
respects, these people may be not only normal, but even
admirable — giants among men. An instance that comes

i2 THE BIOLOGY OF SPIDERS

readily to the mind is that of H. R. Bowers, who, had he not
been involved in Captain Scott's disaster, would undoubtedly
have become one of the greatest polar explorers of the age,
and who yet had such an aversion from spiders as to describe
them as more loathsome than even the land-crabs of South
Trinidad.

Psychologists might be able to discover the origin of
such phobia in an occasion of childish fright. It is
undeniable that no creature is more likely than a house
spider to appear unexpectedly, and, with its straggling legs
and unusual mien, to give a shock to a child. Were this
shock to be repeated, as well it might be, the ultimate result
in the adult mentality might be the " instinctive " horror
which is so common.

It is this attitude of mind which prompts two of the
questions which so frequently recur in casual conversation —
" What is the good of studying spiders ? " and " What is the
use of spiders ? " Both questions, though generally put
without any intention other than sheer banality, implicate
fundamentals of biology, and are well worth answering at the
beginning of such a book as this.

The first question betrays ignorance of the spirit of
research and a lack of sympathy with the whole outlook of
the scientific mind. Scientific studies are not carried out
because of the use to which men may ultimately be able to
put their results, and the existence or otherwise of any such
" practical application " (abhorrent phrase !) is not a reason
either for their prosecution or abandonment. There is a
close parallel in point of view between pure biological research
and polar exploration, and Nansen could exclaim in surprise,
" People perhaps still exist who believe it is of no importance
to explore the unknown polar regions." He ends this
well-known passage with words which ought to be inscribed
in every laboratory, " The history of the human race is a
continual struggle from darkness towards light. It is there-
fore to no purpose to discuss the use of knowledge ; man
wants to know, and when he ceases to do so he is no longer
man." The scientist, like the polar explorer, works because

GENERAL CHARACTERISTICS 13

man wants to know, because both are looking forward to the
distant day when all shall be known. When that day may
come, what that knowledge may mean, he cannot hope more
than dimly to foresee. But it is his faith.

The second question is, if anything, more futile. It
presupposes, first, a purpose for the universe as a whole,
and, secondly, that this purpose is closely connected with the
well-being of Man ; whereas what is actually known is that
the facts of biology seem to arrange themselves in an ordered
plan. That we can thus think out the universe and, however
painfully, arrange it in a definite plan of events that lead to
one another and tend somewhere, though we know not
where, may be taken as showing that there is purpose behind
it all. But this is an altogether different matter from the
assumption that every form of life was created to be of direct
use to man. The use (so-called) of the spider or of any other
creature is that it is a cog in a wheel of this vast machine.
As such it gives things in general an impulse in some
direction. No one knows enough to say whither, but certain
it is that the economy of Nature would be different without it.

A part of this greater purpose, and one which is more the
concern of the naturalist and less that of the philosopher,
is the evident purposiveness in the activities of every animal.
All that it does tends in one direction — to preserve and
increase it and its kind. This is the real distinction between
all that is living and all that is not, this quality which must
have been present in the primaeval living matter, though how
it arose and to what it is due no man can say. In this book
we have to consider first the structure of the spider as
adapted to its various actions, and then to pass to an account
of the habits themselves. We can best appreciate the
latter, when we understand the part played by the spider
in the scheme of things.

CHAPTER II

THE EXTERNAL STRUCTURE OF SPIDERS

In Biology, as in other branches of Science, observation
of facts provides the basis on which all subsequent progress
depends. The discovery of the structure of animals' bodies
is one manifestly important aspect of these preliminaries,
but it is well to recognise that it is only a part of the problems
of biology and to realise clearly the position occupied by
morphology in the wider science.

The progress of Science is an orderly march by recognised
steps, constituting a process generally described as " scientific
method." The procedure has been outlined in a familiar
passage by de Morgan. " Modern discoveries," he wrote,
" have not been made by large collection of facts with
subsequent discussion, separation and resulting deduction
of a truth thus rendered perceptible. A few facts have
suggested a hypothesis, which means a supposition, proper
to explain them. The necessary results of this hypothesis
are worked out, and then, and not till then, other facts are
examined to see if their ulterior results are found in Nature."

The stating of the hypothesis is a process of inductive
reasoning, a passing from the particular to the universal.
This is followed by the reverse process of deductive
reasoning, or passing from the universal to the particular,
while the ultimate test by actual experiment is the most
characteristic feature of the Newtonian or modern scientific
method. It is clear that in this process the greatest risk
is attached to the induction, a risk which was embodied in
the late Lord Rayleigh's oxymoron, " Never base your
theories upon facts, for if the facts are disproved, what

EXTERNAL STRUCTURE

becomes of the theory ? " So great, indeed, is this risk
that it is often assumed, in popular speech, that to argue from
the particular to the general must necessarily be fallacious.
That it is not so, a moment's reflection will prove.

It is now to be emphasised that the Newtonian method
is not invariably applicable to every branch of science. The
method depends on the material, and every student knows
that the Newtonian method is best illustrated by examples
from Physics. Biology must as yet rely very largely upon
more empirical methods and this is especially true of mor-
phology. Experimental treatment is possible and frequent
in dealing with problems of physiology, but morphology has
scarcely passed the stage of observation followed by inductive
inference. Hence the necessity for clearness in compre-
hension of the facts of anatomy and for frequent checking of
observations by comparisons. " Comparative Anatomy "
has long been the name of a branch of zoology, while com-
parative physiology is far less familiar.

These considerations introduce us to one aspect of the
study of morphology, but another is no less essential.
Structure and habits are not unrelated, but are mutually
dependent portions of a whole which is the adaptation of
the organism to its environment. Looked at from this
point of view the facts of morphology become living realities ;
they come alive. It is often clear enough that morphological
facts cannot be understood unless the functions of which
different structures subserve be kept steadily in view.
Often the function is obvious, but in the morphology of the
Arachnida there must also be included a number of facts of
which the functional importance is at present by no means
so obvious. It is, however, unwise to neglect them for this
reason, since advances in our knowledge may well depend
upon our remembering them. Such an outlook gives to the
whole subject of the anatomy of spiders an intense interest.
Spiders are a highly specialised group, with powerful
organs and efficient methods, very well adapted to their
conditions of living. The uniformity, shown as a general
rule throughout the order, is, as it were, emphasised by the

1 6 THE BIOLOGY OF SPIDERS

existence of a proportion of truly remarkable aberrant forms,
possessing peculiarities, now of this part, now of that. It
is specialisation which is responsible for the apparently
technical nature of the descriptions of structure in both this
and the following chapter : for there is no non-technical
way of describing parts which do not exist at all in more
familiar animals.

The Cephalothorax

The forepart of the spider's body has in the previous
chapter been termed the prosoma. The whole of the
literature of spiders, however, uses the word cephalothorax,
to which objection has been taken on the ground that it is
applied, in different orders, to parts not necessarily the same
in origin ; for instance, the cephalothorax of the Crustacea
includes the first thirteen segments of the body. The same
is true of the opisthoma, which is universally called the
abdomen, and both terms are now too well established to
be altered.

The cephalothorax (Fig. 2) is a comparatively uniform
structure. The shield or cara-
pace which bounds it above is
occasionally a smooth, regular
convex surface, but more often
a visible groove divides an ap-
parent head from the thorax
behind it. Upon this thoracic
region there are generally in-
dentations— a " median fovea "
and eight " radial striae " point-
ing towards the legs. These
depressions mark the internal
attachments of the muscles of
the sucking stomach and of the
legs ; they are often deeper in
Fig. 2. — A Spider's Cephalo- colour than the surrounding
thorax. shield and may form the only

pattern borne by the cephalothorax. Sometimes, how-

EXTERNAL STRUCTURE 17

ever, dark longitudinal streaks are present ; indeed, in
many families there is a more or less standard pattern to
which its members conform. Again, in some species the
cephalothorax is surrounded by spines.

The ocular region is sometimes darker than the rest,
and the separate name of clypeus is usually given to that
part of the cephalothorax between its extreme fore-edge
and the first row of eyes. This clypeus is never present as
a definite and distinct part, but its width and its inclination

Fig. 3. — Spiders' Eyes. A, Entelecara acuminata. B, Pepono-
cranium ludicrum. C, Walckenaera acuminata. D, Pholcus podo-
phthalmus.

differ and these diversities may be of use in classifying some
of the genera of spiders. Occasionally an elevation of the
ocular region carries the eyes or some of them in a prominent
position, and when this is exaggerated, it produces a remark-
able aspect in profile. Some of these are shown in Fig. 3.

The Pedicle

The cephalothorax and abdomen are joined by the
characteristically slender waist or pedicle, hidden as a rule

THE BIOLOGY OF SPIDERS

by the overhanging abdomen. This delicate junction is
protected and strengthened by chitinous plates above and
below, known as the lorum and plagula respectively. The
shapes of both lorum and plagula are numerous, but there
seems to be no principle governing the diversities which are
to be found in different families. The lorum is often
composed of two pieces, which fit closely to one another, but
the plagula is always undivided (Fig. 4).

This pedicle is worthy of more admiration than it
generally receives. Even in large spiders its diameter is not

A B

Fig. 4.— A, Lorum of Argyroneta aquatica. B, Plagula of Dysdera
cambridgii.

great and in smaller species and their young it must be indeed
minute. Yet through it there passes an artery, the nerve
cord and a part of the gut.

The Abdomen

The normal abdomen is a more or less elongated cylin-
drical sac, devoid of all traces of segmentation and very often
with no pattern. The greatest possible diversity is, however,
found. Pattern and often beauty of colouring and design
are conspicuous in many families, and where a pattern or
marking of any sort exists, three general features may
usually be recognised. Most frequently a longitudinal
narrow dorsal mark is present, lying above the heart within
and perhaps due to its proximity. In other families,
especially the orb-spinners, a broader leaf-shaped mark is
found, and is called the folium. Thirdly, small depressed

EXTERNAL STRUCTURE

points, hardened within, and due, like the striations of the
cephalothorax, to internal muscle attachments, are often
visible symmetrically arranged, and are seen most easily
on spiders without other markings (Fig. 5).

Segmentation is persistent in the sub-order Liphistio-
morphae. These spiders have several chitinous plates

Fig. 5. — Common Types of Abdominal Pattern.

protecting the abdomen both above and below (Fig. 99).
This persistence of the primitive condition is unknown in
the other sub-orders, save where less perfect traces of
segmented ancestry are found in isolated genera. The
best example of this is the genus Tetrablemma found in

A 6

Fig. 6. — Abdomen of Tetrablemma. A, View from behind.
B, Profile.

Ceylon. The abdomen of this spider is covered above by
a hardened plate, and below two such plates cover most of
the surface. In addition, hard folds of cuticle protect the
sides and the posterior end of the abdomen (Fig. 6).

An unsegmented dorsal plate of chitin is also found
protecting the abdomen in many spiders belonging to the

2o THE BIOLOGY OF SPIDERS

family Oonopidae. It is probable that this plate is a relic
of the earlier segmented terga, which, however, has lost
its metamerism.

The diversities in abdominal shape are extraordinary.

Fig. 7. — Spiders with Spiked Abdomens. A, Phoroncidia trispinosa.
B, Pycnacantha tribulus. C, Araneus pentacantha. D, Micrathena
cyaneospina.

No cartoonist, trying to draw an absurdly impossible spider,
could succeed in achieving a design more bizarre, more
fantastically improbable than some of the forms that meet

EXTERNAL STRUCTURE

one's eye as one turns the pages of a collection of papers
descriptive of exotic Araneae. These caprices of Evolution
may be grouped as follows : —

(1) Forms which protectively resemble objects in their
neighbourhood.

(2) Forms which mimic the shapes of other animals.

(3) Forms which are armoured with spikes.

(4) Forms which seem to have neither rhyme nor reason.
The first two groups are described in Chapter VIII ;

^C-Z=: —

Fig. 8. — Remarkable Shapes. A, Phricotelus stelliger. B, Poltys
ideae. C, Leptopholcus signifer.

some specimens of groups (3) and (4) are shown in Figs.
7 and 8. It may be supposed that the shapes shown in
Fig. 7 act as a discouragement to such of the hungry as have
tender mouths ; but the biological significance of the last
group is harder to fathom. It might become apparent to
competent observers. It is, however, unfortunately true
that much of our knowledge of exotic spiders is limited to
descriptions of the structure of dead specimens, received
by authorities at home from collectors abroad. Observations
of the habits of the animals have been all too rare.

THE BIOLOGY OF SPIDERS

The underside of the

Fig. 9. — Underside of Abdomen. A,
Lung- book ; B, Epigastric furrow ;
C, Epigyne ; D, Tracheae ; E, Spin-
nerets.

omen (Fig. 9) shows more
features than the upper.
The part next to the pedicle
is often more convex than
the rest and is called the
epigastrium. It is visibly
separated from the rest by a
groove, the epigastric furrow.

The two lung-books, or
the two anterior lung-books
of the four- lunged spiders,
lie in the epigastric region
and are conspicuous as paler-
coloured patches. The re-
productive organs open be-
tween them in the middle
of the epigastric furrow.

The Reproductive Orifices

The vas deferens of male spiders has but a tiny median
orifice, very difficult to discern and unprotected by any
epiandrium.- The oviduct of the female has, however, a
larger aperture, in close association with the single or paired
openings of the spermathecae which receive and store the
spermatophores of the male, the whole surrounded by and
forming part of a complex epigynum. This epigynum
shows great diversity in form and in external appearance,
so that it becomes the surest, and often indeed the only, way
of identifying the female of many species of spiders.

In its simplest form the epigynum is merely a transverse
aperture, but this very primitive type is not common. More
frequently an opercular plaque, the scape, surrounds and
protects the actual vulva, and of such a type three different
degrees of complexity may be recognised. In the first of
these there are but two simple apertures on the scape, each
leading to a spermatheca. An example of this is shown in
Fig. 10. The spermathecal openings, however, may be in a

EXTERNAL STRUCTURE

hollow or depression in the scape surface, this hollow being
divided by a longitudinal ridge, the guide, Fig. 10. Lastly,
the posterior end of the guide may be so broad that its end
conceals the openings of the spermothecae altogether.
Sometimes this broadening is so great that one may speak

Fig. 10. — Types of Epigyne. A, Liphistus desultor. B, Pirata
piraticus. C, Tibellus maritimus. D, Micryphantes rurestris. E, Ba-
thyphantes concolor. F, Bathyphantes nigrinus. E and F in profile.

of the alae of the guide as being these lateral parts under
which the spermathecae are to be found.

A more elaborate type of epigynum has a downward
projection from the anterior side of the scape. This is
called the crochet or clavus ; in appearance it often resembles
an elephant's trunk in miniature. The function of this

24 THE BIOLOGY OF SPIDERS

addition is obscure, for it can scarcely be of much use as an
ovipositor : it may play a part in copulation. Its end is
usually hollow. Still a further elaboration is found when
the crochet is accompanied by another projection, the par-
mula, from the posterior edge of the scape. These two are
in close contact and their opposing faces are hollowed. They
form therefore a short tube which acts as an ovipositor.

In many spiders, but not in the Mygalomorphae, nor in
those which possess a cribellum, nor in the Drassidae, a
small pointed appendage is to be seen just in front of the
spinnerets. This is the colulus. It is probably without
any function, being merely derived, as was first suggested
by Menge, from the more primitive cribellum.

Behind the spinnerets a small tubercle, not always very
obvious, carries the anus at its tip. This is sometimes
called the anal tubercle, sometimes the post-abdomen. It
is relatively more conspicuous in the embryo than in the
adult, for it is a vestigial structure representing all that

remains of the last seven of the
twelve original abdominal seg-
ments.

The Sternum

The underside of the prosoma
is formed by two unequal plates
of chitin named the sternum and
labium or lip (Fig. n) The
former is oval or heart-shaped,
slightly convex and as a rule
marked on each side by four
shallow bays or acetabula, oppo-
site the coxae of the legs. Like
the carapace, the sternum repre-
sents a number of fused segmental
plates, and in one sub-family, the
Miagrammopinae, a suggestion of this condition is retained,
for the sternum consists not of one but of two triangular
plates. Since in the Liphistiomorphae the sternum is

Fig. ii. — A Spider's Ster-
num. L, Lip ; M, Maxillary
lobe of palp ; P, Pedicle ;
i-iv Coxae of legs i-iv.

EXTERNAL STRUCTURE

uniformly continuous, this condition in the Miagram-
mopinae may well be a secondary acquisition and not
a primitive survival. In many spiders there is a small
posterior sternite between the coxae of the fourth pair of
legs, possibly reminiscent of a bygone segment and similar
to the labium in front.

The labium is sometimes fused altogether to the sternum,
but as a rule it is joined to it by softer membrane. Its very
variable shape is used frequently in classification — it may
be square or elongated, semicircular or oval. Just as the
sternum lies between the coxae of the legs so the lip lies
between the coxae or the maxillary lobes of the palpi. It
forms indeed the floor of the mouth and is generally
described as one of the mouth-
parts.

The Chelicerae

The appendages of the cepha-
lothorax are the chelicerae, the
palpi and the legs.

The chelicerae (chelae, man-
dibles or fakes) are the spiders'
very efficient weapons (Fig. 12).
Here it may be noted that the
number of alternative names for
almost every organ is a charac-
teristic of descriptive anatomy
in spiders. The cause is the
habit of the nineteenth century
arachnologists who one after
another invented their own
terms, in ignorance or neglect of
the proposals of their fore-
runners. Nor has the process
ceased yet !

The chelicerae are homologous with the second antennae
of Crustacea and not with the mandibles of insects. They
consist invariably of two joints, the proximal one being named

Fig. 12. — A Spider's Chelicera,
showing upper and lower
rows of teeth, and grooved
fang, with strong muscles.

2(»

THE BIOLOGY OF SPIDERS

the paturon or tige, and the distal the unguis, crochet or
fang. In Mygalomorphae, they project horizontally for-
wards, and strike downwards in parallel directions ; in all
other spiders they are articulated almost vertically and
strike transversely so that the ungues tend to meet in the
transfixed prey. Their two parts, though of simple structure,
present a very considerable degree of variation in the
different forms.

The paturon is a more or less conically shaped joint,
generally coated with a few hairs, sometimes, as in Segestria,
with metallic-looking coloured scales. In some families
there is a smooth prominence articulated with the upper end
on the outside and called the lateral condyle. This is
something of a mystery, but it may be the vestigial exopodite
of the primitive biramous pleiopod, the endopodite being
the functional portion. The outside of the lower edge of
the paturon is furnished with stout teeth, forming a digging
organ in those families which have acquired a burrowing
habit. This is called the rake or rastellus of the chelicerae.
The inner side of the distal end is grooved with a furrow
into which the unguis fits when at rest and the two borders
of this furrow are denoted as outer and inner in Mygalo-
morphae, as superior and inferior in other spiders. The
superior border may be armed with a brush of hairs or with
chitinous teeth. The inferior border is either toothed or
altogether unarmed, and this variation in the dentition of the
two borders is often a feature of great value in classification.
The inner edge of the paturon is usually plain, but in a few
spiders it bears a small nipple- like tuber, called the mastidion.
This organ is another mystery, its function being difficult
to guess. The outer side of the paturon is in some spiders
corrugated with a series of ridges which form a stridulating
organ, discussed in a later chapter.

In the angle between the paturon and unguis there is a
tiny plate or sclerite of chitin called the articular sclerite,
and representing, perhaps, an intermediate segment of the
chelicerae.

The unguis is nearly always a plain sickle-shaped joint

EXTERNAL STRUCTURE 27

of very hard chitin, sharply pointed, but it has an unusual
shape in Laches, and in a comparatively common British
genus, Ceratinella. The concave edge is
grooved and the lower or posterior edge
of the groove is usually finely toothed.
Near the tip is the orifice of the duct of
the poison gland, in a protected position
which prevents it from being closed as
the spider drives its fangs through its
prey.

Some interesting divergences from the
typical form of the chelicerae exist. In
the common British spider, Pholcus, whose
chelicerae are small and weak, a projec-
tion from the end of the paturon almost
meets the unguis, so that the organ is
practically " chelate " (Fig. 13). The
very remarkable spiders of the family
Archaeidae have long and conspicuous
cheliderae, and in Landana they project
downwards in a remarkable manner (Fie. Fig. 13.-— Chelicera

x r—. , - . r ..of Pholcus phalan-

14). 1 he chelicerae or many ant-mimics gioides, showing
project forwards, and carry black spots « che* VtV'^ar0
which imitate the eyes of the ant. rangement.

Fig. 14. — Chelicerae of Archaeidae (A) and Landana (B).

THE BIOLOGY OF SPIDERS

The Palpi

The second pair of appendages, the palpi, perform
diverse functions. They are six-jointed limbs, the joints
being coxa, trochanter, femur, patella, tibia, tarsus. In the
Spiders of Dorset, Pickard- Cambridge does not separately
name the coxa, regarding it as a part of the maxilla and names
the remaining five axillary, humeral, cubital, radial and
digital. The distal joints are used by young and by female
spiders as sensory organs, while in the mature male the femur

Fig. 15. — A Spider's Mouth-parts. L, Lip ; M, maxillary lobe ;
C, coxa ; F, femur ; P, patella ; Ti, tibia ; Ta, tarsus.

may be used in stridulation and the tarsus is an accessory
to the reproductive system. In addition there is, except
in the Mygalomorphae, an endite or inside lobe of the coxa
which acts as one of the mouth-parts.

This endite, the maxilla or maxillary lobe, is separated
by membrane from the coxa of the limb. Its function is to
compress the food particles and squeeze out their liquid
contents into the pharynx. Its innermost margin is generally
provided with hairs which may be sufficiently dense to form
a scopula (Fig. 15) and the fore-edge often bears a serrula

EXTERNAL STRUCTURE 29

or row of teeth which, doubtless, help in cutting the food.
In Ammoxenus these teeth are particularly conspicuous.

The main interest of the palpi of spiders lies, however,
in the modification presented by the tarsal joint of the male,
converting it into the sexual intromittent organ. So remote
a separation of this organ from the testes, which lie in the
abdomen, is indeed remarkable enough in itself, but in
addition the elaborations of these parts are so varied that in
no two species are they exactly alike. They provide,
therefore, the most trustworthy way of identifying and
characterising the males of all spiders.

The study of these organs, and especially of the more
complex forms, is by no means easy. Different names have
been given by different writers to the same part and many
descriptions have been written which do not in fact describe.
The palpal organ cannot be analytically studied at all in its
normal resting position, it must be expanded and this is
achieved by a few minutes' boiling in aqueous caustic potash.
The temptation is then to make a microscope slide of the
product, and this is fatal, for as soon as the organ is fixed
and flattened out, any chance of determining the relations
of the parts is considerably lessened. It should be preserved
free, in glycerine, where it is always available for manipula-
tion and examination from every angle. Studied by these
methods, the forms of the palpi of male spiders open up an
interesting inquiry in evolutionary biology.

There are two ways in which the male palp differs from
that of the female, apart from the modification of the tarsus,
and these are both concerned with the preceding joint,
the tibia. The male palpal tibia is relatively shorter than
that of the female, at any rate at maturity, and it frequently
carries on its outer side, a short process, the " radial
apophysis " of Pickard-Cambridge, whose shape is character-
istic in each separate species. This makes it a valuable
feature in identification. In mating this spur is fitted into
a groove in the female epigynum (Fig. 84).

The simplest form of palpal organ is situated near the
tip of the tarsus, in a cavity, the alveolus. It consists of a

3© THE BIOLOGY OF SPIDERS

coiled tube or receptaculum seminis (Fig. 16) in which three
parts are recognisable. These are a basal or proximal swollen
bulb, the fundus, an intermediate reservoir, and, distally,
a daik elongated duct, the ejaculatory duct. This type of
palpus gives a clue to the probable course of evolution of
the organ. The bulb is evidently a modification of the

Fig. 16. — A Spider's Palp. A, Female. B, Male — with simplest
type of organ.

extreme tip of the tarsus, an invagination of which forms
the reservoir, a part which is marked with transverse striations
like a respiratory trachea. This interpretation is consistent
with the invariable absence of a terminal claw from the male
palpus, whereas many females possess a claw in this position.
The first advance from this simple condition is the migra-

EXTERNAL STRUCTURE

ophi-
After

tion of the entire genital bulb to the lower side of the tarsus
and an increase in the size of the alveolus. The tarsus thus
becomes more or less
cup-like and is usually
renamed the cymbium.
At the same time the
palpal organ becomes
divisible externally in
three regions, which may
be described as the basal,
middle and apical divi-
sions. The apical divi-
sion is usually called the embolus. The three regions
contain respectively the fundus, the reservoir and the duct
of the receptaculum seminis. The basal division is united
to the alveolus by a membrane which bears a small chitinous
sclerite, the petiole. This type of palpus is seen in the
Mygalomorphae and is shown in Fig. 17. It is characteristic
of this type that the passage from the middle division to the
embolus is gradual rather than abrupt.

Two changes may be taken as roughly representing the
next stage and producing an intermediate type of palpus,

Fig. 17. — Palp of Sipalolasma
riensis. A trap-door spider.
H. C. Abraham.

Palp of Pachygnatha degeerii.

possessed by many genera of spiders otherwise somewhat
widely separated and agreeing only in being the less
specialised members of their families. The apical division
of the genital bulb becomes divided into two. One of these
only is a duct for ejaculation of sperm, and is consequently
the embolus proper. The other is called the conductor :
its function is protection of the embolus when the organ is

32 THE BIOLOGY OF SPIDERS

at rest in the alveolus. In the figure (Fig. 18) the darker
embolus can be seen passing round and into the coils of the
conductor, which is a fairly thick twisted plate, nearly always
to be recognised by its membranous nature. The tarsus,
too, is sometimes divided into two parts, of which the
smaller is called the paracymbium. It is easy to see in
Fig. 1 8, but in many more complicated organs it is much less
conspicuous.

In the most conspicuous types of palpi there are elabora-
tions of the appendages of the parts already described, rather

Fig. 19. — Palp of Centromerus sylvaticus. An example showing
extreme elaboration.

than a very great development in the parts themselves. As
shown in Fig. 19, the three divisions of the bulb are separated
by more or less distinct membranous necks. The basal
division is attached to the alveolus by a membranous sac,
called the basal haematodocha from the fact that at the time
of pairing it is distended with blood. It contains, however,
no sign of muscular tissue and when the organ is at rest it is
invisible, being covered by a ring-like piece of chitin, the
sub-tegulum. A similar ring of chitin protects the wall of
the middle division and is called the tegulum. From the
distal border of this tegulum there arises a chitinous tooth

EXTERNAL STRUCTURE

or appendage, which in some spiders is large and very
conspicuous. It has been named the median apophysis,
the lamella characteristica, and the scopus. The apical
division is subject to the greatest changes. The embolus
is composed of two distinct parts, a proximal radix and a
distal stipes, and it ends in a strong plate or spike of chitin
called the terminal apophysis. But, in addition, secondary
haematodochas and extra apophyses may be present, to
complete the tale of an extraordinarily complex and remark-
able organ.

The Legs

The legs, always eight in number, are seven-jointed and
the joints are coxa, trochanter, femur, patella, tibia, meta-

Fig. 20. — Leg of Xysticus crista tus.

tarsus and tarsus (Fig. 20). It is interesting to notice that
while these are the old names borrowed from vertebrate
morphology, the tarsus has been placed beyond the meta-
tarsus. Pickard- Cambridge calls the joints exinguinal,
coxal, femoral, genual, tibial, metatarsal and tarsal, and so
produces a confusion when writing of the coxal joint. In a

THE BIOLOGY OF SPIDERS

few spiders false articulations, or rings of softer membrane
between the chitinous parts, produce an apparent increase
in the number of joints.

Normally each joint is a chitinous cylinder, united by
membrane to its neighbours, and each is as a rule straight,
save the femur, which is noticeably curved in some species.
The ends of each joint are not cut off square, but are so
shaped as to allow different degrees of relative mobility
between the parts.

The trochanter scarcely moves at all ; when it does so
it follows the femur, the first long joint, which can move
freely upwards and sideways, but not very far downwards.
Downward bending is the only degree of freedom of the
patella, and the tibia follows the patella, but is capable of a
little sideways movement in addition. Like the patella, the
metatarsus is confined to downward bending, but the tarsus
is able to move freely in all directions. This means that
while the leg may be lowered at any joint, it can only be
raised by the femur and moved forwards or backwards by
the femur, tibia (slightly) and tarsus.

When spiders walk the longest legs, generally the
first and fourth pairs, move along the lines of their own
directions by vertical movements of the femora. The other
two pairs of shorter legs move at right angles to their own
directions by longitudinal movement or rotation of the
femora. The first and third legs of the near side move
together, simultaneously with the second and fourth legs
of the off side, the step being completed by a simultaneous
complementary movement of the other legs. Such a move-
ment may be presented by four men in Indian file, the first
and third marching in step with one another and out of step
with the second and fourth. The sideways movement of
crab-spiders differs from this since the longest legs are those
of the first and second pairs and the rotating motion of the
third legs is slight.

The coxa is marked on its pre- axial face with a furrow
running along almost its whole length and terminating at
a small projection where it touches the trochanter. This

PLATE II

B. Foot of Epeira, with Three Claws and Accessory Claws.

To face p. 34.] [£. A. Robins, photo.

EXTERNAL STRUCTURE

joint has similarly a slight continuation of this groove, and
its lower surface is divided by a semicircular furrow into
two regions.

The femora of some male trap-door spiders carry small
hooks on their inner surfaces. These are a protective device
used in mating, when the male spider thrusts them against
the chelicerae of the female, gagging her for the time being
and so considerably reducing the risks to himself.

It is worth noticing that the legs of spiders take no part
in mastication, as do the legs of the Opiliones, for example,
and that the palpi alone possess the characteristic Arthro-
podan " gnathobase."

It has long been customary among araneologists to use
the relative lengths of the legs in characterising the various
genera, and to express
this in a " leg formula,"
£.£.1.4.2.3. This means
that the first pair of legs
is the longest, then the
fourth, and the third
pair is the shortest. A
good deal is to be learnt
from a careful compara-
tive study of these ratios,
as well as of the relative
lengths of the separate
joints. This work is,
however, at present in
the course of completion,
and its results will be
stated elsewhere. A long-
familiar fact is, however,
the frequent elaboration
of the first leg. Owing
to its position, this is the
limb which must first

Fig. 21. — Examples of Elaborated Fore-
legs. A, 1 st leg of Palpimanus gib-
bulus. B, 1 st leg of Diolenius phry-
noides. After Simon.

convey tactile impressions of the surroundings as the spider
walks. It is therefore usually the longest and two extreme

36 THE BIOLOGY OF SPIDERS

instances of its development are shown in Fig. 21. Another
feature of the first leg, which will be more fully described
in a later chapter, is its decoration in certain male spiders,
so that it may be displayed before the female in court-
ship.

The use which a spider makes of its legs is, therefore,
by no means limited to mere walking. Not only are they
very efficient assistants to the chelicerae in dealing with
captured insects, but, provided as they are with claws, with
hairs, with tactile and auditory setae and with the mysterious
lyriform organs, they are to be reckoned as the most active
organs of the spider's body. A common error describes them
as the most useful organs, a statement which overlooks the
fact that in so complex a system as an animal's body all
parts become useless if only one fails in its function. For
instance, a leg must be nourished, supplied with blood, and
controlled by nerves. It may, indeed, be said that the spider
is sufficiently true to the traditions of the animal kingdom to
see with its eyes and to taste, if it taste at all, which is
doubtful, with some part of its mouth, but it feels and it
hears and it smells with its legs. These last activities are
considered with the senses in Chapter IV, the setae and
claws are dealt with here.

The Setae

Much of the spider's body as well as its legs, is covered
with what would ordinarily be called hairs. Hair in the true
zoological sense of a living outgrowth from the skin is,
however, peculiar to mammals, and the similar possessions
of the spider are better termed setae. Probably all the setae
on a spider are more or less developed as sense organs, but
some of those on the legs are useful accessories to the spinning
organs. On examining a spider it is easy to distinguish
hairs of at least three different kinds. The most conspicuous
are the stout sharp spines on the legs and palpi, generally
described as tactile. The most difficult, to distinguish, even
under the microscope, are the long delicate acoustic setae,

EXTERNAL STRUCTURE

believed to be receptors of sound waves. These two types
are more fully described in Chapter IV.

Intermediate between the extremes of the obviously
stout and the very fine, there are many other kinds, often
vaguely termed protective, on both legs and abdomen.
Several different forms of these hairs are to be found, some
are club-shaped, some spatulate, some with branches, some
like small spines. In many instances one particular type is
limited to a single family. Their exact functions are by
no means easy to determine and more attention might well
be devoted to them.

It is probable that in some spiders, the body-hairs may
exercise a protective function by piercing the skin of any
unwary handler and setting up irritation. The occurrence
is familiar enough to those who have to do with hairy
caterpillars, and it has certainly been shown by some of the
large spiders at the Zoological Gardens. It suggests, of
course, a cutaneous or subcutaneous gland, the secretion
from which flows either through the hollow within the hair
or over its surface.

That such glandular hairs may be possessed by some
spiders is rendered the more probable by the existence on
the tarsi of many hunt-
ing and jumping spiders
of groups of hairs known
as scopulae. These hairs
are of the peculiar form
shown in Fig. 22, and

are often spoken of as Fig. 22. — A Spider's Tarsus, showing

tenent hairs. They claw and scopula.

seem to enable the spider to adhere to horizontal and
vertical surfaces, as any one who has tried to shake an
Anyphoma accentuata out of a test-tube knows full well !
Some spiders have a similar tuft or scopula on the
metatarsi (Fig. 27).

Another way of regarding these hairs and spines is to
consider not the individual structure, but their arrangement
on the spider's body. Leg spines, for instance, are generally

38 THE BIOLOGY OF SPIDERS

definitely located in superior, inferior, preaxial or postaxial
rows, and the number constituting such a row may be
constant within the limits of a genus. Illustrations of two
such arrangements, possessed by the genera Zora and Ero,
are shown in Fig. 23, where the plan is sufficiently obvious

Fig. 23

. — Arrangement of Leg-spines. A, Zora spinimana.
furcata.

B, Ero

to take the eye at once, but the same principle may be
extended to all spiders. The most obviously useful of all
such groupings is the comb or calamistrum borne by the
metatarsi of all cribellate spiders (except the mature males).
This is used in combing out the fine strands of silk from the

cribellum, the combed
threads giving the webs
made by these spiders
their familiar bluish tinge.

A tarsal comb is seen
in all spiders belonging
to the family Theridiidae and these small spiders use it for
flinging ribbons or sheets of silk upon a struggling capture,
before feeding upon it (Fig. 24).

Fig. 24. — Tarsal Comb of Theridiidae.

EXTERNAL STRUCTURE

The Claws

The extreme tip of the tarsus is sometimes called the
praetarsus, although as a rule it is not a separate part.
From it arise the paired claws which terminate the legs of
all spiders (Fig. 25). When the praetarsus extends between
the claws, the extension is known as the empodium, and is a
valuable part. Sometimes it is unmodified, sometimes it is
pad-like, sometimes it carries adhesive hairs, and sometimes
it is modified into a third median claw.

* 6

Fig. 25. — Spiders' Claws, showing differences in the number of
teeth. A, Sparassus. B, Amaurobius. C, Tegenaria. D, Zora.
E, Ero. F, Gongylidium.

This third claw is of importance in classification. It
is present in the wolf-spiders or Lycosidae and some other
hunting spiders and in certain families of web-spiders.

The paired claws are very hard and sharply pointed,
generally curved and provided with a row of teeth on the
inside of the curve. The number of teeth varies in different
genera and species of spiders, and even, apparently, in the
same individual spider with increasing age. In this respect

4°

THE BIOLOGY OF SPIDERS

sex seems to exert an influence, the number of teeth
increasing in male spiders and decreasing in females.

Finally, there is a type of structure known as accessory
claws present on the tarsi and also on the spinnerets of
orb-weaving or Epeirid spiders. These are straight and
spine-like, but their lower edge is notched with a few small
teeth.

The Spinnerets

The only abdominal appendages persistent in the adult
spider are those of the fourth and fifth segments, where they
function as the spinning organs — namely, the cribellum,
where this organ is present, and the six spinnerets. The
cribellum represents the endopodites of the fourth segment,
whose exopodites are the anterior or superior spinnerets.
The small middle spinnerets are the endopodites of the fifth,
and the exopodites of this segment are the posterior or

Fig. 26. — Spinnerets of Hahnia.

inferior spinnerets. The number of spinnerets differs,
however, from type to type. In the Liphistiomorphae,
the primitive number, eight, is found, occupying the middle
of the lower surface, but only the four exopodites are said
to be active. In most Mygalomorphae there are four
spinnerets, the anterior and median pairs, and in exceptional
instances the spinnerets number only two — sometimes the
two anterior and sometimes the two posterior.

In most spiders, the spinnerets when at rest form an
inconspicuous group at the end of the abdomen and the

EXTERNAL STRUCTURE 41

smaller median pair are hidden by the larger ones. The
relative lengths of the spinnerets in different families are,
however, very variable, a difference which seems to be due
not so much to the amount of use made of these organs as
to the method by which they distribute silk. For instance,
in the highest families of spiders, which spin orb- webs, the
spinnerets are short and almost unnoticeable. In the house-
spiders, which make a flat sheet- web, swaying the abdomen
from side to side, the anterior spinnerets are much the
longest and can be seen from above like two little tails. In
a closely related family, the Hahniidae, the spinnerets form
a row and not a group at the end of the abdomen, a unique
arrangement. In Mygalomorphae, too, the anterior spin-
nerets are long ; and in a curious family, the Hersiliidae, their
length is extreme. Lyonnet has suggested that these tail-
like spinnerets may, by virtue of the hairs which clothe them,
act as tactile as well as spinning organs — a sort of posterior
pair of palpi. The most curious arrangement of all is that
of Cryptothele, an Asiatic genus, whose spinnerets lie in a
mamillary hollow, from which they can be extruded and into
which they can be withdrawn.

The individual spinneret is a finger- like organ, jointed
in the same way as are the false joints of the tarsi, by rings of
softer membrane. The anterior spinneret usually consists
of two such joints, but occasionally of three or even four,
the median spinneret is unjointed and the posterior spinneret
is always of two joints.

It is an important feature of the spinnerets that they
themselves are not the actual tubes through which the silk
is secreted. The sides of the spinneret are slightly harder
than the rest of the abdomen, but the tip is either squarely
or obliquely coated with softer membrane, forming a small
area described as the spinning field. This field is covered
with the battery of minute tubes through which the fluid
silk passes, and these tubes are of two main sorts. The
smaller ones, called spools or fusulae, consist either of a
cylindrical basal portion traversed by a long thin tube or of
a slightly conical base with a curved thin tube (Fig. 27).

42 THE BIOLOGY OF SPIDERS

These are scattered in large though variable numbers over
the fields of all spinnerets. They have two uses. Those
on the anterior spinnerets produce the little band or
transverse sweep of many tiny threads which anchor a
spider's lines to the ground, and are known as attachment
discs ; while those on the other spinnerets provide the much
broader ribbon which the spider wraps round its resisting
victim.

The larger tubes, or spigots, are conical in shape and
more constant in number and position Their complete

Fig. 27. — Spinning-tubes or Spigots. A, Of cylindrica gland of
Tegenaria. B, Of ampullaceal gland of Epeira. C, Of aciniform gland
of Epeira. (B, after Apstein.)

distribution among all or even most of the families does not
seem to have been worked out, but Warburton (1895) has
made a careful study of them in the case of the highest type
of spinners, the orb- weavers, Epeiridae, and his results are
summarised below.

The inferior, median and posterior spinnerets of Epeira
carry respectively one, three and five spigots each. Those
on the anterior spinnerets and one of those on each median
spinneret provide the foundation lines of the web and the
drag-line which many spiders lay down behind them

EXTERNAL STRUCTURE

wherever they go. Four spigots, the two remaining on the
median spinneret and two of the five on the posterior
spinneret, are used only in the making of the cocoon. The
coloured wadding often found protecting the eggs is taken
from them. The three other spigots on each posterior
spinneret produce not silk, but the glutinous fluid which
makes the spiral thread of the web adhesive. Although
deposited round the thread at the moment of formation
it breaks up from the cylindrical to the more stable spherical
form, and beads the line with a regular arrangement of
minute globules. These differently functioning spigots
are connected with different glands in the abdomen, which
will be described in the next chapter.

The cribellum (Fig. 28) is an oval plate found just in
front of the anterior spinnerets in certain families of spiders,
but not in all. It is perforated with a large number of
minute pores, each of which is the orifice of the duct from a
gland. These glands are found only in association with the
cribellum itself, and are not represented by any analogue

Fig. 28. — The Cribellum and Spinnerets of Amaurobius.

in ecribellate families. The function of the organ is quite
clear and may readily be witnessed in many common
spiders. The activity of the glands secreting silk through
numerous pores, produces a broad ribbon of silk composed
of some hundreds of threads. This ribbon is combed out
of the cribellum by the calamistrum on the fourth metatarsus

The Cribellum

44 THE BIOLOGY OF SPIDERS

(Fig. 29) and is by that limb laid upon the plain silk strand
which the spinnerets are simultaneously producing. The
effect is to render the threads of the web more adhesive to
struggling insects, to encumber their legs and wings and
further delay their escape. It produces also a bluish
appearance in the threads of the web as a whole, not by any
pigment in the silk, but by interference of the light, the
process which gives to soap bubbles and oil-films their
evanescent colour. These bluish webs, looking rather

Fig. 29. — The Calamistrum of Amaurobius, showing also a metatarsal

scopula.

untidy, like tangled masses of silk, are frequent enough in
cellars, on wood palings and gate-posts, where they are
spun by spiders of the genus Amaurobius, the commonest
of the British cribellate species.

A good deal of controversy has been held as to the exact
significance of the presence or absence of this organ, a
subject which will be discussed in its proper place in
Chapter XV. Widely divergent views have been held and
cribellate spiders separated from the rest by making them,
on the one hand, a separate genus in the same family, and
on the other, an entirely distinct sub-order.

CHAPTER III

THE INTERNAL STRUCTURE OF SPIDERS

The consideration of the internal structure of spiders or
of any other animal emphasises, more clearly than does the
external appearance, the dual aspect of these anatomical
studies. For with each part and organ we are concerned
in two ways — its shape and its function ; in other words,
with the How-it-is-made and the How-it-works of the
animal body, the twin sciences of Morphology and
Physiology.

The general plan of the Arthropod may be likened to a
hard external tube, from which depend other hard but
jointed tubes, the limbs. Through the middle runs
another tube, a soft one, the alimentary canal, and the
ring-like space between the two tubes is almost wholly
filled with blood. This blood-containing cavity is called
the haemocoel. In it and freely bathed by the blood lie
the various systems of organs — nervous, reproductive,
glandular, and excretory. This all-pervading enlargement
of the blood vessels, forming a haemocoelic body-cavity, is
one of the main Arthropodan characters, distinguishing
them very clearly from the Annelida and from all the
vertebrates. In these types the perivisceral space is called
the coelom, and has a very different embryological origin
from the haemocoel. The blood is confined to definite
vessels — arteries, veins, and capillaries — and the coelom
communicates with the outside world by vessels of two
sorts, nephridia or excretory tubes, and coelomoducts,
whose original function was to serve for the liberation of
the reproductive cells or gametes. But in Arachnida, as in

46 THE BIOLOGY OF SPIDERS

several other groups, true nephridia are not found, and in
such instances the work of excretion is taken over by
coelomoducts. The true coelom in spiders is thus found
only in inconspicuous hollows in the gonads and in the
excretory glands.

With this introduction to the general plan of the
Arachnid we may proceed to the different systems in turn.

The Body- Wall

The body wall is characterised by its assumption of
both protecting and supporting functions — it is in fact an
mm ^mmmmmmmmm ^ exo-skeleton. A section

=r ■— eee^^^^^^^' (Fig. 30) shows it to be

— ^ made up of three layers,

0 m I c of which the outermost, or

7 =5 1 g 1 a 1 e d i 'i i 1 ■ cuticle, is not composed of

Fig. 30. — Section of Body-wall. A, cells, while the Other two

&£S£8&^*S££*- c! are cellular. The pigment-

Hypodermis. D, Basement mem- aiy matter, to which the
brane. Partly after Comstock. colour and most of ^

pattern of the spider is due, is contained in the extreme
superficial layer. Below this the cuticle has a stratified
appearance, where it may be comparatively soft, as on the
abdomen, or may be hardened, as on the legs and cephalo-
thorax, by impregnation with chitin.

Chitin, an invaluable material, found in many inverte-
brates and a few vertebrates, is a nitrogenous organic
compound. More precisely, it belongs to the seleno-
protein group of the polypeptides. Its chief characteristic
is its resistance to ordinary reagents, and thus it is well
suited to form a protective covering to the living animal.

If the body of a spider be boiled in dilute caustic potash
for about a quarter of an hour, the whole of the internal
tissues are dissolved and the chitinous exo-skeleton is left
as a hollow case. The colour can be bleached from it by
hydrogen peroxide or any other weak oxidising agent,
when the residue can be dissolved in pure hydrochloric

INTERNAL STRUCTURE

acid. On dilution with a considerable proportion of water
the chitin is reprecipitated. It is a colourless amorphous
powder, unaffected by alkalis or by any of the ordinary-
organic solvents, and soluble only in concentrated mineral
acids. When boiled with strong acids, it is hydrolysed to
acetic acid and glycosamine. The formula C15H26N2O10
has been suggested for it, when this action would be :

2C15H26N2O10+2H2O

-> 3CH3COOH +4CH2OH(CH.OH.)3CH.NH2CHO

Below the cuticle is a layer of cubical epithelium known
as the hypodermis. This is in-
terrupted only where one of
its cells has become modified
into a hair-producing cell or
trichogen. The body of the
trichogen sinks below the hypo-
dermal level, through which the
shaft of the hair or spine rises,
piercing the cuticle which sur-
rounds it by a diminutive em-
bankment and forming a tricho-
pore (Fig. 31).

On the inner side the hypo-
dermis is lined with pavement
epithelium known as basement
membrane. Thus cuticle, hypo-
dermis, and basement membrane compose together the
body- wall.

The Endoskeleton

But there is also need for internal skeletal structures,
chiefly for the attachment of muscles. The most important
of these is the endosternite in the cephalothorax, a plate of
chitin which it is not very difficult to dissect out, clean,
and examine. Its shape is shown in Fig. 32. When in
position, the endosternite lies below the stomach and above
the ventral nerve ganglia. Many muscles are attached to

Fig. 31. — Section of Seta-
producing Cell of Epeira
diademata.

48 THE BIOLOGY OF SPIDERS

it, some of which are connected to the stomach, some to
the body-wall, and some to the limbs.

It was mentioned in the last chapter that small depressed
points due to muscle attachments are usually found on the

abdomen. When these
are produced internally
into solid prominences, the
latter are known as apo-
demes. The endosternite
has originated from the
development and fusion of
four pairs of such apo-
demes from situations op-
posite the legs, so that
morphologically speaking
it is a part of the body-
wall.

Three small separate
apodemes are found in the
abdomen. Since the ap-
pendages of the abdomen
are so reduced, the in-
ternal skeletal structures
and internal muscles are reduced too.

Muscular tissue is characterised by the elongated thread-
like shape of its cells, which possess the power of contraction
in a high degree. The cells are separated by the minimum
of matrix and in certain instances (voluntary muscles) are
recognised by their transverse stripes.

Students of elementary biology have long been accus-
tomed to make their preparations of striated muscle from
the crayfish, the typical transverse marking being more
easily seen in arthropod muscle than in amphibian or
mammalian. The muscles of the spider are similar in this
respect. When fresh they are very soft and almost colour-
less ; on fixing and staining with suitable histological
reagents the fibres and striations are quite easily made out.
This muscle tissue fills up much of the cephalothorax,

Fig. 32. — The Endosternite.

INTERNAL STRUCTURE

where it has chiefly to do with the alimentary canal and the
movements of the limbs (Fig. 33). The pharynx is fixed to
the sides of the body by several pairs of muscles, and one
median muscle, the retractor of the pharynx, is attached to
its upper end. The sucking stomach, which depends for
its action on alteration of its size, is well furnished with
muscles. Several vertical muscles connect its upper
surface with the under side of the groove of the cephalo-
thorax, and others are joined to the endosternite. The
limbs are necessarily composed largely of muscle within,

Fig. 33. — Vertical Section through Cephalothorax. A, Dilators of
stomach ; B, muscle which retracts leg ; C, muscle which lowers leg ;
D, muscle which advances leg ; E, muscle which raises leg ; F, caecum
of gut. After various authors.

while at the coxal end several muscles join the limb both
to the body wall and to the endosternite. The arrange-
ment of the leg muscles is shown in Fig. 34, which was
drawn from the fourth leg of an Amaurobius, dissected by
G. T. Pitts and M. L. Meade-King, two of my pupils at
Malvern.

In the abdomen the circular and longitudinal layers of
muscle in contact with the hypodermis, which form so
conspicuous a feature in types like the earthworm, are
reduced to mere vestiges. The chief mass of abdominal
muscle lies close behind the pedicle, connected to it and

50 THE BIOLOGY OF SPIDERS

to the anterior of the three abdominal apodemes. Muscles
from the lung-books and reproductive orifices are also

Fig. 34. — Leg-muscles. 1, Extensor ; 2, moves trochanter ; 3,
flexor ; 4, flexor of femur, and extensor of patella ; 5, flexor of patella ;
6, lateral movement of tibia ; 7, flexor of metatarsus ; 8, extensor of
metatarsus ; 9, extensor of tarsus ; 10, flexor of tarsus; 11, 12, claw-
muscles.

Fig. 35. — Abdominal Apodemes. After Schimkewitsch.

attached to this apodeme. Another series of longitudinal
muscles run to the spinnerets from the posterior apodeme.

PLATE III

INTERNAL STRUCTURE

Lastly, the depressed points on the upper surface of the
abdomen are connected to the middle and posterior
apodemes by vertical muscle strands (Fig. 35).

The Alimentary Canal

The alimentary canal, to which reference has been made,
is in spiders a complicated system charged with imbibing,
storing, and digesting the food. It is of a type peculiar to
Arachnida, and does not closely resemble that of any other
class of invertebrates.

The mouth is an extremely small aperture, difficult to
discern clearly. Lying directly above the labium, and in
close contact with it, is a flattened cone of tissue called the
rostrum. If the rostrum and labium are separated the
lower surface of the former is seen to be covered with a
chitinous plate, the epipharynx. Opposed to it, on the
upper surface of the labium is a corresponding plate, the
hypopharynx. The epipharynx and, in Mygalomorphae,
the hypopharynx, are marked with fine grooves forming,
when placed against one another, the stomodaeum up
which the food rises into the oesophagus, partly by surface
tension, partly by the sucking action of the stomach within.
The epipharynx is also marked with fine transverse striations
and edged with minute teeth.

The alimentary canal of spiders agrees, however, with
that of most other Arthropoda in being divisible into three
regions, of which only the intermediate part is lined with
epithelium and is absorptive in action. The fore and hind
portions are derived from the invaginations of the exo-
skeleton at the anterior and posterior ends of the embryo,
forming the stomodaeum and proctodaeum respectively.

The fore-gut, or stomodaeum (Fig. 36), consists of
pharynx, oesophagus, and sucking stomach. All these
parts are lined with chitin and the structure of their sides
is the same as that of the body-wall, with which they are in
continuity.

The pharynx rises almost vertically between the

THE BIOLOGY OF SPIDERS

epipharynx and the hypopharynx. The curvature of the
epipharynx produces a space which is occupied by a median
gland, the pharyngeal gland. This is a minute oval mass
of secretory cells with a duct leading to the end of the
pharynx, near its junction with the oesophagus.

The oesophagus is a much easier part of the canal to
obtain in a dissection and it has long been well known. It
is a slightly curved tube, whose internal chitin is thickened

Fig. 36. — Fore-gut of Spider. A, Epeira diademata. 1, Rostrum ;
2, epipharynx ; 3, labium ; 4, pharyngeal gland ; 5, hypopharynx ;
6, oesophagus ; 7, sucking stomach. B, Oesophagus of Tegenaria
atrica, showing difference in curvature.

above and striated on the sides in a characteristic way. Its
lower surface is thinner and less conspicuous so that the
part is often compared to an inverted gutter.

The sucking stomach is misnamed since it has none of
the functions of a stomach, but is rather to be compared to
a pump drawing in the food from outside. For this reason
it is often referred to as the " so-called stomach," but this
seems a meticulous usage and has not been followed here.
It is formed by a widening of the oesophagus, and lies on

INTERNAL STRUCTURE

the endosternite. Nearly the whole of its upper surface is
hardened, forming a leaf-shaped shield with its point
forwards and with a median ridge below, so that its cross-
section is T-shaped. This ridge is a continuation of the
dorsal thickening of the oesophagus.

The sucking organ is enlarged by the perpendicular
muscles attached to its shield and to the median groove of
the carapace. It is closed by a series of semicircular
compressor muscles attached to the edges of the shield and
to the endosternite. There is no muscle in its own
composition.

The mid-gut, or mesenteron, is the true absorptive
region, and it is in this part that spiders show their most
striking departures from the more general Arthropodan
type of an unbranched tubular canal.

To make food valuable to the spider, the process of
digestion must involve such chemical changes as will make
the food soluble, and so able to pass in solution through the
intestinal walls into the blood which will distribute it to
the tissues. In different animals there are different devices
by which the absorption of the food-products is rendered
as complete as possible, either by increasing the time spent
in the absorbing region or by increasing the absorbing
surface area in contact with the food. The former type is
illustrated by the dogfish, whose comparatively short
intestine encloses a spiral valve. In travelling down the
turns of this spiral the food takes a very much longer time
than it would in passing directly from end to end. The
second method is illustrated by the earthworm, whose
intestine possesses a dorsal infolding or typhlosole. This
largely increases the absorptive area in contact with the
finely divided soil which is passing down it. The two
methods are combined in mammals and many others,
whose small intestine or ileum is greatly elongated, until its
total length becomes many times greater than that of the
animal itself. The spider possesses two such devices for
securing an increased efficiency, which are unlike those of
any other type of animal.

54 THE BIOLOGY OF SPIDERS

The alimentary canal leaves the sucking stomach as a
narrow tube directed towards the pedicle. Before reaching
the pedicle there arise from its sides two diverticula or
blindly-ending tubes which run forwards above the endo-
sternite as far as the poison glands. In some spiders these
diverticula meet in front forming a complete circle, but as
a rule their ends, though lying close together, are separate.
In addition to this, four short lateral caeca arise from the

Fig. 37. — Fore-gut from above, showing caeca directed towards legs.
Partly after Leuckart.

outer side of each diverticulum in the directions of the legs.
They may be prolonged some little way into the coxae, or
they may be bent downwards and inwards under the ventral
nerve mass which lies beneath the oesophagus (Fig. 37).
The liquid contents of these caeca has a digestive action on
meat. They therefore probably act as a reservoir for this
fluid.

The mesenteron then passes back through the pedicle

INTERNAL STRUCTURE

and shortly after entering the abdomen curves upwards and
widens. In the upper surface of this wider portion there
are usually four orifices leading into the complex system of
branched tubules which form the abdominal gland. This
gland occupies the greater part of the inside of the spider's
abdomen, nearly the whole of the upper and lateral portions.
It is penetrated in all directions by the Malpighian tubes,
and its branches ramify round the heart and intestine in a
bewildering confusion. It has long attracted the attentions
and speculations of anatomists and has been successively
described as a stomach, a fat-body, a liver, and a pancreas.
The truth would seem to be that it functions in two distinct
ways. It acts as a digestive gland, secreting a ferment upon
the food, but also as a reservoir, for the food-products pass
into the tubes themselves. Thus they swell out, and a
spider after a large meal becomes bloated to an extent which
would be quite impossible if it were due only to the expan-
sion of the mid-gut itself. It is, of course, not very usual
to find the food entering the digestive glands instead of
merely receiving their secretions through a duct, and the
result is that it grants the spider power to receive relatively
enormous quantities of food at a time. This is stored and
gradually absorbed by the abdominal gland, so that long
periods of fasting can be survived.

The mesenteron passes into the proctodaeum without
any great change in size, but the latter, in addition to its
chitinous lining, is surrounded as well by a layer of muscle
cells. It bears on its dorsal surface an enlargement or
hollow, the stercoral pocket, where faecal matter accumu-
lates in the form of a milky fluid in which float small black
particles. The rectum is a straight tube opening at the
anus, which lies at the end of a small tubercle, behind the
posterior pair of spinnerets.

The digestion of the food is of necessity followed by
three consequences. A small proportion of the nutriment
gained is stored as fat, the rest must be conveyed to all
the tissues by the blood, and the waste matter must be
eliminated.

56 THE BIOLOGY OF SPIDERS

The adipose tissue of spiders consists of cells containing
droplets of fat. These are found in three situations. A
layer of fat-cells lines the interior of the cephalothoracic
caeca, and the space in the abdomen between the branchings
of the abdominal gland is filled with fatty material. Lastly,
a layer of fat-cells lies in the cephalothorax between the
nerve ganglia and the sternum.

The Vascular System

In mammals such as ourselves,
the characteristic of the circulatory
system is that there are two inde-
pendent blood streams through the
heart, one of purified blood going to
the tissues of the body, and one of
blood which, after its return from
the circuit of the body, is going to
the lungs to be oxygenated. In
spiders, as in other Arthropoda, there
is but one course of blood through
the heart, and one circuit of the
body. This circuit, too, is incom-
plete. The blood is not at all points
confined to vessels : there are no
capillaries and the internal organs lie
bathed in blood.

The heart (Fig. 38) is a straight
tube, conical in shape, lying in the
dorsal part of the abdomen, some-
times quite close to the skin and

FlG 3g A Spin's sometimes embedded in the alimen-

Heart. Partly after tary caeca. It is chiefly composed of
Causard' muscle cells, the majority of which

are transversely arranged, but a few are longitudinal.
Outside the muscle is a coat of connective tissue fibres.
The heart is simple within, not divided by valves into
chambers. It lies in a thin-walled sac, the pericardium,

INTERNAL STRUCTURE

which surrounds it at some little distance so as to leave a
pericardial space between the two. Both heart and peri-
cardium are held in position by a complex system of
numerous ligaments, above, below, and at the sides.

The pericardial space is filled with blood which enters
the heart through three pairs of apertures or ostia — four
pairs in Mygalomorphae. These ostia are provided with
valves which prevent the blood from re-entering the peri-
cardium from the heart, so that it is forced to pass out of
the heart by the arteries which lead from it.

The aorta, or forward prolongation of the heart, dips
down and passes through the pedicle into the cephalo-
thorax. Here the posterior dorsal arteries arise from it, to

Fig. 39. — Side View of Blood-System. After Petrunkevitch.

supply the muscles of that region. Behind the stomach it
divides into two branches which lie between the sides of
the stomach and the cephalothoracic caeca. Near the front
end of the endosternite there arise two forwardly directed
cephalic arteries, which supply blood to the eyes and poison-
glands, while the Aortic vessels dip suddenly downwards
and form a centre from which blood vessels run to the
palpi and legs (Fig. 39).

The lateral arteries arising from the heart are eight in
number in Mygalomorphae and six in most other spiders.
They distribute blood among the majority of the organs
contained in the abdomen (Fig. 40).

Posteriorly the heart is continued into the caudal artery.
This branches among the spinnerets and silk glands.

58 THE BIOLOGY OF SPIDERS

Fig. 40. — Dorsal View of Blood System. After Petrunkevitch.
i, Mandibular artery ; ii, cephalic artery ; iii, dorsal artery ; iv, aorta ;
v, pulmonary vein ; vi, diverticular vein ; vii, ventral abdominal artery ;
viii, posterior artery ; ix, recurrent artery.

INTERNAL STRUCTURE

The blood does not return by veins. It is collected in
rather vague channels called lacunae, which deliver it to
spaces called sinuses. There are six of these sinuses, three
in each division of the body. The three in the cephalo-
thorax are longitudinal spaces lying parallel to one another,
close to the sternum. Two of the abdominal sinuses are
also near the ventral surface, the third is below the peri-
cardium. All these sinuses conduct the blood to the lung-
books, where it is re- oxygenated by the air entering through
the leaves. By two pulmonary veins, or, in Mygalo-
morphae, by four pulmonary veins, the blood now flows
back to the pericardium, whence it re-enters the heart by
the ostia. These pulmonary veins are the only vessels in
the spider to be called veins. They are similar in consti-
tution to the cardiac ligaments which hold the heart in
place. Causard has indeed suggested that the other lateral
ligaments are reduced veins, which have lost their original
function of conveying blood and become mere ligaments.

The Blood

The blood which courses in the system is a very pale
blue opalescent fluid, which may be obtained in sufficient
quantity for examination by cutting through the middle of
a joint of a spider's leg. If smeared on a microscope slide,
fixed and stained, it may be seen to contain a number of
clear rounded corpuscles, in which a nucleus is not easily
visible. These doubtless have the same function as the
colourless corpuscles or leucocytes of vertebrates' blood.
That is to say, they attack and ingest invading bacteria,
thus checking their multiplication in what would otherwise
be a very favourable medium. There is nothing corre-
sponding to the red corpuscles of man. The plasma in
which the leucocytes float contains in solution a pigment
known as haemocyanin.

Haemocyanin is of similar constitution to haemoglobin ;
the formula C867H1363N223CuS40258 has been suggested
for it, and it will be noticed that it contains copper instead

6o THE BIOLOGY OF SPIDERS

of iron. It is a pigment widely distributed among inverte-
brates, being present in the blood of most Crustacea and
Mollusca, as well as Arachnida. When reduced or deprived
of oxygen it is almost colourless, but oxy-haemocyanin has
a more or less pronounced blue tinge.

The Respiratory System

We have more than once had occasion to point out that
the Arachnida stand in many respects intermediate between
Crustacea and Insects, and in the respiratory system this
is again noticeable. Most Crustacea breathe by gills and
most Insects by tracheal tubes. Among Arachnida gills,
lungs, and tracheal tubes are found.

Spiders, being land-living creatures, have no gills.
Their lungs are of a peculiar type, known both as lung-books
and book-lungs, to be presently described. Lung-books
and tracheae usually exist together in the same spider, but
there are exceptions to this. In the more primitive sub-
orders of spiders, the Liphistiomorphae and Mygalo-
morphae, and in one family, the Hypochilidae, of the
Arachnomorphae there are two pairs of lung-books and no
tracheae. The majority of spiders possess a pair of lung-
books, and either a single or a paired tracheal opening,
while in an exceptional family, the Caponiidae, there are
two pairs of tracheal openings and no lungs.

The lung-books were mentioned in the last chapter as
conspicuous pale patches in the epigastric region. Each is
a large hollow space, communicating with the external air
by a small pore. The space contains from fifteen to
twenty of the " leaves " which give it its name. Each leaf
is attached to the side of the space in front and at the sides,
being free posteriorly (Fig. 41). It is a fold of the body-
wall and is therefore double, the two halves being kept
apart by numerous vertical supports. The top surface of
the upper lamella of each fold is provided with vertical
knobbed spikes, which serve to keep the leaves apart and
to allow the air to circulate freely between them. The

INTERNAL STRUCTURE

hollows within the leaves are in direct communication with
the blood sinuses of the abdomen. The blood thus enters
the leaves, oxygen is taken in and carbon dioxide is passed
out by direct diffusion through the thin surfaces. The
two lung-books always communicate with one another by a
transverse spiracle.

The tracheae are always paired structures, even when
they open at a single median spiracle. Among Insects the
tracheae form an elaborate system of branching tubes,
conveying air to the tissues, and even, so fine are their
ultimate branches, to the individual cells of the body. The
blood of these creatures has therefore lost its respiratory

Fig. 41. — Transverse Section through a Lung-book. (Only three
leaves are shown.)

function and possesses no oxygen-carrying pigment. As
has been seen, this is not so with Arachnida. Their tracheae,
like those of Peripatus, diverge in bunches at intervals from
the main tube, but do not branch, save in exceptional
instances. This very interesting method of oxygenating
the tissues — by direct supply of air from without — seems to
have been evolved independently by several classes of
Arthropoda, as a result of their leaving the water and coming
to live on land. Sir Ray Lankester has pointed out that
tracheae are most numerous where blood vessels are fewest.
They may be two modifications of the same tissue-elements,
the tracheae containing air instead of blood.

THE BIOLOGY OF SPIDERS

The Excretory System

Excretion of nitrogenous waste-products is performed in
spiders by Malpighian tubules and coxal glands.

A pair of fine branching tubes opens into the intestine
near the stercoral pocket and are known by the name of
their discoverer, the Italian zoologist Malpighi, as Mal-
pighian tubules. Similar vessels to these are found in most
of the Arthropoda, but seem to be not all homologous, or
identical in origin. Those of insects originate in the ecto-
derm and arise from the proctodaeum, those of scorpions,
of some crustaceans (Amphipoda), and probably those of
spiders are of endo dermal origin and join the mesenteron.
It would seem that the possession of these tubes does not
necessarily imply a phylogenetic relationship, but rather
that they represent a method of excretion readily and
variously evolved on passing from an aquatic to a terrestrial
or aerial life. They are absent from Limulus,

There is, however, no doubt of their function. An
extract in water of a sufficient number of Malpighian tubes
can be shown to contain uric acid — a characteristic nitro-
genous waste-product in animals. Moreover, since their
secretion is neutral and sodium can readily be detected in
it, it is probable that the uric acid is present as sodium
urate. Urea seems to be absent from spiders, but there is
ample evidence of the renal functions of the Malpighian
vessels.

The coxal glands have been mentioned above in con-
nection with the vanishing coelom as a type of excretory
organ. Our knowledge of these rather remarkable organs
is due to the admirable work of Buxton, who has studied
their varying forms in many of the orders of Arachnida.

Coxal glands are found most fully developed in the more
primitive spiders of the sub-orders Liphistiomorphae and
Mygalomorphae, and in gradually simplifying conditions in
the higher families of the sub-order Arachnomorphae. In
the highest families of all they exist in an extremely reduced
state.

INTERNAL STRUCTURE

In their typical form, the glands, as seen in the Mygalo-
morphae or trap-door spiders, consist of two large excretory
sacs, lined with cubical or flattened epithelial cells. These
cells have the power of excreting solid particles, such as
those of carmine, if this be injected under the animal's skin.
They are normally found to contain solid particles, which
are probably crystals of urates in the process of excretion.

The sacs lie outside the endosternite opposite the coxae
of the first and third legs. They both discharge their
products into a convoluted tube, the labyrinth, whose many
coils occupy the space from the first to the fourth coxa.
The labyrinth is lined with excretory epithelium, but
apparently does not excrete solid matter. From its posterior
end there runs forwards a straight tube, the internal limb
of the labyrinth, lying inside the convoluted portion.
From the internal limb short exit-tubes open to the exterior
in the body-wall behind the first and third coxae, where the
orifice can be opened and closed at will. These parts are
shown diagramatically in Fig. 42.

The two sacs are probably homologous with the large
nephridia in segments 6 and 7 of Peripatus. In the highest
sub-order of spiders, the Arachnomorphae, three different
types of coxal glands are found, all of which agree in having
lost the sac and outlet of the third leg, retaining only that
of the first.

The first stage is seen in the families Dysderidae,
Oonopidae, and Sicariidae, which for various reasons may
be taken as representatives of the most primitive living
Arachnomorphae, as will be shown in Chapter XV. In
spiders of these families the sac retains its previous character,
but the labyrinth does not. It runs posteriorly from the
sac as a straight tube as far as the fourth leg, where it turns
inwards, widens and runs forwards along the endosternite
to its outlet. Only in exceptional genera are there any
loops in the labyrinth at its posterior end.

The second stage includes the majority of the sub-
order. The capacity of the internal limb is increased by
extensions above and below between the second and third

THE BIOLOGY OF SPIDERS

and between the third and fourth coxae, and by a dorsal
one opposite the orifice. Its function is probably to be

Fig. 42. — Diagram of Coxal Glands. A, Arrangement in Mygalo-
morphae and Liphistiomorphae. B, Arrangement in Dysderidae, Oono-
pidae, etc. C, Arrangement in Lycosidae, Thomisidae, Drassidae,
Salticidae, Agelenidae, etc. D, Arrangement in Epeiridae, Theridiidae,
Pholcidae, and Filistatidae. S, Saccule ; E, external tube of labyrinth ;
I, internal tube of labyrinth ; i, coxa of palp ; ii-v, coxae of legs i-iv.

compared to that of a bladder, for it has no excretory
powers.

In the third and highest stage there is very little of the

INTERNAL STRUCTURE

labyrinth left and the saccule opens almost directly to the
exterior.

It is at first sight remarkable that the evolution of the
families of spiders should be thus accompanied by an
apparent degeneration of an important system. But
degeneration is not the correct term for these changes. In
the third stage noted above the sac and orifice are actively
functional and show no signs of resigning their duties.
The changes in form seem to be rather in the nature of a
simplification following greater efficiency of the parts
retained. The very interesting suggestion was made by
Bernard in 1897 that the excretory products of the labyrinth
have become utilised by the silk glands. That an excreted
substance, originally waste matter on its way from the body,
should be utilised for some purpose is not without parallel
in other creatures. Chitin, mentioned at the beginning of
this chapter, is possibly of such a nature ; so, too, is the
bile of the vertebrate liver. It should obviously be possible
to test this suggestion by experiment, for if it be true, a
coloured substance injected under the skin of a living spider
should make itself manifest in the threads of coloured silk
which that spider ought to produce. The practical diffi-
culty in such an experiment is the extreme dilution which
the pigment would suffer, and which would make its
subsequent visibility in the silk extremely small.

The Reproductive System

The internal reproductive organs of spiders are not
very complex. The testes of the male lie parallel to one
another in the abdomen below the alimentary canal. They
are tubular in form, closed behind, and continued in front
into a pair of much coiled tubes, the vasa deferentia. These
unite at their extremities to form a very short vesicula
seminalis, leading directly to the single median orifice in the
epigastric furrow.

The ovaries occupy a corresponding position, but they
are much larger, especially when the eggs are nearly mature,

66 THE BIOLOGY OF SPIDERS

and thus they are much easier to find. Because of the
ovarian follicles, which project from their surfaces, they
are always compared to bunches of grapes. The eggs pass
through the narrow neck of the follicle into the hollow
within the ovary, whence they travel forwards to the
oviducts. The oviducts are straight wide tubes, which
unite to form a so-called uterus above the vagina. The
vagina is lined with the chitin of the body-wall, and leads
directly to the epigyne above described. Opening laterally
out of the vagina are two narrow ducts leading to the
spermathecae in which the spermatozoa received from the
male spider are stored until the eggs are laid. In some
spiders this is the only entrance to the spermathecae, in
others there are independent openings to the exterior
constituting part of the epigynum. Spermathecal glands
may also be present.

The Nervous System

The spider's nervous system presents a simple external
form — remarkably simple when we consider its great
responsibilities.

When a sense-organ — an eye, a hair, or a spine— is
stimulated by the reception of some impulse from without,
it transmits to the central nervous system the fact of its
stimulation. The central nervous system must appreciate
the import of the impulse received, determine the appro-
priate action and initiate the response. The nervous
system must also discharge the important function of
correlating the activities of every organ of the body so that
all may work as a harmonious whole and respond to changes
in the environment in a way which will secure safety for
the individual and continuance for its race.

In the phylum of segmented worms from which the
phylum of the Arthropoda is derived, the central nervous
system consists of an unbranched double nerve-cord
running from end to end of the body below the alimentary
canal. In each segment the cord swells to form a nerve-

INTERNAL STRUCTURE 67

knot or ganglion from which paired nerves arise. The
" brain " is represented by two supra-pharyngeal ganglia
above the pharynx, joined by nerves to two sub-pharyngeal
ganglia below. These connecting nerves are called
circumpharyngeal commissures and form a " nerve-
collar " through which the pharynx passes.

The form of the nervous system found in the adult
spider (Fig. 43) has been
considerably modified from
this primitive arrangement,
and, as in other examples of
the same process, the modi-
fication consists in an ap-
parent reduction in the num-
ber of ganglia, owing to their
fusion with one another.
Thus the " brain " of the
spider is a composite syn-
cerebrum, composed of three
lobes. One of these is the
so-called prostomial ganglion
and two were the ganglia of
the prosthomeres, or seg-
ments which in development
have passed in front of the
mouth. In the same way
the ganglia of the other seg-
ments of the cephalothorax
have fused instead of remain-
ing separate, and the nerve-
collar through which the fore-gut passes is thick and con-
spicuous.

The ganglia of the abdomen are evanescent, like the
segments themselves. In very young spiders there is a
stage in which as many as six ganglia are present along the
floor of the abdomen, but these disappear in the course of
development, and in the adult there is no trace of a ventral
nerve-cord in the abdomen.

Fig. 43. — The Nervous System.
From Dahl after Blanchard.

68 THE BIOLOGY OF SPIDERS

Glands of the Cephalothorax

The secretory glands of the spider's body are the poison-
glands, the mysterious maxillary glands, and the silk-
producing glands.

The poison or venom with which spiders numb their
prey is secreted by a pair of large sac-like glands, situated
in the first joint of the chelicerae of Mygalomorph spiders
and in the fore part of the cephalothorax of the true or
Arachnomorph spiders. It is possible that these glands
are modified salivary glands, which, since the spider's food

Fig. 44. — Poison gland and Duct, opening at end of fang.

is easy of digestion, have taken on a more sinister function
instead of degenerating. The reservoir of the gland is
quite easy to dissect out in any large English spider, but
what taxes the skill of the dissector to the utmost is the
extraction of both gland and duct unbroken. The latter,
which is very fine, passes down the two joints of the
chelicera, and opens, as already described, just within the
point (Fig. 44).

The secretion is of an acid character. It is rapidly
fatal to the small insects which form the spider's usual
catch ; its effects on larger animals are varied, while its
effect on man has given rise to many years of controversy

INTERNAL STRUCTURE

which has only lately begun to give place to confidence and
certainty. The poisoning powers of spiders are more
fully discussed in Chapter VI. As will there be seen, many
experiments on the virulence of the poison have given
conflicting results, and this is probably due, not to imperfect
experiment, but to the fact that in some instances the bite
was indeed innocuous. The act of biting does not auto-
matically expel the poison from the gland. Fig. 44 was
drawn from a mounted preparation stained with borax
carmine, and it illustrates the fact that the gland is covered
with spirally-arranged muscle-cells. It is therefore pro-
bable that injection of the poison is under the control of
the spider. When it was withheld, the bite was no more
serious than a prick with a needle.

The maxillary lobes or endites of the palpi seem to be
mainly concerned with acting as auxiliaries to the chelicerae,
and the glands they contain are of uncertain function.
Within each maxilla is a group of ten or twelve cylindrical
glands in communication with a plexus of wide intra-
cellular tubes — that is, tubes running through, not between,
cells which have a particularly large nucleus (Fig. 45).

From their position it would seem to be obvious that
these glands serve for the predigestion of the prey, or are
at any fate concerned in some way with the nutritive
functions of the spider. However, they do not react to
microscopic stains as do digestive glands, and they do not
resemble poison glands. Professor Warren has suggested
that they may be preening glands, for when the spider
cleans itself, it may be seen to draw its legs and palpi
through the maxillae as if transferring fluid from them to its
body surface. Of course it is possible that, like the saliva
of a cat, the fluid secreted by the maxillary glands may
serve both purposes. Another possibility is that the
secretion of these glands prevents the spider's legs from
sticking to its own web. This would explain the care with
which the spider periodically anoints itself, and a recent
observation of my own tends rather to confirm this view.
A small orb-weaver, belonging to the very common species

70 THE BIOLOGY OF SPIDERS

Meta segmentata had had a long struggle with a vigorous
crane-fly. The insect was at last tied up at the lower
edge of the web and much labour was then devoted to
hauling it up to the resting place to be eaten. The final
raising of the fly was preceded by cutting the viscid lines
of the web, to which one or two legs were still adhering,
and it was immediately after severing these threads and
before proceeding to anything else that I saw the spider

Fig. 45. — Diagramatic Section of Maxillary Glands and Plexus. (After

Warren.)

pause and pass the four legs of its first two pairs through
its maxillae. It seemed very much as if contact with the
viscid lines of the web had made it necessary to re-coat the
legs with the maxillary secretion.

On the other hand, the possibility that other virtues may
be found in this substance is indicated by the fact that
spiders which spin no webs, and those whose webs contain
no viscid threads, have also the habit of pulling the legs
through the maxillae.

PLATE IV

To face p. 70.]

Sections of a Spider.

[E. A. Robins, photo

INTERNAL STRUCTURE

The Silk Glands

We may fitly conclude this chapter with an account of
the silk glands. Silk is used for several different purposes
by different animals, and it is produced from different
parts of their bodies. Caterpillars, for example, spin silk
from a modified salivary gland near the mouth, and ant-
lions from a modified Malpighian tube near the anus, while
the silk glands of spiders are, as already suggested, probably
modified coxal glands of abdominal limbs. Clearly, there-
fore, silk glands in the different orders of Arthropoda are
not related to each other ; the silk-producing habit has
arisen independently in the several groups.

The silk glands of spiders are, as may easily be imagined,
of considerable complexity in creatures whose lives depend
on their functions. Seven different kinds of glands are to
be found possessing orifices on the spinning organs. These
are :

1. The Aciniform glands.

2. The Pyriform glands.

3. The Ampullaceal glands.

4. The Cylindrical or Tubuliform glands.

5. The Aggregate glands.

6. The Lobed glands.

7. The glands of the cribellum.

No spider possesses all seven kinds of glands, but all
possess the first three. The cylindrical glands are possessed
by all female spiders except those of the families Dysderidae
and Salticidae. The aggregate glands are found only in
the three most highly specialised families, the Theridiidae,
the Linyphiidae, and the Epeiridae ; and the Theridiidae
alone possess lobed glands. Lastly, the cribellum glands
are, of course, found only in association with that organ.

The aciniform glands are, as their name implies, berry-
like in appearance, each " berry " being composed of a
cluster of small round sacs opening into a common duct.
The number of glands in each group is about a hundred in

THE BIOLOGY OF SPIDERS

the Epeiridae, but often fewer in other families. There
are four such clusters, one to each median and each posterior
spinneret, the ducts are short, and the glands lie just inside
the abdomen above the spinnerets.

Corresponding to these, the superior spinnerets have
each a cluster of pear-shaped or pyriform glands, which
also number about a hundred in the Epeiridae and fewer in
other families. These six short multiple glands are used
when a large quantity of silk is required in a short time.
This is the case in the making of the swathing bands or
ribbons wrapped round the prey and the short transverse
band of silk threads called an attach-
ment disc, which anchors a thread of
silk to the ground. The former func-
tion is the task of the aciniform glands,
and the latter of the pyriform glands —
facts which may readily be confirmed
by observation. Careful watching of a
spider performing these actions (pre-
ferably in a glass tube) will show from
which spinnerets the silk threads are
proceeding. The pyriform glands,
which are not difficult to dissect out,
are readily distinguished from the others
because the distal end of the glands,
next to the duct, appears darker than
the rest after treatment with some
stains, but not with all. Fig. 46 shows this.

The ampullaceal glands, which are the remaining type
common to all spiders, are generally four in number,
although in some spiders there are six, eight, or even twelve.
They lie much further forward in the abdomen, nearly in
the middle of the lower portion. Their shape (Fig. 47) is
that of an ovoid sac drawn out at one end into a long thin
coil, and at the other into the long duct. The four ducts
open at spigots on the inner side of each of the anterior
and median spinnerets. The use of these glands is to
supply a continuous thread for a sustained time, in which

Fig. 46. — A Pyriform
Gland.

INTERNAL STRUCTURE

activity the sac, or ampulla, to which they owe their name,
is probably a help, acting as a kind of reservoir. The frame-
work and radial threads of the orb-web and the drag line,
which hunting-spiders leave everywhere behind them, is
produced from these glands. It follows that such threads
consist of two or four components. Normally these threads
are divisible into two halves and two only, since they are
spun from the superior spinnerets, but when extra strength
is required the thread is quadrupled by reinforcements
from the median spinnerets.

The cylindrical or tubu-
liform glands are of interest
because they provide the
only instance of a sexual
difference in the silk glands.
Their number is usually six,
but more may be present

in some families : in male \

spiders they are fewer and J //

may be altogether absent. /

They occupy a position on ////

the base of the abdomen be- |
tween the ampullaceal and

pyriform glands and they \\

open at a spigot on the out- \

side of each median spin- |

neret and at two spigots on |

the inside of each posterior s

spinneret. These glands, Fig. 47--An Ampullaceal Gland.

which are much the easiest to dissect out in any female spider,
are tubular in shape as their name implies, and the tube
may be more or less convoluted. They produce the silk
from which the cocoon is made, including the coloured
wadding which is wrapped round the egg-sac — indeed, this
coloured material may sometimes be seen stored in the
lumen of the gland in a mounted preparation. The
Dysderidae and Salticidae, which have no cylindrical glands,
do not spin a proper egg cocoon.

74 THE BIOLOGY OF SPIDERS

The ampullaceal and cylindrical glands are composed
of a layer of cellular secretory epithelium inside, covered
with peritoneal membrane. The former alone is continued
into the duct, a fact which distinguishes these glands from
the aciniform and pyriform. This is shown in Fig. 48
which was drawn from a double-stained preparation, made
by L. W. Spratt, one of my pupils at Malvern.

The function of the aggregate or tree-shaped glands is

problematical. They are found
only in the three highest
families, the Linyphiidae, the
Theridiidae, and the Epeiridae,
whose species possess six of
these glands, two smaller than
the other four. They lie near
and usually above the cylin-
drical glands and are irregu-
larly-shaped branching masses,
characterised by projecting
caeca on their surfaces. The
proximal part of the duct is
also similarly studded with
knots of cells. The three
glands on each side open to-
gether on the inner side of each
inferior spinneret. While the
function of these glands is un-
certain, it is generally believed

that they supply the very
Fig. 48.-A Cylindrical Gland. dastic gilk of the spiml thread

in the orb-web and the viscid drops which coat it. Such
threads do occur, though rarely, as components of the webs
made by members of the other two families which possess
aggregate glands.

The lobed glands are peculiar to one family, the Theri-
diidae. In the chapter on external structure, this family
was mentioned as possessors of a comb of stiff hairs on the
tarsal joints of the fourth pair of legs. The combs are used

INTERNAL STRUCTURE 75

in a special method of attack and defence which this family
alone has adopted, and which consists of combing out
ribbons of silk from the spinnerets and throwing them over
the insect as it struggles in the web. This band of silk is
supplied by the lobed glands. They are two or four in
number, and open on the posterior spinnerets by short
ducts, so that the glands are only just within the abdomen.
They are broad, irregular masses of cells, larger than the
aciniform and with a smoother surface. Since they have
virtually the same function as the aciniform glands, it is
not surprising to find that the number of the latter is much
smaller in the Theridiidae.

The cribellum glands are most difficult to dissect, as
they are very small and are grouped in large numbers close
to the cribellum, through whose pores they open. They
supply the additional fine threads which the calamistrum
combs out.

Looking back upon our consideration of spider anatomy
as a whole, we see that it is a highly organised body showing
numerous adaptations to the rather specialised mode of
life which the spider leads. The most obvious of these are
the extreme development of the sense of touch, the localisa-
tion of the senses of smell and hearing on the same active
limbs, the increase of storage-room round the alimentary
canal, and the elaboration of the silk-producing glands.

Moreover, all these separate systems act in harmony, a
fact which we have ascribed above to the governing influence
of the nervous system. It should, however, be noticed
that in vertebrates some of the harmonising is due to another
agent, the so-called ' 1 chemical messenger " or hormone.
A hormone is a complex compound secreted by an organ
or by a special ductless gland directly into the blood stream,
which distributes it to all parts of the body. Thus it reaches
other organs, where it usually promotes a special activity.
The most familiar instance is that of the hormone secretin.
When food in the course of digestion passes through the
pylorus from stomach to intestine, the lining of the latter

76 THE BIOLOGY OF SPIDERS

produces secretin. This is conveyed to the rest of the body
by the blood stream, and when it reaches the pancreas it
stimulates the secretion of the pancreatic juice. Thus the
activity of the pancreas is stimulated at the appropriate
moment.

Many such hormones are known, but their presence in
invertebrates like spiders has not yet been proved. It is,
however, possible that they exist, and that they help in
harmonising the activity of the various systems and in
influencing the behaviour of the individual spider.

CHAPTER IV

THE SENSES AND SENSE ORGANS

In all but the very lowest animals there are some portions
of the body specialised for the receipt of information from
without. The stimulating external cause is of a physical
nature — an ether wave, an air vibration, or a material
contact — which excites no activity save in the particular
sense organ suited to its reception. The eye-spots of
Protista, the cnidocils of Hydra, the delicately tactile
prostomium of the earthworm are instances of such organs
in lowly creatures, which seem not to be endowed with the
full complement of sense organs as we know them. How-
ever, it is worth while noticing that such definite organs
are not always a necessity. The simplest of all Protozoa,
Amoeba, has none ; but it can appreciate light and warmth
and probably the smell of distant food. The possession of
sense organs is a consequence of bodily complexity and
division of labour resulting therefrom ; it is a measure of
the degree of specialisation of the race.

Spiders possess very distinct organs of sight and touch ;
they smell by a method of which it is impossible to speak
so decidedly ; perhaps they can hear and taste.

The Eyes

The majority of spiders have eight eyes, but a number
have six only. The Ceylonese spider, Tetrablemma, already
mentioned as the possessor of skeletal plates on the abdomen,
has four eyes. Hexablemma, another spider with the same
abnormal characters, discovered in British East Africa

78 THE BIOLOGY OF SPIDERS

in 1920, possesses six eyes. A South American genus,
Nops, consists of nine species with only two eyes. The
cave- dwelling spiders of the genus Anthrobia have no eyes.

John Blackwell, the founder of the study of British
spiders, proposed during the last century a division of
spiders into tribes based on the number of eyes they
possessed. Such a classification, which at the time seemed
useful and obvious, was not a natural one and had to be
abandoned when systems were based on a more complete
knowledge. The six-eyed spiders of Britain do happen to
form a more or less natural group, but many foreign species
with eight eyes are at least as closely related to them as they
are to one another.

Spiders' eyes are situated on the forepart of the cephalo-
thorax, and so distributed over its curved surface that some
look vertically upwards, some forwards, and some side-
ways. In some species they are grouped on a small
eminence, and sometimes this eye-bearing projection rises
relatively high and gives the spider a very remarkable
appearance (Fig. 3).

In the greater number of species the eyes may be
considered as comprising two rows of four, but in some
instances a first row of four is followed by two rows of two.
It is important to notice the eye arrangement, because this
feature is frequently used in the classification of the families
and genera. The rows of eyes, designated as anterior and
posterior, are seldom straight ; more often they are either
procurved, that is, curved with the convexity backwards,
or recurved, with the convexity forwards.

Owing to its convenience, as well as to the weight of
years of use, this method of description is not likely to
give way readily to the more natural one recently put
forward by Professor Petrunkevitch. As he says, " the
arrangement of eyes has been studied entirely by systema-
ticians and not by morphologists," and he introduces the
distinction between direct eyes and indirect eyes. The
middle eyes of the front row, or anterior median eyes, as
they are usually called, are the direct eyes. It is seldom

THE SENSES AND SENSE ORGANS 79

difficult to see that these two eyes are in some way different
from the others, a point to which we shall return. We
have mentioned already that the part of the spider's head in
front of the mouth consists of two fused segments. The
direct eyes belong to the first segment and receive their
nerves from its ganglion ; the indirect eyes all belong to
the second segment. The optic lobe of the ganglion of
this segment is composed of
three parts, one above the other,
each part supplying a nerve to
an eye. The dorsal nerve sup-
plies the lateral eye of the first
row, the middle nerve the me-
dian eye of the second row, and
the ventral nerve the lateral eye
of the second row. Thus there
is a pair of direct eyes and a
first, second, and third pair of
indirect eyes. Two arrange-
ments for the indirect eyes are
possible. They may form an
incurved row, that is, a curve
convex on the outside, in which
case the third indirect eyes are
the posterior median eyes and
the posterior row is procurved ;
or they may form an excurved
row, convex on the inside, when
the posterior median eyes are
the second indirect eyes and the
posterior row is recurved. Fig. 49 illustrates these alter-
natives. Thus from a scientific point of view it would be
more correct to speak of incurved and excurved rows of
indirect eyes rather than of procurved and recurved rows.

Spiders are sometimes caught in which some of the
eyes are much below their usual size, or even altogether
missing, so that a normally eight-eyed spider has but seven
or six eyes. In his early book, Researches in Zoology,

0 o

6 ^ o

o. o

Ox, ® ^ o

0 O

"O'O 00 C

Fig. 49. — Curvature of Indirect
Eyes. A, Incurved. B and
C, Excurved. In A the pos-
terior median eyes are the
third indirect eyes. In B the
posterior median eyes are the
second indirect eyes. In C
the posterior median eyes are
the first indirect eyes.

8o THE BIOLOGY OF SPIDERS

Blackwall records seven such cases, and four more have
been mentioned by Falconer more recently. These eleven
may be summarised thus :

X. Xysticus cristatus.

2. Theridion varians.

3. Meta segmentata.

July, 1835.
June, 1852.

August, 1842.

Direct and second in-
direct eyes absent.

Third indirect eyes
absent, second very
small.

Left second indirect
eye absent, right very
small.

Right direct eye absent.

Left third indirect eye
absent.

Right second indirect
eye very small.

An extra eye between
the direct eyes.

Totally blind.

First and second in-
direct eyes missing
on one side.

" At various times,
partially blind speci-
mens."

4. Trochosa leopardus. ?

5. Amaurobius atrox. September, 1842.

6. Meta segmentata. Autumn, 1842.

7. Bathyphantes concolor. March, 1835.

8. Undetermined. 1910.

9. Walkenaera acuminata. November, 1908.

10. Hilaira excisa. ?

1 1 . Tiso vagans.

While there is a sporadic distribution among the different
families of spiders, there is apparently a greater tendency
for imperfections to manifest themselves in the indirect
eyes, and especially the second, than in the direct eyes.
The seventh case is of especial interest, as being the only
one in which an extra eye is recorded ; moreover, this
extra eye was centrally placed, preserving the symmetry of
the eye group.

A phenomenon which seems to be somewhat rarer is
the apparent possession of sixteen eyes. A Neriene bituber-
culata showing this was found by myself in Malvern on
April 27, 1925. The arrangement is shown in Fig. 50.
The diagram, showing how the extra eye-pattern is reversed,
affords the explanation. The part of the cast caput bearing
the eyes must, at the time of the last moult, have turned
over and stuck to the new cuticle while the latter was still
soft. The only other instance of this of which I have
heard was in an American specimen sent to the late Professor

THE SENSES AND SENSE ORGANS 81

W. Bateson as an example of reduplication of the eyes —
which it is not.

In outward appearance the eyes of spiders are simple
ocelli, which means that they have a uniformly smooth
surface, not broken up into numerous facets, as are the
large eyes of insects. In many spiders it is obvious that
the eyes are of different types, for some appear black and
others pearly-white or pale yellow. The two types of eye
are generally described as diurnal and nocturnal respectively,
as if some of them were in-
tended for use in the day-
time, while the others took
over the duty at night. The
evidence for this is slight —
indeed it is little more than
a deduction from internal
structure, for there are
internal differences in the
structure of the eyes.

The cornea of the eye is
but a portion of the cuticle,
shaped to form a double
convex lens, and of course
free from hairs and pigment
so that it is transparent. As
the cuticle is shed when the
spider moults, the lenses of
the eyes are shed too, and FlG- 50.-A Spider - with Sixteen

during this process the

spider must be temporarily blind. The hypodermis, already
described, is continuous beneath the lens,* and the retina lies '
below the hypodermis. The visual cells of which the retina
is composed are elongated in form and each has a process
running to the optic nerve. But the characteristic of the
visual cell is the presence of a pair of hard bodies known as
optic rods, which lie adjacent to one another and form a
distinct layer in the retina. In the direct eyes this layer is
next to the hypodermis and above the nuclei of the visual

THE BIOLOGY OF SPIDERS

cells : hence the dark appearance of the so-called diurnal
eyes. In the indirect eyes the optic rods form the base
of the eye (Figs. 51 and 52).

One final structure completes the essentials of the
indirect eyes, and this is the tapetum. A tapetum is
present in the eyes of cats and of many moths, whose eyes
are familiarly said to " shine in the dark." It is a reflecting
layer whose supposed function is to reflect light after it has
entered the eye so that it passes again through the visual
cells and so increases the visibility of objects in a dull

Fig. 5 1 . — A Postbacillar Eye. Sim-
plified diagrammatic section. A,
cornea, forming lens ; B, hypo-
dermis ; C, retina, composed of
visual cells ; D, optic nerve.

Fig. 52. — A Prebacillar Eye.
The optic rods are not next
to the hypodermis, but at the
base of the eye.

light. The tapetum in spiders is composed of a basal layer
of cells containing small crystals, which make the reflecting
surface. This is what generally causes the so-called
nocturnal eyes to appear paler than the diurnal eyes, but in
many eyes in which a tapetum is present, the distribution
of pigment within prevents the eye from looking bright.
A tapetum is never present in the direct eyes, and these
eyes have one other peculiarity — an eye-muscle from the
back of the eye to the body- wall.

It is perhaps this muscle which is responsible for a
puzzling phenomenon connected with these direct eyes.

THE SENSES AND SENSE ORGANS 83

Sometimes when looking at a living spider one sees the
colour of these eyes change, slightly but unmistakably,
from a darker to a lighter shade, or vice versa. When seen
in the living but apparently quite motionless spider, it is
impossible to avoid the impression that it is due to internal
movements under the control of the spider's will, and as
such it was first described. It is, of course, possible that
this may be so and that the change of colour may be pro-
duced by the eye muscles causing some part of the back
of the eye to rotate in the optic capsule, and it is also possible
that this may enable the spider to look in another direction.
It is, in fact, difficult to imagine what other purpose it
could fulfil, and it is noteworthy that the action is most
readily seen in jumping-spiders, whose direct eyes are very
large and certainly keen-sighted. It has also been seen in
crab-spiders, and in trap- door spiders, which have not so
keen a sight. On the other hand, the same colour change
may be seen in the dead spider if the body be tilted very
slightly, and this makes it probable that the whole pheno-
menon is only due to a difference in the angle at which the
light falls on the spider's eye and is reflected therefrom.
This was the view of the Rev. O. Pickard-Cambridge.

Vision

Keenness of vision differs very considerably in spiders.
It is only to be expected that jumping and hunting-spiders
should have better sight than those which spend their time
waiting for the vibration of their web and which catch
their prey largely by the help of the sense of touch. This
has led to the widely held but rather unjustified opinion
that such spiders have so poor a sense of sight as to be, to
all intents and purposes, blind. A secondary deduction,
which, however, may have more truth in it, is that one of
the chief uses of the spider's eyes is to enable it to distin-
guish night from day, and so to moult, spin, and lay eggs
under cover of darkness.

But as long ago as 1880, Pickard-Cambridge in his

THE BIOLOGY OF SPIDERS

Spiders of Dorset, described how he had several times seen
spiders drop on a thread from their usual position in the
middle of the web to secure an insect passing underneath.
This observation has been more than once confirmed by
later workers and shows that even typical web spinners
have a certain power of vision.

Rainbow, an Australian araneologist, published in 1898
the results of some experiments which have a direct bearing
on the subject of vision in hunting-spiders. He found that
crab-spiders, the family Thomisidae, whose habit it is to
lurk in hiding-places and to make darts upon passing insects,
possessed but poorly-developed power of vision. They
could detect their prey at a distance of half an inch only,
and not more. When the insect, previously tied to cotton,
was jerked out of that range, they seemed to be at a loss
and were unable to follow its more distant movements.
The behaviour of spiders of this family when mating bears
out this conclusion. The male grabs at the female with
his chelicerae, thus securing that she does not get out of
sight after he has found her.

Wolf-spiders, hunters by nature, showed a much keener
power, illustrated in particular by two observations of
spiders in natural circumstances. A specimen of Lycosa
godeffroyi leapt upon and caught a beetle three inches
away, although there was a tuft of grass between the spider
and its prey ; while a Dolomedes neptunus caught " at a
considerable distance " prey which closely resembled in
colour the sea-wrack on which it was hunting. Following
up these observations by experiment, Rainbow found that
both species could see clearly at five inches and faintly
at eight.

A hunting-spider was seen by McCook to leap upon a
fly crawling upon the side of its cage and leap back again
to the spot to which its drag-line was attached. McCook
emphasises this particular instance because it showed that
the spider was not only endowed with sight, but also with
the ability to estimate speeds and distances with an accuracy
sufficient to enable it to land upon moving objects. This

THE SENSES AND SENSE ORGANS 85

power was also shown by a captive Pisaura mirabilis which
lived under my own observation. As I described in 1916,
a fly flying at some speed along the cage was caught by the
spider, which suddenly reached up as the fly passed above
it and took it in its jaws as neatly as a cricketer making a
catch in the slips.

As has long been known, jumping-spiders have the
keenest sight. Dr. and Mrs. Peckham's well-known
accounts of the courtship of this family give ample proof of
their ability to recognise their mates up to a distance of
eight or ten inches. Rainbow showed by experiment that
Attus volans and Attus splendidans could see clearly to seven
inches. When we consider the large size of the eyes of these
spiders, as well as their mode of life, this is not surprising.

The general conclusion which may be drawn from the
recorded experiments and observations is that some spiders
can see quite well, but that in others which, because they
live in webs, rely more on their sense of touch, the ability
is not quite so great.

Colour Vision

Related to this subject is that of the appreciation of
colour by spiders. Dr. and Mrs. Peckham were the first
to experiment on the sensitiveness of spiders to colour by
building a cage of pieces of glass so that the spider within
had a choice of freely communicating red, green, blue, and
yellow compartments. Various spiders were confined in
this cage ; whenever they came to rest the colour in which
they were found was recorded ; the spider was then
disturbed and made to choose its resting-place again.
From time to time the cage was cleaned of all threads of
silk and the order of the colours was changed. The result
of all experiments was very conclusive, being,

Red 181

Yellow ..... 32

Green . . . . 13

Blue . . . . . . u

86 THE BIOLOGY OF SPIDERS

There seems to be no doubt that some spiders at any rate
have a very decided preference for red Moreover, it was
found that if a spider was blindfolded by coating its eyes
with paraffin, it showed no preference for any colour.
When placed in the blue quite close to the red, it showed no
inclination to move into the colour which had previously
proved so attractive. These experiments might well be
repeated with a greater variety of species — all the spiders in
Dr. Peckham's experiments were wolf-spiders.

The Spines

The existence of setae of various degrees of stoutness,
and their arrangement in definite situations on the spider's
body, has been described already in Chapter II. Of these
setae those which have the best claim to be considered as
possible sense organs are the strongest and the most
delicate.

The stout and conspicuous spines are probably among
the more important organs of touch. They originate, as

Fig. 53. — Palp of Male Leptyphantes minutus.

do all the rest of these setae, from a trichogen or hair-
producing cell below the cuticle and are characterised by
their strength, by the fact that their bases are often sur-
rounded by a little tubercle of chitin, and by their mobility.
The interior of these spines is filled with cytoplasm.

The tubercle from which they sometimes rise is well
seen in the palpal spines of male spiders of the genus
Leptyphantes and its allies. The most conspicuous of
these is the spine on the tibia of the palp of the male Lepty-

THE SENSES AND SENSE ORGANS 87

phantes tninutus (Fig. 53). This remarkably thick spine
affords the best means of distinguishing this particular
spider from its nearest relations, and raises an interesting
problem. In one sub-generic group there are four very
closely allied species of this genus in which these palpal
spines are in each case quite distinctive (Fig. 54). The
question, as yet unanswered, arises as to the actual use and
significance of these spines, and why should they be so
markedly distinct in species so closely related ?

The large spines on the legs are erectile, but their
erection does not seem to be under the control of the spider
nor to have any special value. It was noticed by Berland
in 191 2 that, during mating, the leg spines of the spider
Dysdera erythrina stood out nearly at right angles to the

A B C p

Fig. 54. — Palpal Spines on the Patellar and Tibial Joints of Lepty-
phantes spp. A, L. minutus. B, L. nebulosus. C, L. leprosus
D, L. alacris.

limb and subsided rhythmically to their usual positions as
the sperms were discharged. The same thing was recorded
by Bristowe in 1922 and by Gerhardt in 1924 for different
species, both these authors claiming priority for the
observation. It is not a general phenomenon, for in many
spiders there is no sign of it. It is probably due to the
pressure caused by the flow of the body fluid within, the
primary purpose of this flow being the ejaculation of the
sperm, and the movement of the leg spines being purely
incidental. This interpretation was put forward by Bertkau
in 1878, and is supported by the fact that the movement
can be induced in a leg detached from a spider long since
dead by appropriately squeezing the end with forceps.

The so-called acoustic setae (Figs. 15 and 55) are the

88 THE BIOLOGY OF SPIDERS

very fine setae situated on the upper surface of the leg-
joints, either alone or in a series. In small spiders high

magnification is neces-
sary to make them visible
at all, and their true
function is, to say the
least, problematical.

It is perhaps partly
owing to the diversity of
these spines or setae and
partly to the absence of
other definite or easily
recognisable sense organs
that the spines have been
believed in the past to
fulfil so many functions.
To them, have been at-
tributed the functions of protection, feeling, hearing, and
smelling — a truly remarkable variety for organs which are,
essentially, fairly uniform in structure ! No one, however,
has as yet suggested that they are not organs of touch.

Touch

It is to this sense that spiders chiefly trust in their
everyday life and all observations of their habits emphasise
its extraordinary delicacy. This is especially true of web-
inhabiting species, for if a single thread be plucked or a
distant corner be touched, the owner of the web, waiting
perhaps in the middle or hiding out of sight in its retreat,
is immediately aware of the occurrence. The very smallest
vibrations of the threads they are holding is appreciable by
them, and they can, moreover, distinguish to some degree
the nature of the visitor to their webs.

It seems, however, to be rather doubtful whether the
sensitiveness of the spider to tactile stimuli is distributed
all over the body as uniformly as are its setae. Major
Hingston has described the behaviour of a Hippasa olivacea

THE SENSES AND SENSE ORGANS 89

which had lost its palpi. The spider made imperfect webs ;
it had formerly been able to run on its sheet-web with
agility and speed, now it crawled about clumsily, catching
its feet in the sheet, tripping up, as it were, and was unable
to catch flies. It is well known that the loss of one or even
two legs is not a serious handicap to a spider, and this
observation would seem to show that the sensations,
presumably tactile, conveyed by the palpi, are far more
important than those received in greater numbers from
the legs.

The discriminating power of this sense is well illus-
trated by an interesting observation of Bristowe's. A
beetle larva was placed in a spider's web, where it wriggled
and squirmed in its attempt to escape. The spider came
to the mouth of its tube but no further ; it would not
investigate the cause of the disturbance. After about a
quarter of an hour a vibrating tuning-fork was placed beside
the kicking larva. The spider immediately rushed out and
attacked the fork, which it did not leave until its vibrations
had ceased, thus showing that it could distinguish between
different types of vibration set up in its web.

Hearing

The problem of the spider's ability to hear is more
difficult than that of any other sense, and, since it is con-
nected with the sense of touch, may be considered here.

Very simple experiments with spiders hanging in their
webs seem to make it quite evident that they can hear, for
they respond to all sorts of sounds by shooting out their
forelegs as if reaching towards the origin of the sound. If
the first pair of legs are missing, the second pair are held
out in the same way, and this response can be elicited by a
whistle, a cry, a sounding tuning-fork, a cough or the bark
of a dog.

When we recall the many stories which have been told
in illustration of the spider's apparent love of music ; how
they have emerged from their hiding-places at the notes of

THE BIOLOGY OF SPIDERS

a violin ; how they have come each night to sit upon a
harmonium as often as it was played, and so on, there
seems to be good enough reason for believing in their
power to hear.

The subject must, however, be considered more fully,
more experimentally. In the first place, the spider's
reaction to sound is a very curious one, evoked in no other
way and quite useless to the spider. If a spider, or any
other animal, can hear in the same way as we can, it must
be able to interpret the sensation received and to react in
an appropriate way. This the spider does not do ; its
response is valueless.

Moreover, the response is not constant, even within
the limits of the same family. The common Epeira
responds when adult in the way described above, but
young individuals of the same species generally drop from
their webs at the end of a thread.

Spiders of the closely related genera Meta and Cyclosa,
belonging to this same family, usually drop too in the
same way, but Zilla scrambles home to its retreat along the
free radius, which characterises its web, as quickly as
possible.

When we extend our tests to spiders of other families
we find contradictory results. All kinds of hunting-spiders
are apparently deaf and cannot be made to respond either
to tuning-forks or to singing grasshoppers. A negative
result of this kind can never be quite satisfactory, especially
when dealing with spiders, for spiders show on occasions a
stoical indifference to disturbances which do not interest
or appeal to them. For example, sometimes a well-fed
house-spider will not only pay no attention to a fly kicking
about in the web, but will allow the fly to walk up to her,
touch her, and even crawl over her without making any
movement. The fact, then, that the spider " takes no
notice " is not a definite proof that it does not hear, and
we must fall back on other tests.

Where, for instance, are the spider's ears ? From what
has been said above it will be obvious that the setae will be

THE SENSES AND SENSE ORGANS

first suggested, and in 1883 Dr. F. Dahl found that some
of them could be made to vibrate in response to the notes
of a violin. These setae gained the name of Horhaare
from that date, and the fact that they are sometimes arranged
in a graded series made it at least possible that setae of
different lengths respond to notes of different pitch. But
even so the auditory capabilities of these setae is not proved,
and Wagner, in 1888, failing to verify Dahl's results, took
exactly the reverse view and insisted that the auditory hairs
were only able to perceive sensations of touch. McCook's
view, too, was that the sense of hearing is very rudimentary
and not really distinguishable from that of touch.

We are thus led to consider the hypothesis that the
delicacy of the spider's tactile sense enables it to feel the
vibrations of the air which constitute sounds, in somewhat
the same way as a deaf person can " hear " the Bourdon
stop of an organ. It is possible that its response is a
mechanical effect — exactly, in fact, what is implied by the
term Barrows suggested in 191 5 — a positive vibrotaxis.
The problem involves principles of resonance, to whose
consideration a paragraph may perhaps be justifiably
devoted.

Sounds are produced by the periodic vibrations of a
solid object communicated to the surrounding air, the main
characteristic of the occurrence being the periodicity of the
vibrating source. Every producer of sounds has its own
natural period of free vibration, dependent on its dimen-
sions, density, and elasticity. This may be likened to the
time of swing of a pendulum, which, a simpler problem,
depends only on the length of the string. If the weight of
the pendulum be suddenly impressed with a force for a
very short interval of time, that is to say, if it receive an
impulse, it will start to vibrate. Further impulses would
increase the amplitude of vibration, or arc through which
the weight moves, but, and this is the essential feature of
the process, the greatest increase in amplitude will be
attained if these impulses are so timed that they recur at
intervals equal to the period of free vibration of the

THE BIOLOGY OF SPIDERS

pendulum. Exact multiples or sub-multiples of the period
produce a smaller effect, and irregular intervals would
produce a smaller effect still. We illustrate our sub-
conscious knowledge of this fact when we swing our children
in the garden swing and attain an acceptable result with
the expenditure of a minimum of effort on our own part.
If we did not push periodically we should work much
harder and achieve less. It is thus clear that the periodicity
of the impulses endows them with the power to produce a
cumulative result, as long as the periodicity agrees with
that of the vibrating object. An incorrect example of this,
due to enthusiastic hyperbole, was the famous suggestion
that a boy with a pea-shooter might knock down West-
minster Bridge if he but timed his shots suitably.

It should therefore be readily understood that a body
may be set in vibration by the incidence of sound waves
upon it, if the pitch of the note is the same as that which
the free vibration of the body would produce. A familiar
instance is the breaking of a glass by a singer's voice.
Therefore, it is possible that a spider might be led to respond
to sound waves, because resonant vibration might be
induced in two situations. The spines themselves might
be set in motion, as Dahl observed, or, and this is probably
more frequent, the threads of the web may be set a-
thrumming. The frequency of vibration of a stretched

i /f

string is given by the familiar formula, n-~ 7 V/ — , which

21 m

shows that n, the frequency, depends on / the length of the
string, T its tension, and m its weight per unit of length.
All these dimensions will vary in different parts of the
spider's web, so that a wide range of possible notes should
be able to evoke a response in some part of the web.

If we accept this hypothesis it is easy to understand
that spiders may be deaf in the ordinary sense of the word,
though they may be stimulated to react to sounds which
provoked an answering vibration in either the threads of
the web or in their own spines.

THE SENSES AND SENSE ORGANS 93
Stridulation

The problem may be attacked from quite another point
of view — that of the ability of the spider to produce
sounds.

Save in a few exceptional cases to be mentioned later,
the sound-producing organs of spiders are of the type

Fig. 56. — Stridulating Apparatus of Steatoda bipunctata. A,
Epigastric region of abdomen after removal of cephalothorax. P, scar
of pedicle ; L, lung-book ; T, tracheae. B, Cephalothorax from above.
R, ridges.

possessed by the grasshopper — that is to say, the sound is
made by rubbing two suitable surfaces together. This
action is known as stridulation.

The stridulating organs of spiders are diverse in form
and situation ; their use remains to some degree a matter

THE BIOLOGY OF SPIDERS

of speculation, for many of them have never been known
to produce a sound audible to human ears. Some .of them
are confined to the male, being absent or rudimentary in
the female, and this naturally suggests that they have some-
times a sexual function, and yet there always remains the
fact that the majority of spiders exist successfully without
them.

Westring, in 1843, was tne first to discover a stridulating
organ in the spider Asagena phalerata. This is a. species
which may be found in Great Britain and belongs to the
family Theridiidae. The abdomen bears just above the
/ pedicle a chitinous collar

whose inner surface is
finely toothed. The hind
end of the cephalothorax
is marked with a number
of fine transverse ridges
over which the teeth scrape
as the abdomen is raised
and lowered. A very com-
mon British spider belong-
ing to the same family,
Steatoda bipunctata, has a
very similar organ, which
is borne by the male alone

(Fig. 56).

In 1880 Campbell de-
scribed the stridulating
organ present on several
spiders belonging to the
genus Leptyphantes of the
family Linyphiidae. This
is the family which in-
cludes the small black
" money-spiders/' as well
as most of the smallest
known. This organ, which is also confined to the
consists of a series of horizontal ridges on the

Fig. 57. — Stridulating Organs on Cheli-
cera and Palpal Femur. A, Lepty-
phantes minutus. B, Scytodes. (B
after F. Pickard Cambridge.)

spiders
male

sex

THE SENSES AND SENSE ORGANS 95

outer side of the chelicerae, up and down which rubs a
small tooth on the femur of the palp. Fig. 57 shows
the organ possessed by the common British Leptyphantes
minutus. Although the movements required to bring these
organs into action have several times been seen, no sound
has ever been heard. Spiders belonging to the genus
Thomisoides or Sicarius^ of the family Sicariidae, found
only in the southern hemisphere, can produce an audible
sound by means of an organ which closely resembles that
of Leptyphantes. The sound resembles the buzzing of
a bee and is produced by striae on the chelicerae, upon

to be relatively common in the Mygalomorph spiders of the
countries between India and New Zealand. These large
spiders produce a sound which is audible to our ears, and
the first to be discovered was the well-known Chilobrachys
stridulans. This was heard by Wood Mason in Assam in
1876. He relates how, at work one day in his garden, he was
attracted by the sound issuing from something which his
gardener was trying to kill with a hoe. It was a large spider
which was rescued and taken indoors. Here it repeated the
sound when molested by a cat. The spider raises itself on
six legs, brandishing its first pair as it emits the sound,

which work a series of teeth on
the palpal femur.

This is the most frequent
position for stridulating organs,
which have since been found

Fig. 58. — Lyra on First Joint of
Palp of Psalmopoeus cam-
bridgii. After Pocock.

Fig. 59. — Pecten on Chelicera of
Psalmopoeus cambridgii. After
Pocock.

96 THE BIOLOGY OF SPIDERS

which Wood Mason described as " both peculiar and loud ;
it resembles that made by pouring small shot on to a plate
from a height of a few inches, or better still by drawing the
back of a knife along the edge of a strong comb."

In these Mygalomorph spiders the stridulating organ is
possessed by both sexes. The two halves, which may be
distinguished as the lyra and pecten, consist of modified
setae. The lyra (Fig. 58) is a series of hard, stout rods of
chitin, generally club-shaped at the end, but of different
lengths and forms. They lie parallel to the surface to
which they are attached, generally in a small hollow,
designed to receive them. The pecten (Fig. 59) consists
of stout spines. The stridulating organs of Mygalomorph
spiders are divisible into four types :

(a) Lyra on chelicerae, pecten on palpi. This is the

commonest arrangement.

(b) Lyra on palpi, pecten on chelicerae — the exact

reverse of (a). This is the type illustrated in
Figs. 58 and 59.

(d) Pecten on palpi, lyra on trochanters of first pair of

legs.

It seems almost certain that in those spiders which
possess the organ in both sexes, the sound produced is
made with the purpose of frightening enemies, such as
the cat and the wielder of the hoe. It might act by warning
the hearer of a formidable enemy, better not encountered,
or it might, as in the case of Sicarius, have the effect of
leading the hearer to think that it was made by a bee and
not by a spider. The important and obvious fact is that
in neither instance is it at all necessary that the sound
should be audible to the spider that makes it. Therefore
the possession of stridulating powers is not evidence from
which the ability to hear may be deduced.

In those spiders, like the Theridiidae and the Liny-
phiidae, in which the males alone carry the organ, it is
necessary either to postulate an ability on the part of the

THE SENSES AND SENSE ORGANS 97

female to hear the sound, or to assume that the vibrations
produced in stridulating are transmitted as such along the
threads of the web, and that the female feels them in the
ordinary way. This is at least probable and enables us to
retain our belief that the spider is really deaf.

However this may be, there is no doubt that the power
to stridulate has proved of value, for it has been evolved
in so many different groups of spiders. In addition to
the types of organ already mentioned, at least three others
are known and are of interest because they occupy different
positions on the body. This would tend to show that the
various types of stridulating spiders have acquired the
power quite independently and therefore do not always
possess the organ in the same place.

In Selenogyrus, a trap-door spider from West Africa,
the action is between two small rods, one on the inner
surface of each of the chelicerae. This type, discovered
by Hirst in 1908, is unique in that the two halves are alike.

In Cambridgea antipodiana, a spider belonging to the
same family, Agelenidae, as our house-spiders, there is a
hollow in the front of the abdomen lined with six shining
black arches of hard chitin. Upon these plays a heart-
shaped tooth borne by the hinder end of the cephalothorax
and projecting into the hollow. This was discovered by
Pocock in 1895 when examining the preserved male spider
in the British Museum, and thus no occasion of its use
has been described.

Finally, perhaps the most remarkable of all, is the
stridulating organ possessed by the very small British
Linyphiid spiders, Entelecara broccha and Eboria caliginosa.
In these it is confined to the male sex. Each lung-book is
protected by a chitinous cover or operculum (Fig. 60) with
a roughed surface, and on this surface scrapes a sharp
tooth-like projection on the inner side of the fourth coxa.
There are thus at least eight or nine distinct types of
stridulating organs known.

In addition, by at least three known methods spiders
have been heard to produce sounds. In Staten Island the

98 THE BIOLOGY OF SPIDERS

wolf-spider, Lycosa kochii, is known as the purring spider
from its habit of drumming with its palpi on the dead
leaves over which it runs. It runs about and stops at
intervals to purr. Many other members of the same family
perform the same action when excited by the presence of a
female, but no sound has been heard from them. Prell
has lately investigated the habit, which, he concludes,
makes it easier for the two sexes to find each other. He

Fig. 60. — Stridulating apparatus of Entelecara broccha between
fourth coxa and lung-book. After Falconer.

has been able to imitate the sound or the vibration or both
with a wet file, and has observed that the spiders upon
which he was experimenting would only look for each
other while his artificial notes were sounding.

Bristowe has recorded the production of sound by
another wolf-spider, Tarentula pulverulenta, as its pulsating
abdomen strikes the ground, and also by a jumping-spider,
Euophrys frontalis, on raising its legs and lowering them so
that the tips of the second pair hit the ground.

Scent

While there is no doubt that spiders can smell, there
is considerable difficulty in determining the nature and
situation of the structures concerned.

Dr. and Mrs. Peckham investigated the response of
spiders to the scent of various essential oils as long ago as

THE SENSES AND SENSE ORGANS 99

1887. They were careful to use no substance which could
have an irritant effect, and simply presented to the spider
first a clean glass rod and then the rod dipped in the
scented liquid. They found that web-spiders responded
by raising their legs, while hunting-spiders gave evidence
of their being aware of the odour by leaping upon the rod.

More extensive experiments were made by Pritchett in
1905. Her spiders were confined in triangular cages with
mosquito-netting for bottom, and scented glass rods were
brought under them as they stood in the cage. The smells
of many different sorts of liquid caused spiders to respond
by vibrating their palpi and by raising their legs. The
loss of various legs did not impair the spider's power to
respond. DahPs suggestion that some of the leg spines
are organs of scent was tested by cutting off all the spines
of one spider and then sand-papering its legs smooth.
The response to smells was not affected by this treatment,
and the conclusion drawn was that spiders possess a good
sense of smell and that the spines are not the scent organs,
which must be scattered over the body.

It was at this point that the mysterious lyriform organs
were suggested as possible organs of smell, and these must
now be described.

If the legs of spiders are carefully examined with a
microscope, there will be found in certain situations,
generally near the ends of the joints, darkish patches which
seem to consist outwardly of ridges in the smooth chitin.
These are the lyriform organs. They are present in all
spiders, in Opiliones (harvestmen), and false-scorpions, but
absent from mites, scorpions, and solpugids. Their
positions in spiders are remarkably constant, and Gaubert
gave in 1890 the following table, indicating the occurrence
of sixty-eight such organs on the legs and palpi.

Joint 1. Joint 2. Joint 3. Joint 4. Joint 5. Joint 6.

Palp 1 1 2 — — —

Leg 1 . . — i 1 3 3 1

Leg 2 . . — 1 1 3 3 1

Leg 3 — 2 1 1 1 1

Leg 4 — 2 1 1 1 1

ioo THE BIOLOGY OF SPIDERS

In addition there are thirteen lyriform organs on the
cephalothorax, sixteen on the sternum, and some on the
chelicerae and abdomen. Their situations and structure,

Fig. 6-1. — Diagrams showing the positions of the lyriform organs on
the chelicerae and sternum. After Gaubert.

shown in Figs. 61 and 62, have long been familiar, and it
was at first believed that they were auditory organs.
Gaubert denied their auditory function ; he tried the effect
of varnishing the organs and found as a result that the

Fig. 62. — A Lyriform Organ. Diagrammatic section, after Gaubert.

spider was less sensitive to heat. He believed that their
structure bore out his hypothesis that they were per-
ceptors of heat, yet in his conclusion admitted that they

THE SENSES AND SENSE ORGANS 101

might receive " peut-etre aussi d'autres sensations gene-
rales."

These are the organs to which appeal has been made to
support the contention that spiders have scent organs in
various situations. The idea is based chiefly on the work
of Prichett supported in 191 1 by further investigations of
Mclndoo. After obtaining the usual response to smells,
Mclndoo endeavoured to cover the lyriform organs with a
coat of vaseline. He then found that the time of response
to smells was very much increased, and so concluded that
the lyriform organs were organs of scent.

An alternative view was, however, put forward in 1916
by Hewitt. His subject was a Mygalomorph spider
belonging to the genus Stasimopus , and he presented the
scent to it on a hat-pin. This, being much finer than a
glass rod, enabled the experimenter to make a more exact
localisation of the stimulus, and hence a more accurate
discernment of the positions of the scent organs. Hewitt's
experiments showed that a scent placed near the tip of a
leg resulted in that leg being raised and moved away, but
if the leg was amputated at the centre of the penultimate
joint, the metatarsus, it did not respond at all. This
points to the concentration of the scent organs near the
tips of the legs, rather than to their scattering over the
body, and Hewitt suggested that they were localised in the
scopula hairs. He also showed, as his predecessors had
done, that the first and second pairs of legs are more
sensitive than the posterior pairs, and that males are better
endowed with smelling power than females. It will be
seen that if the scent organs are either the scopula hairs
themselves, or are situated in their immediate neighbour-
hood, the lyriform organs are left without a recognisable
function and remain a problem. This is indeed the view
held by Vogal as recently as 1922.

Finally, we come to Bristowe's recent observations on
courtship in wolf-spiders, in which he showed quite con-
clusively that the male wolf-spider recognises the presence
of the female by smell. Further, the male can follow the

102 THE BIOLOGY OF SPIDERS

track of the female and can be seen excitedly feeling the
ground over which she has passed with the upper surface
of his palpi and the tips of his legs. This tends to support
the view that the scent organs are placed near the tips of
the tarsi. In an experiment of Bristowe's the tips of the
palps and of the tarsi were removed from a male spider
under chloroform. In twenty-four hours it had apparently
recovered, and fed on a fly. It responded, however, very
feebly to a scented hat-pin and seemed quite unable to
recognise the scent of a female.

The lyriform organs are not glandular and it seems
certain that they are sensory. Bristowe makes the suggestion
that they are indeed organs of scent, used, like the scent
organs of some male moths, for recognising smells at a
distance. When, however, the origin of the smell is close
at hand, as, for instance, in following a track on the ground,
the hypothetical tarsal organs are used.

The value of Bristowe's work is that it indicates for the
first time what advantage a sense of smell may be to the
individual spider. Scent is not used to any extent in
catching food. This was proved by Rainbow, in his experi-
ments already mentioned, when he found that spiders
would leap upon rude imitation insects dragged into their
range of vision.

Taste

It is well known that the sense of taste and smell are
related, at any rate in man. No further reminder is needed
than the monotonous insipidity that all food acquires when
we suffer from a cold.

The tasting ability of spiders is not a subject that has
been much investigated, and on a priori grounds it would
not seem that they possessed the sense to any great extent.
It seems that spiders do not select their food but are
willing to accept all that comes their way, and if it be the
normal behaviour of a creature to eat everything that becomes
available without discrimination, the sense of taste is not
to be expected. Moreover, Boys, many years ago, tried the

THE SENSES AND SENSE ORGANS 103

experiment of drowning a fly in paraffin oil and throwing
it into a spider's web. By touching the fly with a tuning-
fork, the spider was made to come out and attack it, and by
repeating the process was induced to eat a large portion of
the fly, paraffin and all.

On the other hand, some facts point to the reverse
conclusion. The most familiar is contained in Fabre's
description of an Agelena labyrinthica which he fed on
locusts. " The bite," he says, " is usually given at the
lower end of a haunch : not that this part is more vulner-
able than any other thin-skinned part, but probably because
it has a better flavour. The different webs which I inspect
to study the food in the larder show me, among other
joints, various flies and small butterflies and carcasses of
almost untouched locusts, all deprived of their hind legs,
or at least of one."

It is, therefore, also of interest to see occasionally a
house-spider pick up detached legs and suck them, as if
they were, as Fabre suggests, " a dainty, the equivalent on
a very small scale, of the larger legs of the crayfish."

A recent experiment of Hingston's may also be cited.
He chose quinine as a substance possessing no smell and
no irritant action, and tried the effect of feeding a spider
on a fly soaked in quinine. The spider came out and bit
the fly, after which it returned to its resting-place and
vigorously brushed its palpi over its maxillae. This action,
coupled with its immediate rejection of the fly, seems to
prove that it was well aware of the quinine, and it is
difficult to imagine that anything other than the taste was
concerned.

CHAPTER V

THE BEHAVIOUR OF SPIDERS

We have described the spider's body in some detail, analysing
it into systems and organs and cells and synthesising it as
an organised unit capable of response to changes in its
environment, and in so doing we have looked upon the
organism from one aspect only. A second remains, for
every living creature is properly to be regarded as a dual
entity — a physical body and a psychical mind. What can
we learn about the spider's mind — the subtle inner power
that sits in control of the cells, the organs, the systems ?

We are ignorant of the true nature of the connection
between the mind and the body : that is to say, we do not
know what difference, if any, in the cells of the nervous
system is responsible for the passage of a thought, the per-
ceiving of an impression, the creation of an idea. The
interpretation of the animal's actions as they reveal the
character of the controlling mind within is as far as we are
able to go, at present.

It is clear enough that the diverse types of animal
behaviour are of different degrees of complexity, even as
are the diverse types of animals' bodies. Structure, not
behaviour, reveals evolution as a racial history of the body,
and similarly behaviour, not structure, reveals the history
of mind. So we come to perceive an evolution of mind
comparable and perhaps contemporary with evolution of
body. Therefore we ought to look upon the mental and the
physical as two allied aspects of the life of the organism.
Perhaps they are only two ways of looking at the same thing.

104

BEHAVIOUR

105

Reflex Actions

The simplest type of behaviour which the spider well
illustrates is the reflex action. We ourselves blink at a
sudden appearance near the eye, we draw back our hand from
too hot a surface : these are reflex actions. We are conscious
of them, but they are involuntary. They depend on well-
established connection between certain nerves and certain
muscles and are performed without our " stopping to think."

The spider's most frequent reflex is its habit of " sham-
ming dead," as it is generally and inaccurately termed. The
spider draws up its legs and remains absolutely motionless
in a cataleptic condition. The habit is general in all
families of spiders and is the usual response to a threat of
danger such as a sudden jarring of its surroundings. Thus a
spider in a box may be made to assume the position by a
tap on the lid. Experiment has shown that this action is
carried out perfectly by spiders whose abdomen has been
completely severed at the pedicle. We are reminded of the
familiar automatic actions of the headless frog. Moreover,
in some cases it was found that if the spider was again
bisected, so that each half of the cephalothorax carried two
pairs of legs, the two halves still retained the power to
respond to a neighbouring tap. The withdrawal of the legs
was slower, but the same power was at work.

Sometimes a reflex action involves more than this. We
rise a step in the ladder of behaviour when we come to such
compound reflex actions as demand the co-operation of
several parts of the body. When, for example, the cata-
leptic reflex is called forth in the web-spider, when, as we
say, " the web-spider is frightened into shamming dead,"
it simultaneously drops from its web. But it does so on a
thread, and the silk glands must co-operate in the action and
in the checking of the stream of silk after a certain fall.
Other web-spiders re-act in another way, very familiarly
shown by the common garden spider. They shake their
webs into rapid vibrations by rigorous rhythmical jerks of
their legs. This demands suitable co-operation of all the

io6 THE BIOLOGY OF SPIDERS

leg muscles and a proper timing of their contractions.
There is more in this than in mere quiescence, but it is still
a reflex action, an automatic response under the control of
a part of the central nervous system which is not concerned
in volition.

To describe the performer of any of these actions as
cunning is an anthropomorphism quite unjustified by the
facts, and nowadays is less commonly heard. It is the
rule of behaviourists to interpret the actions they witness in
the simplest possible terms — to credit the animal with a
minimum degree of mentality. A stage will certainly be
reached at last when the creature's behaviour cannot be
properly described without the use of psychological terms.
It must then be admitted that the animal is showing some-
thing akin to conscious judgment, and the psychological
aspect is dominant over the physiological. Before this was
realised, the habits of animals were often described in the
most extravagant terms. Most popular Natural Histories
of the eighteenth and nineteenth centuries will afford
examples, but none is better than Evelyn's oft-quoted
description, in his Travels in Italy, of jumping-spiders.
" I have beheld them instructing the young ones how to
hunt, which they would sometimes discipline for not well
observing ; but when any of the old ones did, as sometimes,
miss a leap, they would run out of the field and hide them-
selves in their crannies, as ashamed, and haply not to be
seen abroad for four or five hours after."

Tropisms

Tropisms are allied to compound reflexes, but differ in
two respects. They generally involve movements of the
whole body rather than of a part, and they are generally
due to an automatic adjustment of the body so that the
stimulating impulse is received equally by both sides. The
most familiar examples are the flight of the moth to the light
and the tendency that young eels show to swim persistently
upstream.

BEHAVIOUR

107

Spiders show at least two well-defined tropisms. In
youth they are negatively geotropic and tend to climb
upwards ; and at all ages they are usually negatively
heliotropic, tending to move away from bright light.

The geotropism of the young spider is associated with
the method of dispersal in which it floats away on a gossamer
thread. When once the flight has been made and the
dispersal effected, the tropism fades away from the spider's
constitution. In one of Fab re's experiments, a cocoon of
the eggs of the garden spider, Epeira diademata^ was allowed
to hatch at the bottom of a fifteen-foot bamboo. When the
young spiders hatched they began to mount. They climbed
only at certain hours in the day and spent the night resting
together in their customary globular formation under a
cone of silk. And so they climbed on until after four days
they reached the top of the bamboo and none ever turned to
come down again.

Young wolf-spiders, even though their whole adult life
is spent running on the ground, will show the same pro-
pensity. They will climb once as high as possible, and
thereafter no more.

That spiders tend to shun the light is perhaps the first
characteristic that any observer would notice. Indeed, it
is possible that their apparent preference for red may be a
result of this tropism rather than of any real appreciation
of colour, and some experiments might well be devised to
test this. There is, however, one particularly good example
of the light-shunning habit. On the beach at Wood's Holl,
Massachusetts, a little spider, Grammonota inornata, is found,
hiding under clumps of eel-grass. On lifting a clump of
the grass when the sun is shining from any point in the sky
save directly overhead, all the disturbed spiders run land-
wards. This universal choice of the same direction is not
affected by the slope of the sand, for they will run uphill or
down, nor by the presence of water, for they will run over
it, nor by the direction of the wind. But if the grass-clumps
are lifted at midday, or in sunless weather, or at any time
under the shade of an umbrella, the spiders will scatter

io8 THE BIOLOGY OF SPIDERS

indiscriminately in all directions. Montgomery, who
described this curious phenomenon and carried out labo-
ratory tests on the tropisms of the spiders, explains it as a
running away from the glare of light reflected from the
surface of the sea — in fact as negative heliotropism.

There are, of course, some spiders which do not so
generally shun the light. Many wolf-spiders, which are
seen in immense numbers in the sunshine, have an incredible
way of disappearing altogether if the sun is temporarily
obscured by a cloud.

It is possible, too, that the orb-spider's response to the
shaking produced by the entangled fly at one spot in its
web is an action of this type. This vibrotaxis was investi-
gated by Barrois by shaking one spot of the web with an
electrically-driven oscillator and photographing spider and
web by a timed flashlight. The photographs revealed both
the speed of the spider's response and also the distribution
of the vibration along the threads of the web. This made it
clear that the spider was being directed to the centre of
disturbance, as it were mechanically. A few simple experi-
ments in blowing a puff of air on to the web soon lead one
to the same conclusion. There is no need for the sight of
an insect nor the sound of its wings nor the continuance of
its struggles to make the spider dart out.

Simple Instincts

On a plane above these reflex and tropistic responses
come the many actions which we ascribe to instinct.
Instinctive actions are distinguished by two important
characteristics — the fact that they are carried out perfectly
on their first performance without previous learning, even
though they are often of considerable complexity, and the
fact that they must be initiated by some particular stimulus.
In this latter aspect they recall what we have previously
said about reflexes, but differ in this — that each of the suc-
cessive actions would seem to be set in train by its predecessor
and not by a succession of external stimuli. Further, the

BEHAVIOUR

109

psychological aspect is more prominent in instinctive
behaviour than in reflex actions. There is a degree of
consciousness or awareness about instinctive actions which
not only enables them to make a contribution to experience,
but which, as a result of this, also makes it sometimes
possible for individual experience to modify the instinctive
actions themselves.

It is clear, however, that instinctive behaviour depends
on the inherited structure of the nervous system ; in no
other way could learning be dispensed with and the linked
semi-reflex actions follow one another to completion. Nor
from any other source could there arise that imperious
coercion which often drives the animal through a long series
of instinctive actions when an accident or an alteration of
circumstance has made those actions useless.

Instinctive behaviour is well developed in spiders and
includes the majority of their activities ; it is therefore
not difficult to select some which illustrate the chief features
mentioned above. Probably the most obvious of all is the
ability of the young spider to spin its own web as soon as it
begins to lead an independent life — a web which follows in
every respect the design of the webs of the adults and is just
as well adapted to its purpose. The achievement of spinning
a web is more complicated than is the swimming of a young
bird, and yet no parental instruction is given to the spider-
ling, as it sometimes is to the bird. In the majority of cases
the parent is long since dead.

The behaviour of spiders illustrates the modification of
instinctive actions in special conditions much less frequently
than the contrary fact of their tyranny, but the following is
perhaps an example. Major Hingston, watching an orb-
spider spinning the radii of its web, tried the experiment of
cutting a radius as soon as it was laid down. Twenty-five
times the spider replaced the missing radius before it gave
up and altered the usual plan of its web, spinning one with
eighteen radii. To obtain these eighteen it had had to spin
twenty-five extra radii, making a total of forty-three instead
of the usual twenty-four.

no THE BIOLOGY OF SPIDERS

But as we have said, instinctive behaviour in spiders
remains in most cases unmodified. The house-spider, for
example, usually coats its egg-cocoon with a layer of small
pieces of brick-dust and grit which have the effect of making
it far less conspicuous and probably also more resistant to
the attacks of parasites than it would otherwise be. But a
spider in a cage makes its cocoon conspicuous by gluing to it
the wings and legs of dead flies, which would not protect it
at all.

Similarly, when Moggridge removed from the neigh-
bourhood of trap-door spiders' tubes the moss with which
they generally coated their doors and scattered about pieces
of bright wool, the door was coated with the wool and made
conspicuous instead of invisible.

The wolf-spider, Lycosa narbonnensis \ is one of the few
European members of its family which lives in a permanent
home — a burrow excavated by itself. But Fabre showed
that if it was taken away from the burrow which it had dug,
it showed neither inclination nor ability to dig another. Its
instinct impelled it to dig a hole and to live in it, but was not
prepared to cope with a situation so altered that a succes-
sion of holes might be necessary. So the spider went
homeless, but showed itself wise enough at least to take
possession of a hole made for it by pushing a pencil into the
soil.

It is evident that no very great degree of consciousness
lies behind these straight-forward instinctive actions ;
otherwise their modification in special circumstances would
be less rare. When an animal modifies its behaviour in
accordance with circumstances — that is to say, when it
appears to be profiting from its past experience — it is pro-
viding us with all the evidence we have that the past experi-
ence was indeed a conscious one. The house-spider, making
its sheet- like cob- web, shows no sign of profiting by experi-
ence. It never spins more rapidly nor more wisely nor more
efficiently : it never improves. Previous experiences of
web-making and of the hazards of the chase have taught it
nothing, and we are scarcely sure that it actually knew that

BEHAVIOUR

it was spinning. There is not, as Romanes has long since
pointed out, " any necessary knowledge of the relation
between the means employed and the end attained." Thus
we can understand, perhaps, the apparently absurd way in
which spiders will spin their webs in sealed museum cases,
or even in small cages. They do not spin until they have
discovered that they cannot escape, but it is too much for
them to realise that this means that insects cannot fly in.
So they spin — instinctively, irresistibly, irrationally.

Chain-Instincts

Proceeding, we may find instinctive actions which are so
complex, so prolonged, and so dependent one upon another
as to deserve consideration as a higher stage of behaviour.
These are termed chain-instincts.

In the example last quoted, the spinning of the house-
spider, the cob-web is made almost entirely of one kind of
silk and by one kind of action. But the geometrical web of
the orb-spider is, as will be seen in a later chapter, a more
elaborate work. It consists of at least five parts made by
methods and of materials so different that a Labour news-
paper has commented on the fact that, if spiders were
trade unionists, five spiders would be required to spin each
web. The extended series of processes by which it is made
thus form a good example of what is meant by chain-
instincts — a succession of different instinctive actions
forming integral parts of a unified performance.

Every spider provides an illustration of chain-instincts
in the making of its cocoon, a process which, as will be
described later, consists of several different stages. The
finished cocoon, often so beautiful and elaborate an object,
is produced by an unvarying succession of processes,
initiated by the internal stimulus of the matured ovary.
Probably also the courtship actions of male spiders are to
some extent similar in character. Instigated by the sight or
scent of a female, the male carries out a series of peculiar
rhythmical movements, different for each different species.

I 12

THE BIOLOGY OF SPIDERS

These chain-instincts serve to emphasise most strongly
the way in which an instinct drives the animal through its
task with very little chance of altering the procedure. The
egg-cocoon once begun is finished, even if the eggs are taken
away or have fallen to the ground. This fact has often been
spoken of as remarkable, but it is what might be expected
from the nature of the case, and it is misleading to use it as
an instance of the spider's stupidity. The spider cannot
know what eggs feel like or look like, and therefore cannot
realise either their absence from the sheet or their presence
on the floor of the cage. In the same way a male spider can
be persuaded to go through his initial courtship antics
without a female being present at all, simply by putting him
in a cage which she has lately occupied and in which her
scent still lingers.

But web-spinning is by far the best illustration of the
tyrannical character of instinctive actions, because it lends
itself well to such a variety of experiment. Fabre was the
first to describe the effect of cutting the orb-web in half
as soon as it was made. The spider remained on the
tattered and useless wreck, and showed no inclination to
make another. This was repeated by Hingston, who made
many other experiments of a similar character. For example,
if a piece of the temporary spiral line which the spider uses as
a scaffolding is cut, the spider does not replace it. Each
time that it comes to the place as it circles round the web,
it has to make a longer journey because of the missing
thread, but it will do so invariably. It cannot break off a
process in the middle and go back for a moment to a point
earlier in its course. In an extreme case, Hingston removed
the whole of the scaffolding. This meant that as the spider
laid down the viscid spiral thread it had to travel from the
edge to the centre and back again in each segment of the
web, instead of merely stepping from radius to radius with
the help of the scaffold. And yet the spider did this and
spun, in this laborious way, a crude and imperfect web,
instead of re-laying the few turns of scaffold.

As an alternative, the radial threads were removed. This

BEHAVIOUR

113

destroyed the balance and symmetry of the system, but the
spider took no notice. Even when seven radii were removed,
it still spun on as best it could.

In a most illuminating experiment, Hingston removed
the first ten turns of the viscid spiral thread. The spider,
alarmed, retired to its hiding-place, but, some time after,
came back to the web, where all was quiet. And there it
began at the place where it had left off, and put down
the second half of the viscid spiral. It could not go
back and start this thread again ; it could only go
blindly on.

It is important to look upon these facts rather as illus-
trating the character of instinctive behaviour than as afford-
ing grounds for criticising an animal's abilities. An animal
has as much mental endowment as it wants, and no more ;
or, to put it another way, an animal's habits are adapted to
the limits of its mental capacity. In the life of the spider,
the chain-instincts are capable of carrying on the spider's
essential businesses and securing its survival. They do so
in a very efficient and, it must be admitted, a very successful,
way without waste of time or energy. We must not in any
way condemn the spider for a fool as a result of our experi-
ments. Nature does not play tricks like ours ; she does not
steal spider's eggs nor tease them with scents nor juggle with
webs in the making. At her worst she makes a hole in the
web as soon as it is finished. And so we do not and should
not expect to find a mental equipment designed to cope with
situations which are unlikely to arise.

This is illustrated by this very question of repair. It
has been seen that a bisected web is not replaced ; in the
same way, if we push a finger through the web, the spider
cannot mend the hole. But when, in the natural course of
events, the spider itself tears a large and struggling fly from
its toils, it almost invariably puts down a few threads, which
support the web as a whole by preventing the rent from
getting worse. Warren has noticed the same power in
Palystes natalius, a Natal hunting-spider. Many of these
laid eggs and spun cocoons in his laboratory and, if the egg-

THE BIOLOGY OF SPIDERS

sacs were injured, the mothers made attempts to repair
them, with varying degrees of success.

Behind all instinctive actions there is a feeble awareness
and a faint endeavour.

Intelligence

The last of our stages of spider behaviour gives us a
glimpse of intelligence. Mere associative learning passes
on to experimental learning ; there is a conscious adaptation
of means to an end which implies the possession of some
degree of memory and imagination.

Intelligent behaviour in the true sense is very rare among
Arachnida. It has been seen that instinctive behaviour
suffices for most of their needs : they are pre-eminently
creatures of the instinctive type. Animals of this type,
reaching a climax in bees and ants, are possessors of small
brains, but are inheritors of fully developed instinctive
powers. They are adapted to a constant environment and
are difficult to educate. On the other hand, birds and
mammals represent the big-brained type. They inherit a
relatively small endowment of instinctive behaviour, but
they stand a far better chance of survival in a world of
shifting scenes and problems, for they possess the power to
learn, and to learn intelligently.

Like almost all other creatures, spiders can learn by
association. When they are kept in cages, for example,
they will at first always retreat when the cage is opened to
put in the flies on which they are fed. As time goes on the
speed of their retreat grows less, and at last it is very difficult
to believe that the expectant spider within does not associate
the opening of the cage with food.

That spiders can so far be " tamed," as we say, as to
take a fly from one's fingers is only a further example of the
same power. That they will ultimately refrain from running
out to a tuning fork that is used to shake their webs is another.

For learning of any sort to be valuable, a memory is
necessary. The spider's memory is usually short, and there-

BEHAVIOUR

fore it learns very slowly. Dr. and Mrs. Peckham tried to
teach a Cyclosa conica that it need not drop from its web at
the sound of a tuning fork, for no harm resulted. The
spider was tested with the fork daily and for a month it
dropped at every sound. For another fortnight it dropped
six or seven times daily before " remembering," and at
last after six weeks, it remained unmoved by the sound.

Probably the highest exhibition of the spider's intelli-
gence is seen when it has caught a large and heavy insect.
It poisons it and ties it up by actions which are undoubtedly
instinctive, but before it enjoys its meal it has to raise the
captive to its own retreat. One may watch small orb-spiders
thus dealing with crane-flies.

The conditions of the problem before the spider are
bound to vary. The insect may be firmly stuck to the viscid
spiral, or not ; it may catch the wind, or not ; and so on.
Yet the spider goes busily on, fixing threads and cutting
threads, every action apparently well-chosen and directed
towards the same end. The fly is raised stage by stage,
first one end and then the other, as if an intelligent foreman
were calling out directions all the time.

Probably the spider is doing little more than experi-
menting. It fixes some threads and then pulls up the fly
and repeats the process if necessary. But here, more than
elsewhere, the spider shows ability to deal with uncertain
problems.

CHAPTER VI

THE QUEST FOR FOOD

It is common knowledge that spiders are normally insect-
eaters and that they spread their webs and direct their
energies to catching flies. The closest study of spiders can
but modify this by amplification, for web-spiders are usually
ready to eat everything that shakes their web and the
hunters will attack anything small enough that comes their
way, without pausing to determine whether or no it has six
legs and a head separated from its thorax. Instead of
describing them as insectivorous, it is therefore a little more
accurate to say that they are carnivorous and eat only living
food.

The Choice of Food

The spider's wide choice of acceptable fare has already
been referred to in discussing its sense of taste. Experience
shows that spiders will eat all kinds of flies as well as wasps,
bees, ants, beetles, earwigs, butterflies, moths, harvestmen,
and woodlice, and other spiders, whenever opportunity
occurs. More rarely they have been known to consume
caterpillars and pupae, worms and small fish ; they show no
trace of discrimination. Abraham (1924) has, however,
recorded of a captive Cryptothele sundaica that in five
months it could not be induced to eat anything except
termites.

This varied menu should not be interpreted as a sug-
gestion that the spider unhesitatingly rushes at everything
which entangles itself in its web. In the first place, the
actual vibration conveys a certain amount of information.

116

PLATE V

B. House-Spider {Tegenaria derhamii). X 2.
To face p. 116.] [E. A. Robins, photo.

THE QUEST FOR FOOD 117

An instance of the spider's treatment of a struggling beetle
larva as being unworthy of its attention has already been
given, and the female spider is also able to distinguish the
tune played by a male spider when he comes a-courting on
the edge of the web.

On occasions, too, the web entraps formidable insects
with stings, like wasps, or with powerful jaws, like the
praying mantis. The spider has then to determine whether
to allow the struggling insect to force its way out of the
web, or whether to attack it by special methods. The
ordinary large English house-spider, Tegenaria atrica, will
generally allow a wasp to escape, and I have seen one
to whom the wasp in its struggles had approached too
near, hurriedly bite a hole in the sheet of the web and,
evidently frightened, force its way through into a less
dangerous neighbourhood. On the other hand, many a
hungry house-spider attacks and overcomes wasps. The
method by which they do so, as well as the possibility that
sight may help the spider to distinguish between its welcome
and its undesirable captures, is suggested by an observation
of Pocock's on a spider, Agelena labyrinthica, belonging to
the house-spider's family. The Agelena* s web had entangled
a bee, of whose sting the spider was evidently afraid. It
therefore attached a thread to a point near the bee and
walked round and round it so that the thread hampered the
insect's movements. Then quickly it darted in and bit the
bee in the leg. As soon as this had been accomplished,
the character of its actions entirely changed. It seemed to
worry no more about the possibility of the bee's escape,
trusting in the effects of the poison, which, in fact, soon
paralysed the bee.

It is evident that sight played its part in determining
the spider's course of action, for it would unhesitatingly
bite a bluebottle as large as the bee and carry it into the
corner at once. However, when given a drone fly, Eristalis,
it treated it in the same way as it had treated the bee. Clearly
it mistook it for a humble-bee, even as a man might do.
Campbell recorded an observation which points in the same

n8 THE BIOLOGY OF SPIDERS

direction : he was keeping a house-spider in a bottle and
says that when searching for flies she could be seen to tilt
her whole body as if making the best use of her eyesight.

The Treatment of Captives

Pocock's observations on the actions of Agelena illustrate
what may be called the direct and indirect methods by
which the web-spider deals with its captures. If the
insects are not too large or are well entangled, or if they are
quite powerless to harm the spider, the latter hurries to the
scene as soon as they arrive, seizes them and drags them
home to be eaten. The indirect method is used when the
booty is formidable and likely to hurt the spider, or when
it is so strong that its continued struggles might tear un-
desirably large holes in the web and allow it to escape.

The common garden-spider, Epeira diademata, shows the
most familiar of these methods of treatment. The fly is
grasped with the first and second pairs of legs and turned
round with the help of the third legs and the palpi, while
the tarsal joints of the fourth legs guide the broad ribbon
of silk which is issuing from the spinnerets.

The house-spider, Tegenaria, uses an interesting modifi-
cation of this plan which achieves the same result. It holds
the captive with its jaws and, pressing it down into the sheet
of the web, walks round it and so twists it up in sufficient
silk to keep it quiet.

The method of drawing a thread round the struggling
victim, used by Agelena, has already been mentioned, and
there are still some others.

Our holly bushes often carry in the summer months the
webs of spiders of the genus Theridion, webs which consist
merely of a maze of threads crossing in all directions. The
spiders of this family have been mentioned in Chapter II as
the possessors of a comb of spines on the tarsal joints of the
legs of the fourth pair. These combs draw out silk bands
from the spinnerets and throw these ribbons and sheets of
silk over the captive. This is so effective a method of

THE QUEST FOR FOOD 119

encumbering the insect's limbs that these small and com-
paratively weak spiders are able to overcome insects much
larger and stronger than themselves.

Another type of web which is very familiar in all our
gardens is the flat sheet type, the spider living beneath it,
hanging and running upside down. When it arrives at an
entangled insect, it usually bites it and pulls it through the
sheet at once, but I have also seen the spider stop beneath
a struggling insect and pluck at the sheet with a sharp jerk so
as to entangle the insect further.

This plucking at the web is a common action of many
spiders when their web has been shaken by a single isolated
twinge. Such a twinge may mean either that the insect
merely brushed the web in passing and so has escaped, or,
as is frequently the case, that it has been caught and is lying
still. The pluck at the lines of the web tells the spider
whether the threads are loaded or not and also stimulates
the insect, when there is one, to further struggles, which
entangle it more securely. Garden-spiders can often be seen
turning about in their webs and testing their luck in this way,
while house-spiders gently withdraw their fore-legs, which
pull on the sheet, so that one can see the little cones of silk
pulled up by their claws.

Specialised Webs

There are, moreover, many kinds of specialised webs,
whose use is more intricate than that of the simple wait-and-
see type.

Probably the best-known of these is the sectoral web of
Hyptiotes, the triangle-spider. The web of this spider is
best compared to three sectors of an orb-web with a silk
thread attached to the apex (Fig. 63). At the other end of
this thread the spider waits hidden under a leaf, the thread
hauled in and coiled up by its forelegs. If an insect flies
into the web, the spider lets the thread go, jerking the triangle
of web.

Two of the most remarkable methods of using webs

120 THE BIOLOGY OF SPIDERS

have been described by Dr. Conrad Akerman, of Pieter-
maritzburg.

Near the south coast of Natal, a fairly large spider,

Fig. 63. — Web of Hyptiotes.

Menneus camelus, spins its webs on bushes in the neighbour-
hood of streams. The web (Fig.
64) consists of a few irregularly
placed threads supporting a band
of about twenty threads of silk.
These are adhesive, being
covered with the loops of the
viscid silk produced by the cribel-
lum, the supernumerary spin-
ning - organ already described.
This little band, scarcely bigger
than a postage stamp, seems at
first sight far too small to catch
anything. But that view disap-
pears when the method of using
it is discovered. The spider
stands close beside it with its
four front legs holding the

Fig 64.-Expanding web of corners of the band. Tf a moth
Menneus camelus. Ihe

points A, B, C, and D are approaches, the spider suddenly

held in the anterior tarsi. stretches the web until it is five

or six times its former size and simultaneously hurls itself

THE QUEST FOR FOOD 121

forward. The web is thrown round the moth and closed
with the forelegs ; the moth is helpless in the sticky toils
and the spider at once bites it. The principle is exactly
the same as that of the old-fashioned butterfly-net, which
was used with two hands and folded over the butterfly.
The spider does not always succeed in catching the moth :
it may lose its grasp of the web, which is sometimes
damaged by the twigs. But the spider picks it up again
carefully by the four corners, tests it to see if it is working
and resumes her vigilance. She never makes a second net
in the same evening, but continues to use the same one,
however damaged it may become.

An even more striking method is that adopted by the
spider Cladomelea dkermani. This is a large Epeirid spider,
1 5 mm. long, with 24 pointed tubercles on its abdomen. It
does not seem to spin a web ; instead it drops a single thread
about 2 cms. long, having at the end a globule of viscid
matter a little larger than the head of an ordinary pin. It
holds this thread with one of its shortest legs — the third
pair — and whirls it rapidly round in a horizontal plane.
This is continued for about a quarter of an hour without
stopping ; then the spider draws up the thread and swallows
the globule. After a few minutes' rest another line and
globule is spun and the process repeated for another fifteen
minutes. This may continue for several hours. If any
insect were to come within the radius of the spinning drop,
it would probably be struck by the line and captured.

In Australia there is a spider, Dicrostichns magnificus,
related to Cladomelea, which spins a similar thread and
droplet. It does not twirl this round, however, but holds it
in readiness, on its extended first leg, until the prey appears,
when the droplet is hurled at it. If the aim is good, the
sticky drop will capture the fly, which is pulled up by the
spider.

It is rather interesting to note that three devices of
man, the fishing-net, the net of the retiarius, and the bolas
of the Gaucho had long been anticipated by spiders.

122 THE BIOLOGY OF SPIDERS

Hunting-Spiders

The spiders which do not spin webs catch their prey as a
rule by far simpler means. They might be divided into : —

1. Simple wandering, picking up what is encountered.

2. Hunting, overtaking prey by speed.

3. Jumping from a distance.

4. Lurking in concealment and seizing the passers-by.
Many of the Mygalomorphae are content to wait in their

burrows with the lid raised just enough to enable them to
peep out. If an insect chances to alight within their range
of vision, they spring upon it and are back in their burrows
with the lid closed down almost as quickly as the eye can
follow them.

Many spiders are simple nocturnal wanderers with no
permanent home. They rest hidden during the day and
roam about in the dusk, seizing anything they may happen
to come across. A common British spider which illustrates
this is Scotophoeus blackwallii and it makes its habits evident
to us when, as often happens, it gets into the bath or a basin
and cannot escape. And so we find it there next morning.

The Lycosidae or wolf-spiders form the chief family of
huntsmen. These spiders catch their prey by speed. The
wanderers, Drassidae and Clubionidae, have perhaps the
simplest possible task, for they merely grasp what comes
their way, and the wolf-spiders show the first adaptation in
the development of fleetness of foot.

Something a little more subtle is shown by jumping-
spiders and crab-spiders.

Jumping-spiders, Salticidae, mentioned already because
of their keen eyesight, form an extremely numerous group,
widely spread throughout the hotter parts of the world, with
representatives in the temperate regions. The little zebra
spider, Salticus scenicus, is the commonest British species,
and one which must be a familiar sight to many as it hunts
over wooden palings. A jumping-spider creeps about its
chosen area, whose colour it usually matches somewhat
closely, and every now and again stops, and by straightening

THE QUEST FOR FOOD 123

its forelegs, raises its head and gazes round its neighbourhood.
It may be that it espies an insect recently alighted, where-
upon it approaches with such caution that its movements
are quite imperceptible until it gets within jumping distance.
Then it suddenly leaps with practically unerring aim and
fixes its chelicerae in its prey. To hunt in this way on
perpendicular surfaces demands a very secure foothold,
which the spider obtains by the pad of hairs or scopula
already described. At the same time an accident or an
inaccurate leap is to be guarded against, and the spider does
this by laying behind it a silk thread, bound down at frequent
intervals. Like the mountaineer's rope, this thread will
protect it from anything more serious than a few moments'
dangling at its end.

Crab-Spiders

A third method is adopted by crab-spiders, the family
Thomisidae. Many members of this family lurk among the
fallen leaves which collect under hedges and in similar
situations. Their speciality, to which they owe their name,
is their ability to run backwards and sideways upon their
unsuspecting victims. This simple method may be taken
as the starting point from which some other more ambitious
members of the family have diverged.

Instead of stopping on the ground, some Thomisidae
conceal themselves in flowers. In colour they match the
petals among which they lie, and thus may be overlooked
by bees or butterflies which visit the flower in their search
for pollen or nectar. A very well-known British spider,
Misumena vatia, is a good example of this. It is a particu-
larly interesting species because it has the power, more fully
described in the next chapter, of altering its colour to suit
its surroundings.

It is in a genus of crab-spiders that is found the most
striking adaptation for disguise. This is Phrynarachne, an
inhabitant of the East. The first species described was
Phrynarachne decipiens, found in Java by H. O. Forbes.
There is a butterfly in Malaya which has the habit of coming

i24 THE BIOLOGY OF SPIDERS

to rest upon leaves which carry the droppings of birds.
Upon leaves Phrynarachne spins a small irregular patch of
white silk, which exactly resembles the outline of the
dropping, even to the rounded drop on the lowest side where
the more liquid portions start to flow away. In the middle
of this web the black and white spider takes its stand and its
black markings complete the deception by resembling the
particles of black solid which customarily float in this
material. On the occasion of Forbes' discovery, he saw the
butterfly feeding, as he thought, as usual, and started to
investigate what seemed to be its curious taste. To his
surprise the butterfly allowed itself to be picked up, and it
was not until then that he realised that it was being eaten by
the spider. The little patch of web deceived both butterfly
and man.

His first description of the occurrence naturally aroused
a considerable interest, which was enhanced by what fol-
lowed. More than a year later, when Forbes was collecting
in Ceylon, the sight of a bird's dropping made him wonder
why he had never found here the spider which he had
previously encountered in Java. Then he looked again,
more closely, and saw that here was indeed the spider,
deceiving man for the second time. This species is known
as P. rothschildi.

The Spider's Bite

Many of these spiders have to face an important problem
when they tackle animals which possess poisonous stings.
In many cases, their solution is the very remarkable habit of
biting their prey in the one spot where an instantaneous
quietus will follow — namely, the cervical ganglion. Fabre's
experiments with wolf-spiders and large bees with formid-
able stings showed that a bite in the nape of the neck killed
the bee instantaneously, but that a bite elsewhere did not
prove fatal for several hours. The spiders were apparently
aware both of this fact and of the dangerous character of
their enemies, or at least they acted as if they were. For
if they came upon the bee in a favourable position, they bit

THE QUEST FOR FOOD 125

it unhesitatingly, whereas in other circumstances they
tended rather to avoid risks and to protect themselves.

Fabre's conclusions have, however, lately been questioned
by Rabaud (1921).

Other Kinds of Food

Insects have been the quarry in all the foregoing instances
of spiders' wiles, but there are a few spiders which hunt
other game. Perhaps the most interesting is the spider
first discovered in Natal, and since found also in the Persian
Gulf and elsewhere, Thalassius spenceri. This spider, a
member of the family Pisauridae, has very long legs and
lives close to the water. It takes up its position with its two
posterior legs resting on a stone ashore, and with the other
six spread out upon the surface of the water, covering a large
area. The tarsi indent but do not pierce the surface film
and in this position the spider waits. If a fish passes below
it, it makes a sudden dive, its whole body going under water.
Its long legs are wrapped round the fish, which is bitten and
dragged ashore. The spider then eats the fish with unusual
speed, leaving nothing except the backbone ! It has also
been seen to eat tadpoles of the toad Bufo carens and adults
of the small frog, Rhappia marmorata.

Spiders are, therefore, not exclusively insect-eaters.
The bird-eating Mygalomorphae described in Chapter XIV
illustrate a wider choice of food, and McCook's great work
on American spiders gives instances of the capture of fish,
mice, and snakes. Some of these are clearly much larger and
stronger than the victorious spiders and raise the important
question of the spider's poisoning powers.

The Venom of Spiders

Spiders' attacks on larger animals have been studied
both in natural circumstances and in the laboratory. To the
former group belong most of the cases described by McCook
and the many similar instances scattered throughout books

126

THE BIOLOGY OF SPIDERS

of travel. There is no ground for doubting any of these,
but in only a few instances has it been possible to be
sure that the victim was in active health before the spider
bit it.

On the other hand, the experiments of Fabre are more
than mere descriptions of finding a large corpse in a spider's
web. Fabre was working with the wolf-spider, Lycosa
?iarbonnensis, common in his neighbourhood, and he induced
it to bite a young sparrow in the leg and a mole in the nose.
The bird almost immediately lost the use of its leg ; after
two days it refused food and died. The mole, too, gradually
ceased to feed and died before the third day.

From these results it is justifiable to conclude that the
bite of large spiders might be not wholly negligible in its
effect on man. The ordinary European species do not seem
to be dangerous, but they may be irritating. But it has been
already explained why irritating results do not always
follow, and why many experiments with artificially induced
bites have given conflicting results. Walckenaer was unable
to distinguish between a spider's bite and a prick with a
needle, and the same result was stated by Blackwall after
several experiments, described in his Researches in Zoology.
Pickard- Cambridge noticed the discrepant nature of conse-
quences, for spiders' bites on the fingers of one of his sons
produced a small white swelling with surrounding inflamma-
tion and considerable itching and smarting ; while similar
bites on his own fingers were followed by none of these
symptoms. Bertkau has also stated that he distinctly felt
irritant poison, and my sister has given similar evidence.
In August, 1926, she was, at my request, catching the spider
Segestria florentina in Brittany. One spider showed
vigorous resistance, in the course of which " it gave my finger
a fierce bite and made it quite sore." The soreness lasted
for the rest of the day, and it is noteworthy that this par-
ticular spider was being harried about and was consciously
on the defensive.

The effect of spiders' bites on man is a very old problem,
which has only lately emerged from contradiction and

THE QUEST FOR FOOD

obscurity to definite certainty. The early confusion was
partly traceable to the legends surrounding the Tarantula, a
small wolf-spider found in south Europe. As is well known,
the supposed consequences of the spider's bite were a general
melancholy, which proved fatal at last, unless a cure could
be found in time. The sole cure was music. Those bitten,
the tarantati, summoned a musician who played before
them a variety of airs, or tarantellas, until he hit upon one
that inspired the patient to dance. The following descrip-
tion is at least two hundred years old. " At first she lolled
stupidly on a chair, while the instruments were playing some
dull music. They touched, at length, the chord supposed
to vibrate to her heart ; and up she sprung with a hideous
yell, staggered about the room like a drunken person, holding
a handkerchief in both hands, raising them alternately, and
moving in very true time. As the music grew brisker, her
motions quickened, and she skipped about with great vigour
and variety of steps, every now and then shrieking very
loud/' Such activity was supposed to cure the disease, the
theory being that the poison was worked out of the system in
perspiration.

Several writers in the seventeenth century devoted them-
selves to a discussion of tarantism, some of them with the
avowed intention of discovering whether it were a genuine
malady or not. Their descriptions of the symptoms agree
well with one another, and not a few have been forced
to conclude that the stories " were, in the main, true."
Denial began in the Philosophical Transactions as long ago
as 1672, where a Neopolitan doctor records the observed
results of the tarantula's bite. " In a few hours after, the
poor man was sorely afflicted with violent symptoms ; as
syncopes, very great agitations, giddiness of the head, and
vomiting ; but that without any inclination at all to dance,
and without a desire of having any musical instruments."

As a matter of fact, the descriptions of the cures of
tarantism give a clue to its origin. Wherever the tarantati
are to dance, a place is prepared for them, hung about with
ribbons and bunches of grapes. " The patients are dressed

i28 THE BIOLOGY OF SPIDERS

in white, with red, green or yellow ribbons, those being their
favourite colours. On their shoulders they cast a white
scarf, let their hair fall loose about their ears, and throw
their heads as far back as possible. They are exact copies of
the ancient priestesses of Bacchus.' ' When the introduction
of Christianity put a stop to the public exhibition of heathen
rites, the Bacchantes continued their profitable profession,
but were obliged to offer some irrelevant explanation. The
local spider best supplied their need.

The Tarantula myth died hard, partly because the name
became appropriated for any large spider encountered by
travellers and collectors in distant countries, while at the
same time stories of the dangerous spiders, well known and
feared abroad, were continually circulated. There was the
Malmignatte of Corsica, the Vancho of Madagascar, the
Katipo of New Zealand, the Black Widow of America. The
fact that all these spiders have special names of their own is
proof of the general dread they inspire, and the Cambridge
Natural History may be referred to for typical instances of
the supposed results of spider bites. For many years
these reports had to be accepted with caution, for it was
difficult to get indisputable evidence that a spider's bite had
really been the cause of the symptoms described.

Quite recently, however, the whole question has been put
on a scientific basis. The spiders which have so long been
dreaded all belong to the genus Latrodectus. This genus
belongs to the family Theridiidae and most of its species
are black in colour with red or yellow markings. When
once this fact is realised, it is possible to make experiments
with the guilty species, and, as a result, American doctors
have settled the question. Spiders of the genus Latrodectus
will eat almost anything, including tarantulas, scorpions,
woodlice, and lizards. The poisonous Spanish fly,
Cantharides, is also eaten, apparently without its peculiar
effect. The bite of the spider is dangerous to horses and
camels ; in 1903 Schtscherbina recorded the death of a
camel due to a Latrodectus-bite in the upper lip. On the
other hand, sheep and pigs can eat the spider unharmed,

THE QUEST FOR FOOD

and the former may be used to clear a field of the spider as
an alternative to the usual method of burning.

Reese found that extracts from the poison-glands of
Latrodectus mactans would quickly kill a cat. Kellog made
the poison into pills with sugar and determined the effect of
swallowing them. He experienced pains, depressed heart-
beat, and constipation. Dr. Bogen, however, has furnished
the most convincing evidence, based on fifteen patients
which have been in his care at the Los Angeles General
Hospital. In nearly all these cases the spider's bite was
witnessed by the patient ; the symptoms were pain in the
legs and abdomen, extreme abdominal rigidity, high blood
pressure, and high temperature. The chief remedies were
warmth and large doses of opiates.

The most remarkable feature of arachnidism, or spider-
bite poisoning, is its limitation to the spiders of one widely
distributed genus. The bites of other spiders, often larger
and stronger animals, do not seem to produce anything more
than the inconvenience described above. Local pain and
swelling have been recorded as the only results of the bites
of the spiders Tegenaria parietina, Chiracanthium nutrix,
Argyroneta aquatica, Trochosa singoriensis, and Dendryphantes
noxiosus.

Few instances have been recorded of a dangerous bite
from a spider other than a Latrodectus. One of these is a
rather rare Australian trap-door spider, Euctimena tibialis,
which bit a child in Sydney in February, 1927 : the child
died shortly afterwards. Tragedies like this are fortunately
uncommon.

Another spider, locally known to be poisonous, is the
Argentine species, Glyptocranium gasteracanthoides , called
familiarly the Podadora. This spider lives in vines where
it sits with its legs drawn in and closely resembling a vine-
bud. It is thus unnoticed by the workers among the vines,
who may get bitten in the hand, or in the foot when the
spider has dropped to the ground. The bite becomes
inflamed and swollen and takes from six to ten days to heal.
Fatal cases have been known when the victim was bitten in

130 THE BIOLOGY OF SPIDERS

the throat and the swelling caused suffocation, or from blood-
poisoning.

Walbum (191 5) and Levy (19 16) have investigated the
chemical nature and physiological action of spider poison in
some detail.

The poison is a strongly alkaline fluid, containing
proteids which coagulate at 65°-75° C. It is soluble in
water, and insoluble in alcohol or ether. Walbum showed
that the body of the common garden-spider, Epeira dia-
demata, contains four poisons :

(i) the poison of the chelicerae,

(ii) epeiratoxin,

(iii) epeiralysin,

(iv) epeiratrypsin.

The chelicerae-poison is less poisonous to warm-blooded
animals than to flies or other arthropods, such as crayfish.
This is in accordance with the spider's usual habits. Epeira-
toxin is confined to female spiders and is contained in the
developing eggs. It cannot be found in the spider in the
summer, but appears towards the end of August and reaches
a maximum concentration in late September. Its poisonous
constituent is an albuminoid, which has a fatal effect if
injected subcutaneously into the bodies of mice or cats.
Epeiralysin is contained in spider's blood and epeiratrypsin
in their digestive fluids.

Robert and Schtscherbina have shown that from
spider's blood an antitoxin against their chelicerae-poison
can be prepared. The latter in 1903 so immunised a camel
that it suffered only temporary effects from the bites of six
Latrodectus. The antitoxin has not, however, been perfected
for use outside research laboratories.

Drink

We turn to the less familiar fact that spiders frequently
drink. In disposing of its captures the spider sucks out
only the fluid parts of its prey. There is very little mastica-

THE QUEST FOR FOOD 131

tion, as we understand it, merely a chewing of the food
between the mandibles to squeeze out the liquid. It is,
therefore, rather surprising that they should require much
else to drink, and yet they certainly do.

An early and well-known occurrence affords an instance
of this. The arrival of many small gossamer spiders aboard
the Beagle when sixty miles from the American coast was
recorded by Darwin and has often been quoted as proof of
the distance which spiders are able to travel by this means ;
but Darwin also recorded a fact which was quite as inte-
resting, though seldom referred to, that the little creatures
were very thirsty and eagerly drank up drops of rain-water.

Spiders kept in observation cages in the laboratory have
to be given water at intervals and may often be seen to drink
it ; in fact some, particularly wolf-spiders, are incapable
of living without it, however well they may be fed. The
rearing of young spiders is never an easy task and it becomes
even more difficult if water is not freely given. Help may be
obtained from the fact that water is not the only fluid they
will drink. I have supplied them at various times with
drops of bovril and drops of beer, to their evident satis-
faction, and there is also a record of their being fed on milk.

A particularly interesting record of the spider's necessity
for water was published as long ago as 1882, by Campbell.
He had a captive house-spider, which one day he found in
a state of collapse on the bottom of the cage, evidently in
extremis. He poured some water into the cage and the
spider at once crawled to it and drank it. The long drink
completely revived her, and her abdomen, previously
shrunken, rapidly distended.

This distension of the spider's abdomen, which is often
particularly obvious after a large meal, leads us to consider
an important adaptation which spiders and some other
Arachnida exhibit. They are capable of taking a relatively
large quantity of food, when they are fortunate enough to
obtain it, and it is, of course, when under observation in
cages that their capabilities in this respect may best be seen.
A spider which has killed and eaten another almost as big

132 THE BIOLOGY OF SPIDERS

as itself and is in consequence bloated with food will none
the less not refuse to catch and suck flies. If a small spider
is able to overcome a much larger one, as is often the case,
the small victor may be seen feeding almost continuously
for the next twenty-four hours. It is only before a moult
that a spider refuses food.

Fasting

If overfeeding is continued it is not without effect.
I had a particularly favoured Tegenaria, which, in response
to a very liberal diet, laid twelve cocoons instead of the usual
two or three. But the power to take these large quantities
of food has a biological value — it is not a mere curiosity.
The spider does not and could not use all the nutriment at
once ; much is stored in the branching diverticula of the
abdominal portion of the intestine. This explains the
distension of the abdomen, which could not possibly be
caused by expansion of the central canal itself. From these
diverticula the stored food is absorbed as required, and so it
comes about that the spider is able to survive extraordinarily
prolonged fasts. It should be pointed out that this state-
ment is not a mere assumption, but one capable of experi-
mental demonstration. If two spiders are kept for a week
or so, one being starved while the other is well fed, and if
they are then both killed, fixed, sectioned and suitably
stained, with stains that differentiate the contents of the
abdomen, the presence of the stored food-products in one
and their absence from the other is perfectly clear.

It can be seen, therefore, that the spider may be indif-
ferent to Fabre's question, which most animals must seek to
answer with an affirmative, " Shall I dine to-day, or not."
This is the power which enables the young spider to survive
the period which elapses before it can feed itself ; it con-
tinues to live on yolk, of which it is able to carry an unusually
large amount. Fabre was considerably disturbed by the
great activity displayed by young wolf-spiders during that
period in which they are carried on their mother's back.

THE QUEST FOR FOOD

For they are continually being knocked off and forced to
climb up again, and during these days they do not, according
to Fabre, feed at all. It was this that led him to elaborate
the fanciful hypothesis that they must be able to convert
the radiant energy of the sun's heat into mechanical work,
and so literally to live on sunshine. It is a pretty idea,
typical of a philosopher-poet, but it need not be considered
seriously. The spider's economy is not that of the green
leaf. It is very difficult to be sure that the spider never eats
an insect even smaller than itself, and they have been seen
to leave their mother's back in order to drink, climbing up
again when their thirst was assuaged.

We must conclude this account of the spider's power of
abstinence by quoting Blackwall's testimony as to the length
to which it may be carried. A female Steatoda bipunctata
was caught in August, 1829, and fed until October 15th,
when it was mature. It was then corked up in a bottle and
kept in a bookcase, and was no longer fed. This spider
fasted for thirty months, and died at the end of April, 183 1.
During all that time it was able to spin a new web when the
old one was removed, which makes its feat of much greater
interest than the prolonged fasts of such creatures as
molluscs. These may survive years, but they do so in a
state of suspended animation, in which the vital processes
are reduced to a minimum.

CHAPTER VII

THE SPIDER'S WEB

The most characteristic feature of the spider's life is its use
of silk. As one writer has expressed it, the spider has hit
upon the device of turning its food into silk and using it
as a net to catch more food. Of the origin of this silk-
producing habit it is difficult to speak definitely. In
dealing with coxal glands, it has already been indicated
that the silk glands may have originated by modification of
this part of the excretory system. Thus silk was originally
a waste product, but now fulfils a useful function ; yet
how the change from waste matter to a valuable substance
came about must remain a matter of speculation.

Spiders' Silk

As things are now, we find that the spider produces
relatively large quantities of a proteid in the form of a
viscous fluid which rapidly hardens on exposure to air.
The chief physical properties of the threads thus formed
are their great tensile strength, which is second only to that
of fused quartz fibres, and their high coefficient of elasticity.

Observation of spiders' habits soon shows that the
making of a web is only one of the many uses to which the
spider puts this valuable material. Through life the
spider is completely dependent on its silk. At least two
different classifications of the spider's silken products have
been suggested, the first by Wagner and a later one by
Montgomery. Yet another, more extensive than either, is
suggested here, taking account of the three dimensions.

134

THE SPIDER'S WEB

135

L Linear Constructions.

(i) The drag line.

(ii) The parachute.

II. Ribbons and Plane Structures.

(iii) The attachment discs.

(iv) The swathing band.

(v) The sheets of Theridiidae.

(vi) The hackled band of cribellate spiders.

(vii) The sperm- web.

III. Solid Structures.

(viii) The web or snare.

(ix) The egg-cocoon.

(x) The nest or retreat. This may be

(a) a mere tube ;

(b) a silk-covered excavation ;

(xi) The moulting chamber.

(xii) The mating chamber.

(xiii) The hibernating chamber.

The present chapter is mainly concerned with No. (viii)
of the above list, most of the others being described in more
appropriate places.

It is worth pausing a moment to settle the very old
question of the value of the spider's silk to man. As long
ago as 1 710 a M. Bon, of Languedoc, make some silk
stockings from this material. The Paris Academie des
Sciences thereupon invited Reaumur to investigate the
possibility of further use of spiders' silk, and his experiments
proved conclusively that its utilisation on a large scale was
impracticable. The ordinary silk of which the web is
made is of no use whatever it cannot be worked. Only
the cocoon silk is strong enough to stand manipulation, yet
a single thread of the silkworm is equivalent to four or five
spider threads. The silk is so torn in the process of spin-
ning that its lustre is much impaired, and the larger number
of threads which must be used means a corresponding
increase in the air-spaces between them, which further

136

THE BIOLOGY OF SPIDERS

reduces reflection. The spiders themselves must be
separated one from another to overcome their cannibal
propensities. This involves much greater labour in feeding
and housing them, and when, finally, it is realised that
57,000 spiders would be required to produce but a pound
of silk, the project of profitable utilisation is seen to be a
manifest impossibility.

Of course, this does not mean that the silk can never be
spun, for several well-known and often-quoted examples
prove the contrary. But these are isolated efforts.

There is one purpose for which a thread of spider's
silk is the best material that can be obtained. Nothing
else is so satisfactory for the threads which are placed across
the lenses of optical instruments such as range-finders,
cathetometers, and microscopes, for marking the centre of
the circular field of vision. Even the scratch of a diamond
is broad by comparison. The silk is collected in the
autumn from the common orb-spiders, Epeira diademata
and Zilla atrica. If a spider is picked up and the silk
thread which is normally hanging from its spinnerets is
gently pulled, the spider will emit more silk, and if the
pulling is continued quite steadily a very long thread may
be drawn out. In practice the thread is wound upon cards
from which the centres have been cut, and which have been
painted with gold size to hold the thread in position. On
cold days, a spider must often be taken indoors to induce it
to spin actively. When a card is wound, it is stored until
the silk is required ; this may not be until two years later,
but the silk retains its elasticity and is just as workable as
when fresh.

Sometimes the thread has been provided by all four
ampullaceal glands, and is split, by skilled workers, into
its four components. When once in position the threads
remain in use for many years, and the whole process is of
interest, because it is the only instance of commercial
value in the spider or its products.

THE SPIDER'S WEB

137

The Origin of the Web

One cannot do more than speculate as to the origin of
the web. The primitive spider was undoubtedly a hunts-
man and the first use of silk was probably to form the
drag-line which nearly all wandering and hunting-spiders
still pay out behind them as they move. The glands which
to-day produce this drag-line are present in every spider,
and serve the same or similar function, such as the forma-
tion of the foundation lines of the web. Moreover, it is
not impossible dimly to perceive how the excretory matter
which was the forerunner of silk, might perhaps have been
used occasionally in somewhat the same sort of manner.
Granting this, we start with what may be called the drag-
line habit. If this coexisted with the habit of taking
shelter in a crevice, it is clear that the home or shelter of
the spider would be coated within with the silk of accumu-
lated drag-lines. Many of these, laid down when the
spider left or returned to its retreat, would run outwards in
all directions from the mouth of the crevice ; and the next
assumption it is necessary to make is that the spider dis-
covered that, as it rested at home, movement of these lines
would imply the tripping-up of some passer-by, who
might well be caught and eaten.

The Evolution of Webs

What has been sketched is, in any case, the possible
origin of a common type of spider's domicile. The most
primitive spiders known, the Liphistiomorphae, which have
persisted almost unchanged since the Carboniferous Age,
make homes which, with one addition, resemble precisely
the one we have pictured. They consist of a tunnel-like
hole lined with silk, with the edge of the lining drawn out
all round the mouth in a fringe and held in position by
radiating threads. The distinguishing feature of the
Liphistiid nest is a trap-door, which may well be assumed
to have been a later addition. Excluding the trap-door for

138 THE BIOLOGY OF SPIDERS

a moment, there is here the primitive type of web, con-
sisting of an expansion of the tube which lines the burrow.
Wandering insects which trip over the guy ropes or trespass
upon the fringe give notice of their arrival to the spider
within, who rushes out and secures them if possible.
Liphistiidae are spiders practically confined to Indo-Malay,
but webs of just this type are made by all the primitive
web-spinners, such as the Dysderidae, a primitive family,
not well represented in this country, though common in
Europe. Almost every stone wall in northern France
harbours the fine large spider, Segestria fiorentina, which
lives in a web exactly corresponding to the description
given above. A tap with a spike of grass on the fringe at
once brings out the spider to investigate, and shows us a
new feature.

It is evident that the gaping bell-mouth of our primitive
web is not well protected against marauders, and it may be
supposed that it was a reaction to this fact that resulted in
both Liphistiidae and the Mygalomorphae spinning trap-
doors to close the aperture. The trap-doors are thus
conspicuous characteristics of these two sub-orders of
spiders. In the third sub-order, the Arachnomorphae,
there are no trap-doors : the primitive web is used in its
open form, as in Segestria. But the spider rests in the
tube with its third pair of legs turned forwards, so that it
may use all six limbs against intruders.

The nearest British approach to the Segestria type of
web is the cribellated web of the Amaurobiidae. These
are the bluish, rough-looking webs so common in the
corners of windows, in cellars and sheds, seen often
diverging from crevices in wooden palings or keyholes of
gates. With the addition of the carded silk laid on by the
calamistrum this web resembles our primitive type in all
essentials. It differs from it only in having the fringe
portion relatively much larger ; and the advantage of
making the fringe cover a wide area is obvious. It not
only gives greater opportunity for catching flies, but it
affords greater protection. It becomes so difficult to

THE SPIDER'S WEB

139

approach the open tube without becoming entangled, that
the spider has less need for caution when it is at home, and
the third pair of legs have resumed their more convenient,
normal, direction.

The next stage leads to that type of web seen most
familiarly in the ordinary cobweb, spun by the house-
spiders, Tegenaria. Here a silk tube is still present as the
resting-place of the spider and the expansion of the fringe
has been almost confined to its lower edge, which is now
spread out horizontally as a hammock-like sheet. In
favourable situations, as, for instance, between the rafters
of a shed roof, this hammock may reach great lengths. In
its simplest form this type of web is spun by the genus
Coelotes, belonging to the same family, the Agelenidae, as
house-spiders, but living out of doors, in dark, damp
situations under stones. It is seen again in the common
Agelenq labyrinthica, whose gleaming white web is a con-
spicuous ornament to gorse bushes in August ; and it is a
significant fact that the young of Agelena spin their webs
close to the ground, only the adults occupying high situa-
tions in the bushes. \ These webs well illustrate the next
addition, that of threads whose original function was to
support the sheet, being stretched above and below it
among the branches. Flying insects would strike against
these supporting threads and be thrown down on to the
sheet, and now there are many more threads above the sheet
than would really be necessary for support. They make a
valuable addition to the effective area of the web, and it
may be supposed that they have been multiplied for that
purpose.

This indicates a gradual change from the fringe, which
caught the wandering creature, to the hammock and its
superstructure more likely to catch those that fly. The
web is assuming its true function.

The tendency to raise the web to places where flying
insects are more likely to blunder into it can now be under-
stood, but in such situations the tube will have no place.
The Agelenidae retain it, but for most it is too conspicuous

140 THE BIOLOGY OF SPIDERS

and is accordingly abandoned, while the spider itself takes
its position on the underside of the sheet. This common
type of web is spun by the family Linyphiidae. Every
bramble bush shows examples ; the hammock-like sheet
and the inverted position of the spider beneath it make
webs of this family easy to recognise. Numerous spiders
have adopted this type, a fact which is evidence of its success.
Yet it is none the less open to objections. It has to be
spun in conspicuous places, and the closely woven sheet
offers dangerous resistance to the wind.

It seems that two different means have been adopted
to avoid these disadvantages. A sub-family of the Liny-
phiidae has taken the web down again to situations near the
ground. Here among grasses and over depressions in the
soil they spin a sheet with generally but a minimum of
superstructure, and the immense numbers of these small
" money-spiders " is proof that both web and situation are
satisfactory. The alternative is to abandon the sheet, but
to keep the branching threads, with the addition of a small
cup-like retreat to protect and conceal the owner. This is
the web of the family Theridiidae, whose members are very
common in hedges and holly trees in summer. The web
consists merely of an apparently haphazard tangle of
threads, of all lengths and in all directions. It is interesting
to notice that such a maze might well be thought to be the
simplest possible type of web, the starting-point from which
the other designs might have been evolved, as chaos gave
place to order. On this assumption McCook has, indeed,
worked out a partial scheme of evolution of spiders' webs.
But our present train of thought does not support this
view ; the tangle of the Theridiidae is seen to be degenerate
rather than primitive, simplified rather than simple.

The last remaining type of web is the circular orb-web
of the Epeiridae, as beautiful as it is familiar. It is at first
sight impossible to derive this web from any of the others
which have found their natural places in the series, and no
doubt the step which produced the finished product of
to-day was a long one. The difficulty is partly in our own

THE SPIDER'S WEB

141

mind, for the symmetry of the web produces the sub-
conscious idea that the manufacture of such a masterpiece
must be a complex, and even a deliberately skilful process.
It has, however, been shown in Chapter V that the working
of the spider's mind is such as to discount at once any idea
of conscious design or elaboration. It is useless to look
for signs of a higher mentality, and search must be made
elsewhere.

Can there be found any cause for dissatisfaction with the
Linyphiid web ? Surely there can, for in its attempt to
render more or less impenetrable not an area but a space it
is wasteful of silk. Human fishermen are content with a
plane net of two dimensions, and there can be no advantage
to the spider in trying to work in three. It is therefore
necessary to make the apparently surprising assumption
that the evolution of the orb-web was yet another process
of simplification. This view is supported by the following
considerations.

If one of the webs of the Linyphiidae be examined, it
will be seen that many of the superstructural threads are
independent perpendiculars. These were probably put
into place by the usual method of dropping on a thread and
anchoring it at the point of arrest. The Epeiridae use the
same method for placing the outlines of their webs. Is
not the clue to be found here ? The web of the Linyphiidae
was improved by the Theridiidae, who merely omitted the
sheet ; the Epeiridae have made the next step by rearranging
the tangle that was left. To drop a pair of vertical threads
and to pass across from one to the other is, by slight repeti-
tion, to produce a structure that cannot but suggest some
of the radii of the orb- web. If these radii multiplied and
were then cross-connected, a crude form of orb-web might
result, without as yet, of course, any of the conspicuous
symmetry which forms so characteristic a feature of the
orb-web to-day. It may be suggested that the symmetrical
result is produced by the simplest process which covers the
given area uniformly. Simplicity of movement is the
keynote of the spider's method, and is later described.

142 THE BIOLOGY OF SPIDERS

Man is deceived by the beauty and symmetry of the result
into imagining that the web must have been made by
intricate means, such as would, for him, involve much
preparation and practice. The point to be emphasised is
that simplicity of construction has selection-value, and that
beauty is a secondary accompaniment. Many instances of
this may be found elsewhere.

The Making of a Web

The primitive types of web are not so much made as
allowed to grow. A spider like a Segestria or an Amauro-
bius, after choosing its crevice does not immediately set
about lining it and spinning the surrounding fringe, but
during the evening it may be seen to be making a beginning
by surveying its immediate neighbourhood and trailing silk
as it goes. Repetition of this process will soon produce
the web as we see it, but it may be some days before it
reaches an advanced state.

The house-spiders which spin the common cob-web
have not altogether abandoned this rough-and-ready method,
and since they live most contentedly in captivity, their
operations may readily be watched. When a Tegenaria is
first put into a new cage, she devotes some time to explora-
tion, without showing any extreme desire to escape. When
she has found the darkest corner, she settles down into it
and seldom moves again until the evening. During the
first night she produces a passable tube of silk in this corner,
with two or three main threads diverging from it and
attached to distant points on the side of the cage. The
cross- threads between these main lines are few, and indeed,
during the first day, the spider is lucky if she succeeds in
catching anything with this skeleton of a web. Every
evening thereafter the spider repeats the promenade about
its domain. Its long anterior spinnerets diverge from each
other as they actively secrete silk, and the abdomen is
moved from side to side with a peculiar swaying motion.
As a consequence, a criss-cross of threads is laid down all

THE SPIDER'S WEB

over the sheet, and the whole of the web gets thicker and
thicker as long as it is inhabited. The spider can often be
seen adding silk to the sheet while she is trying to catch
an insect. If the web is shaken once or twice by the
insect, while it moves about without being as yet entangled,
the spider usually comes out to investigate. In so doing
she spreads out her spinnerets and starts to broadcast silk.
This might be generously interpreted as actuated by the
idea of so improving the web that the elusive fly will soon
be caught ; but it is better interpreted as a survival of the
dragline habit of the hunting ancestor, evoked by the
action of hunting for promised food.

By these occasional additions of silk the holes which
appear in the web as the result both of accidents and of
normal use are gradually mended. As previously indicated,
the spider's mental powers do not enable it to enter upon
any instinctive process in the middle, so to speak ; and the
operation of putting a patch over a tear would be quite
beyond it. The patching or mending is, however, effected
by this gradual desultory activity to which we have referred.

Spinning the Orb-web

Only in the webs spun by the higher families of spiders
is the operation of spinning carried out in its entirety by a
sustained effort. The process of spinning the orb-web is
one which many have watched, at least in part, and one
which has been several times described. It is one of the
many sights which must be seen to be appreciated, and it
is really impossible to do justice to it in words.

The finished orb-web consists of five essential parts —
the framework of foundation lines, the radial threads, the
viscid spiral, the notched zone, and the hub. In addition
to this there is a temporary non-viscid spiral used as
scaffolding during the spinning, and there is often a thread
which joins the hub to the spider's retreat.

The making of the web begins with the laying of the
foundation lines. Fixing a thread to its starting-point, the

144 THE BIOLOGY OF SPIDERS

spider pays out a horizontal thread to some distant spot,
crawling there with the silk held clear of obstacles by one
of its fourth legs stretched out behind. The spider then
allows itself to drop from the two ends of this line on
threads which are ultimately attached to whatever it may be
that brings the spider to rest. Lastly, the quadrilateral is
completed by taking a thread, fastened to the bottom of
one of the perpendiculars, to the bottom of the other, by
walking round the three sides.

In this description it is assumed that a favourable
situation for laying the first thread has been found. The
spider, however, is often in a position from which it is
impossible to pay out this line by merely crawling. In
these circumstances, the spider makes use of the wind.
Turning its spinnerets upwards, it exudes a droplet of silk,
which the least breeze carries out into a long floating
thread. This thread secures the necessary additional
buoyancy by having a tuft of silk at its far end. While it
is being wafted about the spider holds it up on the claws
of one of its second pair of legs, and thus is able to feel
when the thread comes to anchor on some suitable object.
The framework is now strengthened by the spider, who
travels all round it two or three times, adding a thread on
each journey.

The radii are now added. The first two are stretched
from corner to corner, after which the spider places them
alternately on opposite sides of the centre, and with a truly
wonderful ability makes almost equal angles all round.
When the last radius is fixed to the framework, the spider
returns to the centre and spins a rough spiral of four or
five turns of ordinary thread. This is, of course, spun
from the hub outwards, towards the circumference. Its
purpose is that of a temporary scaffolding, to provide foot-
hold to the spider when fixing the viscid spiral.

When the laying down of this spiral commences, the
spider changes the character of its movements, which,
from being rapid and spasmodic, become slow and deliberate.
It is all but imperturbable, circling on, heedless of noise,

THE SPIDER'S WEB

heedless of winds, or anything save actual disturbance of
itself. The viscous thread is applied to the radii from the
outside, working inwards, forming a nearly perfect loga-
rithmic spiral. As each attachment to a radius is made, the
viscous thread is rapidly stretched by the outside leg of the
fourth pair. This causes the sticky secretion which covers
it in a uniform cylinder to break up and collect, under the
action of surface tension, in a number of equally spaced
drops. The spider can work either clockwise or counter-
clockwise with equal speed and accuracy ; it avoids treading
on the new viscid thread, and as this line approaches each
turn of the scaffolding, the latter is rolled up.

Finally the viscid spiral comes to an end a little way
from the centre. The spider returns to the hub, where
she eats the small silk ball made from the rolled-up
scaffolding, and sometimes converts the centre of the web
into a circle by eating also the cushion formed by the
crossing radii.

The notched zone is added last. It consists of a few
turns of spiral in which the circular thread leaves each
radius slightly below the point at which it arrives. This
gives stability to the central area and provides the spider
with something to stand on.

The entire process of web-spinning is completed in
less than an hour ; and, since the web is often seriously
damaged in the course of a night's chase, it is generally
repeated each suitable evening during a great part of the
spider's life. The same foundation lines are used as long
as circumstances permit.

Geometry of the Orb-web

Fabre, who devotes a chapter to the geometry of the
orb-web, makes little effort, beyond a few speculations, to
decide how the symmetry is obtained. Hingston, however,
has more recently examined with extreme care the methods
by which the spider makes her " measurements " of angles
and distances ; and he has, at each step, confirmed his

146 THE BIOLOGY OF SPIDERS

ideas by direct experiment. In this he has made a very-
real addition to our understanding of the spider's art.

It is worth noticing here that the spider's accuracy,
although of a high order, is not perfect. The finished web
satisfies the eye, but looked at critically, it shows several
places where the arrangement is not absolutely precise.
If corresponding parts of the web be measured, the
asymmetry becomes more obvious. It is asking too much
of the spider to expect mathematical exactness ; Nature
does not concern herself with unnecessary refinements, and
the spider's web is accurate enough for its purpose.

The first problem is the symmetrical disposing of the
radii. The spider, standing at the middle of its web, feels
with its forelegs the radii which have been already laid
down, as if determining their positions. When it finds
too big a space, it starts to fill it up by carrying out another
radius. It runs along the neighbouring radial thread, and
when it reaches the circumference, determines the position
of the new radius by taking a fixed number of steps along
the foundation line. Thus it is putting down a series of
radii separated by angles which are subtended by equal
arcs along the circumference. If the foundation lines were
in the form of a circle, the angles at the centre would be
accurately equal. The foundation lines, however, form a
quadrilateral or a triangle, so that the angles cannot be
exactly equal, but the spider is employing a simple method
of obtaining results which are satisfactory. On occasions,
too, something causes it to modify its usual method to the
extent of attaching the radius to the circumference with a
Y-shaped bifurcation of the thread. This often occurs in
the corners of the original quadrilateral.

The second problem of measurement is the position of
the non-viscid spiral. The spider begins this from near
the hub ; one of its forelegs touches the centre where the
radii cross, and with the length of its own body it measures
off the distance at which the first spiral is to start. There
it applies its spinnerets to a radius, and begins to pay out
the spiral line, rotating about the centre. But this process

THE SPIDER'S WEB

would make a circle, not a spiral ; therefore as the spider
turns round, the foreleg is gradually extended more and
more until, when the first round is completed, the leg can
be drawn in and placed on the spot at which the spiral
began. Further circlings with the foreleg on the inner
spiral turn, and the spinnerets still paying out the thread,
will complete the four or five circles of non- viscid spiral,
each a measured body-length from the turn within.

The third and last problem is the accurate placing of

Fig. 65. — Making an Orb-web.

the viscid spiral. The spider puts down the outermost
ring of this by taking the same number of outward steps
from the last ring of the first spiral before it fixes the viscid
thread in position. In this way the first ring is measured
out all the way round, and all the inner turns of spiral are
" reckoned " from it. At the moment of attaching the
viscid thread with the fourth leg, the spider is feeling with
its first leg the position of the point of attachment of the
outer ring in the segment next in front. Thus, in Fig. 65,

148 THE BIOLOGY OF SPIDERS

the first tarsus is touching the point A when the fourth
tarsus attaches the thread at the point B. This vital feature
of the process of web-spinning is one of Hingston's best
discoveries. It explains the apparently miraculous geometry
of the spider, and it can be tested experimentally. Hingston
himself did this, with the result shown in Fig. 65. The
portion CDE of the spiral was removed, with the result
that the spider, feeling on its next round for the point D,
found instead the point F. It thus attached its thread at
C instead of at G. The alternative method of testing this
explanation is the removal of the tip of the foreleg. When
this was done, the result is a badly made, untidy web.

By these devices, then, the orb- web is completed and
the importance of the fact that it is constructed by an
instinctive process, and not by imitation or learning, has
already been mentioned. The webs which are spun by
immature and very young spiders afford additional proof of
this. Ten minutes' observation of the orb-webs on any
blackberry bush in August will illustrate the point, for the
webs will be found inhabited by spiders of all ages and
sizes, and yet all will be perfect in form and symmetry.
Montgomery has made a particularly careful study of this
fact, as illustrated by the orb-weavers, Epeira sclopetaria
and Epeira marmorea. After an exhaustive comparison of
a number of webs of these two species, he was able to
state that the first webs which the newly-hatched spiderling
spins show all the essential parts of the webs made by the
adults. The adults' webs are bigger when absolute dimen-
sions are compared, but then the spiderling is a very much
smaller animal and its web is relatively quite as efficient.
It catches less, but less is required. The following figures,
given by Montgomery, compare the first and last webs of
Epeira sclopetaria.

The Webs of Young Spiders

First web .
Adult web .

Average number
of radii.

. 15
. 19

Average
diameter.

7*6 cms.
35*6 cms.

THE SPIDER'S WEB

149

The webs spun by the male Epeirid spiders are indis-
tinguishable from those of the females, until the penultimate
moult, when the male webs are of smaller diameter. This
might be expected, for at this age the males are smaller
than their mates. The adult males of most spiders make
no webs, only a nest close to the web of the female.

Divergences from Pattern

The orb-web described in the past few pages might be
called the simple or primary type. A number of modifica-
tions of this pattern are made by members of the very large
family of Epeiridae, and some of these are of interest.

The commonest type of minor divergence from the
standard is found when the situation for the original frame-
work is not altogether favourable. In such circumstances,
the foundation lines often form a triangle instead of a
quadrilateral, and the result is that the hub, where the
radii cross, is much nearer to one side of the space than the
other. If a web were made about such a hub in the ordinary
way, a large proportion of the space would be empty of
spiral and therefore wasted. The spider therefore spins
an asymmetrical web which has more turns of spiral thread
on one side than on the other. It does not add these extra
turns all together at the end or at the beginning of the
spinning of the spiral, but interposes them now and again
by reversing its direction and passing over an arc twice or
more. The question to be answered is — how does the
spider know when to reverse and put an extra thread into
a given arc ? Hingston has observed that it turns on
reaching a radial thread of sufficient length. If the hub is
excentric, it must be supported by radii which are all of
different lengths and therefore of different tensions, the
tension in the short threads being greater than in the long
threads. In other words, short radii are tight, long radii
are slack. It is the spider's perception of a sufficiently
slack radius which induces it to turn. There is perhaps no
better example of the delicacy of the spider's sense of

150 THE BIOLOGY OF SPIDERS

touch than this ability to differentiate between the tensions
of these threads, minute as such differences must be.
There is, however, no doubt that tension is the determining
factor, for when, in Hingston's experiments, he had cut
certain threads and thereby caused some of the radii to
slacken, the spider, as it spun blindly on, reversed at such
points, even though reversal was unnecessary and destroyed
symmetry instead of improving it.

The modification of the orb-web which is oftenest seen
in England, is the sectoral web of the genus Zilla (Fig. 75).
This resembles in every way the ordinary Epeirid web,
save that the spiral thread is missing from two adjacent
segments, leaving a bare radius. At the end of this radius
is the retreat of the spider, who runs along it from its hiding-
place to the centre of the web. The interrupted spiral of
this web is not put in by a series of broken circlings, but
by repeated reversals, the spider spinning clockwise and
counter-clockwise alternately. It is interesting to note, in
this connection, that the radii bounding the bare sector are
longer than their immediate predecessors, and the peculiarity
of the web may have originated from this fact. But the
web is often spun so that the centre is asymmetrically
placed, in which case these radii might not be as long as
many others.

Protection for the Web- Spider

It must often have occurred to naturalists that the
customary position of a spider in the middle of its web is
one in which the creature is continuously exposed to every
enemy with no protection whatever. One must assume
that the risks are not sufficiently great to imperil the
survival of the different species, and in temperate parts of
the world this is probably true. In warmer countries,
however, the case is different. Where the forms of life
are numerous, competition is fiercer and living more
strenuous. It becomes necessary for the web-spider to
adopt some protective device.

H L__l

THE SPIDER'S WEB

Since a large proportion of the study of spiders has
been by European zoologists, these methods of protection
have been naturally neglected. Moreover, some of them
were misunderstood and thought to be methods of strength-
ening the web, though there is no evidence that any spider
ever requires a stronger web than it usually makes.

A recent paper by Hingston, however, describes a
number of protective devices in orb-spiders' webs, all of

Fig. 66. — Web of Uloborus scutifaciens. After Hingston.

which take the form of an addition to the plain web. Some
of these completely hide the spider, others make it so
inconspicuous that it is as well protected as if it were
invisible, others merely deceive the observer by methods of
camouflage, by distracting attention or providing alter-
natives. Many present combinations of two of these
methods.

Complete concealment is the most straightforward.

152 THE BIOLOGY OF SPIDERS

For example, a Tetragnatha, found in the Nikobar Islands,
rolls up a leaf which it attaches to the middle of its large
web. It rests inside the leafy cylinder, completely hidden.
The majority of spiders which seek concealment in this
way make their shield for themselves. The Uloboridae are
a family of spiders which possess a calamistrum and a
cribellum, and spin orb-webs like those of the Epeiridae.
One of their species, Ulobortis scutifaciens, adds a thick silk
mat, interwoven with pieces of debris, to the centre of its
web. Sometimes it is drawn out at one side so as to
stretch from the centre to the edge of the web, sometimes
it reaches right across from top to bottom (Fig. 66). The
spider gets behind the central shield, between the web and
the tree-trunk against which it is usually spun, and is quite
hidden. A similar concealing shield is made by an orb-
weaver found at a height of 15,000 feet on the Tibetan
plateau, and is of interest because it shows that tropical
conditions are not necessarily co-extensive with these
protective schemes.

Another Uloborid spider adds either a well-defined
white strap of silk lying obliquely across the centre of the
web, or two such straps in the form of St. Andrew's cross.
It similarly hides behind the strips of silk.

A Cyclosa from Burmah illustrates an extension of this
mode of concealment. It spins the central shield, and
round it adds a rough spiral of thick silk ribbon. This
spiral has a protective value, for it tends to distract the eye
from the centre, the vital point. We shall see that the
other modes of protection which spiders adopt are all
found acting either by themselves or in combination with
a similar dispersal device.

Cyclosa is a widely distributed genus, and the single
species which inhabits Great Britain illustrates the second
type of protection — that of protection by blending. The
British Cyclosa conica spins the usual orb-web, to which it
adds an accumulation of silk, dry corpses, and other debris
in the form of a band across the web. The band is inter-
rupted in the middle, and in this space the spider sits.

THE SPIDER'S WEB

*53

Several spiders, including both Epeiridae and Uloboridae,
from Asia and also from America, spin similar webs, all
with the addition of a band of fluffy substance diametrically
placed. In all cases there is a central gap into which the
spider exactly fits. In the tropical examples, the spider's
pattern makes it blend so perfectly with the bands that they
seem to be a continuous strip. In Cyclosa conica the
blending is far less perfect, so that the purpose of the

Fig. 67. — Web with dispersing bands. After Hingston.

fluffy strips was not understood, and they were thought to
help in the entanglement of insects. A study of tropical
forms makes it clear that the self-protecting habit has
degenerated where competition is less severe.

These blending ribbons may combine with additional
bands which encircle them, the result being to disperse and
distract the sight. A spider from Burmah spins the two
together as shown in Fig. 67. Another, a Cyclosa, spins a

i54 THE BIOLOGY OF SPIDERS

central mat, and rests upon it, not behind it. It is incon-
spicuous because it blends with the mat, and a spiral of
silk surrounding it assists in concealing it by distracting
the eye.

A degree more subtle than either of the foregoing
methods is the method of confusion, as illustrated in
Fig. 68. In this method the spider is in sight, but owing

Fig. 68. — Web with dispersing zigzags. After Hingston.

to the confusion of threads around it, it is difficult to
distinguish. The example shown has the addition of a
zigzag thread round it which helps matters by dispersing
sight, and others are known in which the central confusing
threads alone are used.

Some of the most beautiful examples of protection show
a combination of blending and confusion. The zigzag
cross spun by Argiope pulchella and several other Indian

THE SPIDER'S WEB

i55

spiders is shown in Fig. 69. In four places, two adjacent
radii are bound with a broad thread of silk, forming an
X-shaped figure. The spider occupies the centre, its legs
grouped in pairs along the arms of the cross, and its body
coloration so assists in the deception that it no longer looks
like a living object. One species, Argiope catenulata, spins
three of these silvery zigzags. Its own cephalothorax is of
the same silvery colour, and on its abdomen three bands of

Fig. 69. — Web of Argiope pulchella. After Hingston.

this colour fall into continuity with the silk bands of the
web. As a result, the spider, strikingly coloured when
seen elsewhere, is almost invisible in the centre of its web.

A type of protection rather different from any of the
foregoing is adopted by spiders who add to their webs
objects which might be mistaken for themselves. Clearly,
if a web holds four apparent spiders, three of which are
dummies or decoys, the real spider has a more than sporting

156 THE BIOLOGY OF SPIDERS

chance of escape from any visiting raider. A Himalayan
Cyclosa has the common habit of swathing its captures in
silk, and these it hangs up one beneath the other in its web.
It exactly resembles one of these parcels itself. So close
is the imitation that it is impossible to distinguish the
spider from its mummied flies by sight alone. Observers,
even when encouraged by a bet, have failed to pick out the
spider from the row.

Other spiders make their decoys in other ways. Thus
Cyclosa centrifaciens makes two heaps of silk and insect-
remains above and below the centre of its web. Each heap
closely resembles the spider itself, as it sits in the web
between them, and it improves the resemblance by spinning
a loose tangle of silk round each heap, imitating the notched
zone round itself

The addition of encircling dispersal bands round a row
of imitative pellets is also known, being found in the web
of a spider in Northern India.

One may conclude that web-spinning has been a
thoroughly successful habit, and that, as such, it has evolved
along various directions. In its last stages, however, it is
open to the objection that it entails too great an exposure
of the web-spinner itself, to meet which there have been
evolved the remarkable protective devices which we have
just described.

CHAPTER VIII

THE SPIDER AND ITS ENVIRONMENT

The problem which continually faces every spider, as well
as every other adult creature, is that of survival. During
extreme youth, the solution of this problem is sometimes
undertaken by the mother, but maternal care is not con-
spicuous among spiders. During immaturity, the survival
of the individual is all that needs to be taken into account,
until later in life there is added the more serious question
of the survival of the race. This comes to mean that the
actions of a spider will in general be directed towards one
of four ends : protecting itself, feeding itself, reproducing
itself, and, less frequently, caring for its young. Let us
consider the first of the aims — that of self-protection.

Apart from the physical conditions of heat and cold,
flood and drought over which the spider has no control,
and of which it seems to take little notice, the spider is
at all times exposed to the attacks of enemies. We shall
conclude this chapter by a special consideration of these
opponents, which include larger animals, to whom the
spider is less than a mouthful, smaller one whose envenomed
sting may pierce nerve-centres and paralyse limbs, and
still smaller ones that insidiously lay their eggs as parasites
upon the spider host. All these enemies have to be avoided,
if possible, and it is this that the spider largely spends its
time in doing. " Life," as Brindley used to say at Cam-
bridge, " is one long struggle to get out of the way."

The spider's solution of the difficulty is in the main a
passive one — that of not being seen, or, if seen, of looking
like something that is not a spider. To achieve this it has
peculiarities of colour and shape.

157

158 THE BIOLOGY OF SPIDERS

The Colours of Spiders

According to their general colouring spiders may be
roughly arranged in four groups.

The arboreal spiders, which live among flowers and
among the alternating light and shadow of the leaves, have
usually a variegated colour pattern. Their relatives, who
live lower in the bushes, are darker. The Linyphiidae, for
example, which hang beneath their hammock webs have
the lower surface of the abdomen dark, and the upper side
marked transversely with bars of black and white. This is
an interesting arrangement, because it reverses the usual
colouring of animals. As is well known, many creatures,
such as birds and fish, are dark above and light below,
thereby acquiring a degree of invisibility against either the
ground beneath them or the sky above. The Linyphiid
spiders retain this by themselves living upside down.

The webs spun close to the ground, in hoof marks and
similar small depressions, are inhabited by a numerous race
of tiny " money-spiders," practically all of which have
black abdomens with no pattern at all. Then, again, the
house-spiders and others that live in tubular webs show a
colour-scheme that may best be described as dusky, while
the spiders that wander in search of their prey are of a
greyish colour which blends well with the ground over
which they hunt. All these varied colour schemes render
the spider inconspicuous in their normal activities, but
there are some instances in which colour plays a more
active part.

There is, for example, a common British wolf-spider,
Trochosa picta, which lives in sandy places and shows a
pattern extremely inconspicuous against its sandy back-
ground. What makes it more interesting is the variation in
the intensity of its colour to match the particular shade of
sand prevalent in its neighbourhood. It is therefore of
interest to inquire whether a colour which is apparently
so vital to the spider that it changes in this way is, in actual
fact, a protection. This has been tested by Bristowe, in a

THE SPIDER AND ITS ENVIRONMENT 159

haunt of the species where it lives in company with two
others, Trochosa terricola and Tarentula barbipes. These
two spiders are not protectively coloured to any great
extent ; and all three are exposed to the attack of wasps,
which store them in cells as food for their grubs. Bristowe
opened some of these cells and classified 35 spiders that
he found inside. Two were Trochosa picta and all but
one of the rest were Trochosa terricola, a fact that proves
in a striking way the value of the coloration.

Colour is also of vital importance to the crab-spiders
which lie in wait among the petals of flowers. None is
more notable in this respect than the species called Misumena
vatia, quite common in many parts of Britain and also
found in America. This spider does not confine itself to
flowers of one colour, but has the power of altering its
colour to suit its surroundings. Almost white specimens
are found in white flowers, yellow specimens in yellow
flowers, and pale green specimens are sometimes to be
found on holly leaves. The ability of this spider to change
its colour has been the subject of several investigations, of
which the most recent are those of Gabritschevsky. He
bred the spiders from the cocoon, feeding them daily on
the fruit-fly Drosophila or larger insects. They were kept
in glass flasks and^ exposed to backgrounds of either white
or yellow paper.^The results of these experiments showed
that only when mature were the spiders sensitive to the
colours of their backgrounds. The white spiders when
transferred to yellow paper assumed a yellow colour in a
time which varied from as little as 24 hours to as much as
20 days. When these yellow spiders were replaced on
white paper, they resumed their white appearance in five
or six days. Their whiteness was due to the transparency
of the hypodermis, which exposed guanin crystals present
in the cells beneath ; the yellow colour was caused by a
yellow fluid which accumulated in some of the superficial
cells/

" There is still another way in which coloration may
assist concealment, and that is by the exhibition of the so-

i6o THE BIOLOGY OF SPIDERS

called flash-colours. These are best shown by certain
tropical tree-frogs, whose general green colour is broken by
patches of vivid red or yellow in the angles of the arms and
legs. The result is that as the frog leaps from branch to
branch, these colours appear momentarily as bright flashes.
As the frog alights and resumes its resting position, the
colours are suddenly eclipsed. The enemy in pursuit,
following the conspicuous flashes, is actually looking a little
ahead of the escaping frog. When the bright colours
unexpectedly vanish, the eye must be brought back in
search for the object, which has now faded into invisibility
against the green leaves. Such a method of escape does
not sound very convincing when thus described in print,
but in reality it is remarkably efficient. It is a most
astonishing experience when human eyes are looking for
the spiders which illustrate the phenomenon.

The best known of these are Tibellus oblongus and its
ally Tibellus maritimus, members of the family of crab-
spiders. In form these spiders are very different from the
majority of their family, for they are long and narrow ;
their colour is pale yellow marked with longitudinal brown
streaks. They haunt sandy grass-grown spots such as
sand-dunes, and when they run among the grass stems
they are conspicuous enough. Then, suddenly, they stop,
crouching along a blade of grass, their legs stretched out
before and behind. In this position their brown marks,
previously so clear, enable them to melt into their back-
ground and become extremely hard to see.

A really better example of the method is seen in the
common British six-eyed spider, Segestria senoculata,
which lives under the bark of fallen trees and in similar
situations. Its abdomen has dark lozenge-shaped marks
on its upper surface, and the femora of the legs have a
bright tawny colour. As the spider runs the bright femora
flash to and fro and catch the eye. When it suddenly
stops, it folds its legs over its cephalothorax with the
femora underneath, and the other joints stretched out
above them. The bright colour of the femora thus suddenly

THE SPIDER AND ITS ENVIRONMENT 161

disappears, the spider apparently vanishes into thin air, and
the closest scrutiny often fails to reveal it for several
minutes. Perhaps the most remarkable feature of this
method of protection is that it is not at all noticeable when
one examines dead spiders in the laboratory. It is only
when one has come up against it in collecting that one
realises that it exists and how efficient it is.

The last way in which colours may be of value to a
spider, apart from the colour patterns which are involved
in mimicry, is as a warning. That is to say, they may be
colours which other creatures have, by past experience,
learnt to associate with a formidable antagonist. Such
warning colours are oftenest yellow and black bands, shown
most familiarly by the common wasps. There are certain
trap-door spiders belonging to the genus Poecilotheria
whose upper surface is dark coloured in the usual way, but
whose sternum and underside are black, slashed with bands
of yellow and white. When the spider is frightened it
rears on its hind-legs, thus exposing its warning colours to
any creature that may be threatening it.

The Shapes of Spiders

It has already been mentioned, in Chapter II, that
many of the shapes of spiders seem to be without much
purpose, although this is probably only another way of
expressing our ignorance of the details of their mode of
life. On the other hand, many of the shapes of spiders'
bodies are of obvious protective value. They give the
spider so close a resemblance to stationary objects in its
neighbourhood that it must be very difficult for other
animals to discover it.

Two instances of protective resemblance have been
mentioned in the last two chapters — the spider Phrynarachne,
which looks like a bird's dropping, and the Cyclosa, which
hangs in its web a row of pellets each exactly like itself.

The African spider, Cladomelea akermani, is another
very good example. It attaches its egg-cocoons to the

1 62

THE BIOLOGY OF SPIDERS

grass, binding several blades together to form a strong
enough support. Here the row of five or six cocoons is a
somewhat conspicuous object, but one which might easily
be taken for the fruit of a shrub. The spider takes up a
position beside the cocoons, and in her usual huddled-up
state is almost indistinguishable from them. Close scrutiny-
is needed to determine which is the spider, and which
her eggs.

Another African spider, Menneus camehis, is equally
well protected. Akerman, who first described the way in
which it uses its web, for some time believed that during
the day the spider dropped from the bushes to a retreat
near the ground. It was only by searching diligently along
each twig that the spider was finally found. It sits close
against the twig, which it grasps with its two pairs of hind
legs, its fore-legs stretched out in front. In this position
it looks like a part of the twig. Its abdomen bears a conical
hump, to which it owes its name, and this, resembling a
thorn or broken twig, adds largely to the deception.

Protective resemblances as close as these, which often
defy men who are searching as carefully as they can and
with a knowledge of what to expect and what to look for,
cannot but be of value to the spider by enabling it to avoid
detection.

Here it may well be pointed out that the concealment
afforded by protective coloration and resemblance is
enhanced by, if indeed it is not mainly dependent on, a
disability of the vertebrate eye. For to the eye of the
observer there is a clear distinction between seeing and
perceiving.

The most familiar instance, which will explain this
distinction, is the puzzle-drawing of one's childhood,
which contained a " hidden " face. At first, even on close
inspection, the face was quite invisible ; but when at last
it was recognised it became for ever after so conspicuous a
feature of the picture that it seemed impossible that it
could ever have been hidden,

The same must surely be true of the spider (or any

THE SPIDER AND ITS ENVIRONMENT 163

other animal) at rest, full in sight but protected by one of
these methods. It is the collector's experience that such a
spider is exceedingly difficult to detect ; but when it has
betrayed itself its outline, its light and shade take on an
altogether new significance and the spider is easily perceived.
Its hope of safety depended on its keeping still so as not to
attract attention.

The whole thing emphasises the distinction between
mind and brain, and may perhaps be due to the imper-
fection of the human eye. We are accustomed to regard
the eye as wonderful, as it is, but that it is not faultless is
also true. It has indeed been said that " it is so inexact
and imperfect that one might almost suppose nature was
trying to keep us from knowing what the world really looks
like."

Mimicry in Spiders

In many other instances, the colours and shape of the
spider give it a degree of resemblance to some other animal,
on which the spider's enemies are not accustomed to prey.
This is the phenomenon of mimicry, which is of wide
occurrence through the animal kingdom. It is most
strikingly shown by butterflies, which include many examples
of models and mimics. The models are conspicuously
coloured insects belonging to the pharmacophagous or
poison-eating group. Because of their habit of feeding on
plants with an unpleasant taste, they acquire an unpalatable
flavour, and are therefore avoided by birds which have
learned to associate their patterns with their nasty taste.
Thus any other butterfly which can resemble this pattern
will have a chance of sharing their immunity. Mimicry is
an extremely specialised form of adaptation to environment,
and in its explanation in the usual terms of natural selection
there are many grave difficulties. With this, however, we
are not at present concerned. The mimicry shown by
spiders is slightly different in kind from that common
among butterflies, since spiders do not mimic one another.

1 64 THE BIOLOGY OF SPIDERS

Instead they mimic other animals — among which are
caterpillars, snails, beetles, and ants.

The spider Ariamnes simulans (Fig. 70) was discovered
in Calcutta in 1880. It has a very remarkable abdomen,
whose posterior end is produced into a long tapering " tail."
Thus the spinnerets seem to occupy a position in the fore-
most quarter of the abdomen. The tail and abdomen are
of a prevailing green colour, with silvery and yellow-brown
marks, and the resemblance of the whole spider to a
caterpillar is very close.

Several spiders are known which mimic snails, in
Ceylon, Borneo, and North America. These spiders cling
to the undersides of leaves with their legs drawn in, and in
this position they are very like small snails, common in

Fig. 70. — Ariamnes simulans.

summer in similar situations. The spider remains im-
movable if the leaf is plucked, behaving as a snail would
do in similar circumstances.

The beetles chiefly mimicked by spiders are the lady-
birds, Coccinellidae, which are known to possess an un-
pleasant taste, and which flaunt vivid colours. These are
closely imitated by several species of spiders belonging to
the genus Paraplectana (Fig. 71) found in the East Indies,
in Brazil, and in other tropical parts. Thus Paraplectana
thorntoni is coral red with black spots, and exactly resembles
a beetle, Chilomenes lunata, common in Natal. In Borneo
the same or a closely related spider mimics the beetle
Caria dilatata.

In addition, there are jumping-spiders of several genera
which mimic little beetles of a squat oval shape. It is

THE SPIDER AND ITS ENVIRONMENT 165

probable, according to Pocock, that this resemblance is one
of general shape and appearance, rather than precise
mimicry of some particular species. All the beetle-
mimicking spiders have short legs and a smooth regular
abdomen which overlaps
the cephalothorax to the
extent of hiding the
pedicle.

A Madagascan spider
has been described with
a curious flattened ab-
domen so shaped and
coloured that the spider
somewhat resembles a
small butterfly. The
likeness, however, is not
very close, and it is
doubtful whether this
ought to be regarded as
a true case of mimicry,
especially since nothing
is at present known of
the spider's habits and
habitat.

Most frequent and
most precise is the mi-
micry of ants, and in
Pocock's well - known
paper on this subject no
fewer than thirty-one
different instances are
mentioned. The general
structure of ants is very different from that of a typical
spider, so that considerable modifications in the spider's
normal form have been needed to produce any degree of
resemblance. Yet this has been done so thoroughly that
in many instances the mimicry is remarkably perfect.

The cephalothorax is constricted in the middle to

Fig. 71. — Beetle-mimicry by spiders.

A, Paraplectana walleri. After Simon.

B, Lysommanes tenuipes. After Pick-
ard- Cambridge.

1 66 THE BIOLOGY OF SPIDERS

imitate the ant's head and thorax, while the sides of the
constriction are often masked by white hairs. The ends of
the cephalothorax and abdomen are pointed, so that they
grade into the pedicle and represent the ant's waist. In a
few cases, even segments of the abdomen may be suggested
by transverse bands of hairs. The legs of ant-like spiders
are slender, and the first pair are frequently held out in
front in imitation of antennae. Yet the resemblance does
not end here. The characteristic activity
and bustle with which the ant runs
about is copied by the spider : it seems
that it is not enough to look like an
ant, there must be a mimicry of an
ant's activity as well.

Only a few British spiders, such as
Micaria scintillans, Micryphantes beatus,
and Linyphia furtiva, show any resem-
blance to the ants among which they
live, but ant-mimicry is much more
common abroad. Ant-like spiders have
been described from North, Tropical,
and South America, from India, Ceylon,
Malaya, and Japan. They include mem-
bers of most of the families of wander-
ing spiders, of the crab-spiders, and
even of the web-spinning families,
Epeiridae, Linyphiidae, and Theri-
diidae. The wolf-spiders seem to be
without ant- like species, but there are
many among the Salticidae or jumping-
spiders. It is to this family that the mimicry is apparently
most valuable. It is found in a few species of many of its
genera, and one genus, Myrmarachne, of nearly a hundred
species, is entirely given up to the mimicry of ants. The
same thing is true of the family Clubionidae, one of whose
genera, Myrmecium, consists entirely of ant-mimicking
species. One species, Myrmecium nigrum, is shown in
Fig. 72. It mimics the ant Pachycondyla villosa. Other

Fig. 72. — Myrme-
cium rufum. An
ant - like spider.
From Simon.

THE SPIDER AND ITS ENVIRONMENT 167

species of the same genus are yellow or red in colour, with
brown or black abdominal stripes, resembling the ant genus
Megalomyrex.

As among butterflies, the two sexes do not necessarily
share the mimetic adaptation. A South African spider
belonging to the family Eresidae, Seothyra schreineri, illus-
trates this. The females and immature males, which live
in burrows in sandy parts of the veldt, are light brown and
grey in colour, harmonising well with their surroundings.
The mature males, which have to roam about, are quite
different in colour, and mimic a vicious ant, Camponotus
fulvopilosiiSy common in the locality.

It is noteworthy that the ants used as models are
frequently those of formidable character. For example,
Myrmarachne providens is an Oriental jumping spider which
mimics the ant Simo rufo-nigra. This ant is a pugnacious
creature, apparently quite fearless. It will attack almost
anything it meets and its bite produces painful effects in
human beings. Mutillidae are ants of similar aggressive
habits, possessed of powerful jaws and frequently mimicked
by spiders in many parts of the world. In Ceylon the
spider Coenoptychus pulchellus is a well-known mimic of
these ants. The spider has a reddish cephalothorax and a
black abdomen, which in the male is marked with six
large white spots, and in the female with four yellow spots.
The male spider mimics the wingless ant, Spilomutilla
eltola, and the female mimics the wingless female of the
ant Mutilla subintrans. So close is the resemblance that at
least two naturalists have recorded the fact that they have
been deceived into picking up the harmless spiders with
the precautions they would properly observe for ants !
Mutillids are also the models for the Epeirid spider, Ildibaha
mutilloides of tropical America : in this species the male alone
is ant-like, the female is protected by a spiny abdomen.

One of the most curious instances of ant-mimicry is
that of an Oriental crab-spider, Amycioca forticeps, which
mimics the tailor-ant Oecophylla smaragdina. The spider is
orange-red in colour, its cephalothorax is high and rounded

1 68 THE BIOLOGY OF SPIDERS

in front but narrowed and prolonged behind. Its abdomen
is narrow and cylindrical, with a median constriction and
narrowed at both ends. The hind portion bears two black
spots. Thus the cephalothorax of the spider resembles
the abdomen of the ant, while the abdomen of the spider
resembles the ant's thorax, head, and eyes. When the
spider escapes by running backwards, as is its usual habit,
it mimics the ant running forwards.

This particular case illustrates another feature to which
parallels are known among butterflies. The term " mimicry
ring " is applied when the same model is mimicked by
several different species, not necessarily members of the
same family. The tailor-ant in question, Oecophylla
smaragdina is mimicked in Singapore by another crab-
spider, Amycioea lineatipes*, in Ceylon by the jumping spider
Myrmarachne plataleoides, as well as by other spiders and
by the larvae of a moth. The Ceylonese mimic, Myrma-
rachne plataleoides, runs forwards in the usual way : the
chelicerae, which are stretched out in front, are swollen
at the ends and bear the black dots which represent the
eyes of the ant.

There is, therefore, no doubt that mimicry is both real
and useful, and constitutes an adaptation which confers
great benefits on those that show it. This is proved by
the fact that ant-like spiders often lay small numbers of
eggs. The mimicry of ants by spiders is mimicry of the
Batesian type, that is to say, it is mimicry of a dangerous
animal by a harmless one, and benefits only the latter.
Among butterflies a second type of mimicry, known as
Mullerian, has been described. In this type two formidable
species resemble each other, with the result that their
natural enemies are educated to associate their appearance
with their dangerous character twice as quickly as if their
appearances were different. Those which are sacrificed in
this education will be shared by the two species, each of
which will lose only half the number they would otherwise
have to give up. Mimicry of this type has not yet been
detected among spiders.

THE SPIDER AND ITS ENVIRONMENT 169

It is of particular interest to note in conclusion that in
this single order of spiders there are found good examples
of protective coloration, protective resemblance and mimicry,
adaptations which are usually illustrated by examples from
widely different types.

Protective Habits

It must not be forgotten that these examples of colora-
tion and mimicry include the exceptional spiders, rather
than the great majority — at the outside a few hundred of
the sixteen thousand known species. The rank and file
are not protected in these ways, and it is only when we study
their habits that we realise that they have evolved methods
of self-protection which may counteract even the dis-
advantage of conspicuous colouring. Probably the most
familiar example of a protective habit, which must tend to
confuse and startle the onlooker and thus protect the
spider, is the way in which garden-spiders shake their
webs. The habit is common to several members of the
family Epeiridae and is shared with the Pholcidae, of which
the curious Pholcus phalangioides is the only representative
in Great Britain. By vigorous contractions of the legs, the
spider causes the whole web to oscillate with great rapidity,
while it becomes itself no more than a blur.

Preening

We are justified in considering as one of these protective
methods any action or habit which tends towards individual
efficiency and proper functioning of the sense organs.
Indeed, we often perform similar actions ourselves. The
habit of preening, which makes for efficiency, is common
among spiders, which are scrupulous in their attention to
personal cleanliness and quite belie the popular notion that
they are dirty. The habit was first described by Dufour,
and is most frequently seen after the spider has finished a
meal. It brushes the spiny tarsal joint of its palpi over the

1 7o

THE BIOLOGY OF SPIDERS

front surface of its chelicerae, continuing to do so for
some moments. It carefully brushes out the angle between
the two joints of the chelicerae, as well as the narrow space
between their two bases, and while it is doing this it is
opening and shutting both parts of the chelicerae and
moving them backwards and forwards.

I believe that the extending of this process to clean up
all parts of the body was first described by myself in 191 6.
After examining the way in which large house-spiders are
able to struggle along the surface of water, I noticed that,
on their return to their cages, they one and all began to
clean and dry themselves. This was a far more elaborate
process than the mere rubbing of the chelicerae, and
included the following operations :

1 . The second and third pairs of legs were pulled slowly
through the space above the lip between the maxillae.
When the tip of the tarsus reached the maxillae it was held
there motionless for some seconds.

2. The palpi were treated in the same way.

3. The first and fourth pair of legs were treated a little
as in 1 , but they were also carefully rubbed with the second
and third legs, which were then immediately drawn through
the maxillae again.

4. The sternum was rubbed by one of the metatarsi.
The separate actions did not take place in an orderly

manner. A little of one was followed by a little of another,
and often 2 and 3 were simultaneous. The spider worked
from limb to limb and from side to side with no particular
sequence. The whole operation took as long as half an
hour.

It is probable that these actions are more than a mere
scraping of the spider's surface. It will be recalled that
the maxillae contain a system of rather mysterious glands,
and the spider's actions lend support to the idea that the
secretion of these glands is used as an ointment for the
external surface of the body. There seems to be very little
doubt of this in the particular instance recently described
by Locket, and considered in Chapter XI.

THE SPIDER AND ITS ENVIRONMENT 171

The importance of this habit of cleaning the body is
emphasised by the existence of a metatarsal comb specialised
for this work, and found on the legs of certain spiders of
the family Drassidae. On the undersides of the metatarsi
of the four posterior legs, close to the tarsi and slightly to
the outside, are two regular transverse rows of ten to twenty
stout hairs (Fig. 73). These may be present in both sexes
and at all ages. Berland has given an
attractive description of his discovery of the
use of the comb. He had caught near Paris
a Zelotes subterraneus , and was about to kill
it, thinking it could teach him no more,
when it suddenly showed him the use of
this " veritable peigne au sens propre du
mot." It brushed different parts of its body,
apparently to burnish the hairs and remove
dirt. The third and fourth legs were used
alternately, and the effects of the combing
were so obvious that one could detect just
where the comb had been applied. This
comb is not found in every species in any
one genus, and it does not seem to be confined to the
Drassidae. What seems to be exactly the same thing is
mentioned and figured in a paper by Pocock on Mygalo-
morph spiders of the Ethiopian region, published in 1897.
It there occurs on the spider Stasimopus oculatus and is
specified as part of the distinction between that species and
Stasimopus rufidens.

\ \

Fig. 73. — Meta-
tarsal Preen-
ing Comb.

Catalepsy

The most generally distributed of these protective
habits and one which is shown by spiders of practically
every family is that already mentioned as the cataleptic
reflex. This is usually described as " shamming dead,"
for several reasons an unfortunate term. In the first place,
the positions assumed are not those of death, and it would
be of little use if they were. As mentioned at the end of

172 THE BIOLOGY OF SPIDERS

this chapter, dead spiders are seldom found in Nature, and
when, in collecting, one does chance upon a spider's corpse,
it is very easily recognised. On the other hand, numberless
small pieces of vegetable debris have to be looked at twice
or more before one can be certain that they are not spiders
in the cataleptic state.

Hunting and wandering spiders are generally induced
to assume the cataleptic pose by a sudden tap in their
neighbourhood, which causes them to draw in their legs,
generally folded over their cephalothorax. Web-spinning
spiders share the habit, and spontaneously drop from their
webs on a thread of silk, an action which is familiar to
most of us, since the commonest garden-spiders show it
very readily. The spider seldom drops to the ground, if it
can avoid doing so. If it passes a leaf on its fall, it usually
checks its descent and creeps beneath the shelter until
danger no longer threatens. It then climbs back to its
web. Some spiders will drop from their webs far more
easily than others. The commonest Linyphiid, Linyphia
triangularis, whose web is to be found on every bush, is a
particularly sensitive subject in this respect. The hand of
the blackberry gatherer may but jar a twig more than a
foot from its web, but down drops the spider into the
prickly sanctuary beneath. A rarer English spider, Theri-
dion lunatum, is, however, even more nervous. Its irregular
webs are easily seen on the branches of trees in the few
localities where it is plentiful, and to catch the spider it is
only necessary to hold the net below and to touch the web
ever so slightly. Down comes the spider without a second's
delay.

W. H. Hudson described one of the prettiest instances
of this habit, as shown by two South American spiders.
These two spiders are found together ; one of them is the
colour of the fresh green leaf, the other yellowish-brown,
like a leaf that has faded and withered. The green spider
falls somewhat quickly, as a green leaf would fall ; the brown
one falls more slowly, as if it were lighter, like a dried leaf !

THE SPIDER AND ITS ENVIRONMENT 173

AUTOTOMY

Another and a very familiar protective device, which
spiders share with many of the lower animals, is that of
casting off a leg. This is usually first encountered in
collecting, for if one grasps, with fingers or forceps, the
leg of an escaping spider, it is not long before that leg
alone is all that remains in one's possession. This autotomy
is closely associated with the spider's power of regeneration,
or the reproduction of lost parts at the time of ecdysis.
Autotomy is therefore more readily shown by immature
spiders, which do not suffer a permanent loss, than by full-
grown ones, which will not moult again. Regeneration is
dealt with in Chapter XII.

It is important to understand that autotomy is quite
distinct from forcibly wrenching off a limb. It is a reflex
action, under the control of the nervous system. This
may be proved by anaesthetising a spider with chloroform
or ether. It may then be picked up by one leg, swung
about and subjected generally to treatment which, in
normal circumstances, would certainly provoke it to cast
the leg. Again, if the spider is held in the fingers by one
leg, it is possible to understand the action better. The
other seven legs strain against one's hand, and the liberation
follows a quite obvious jerk. If one holds the spider by
two legs it seems to be unable to free itself in this way.

There must be some peculiarity of the blood system
associated with the autotomy, or the spider would bleed to
death. In the case of lobsters it is well known that the
breaking point is constant, between the second and third
joints of the limb, and that a special preformed membrane
staunches the flow of blood. There must be something
similar in spiders. The leg is cast from the trochanter,
and no serious loss of blood follows. Indeed it is remark-
able how little inconvenience the spider seems to suffer.
But artificial amputation with scissors at other points in
the leg is evidently a very different matter. Bleeding is
profuse, until the spider puts the cut stump in its mouth.

174 THE BIOLOGY OF SPIDERS

In at least one instance, where the leg was cut through
the middle of the femur and the remnant would not reach
the mouth, I have known death to follow soon after the
amputation.

Myrmecophilous Spiders

Many spiders have been driven by force of circumstance
to adopt a life in close association with ants. In this they
are not peculiar, for ants' nests might well be described as
the caravanserai of the Arthropod world where visitors of
many kinds are frequently in residence. The " Guests of
British Ants " have recently formed the subject of a work
by Donisthorpe, and amongst them spiders take a notable
place. Spiders that associate with ants may be divided
into three groups :

(i) Spiders that always live in ants' nests, where they
are passively tolerated.

(ii) Spiders that hunt and prey on ants and are therefore
found outside and near the nests.

(iii) Spiders which mimic ants and live near their nests.
These groups are not absolutely distinct, for a spider

may belong to two of them, but they broadly indicate the
nature of the relations between the spiders and the ants.

The commonest European spider in the first group is
the little Thyreosthenius biovatus. This spider may be
found at any time and in any place in the nests of the red
ant Formica tufa. Spiders in this group do not feed on
the ants. They use the ants' nest as a shelter and they eat
small insects of various kinds which are also sharing the
same nest. The ants themselves pay no heed to the
spiders. On one occasion an ant was seen to pick up a
spider in its jaws, but it soon dropped it, and the spider
ran away unhurt.

Spiders of the second group are not very numerous.
The commonest British examples are the six-eyed spider
Harpactes hombergii and the pretty little Asagena phalerata.
These spiders may also be found in neighbourhoods not
inhabited by ants.

THE SPIDER AND ITS ENVIRONMENT 175

The group of ant-mimicking spiders has been described
above. As an illustration of the closeness of the mimicry
it may be recorded that on one occasion Donisthorpe
captured the spider Micryphantes beatus in the belief that
it was an ant ; while of an association of the spider Linyphia
furtiva, the workers of the ant Formica sanguinea and the
larvae of a bug, Aludis calcaratus, he writes, " I certainly
did not know which I was bottling.,,

It is well worth remembering that ants' nests are
among the best places to search for rare spiders, and that
many species have been discovered in this way.

Social Spiders

The adoption of a communal life as a means of avoiding
attack must, of necessity, be rare among cannibals such as
spiders ; nevertheless a few instances are known.

Stegodyphus is a genus in the Eresid family. The
Mediterranean members have ordinary habits ; but there
are species of the genus in Africa and elsewhere which live
in societies. Three gregarious species are found south of
the Zambesi — Stegodyphus africanus, a northern type
reaching Mashonaland, Stegodyphus gregartus, found in
Natal and also common in Ceylon and the East Indies, and
Stegodyphus dumicola, which extends from Mashonaland to
Cape Colony.

The society begins as a single cocoon, protected by a
silk chamber about the size of a walnut. When the young
hatch, they gradually enlarge this and at the same time
construct a snare or web above it by merely crawling about
and leaving a network of draglines behind them. These
building operations go on and on unchecked, until the
nest in the middle is as large as a football, and is traversed
by galleries and passages leading from chambers within to
the web above. The web is now many yards in extent and
I may cover a whole tree — the prickly pear is a favourite
j haunt — so that the leaves are scarcely visible. In winter
I the upper web is considerably thickened.

176 THE BIOLOGY OF SPIDERS

The nest includes from forty to one hundred spiders,
and it has been found in some nests that there are seven
times as many males as females. The females do all the
spinning required for the repair of the web and nest ; the
males think of nothing but feeding and courtship, often
interrupting the work of the females with their importunities.
When an insect strikes the web, numbers of spiders hasten
to the spot and join in the capture. When the prey is
killed, the spiders together drag it nearer the nest, though
they take nothing inside. All feed on it together. The
instinct to drag objects from the web to the neighbourhood
of the nest is firmly implanted, and many a piece of useless
rubbish is laboriously carried down. Even drops of water
are picked up and treated in the same way.

Among some species at least, in-breeding appears to be
the general rule. Mating occurs in the web and the eggs
are laid in chambers in the nest. As the younger generation
grow up, the old ones die or go off to found another colony.

Some of these webs harbour a guest in the form of a
small moth, Batrachedra stegodyphobius . The larvae creep
about the web and are, for the most part, unmolested by
the spiders, although they finish up the food which the
spiders have caught. The moths into which they develop
continue to live in the colony, although why they should
do so is still something of a mystery.

Simon has recorded another instance of communal life
in Uloborus republicanns, a spider found in Venezuela and
Cuba. A peculiarity of this society is that the males
generally live all together in one corner of the mass of webs.

The Enemies of Spiders

The natural enemies of spiders fall into three groups.
In the first group come the many animals whose usual
food consists of insects and which do not refuse to eat
spiders when they get the chance. In the second group
come the Ichneumon flies, and in the third the wasps.

Birds are the most active members of the first group.

THE SPIDER AND ITS ENVIRONMENT 177

Warburton has recorded the sight of a hedge-sparrow
" going conscientiously over a trellis- work and picking out
all the spiders from the nooks and corners." In one
recorded instance of the contents of a bird's crop, spiders
were found to compose eight per cent. In addition to this,
spiders' cocoons are often used by birds as lining for their
nests.

This group will also include harvestmen, toads, lizards,
and all the insectivorous mammals, even monkeys, as well
as the spiders themselves, for they often prey on one
another.

The Ichneumonidae, which compose the second group,
are a huge family of Hymenopterous insects which threaten
spiders in two ways. Nearly all ichneumon larvae are
parasites, and the egg of the ichneumon may be laid either
in the spider's cocoon or in the body of the spider itself.

In the former case the egg of the ichneumon hatches
before those of the spider, and the larvae use the spider's
eggs as food. The complex architecture and the hard coat
of grit which characterise some of the cocoons of spiders
are no doubt adaptations which tend to prevent the
ichneumon from successfully placing its egg, but in spite
of these precautions, few cocoons are really ichneumon-
proof, and a large proportion will be found on examination
to be sheltering these parasites. It is probable that many
species of ichneumons in all countries lay their eggs in the
cocoons of spiders.

Other ichneumons lay their eggs on the body of the
spider itself. Members of the web-spinning families seem
to be the victims usually chosen, and it appears that the
spider is demoralised by the approach of the ichneumon
fly and offers no resistance. The egg is placed by the
ovipositor just below the skin on the " shoulder " of the
abdomen, and in time the small larvae hatches and clings
to the same spot. In the summer it is seldom that one
passes a week's collecting without coming across a spider
carrying the burden of the small white " worm." If these
spiders are kept alive in cages they continue their usual

178 THE BIOLOGY OF SPIDERS

habits for some time, but, as has long been known, they do
not cast their cuticle. It may be that the demands of the
parasite prevent the host from increasing in size and so
render moulting unnecessary, or, as is perhaps more
possible, the subtle relation between the two organisms
includes the production of a toxin which prevents moulting.
However this may be, the death of the spider, even in the
presence of food and drink, seems to be unavoidable. The
writer has kept many parasitised spiders and plied them
assiduously with all the food they would take, but never
has he so far succeeded in tilting the equilibrium the other
way and enabling the spider either to get rid of the larva
or to stave off an early death.

Soon after the death of the spider, the ichneumon larva
pupates and its beautiful little cigar-shaped cocoon may be

found in the cage (Fig.
74). The imago appears
about a fortnight later
and, in the circumstances
mentioned above, soon
dies because it can
neither feed nor escape
from the spider's cage.
Social wasps occasionally
use spiders as food for their larvae. They catch the spider,
sting it to death, and carry it to the nest, where it is cut
into pieces and fed to the young.

The solitary or fossorial wasps are, however, the spider's
chief enemies, and it is probable that they are responsible
for a greater number of casualties among spiders than all
other causes taken together.

The family Pompilidae, the largest and most important
of the group, is spread over almost the whole of the world,
and all its members make spiders the chief food for their
larvae. Their custom is to excavate a hole in the earth,
store it with spiders, deposit an egg, and then seal up the
hole. By the exercise of one of the greatest marvels of
instinct, these wasps sting the spiders in the nerve ganglion

Fig. 74. — Cocoon of Ichneumon from
spider's web.

Wasps form the third group.

THE SPIDER AND ITS ENVIRONMENT 179

of the cephalothorax. This prevents the spider from
struggling, which might kill the wasp grub, and also from
decaying, which would render it unfit for food. These
paralysed spiders have been known to live for seven weeks,
during which they were unable to feed or to make any
movement whatever.

Sometimes only a single spider is thus imprisoned, but
sometimes there are many. The wasps show the greatest
energy in attacking even comparatively large spiders.
They try to come upon them unawares, and, grasping a
leg, to jerk them suddenly from their burrows or webs.
Thus thrown down, the spiders seem to offer but a feeble
resistance, and wasps of the South American genus Pepsis
can overcome Eurypelma hentzii, one of the largest known
spiders. Wasps of the family Sphegidae also use spiders
on occasions for the same purpose.

There is little doubt that the protective adaptations
described earlier in this chapter, as well as the great fertility
of some spiders, are largely necessitated by the persecution
which spiders suffer at the hands of wasps. Peckham has
recorded how in a single haystack some six hundred wasps'
cells were constructed in the space of six weeks, and each
cell contained about ten spiders. Some wasps, such as
Sphex cyanea, store twenty to thirty spiders in a cell. A
similar account of the immense slaughter of spiders by
wasps has been written by Hingston.

Another description of a different character has been
given by Montgomery. The wasp Boeus montgomeryi is a
tiny insect, little bigger than the spiders' eggs ; it bores
its way into the cocoon and can be seen, with a microscope,
piercing the eggs with its ovipositor as it crawls about.
Not all the eggs of a cocoon were thus infected, and if
hatching occurred in a closed space, the luckier spiders,
which hatched at about the same time as the wasps, ate
their unwelcome visitors.

i8o THE BIOLOGY OF SPIDERS

Longevity

After this consideration of the enemies of spiders,
which almost make us wonder how any spider ever survives
at all, it becomes of interest to inquire what age spiders
are capable of attaining. Such an inquiry has, as a matter
of fact, very little biological significance, since death from
old age is practically unknown in Nature. The normal end
to the life of an animal does not come as a climax to that
gradual slowing of all the body's functions which men call
ageing ; it comes when first the creature fails to get out of
the way. Such a death we are accustomed to call violent,
but, biologically speaking, it is natural and usual.

None the less the interest remains, for if the survival of
the individual is due to a succession of escapes from death,
Chance may occasionally permit these escapes to continue.

The majority of spiders are hatched in the autumn or
spring, mature during the spring or autumn following, and
die in the winter. They are creatures of a single season,
whose life-work is done when they have spun their egg-
cocoon. Some, however, survive the winter by " hiber-
nating " in hidden silk-lined cells. Blackwall many years
ago showed that the six-eyed spider Segestria senoculata
can live four years, and Fab re has given reasons for believing
that the wolf-spider Lycosa narbonnensis reaches the age of
five.

More recently the deaths have been recorded of two
house-spiders, Tegenaria derhamii, which had been kept
and fed by Dr. Oliver of Bradford. One of these had been
in his care for five, and the other for seven years. We may
take these as quite exceptional ; probably five years is the
limit for all those spiders that survive more than a single
season.

^ >

CHAPTER IX

THE DISTRIBUTION OF SPIDERS

The study of the present-day distribution of any group of
animals is always of interest and importance, for the facts
of distribution shed light upon the past history and evolution
of the group.

The extent to which a race has spread over the surface
of the earth must clearly be dependent in no small degree
upon the methods of dispersal of which it has been able to
avail itself. Thus flight, or a power of sustained travel on
foot, or an ability to remain alive in crevices of floating
logs, may all play a part in carrying different types away
from their centres of origin.

It is obvious that in the spread of the race of spiders the
well-known gossamer habit must have played a prominent
part.

Gossamer

Gossamer- making is not only well known, but universally
attractive. Be the spider, in popular esteem, never so
dirty, cruel, or blood-thirsty, there is nothing but admira-
tion, and even poetic praise, for the small aeronaut.

We have already tried to trace the origin of much of
the spider's spinning-work from the habit of leaving a
dragline behind it, and it seems not unreasonable to
imagine that the use of a single thread for aerial migration
arose from the same beginnings. The spiderling to-day is,
as we have seen already, different from its elders in being
positively heliotropic and negatively geotropic for a fleeting
period of its young life. Almost as soon as it is free from

181

1 82 THE BIOLOGY OF SPIDERS

the cocoon it must guard against overcrowding and conse-
quent fratricide, and it avoids these calamities by its
obedience to the instinct of dispersal.

Its first impulse is, therefore, to climb as high as possible
on the plants or other objects about it. When it has
reached the top, it turns its head to the breeze and raises
its abdomen. The spinnerets secrete a drop of silk which
the slightest breath of air will draw out into a thread, or
sometimes into two diverging threads. There is no doubt
that movements of the air, even those too slight to be
noticeable to ourselves, act on the silk droplet in this way,
for it has been found that spiders, unable to set sail in a
room in which door and windows were closed, will imme-
diately do so on the admittance of a slight draught. When
the streamer is pulling with a sufficient buoyancy, the
spider lets go with all its eight legs at once and launches
forth on a voyage which may carry it yards — or miles.

The most remarkable feature of this process is its swift-
ness. It sounds, when described, as though it were a
matter of climbing, turning, spinning, and waiting, whereas
in actual fact it is often far otherwise. It is one of the
many surprises of spider-study to have a small spider run
up one's finger and apparently run straight on into the air.
The turning, spinning, and setting forth may be, in certain
circumstances, all but simultaneous.

There are two particular instances of gossamer spiders
in well-known literature, which are often quoted, and
which happen to illustrate two important features of this
method of dispersal.

The first is Darwin's record of their arrival on the
Beagle when sixty miles from land. We have mentioned
this already in a former chapter : it is of interest as illus-
trating the great distances to which migrating spiders may
sometimes be carried. McCook records another occasion,
in which the ship upon which the spiders embarked was
upwards of two hundred miles from land, and the little
creatures, after a short rest, set sail again.

Both Captain Scott's Antarctic expeditions, in the

DISTRIBUTION

183

Discovery and the Terra Nova, visited the remarkable
island of South Trinidad, and made collections of spiders
there. The island lies in the course of the south-east trade
winds, about lat. 200 S. and long. 290 W., and there is
little doubt that it has received its spider population
by gossamer migrants coming from great distances. The
spiders which frequent mountains, where they often reach
very considerable altitudes, have usually made the ascent
in a similar way.

The second instance is that described by Gilbert White,
in Letter LXV from Selborne. A prodigious shower of
flakes of silky web fell all day (September 21, 1741) over
an area which was, at the least, a triangle with sides some
eight miles in length.

So great a quantity of gossamer is not a common occur-
rence in England, and is really a different phenomenon
from the ordinary migrations. In parts of America, how-
ever, it is said to be an annual occurrence. It is probably
associated with unusual weather conditions, which in this
particular instance White describes as " cloudless, calm,
serene, and worthy of the South of France itself." This,
in the first place, provokes a general awakening into activity
of all the small spiders hiding and resting near the ground,
and, secondly, raises a convection current of warm air. In
these circumstances, the spiders are constantly producing
webs and threads among the grass, and these threads are as
constantly wafted away by the upward currents. Many of
these threads get tangled and crossed with others, so that
much of the floating silk consists of flakes or rags, rather
than the single threads of migration. White describes
some as nearly an inch broad, and five or sjx inches long.
But only a small proportion of these floating webs are
inhabited by spiders, and it is probably quite incorrect to
regard the days on which these phenomenal showers occur
as days of great migration. They are certainly days of great
activity among spiders, for it is invariably true that much
gossamer in the air is accompanied by much business
among spiders on the ground. Gilbert White's settlers had

1 84 THE BIOLOGY OF SPIDERS

constantly to " lie down and scrape the incumbrances from
their faces with their forefeet." The fact is that both the
awakening of the spider populace and the floating of their
silk into the air are prompted by the peculiar state of the
weather, but the frequent entanglement of the threads
prevents many aeronauts from making a successful start.

It is a rather common belief that the spiders whose
migration threads are seen floating across the fields in
spring and autumn belong to one species — the " gossamer
spider " — or at least to one family, whose members have
made a speciality of the habit. This is not so. It is, how-
ever, generally true that the habit is confined to spiders
which do not avoid the light and the warmth of the sun —
that is to say, to the web-spinning, the hunting, and the
jumping families. The spiders which wander about at
night, which live in burrows, and which hide themselves
away under stones, do not, as a rule, practise the habit to
any great extent.

The necessary result is, therefore, that the light-loving
spiders are very widely spread over almost the entire globe.
Their distribution is much more nearly that of a creature
able to fly than that of a terrestrial animal, as a spider
must properly be considered. When, however, we look a
little more closely at the distribution of these ubiquitous
spiders, we discover facts of great interest, not free from
difficulty. They show how much is still to be discovered
about the conditions of existence among invertebrates.

Spiders* Stations

The statement that spiders may be found everywhere
is true in a general sense, but it is not always the same
spider !

Malacologists have long been familiar with this distinc-
tion. Many species may be represented over a certain
area, yet each is to be found in its own particular station.
A given species may perhaps be confined to a few square
yards, within which it is abundant, while it is useless to

DISTRIBUTION

look for it elsewhere. Seekers after spiders meet with
exactly the same state of affairs.

In most localities in England, about a hundred species
of spiders can be found without much difficulty in a season
or two. Several of the commoner species are found in the
sheds and stables at home, and occur again, but with
striking additions, in the conservatory and greenhouses.
Running in the open fields are many wolf-spiders, but to
complete the survey of this family alone, the banks of

Fig. 75.— Web of Zilla.

rivers and streams, the sandhills and the seashore must also
be searched. An entirely different bag is the reward of
beating and sweeping the hedges and lower branches of
trees. A multitude of the smaller fry are taken by sifting
dead leaves, pine-needles, moss, and grass roots. Quarries
harbour others, heather conceals many seldom seen else-
where, others again are hiding beneath the bark of trees.
Many of the rarest are found under stones loosely bedded
in the earth ; one species, and only one, lives in fresh
water, a few are guests in the nests of ants, and finally,

1 86 THE BIOLOGY OF SPIDERS

there are some spiders that do not live much below the
thousand-foot contour.

All this may be familiar, but its significance begins to
appear when the distribution of the different families
among the diverse habitats is realised. Let us take a few
examples to illustrate this big subject.

The genus Zilla, which spins an orb -web with one
isolated radius (Fig. 75), is represented in Great Britain by
three species, one of which, Zilla stroemii, is rare, while
the other two, Zilla atrica and Zilla x-notata, are exceedingly
common, being both numerous and widely distributed.
These two species are so closely allied that the separation
of the two females, lying on the laboratory bench, is a
matter demanding the greatest care. But in collecting
them it is found that Zilla atrica is taken out of doors,
from bushes and shrubs, while Zilla x-notata lives in the
angles of doorways and window-frames, both inside and
outside the house, but never far removed from buildings.
It is quite hopeless to look for either of these spiders in
the place occupied by the other, and the problem under
discussion is emphasised by the very close structural
resemblance between the two species.

Choice of Environment

Two hypotheses might be framed to explain the facts :
either that there is no connection between structure and
environment, or that each spider receives from the station
it adopts, and would lack in the one it abandons, some
advantage in the struggle for existence. The former
hypothesis is clearly untenable, for its acceptance would
practically amount to a denial of the adaptation of the
organism to the environment. If this were so, every spider,
and indeed every animal, could live everywhere.

We are therefore driven to assume that each of these
two closely allied spiders must receive from the environ-
ment it has chosen some benefit which the other has not.
This benefit must be such that it is not appreciated by a

DISTRIBUTION

structural difference, for such differences do not exist, or,
if they do exist, are not yet recognised.

The alternative interpretation is that the environmental
differences may be correlated with differences in habits.
This is quite conceivable. It may be that it is a difference
in activities, or in response to external change, that confines
the two species to their separated spheres. The hypothesis
is capable of being tested by a sufficiently intensive study
and comparison of the habits of the two species, a study
which would be almost sure to yield interesting results.
Although it is impossible to suggest a lack of connection
between habits and structure, it is none the less possible
that the reactions of two spiders might diverge without
producing a corresponding and obvious difference in their
structure.

The relationship between the spider and its environment
is threefold, inasmuch as the latter provides the former
with (i) food and water ; (ii) concealment from enemies ;
(iii) warmth and shelter. If we apply these considerations
to the case of the two Zillas, we can easily rule the first two
out of court. For, as has been noted in an earlier chapter,
a spider will feed upon anything that it can catch. To
suggest, as some have done, that the distinction is due to
each spider's habit of specialising in some particular brand
of fly, shows unfamiliarity with the ways of spiders. Both
environments, too, supply all the concealment necessary,
for the spider rests in a silk retreat of its own making,
which may be under a leaf or in the window-corner. From
any of these points of view, therefore, it is exceedingly
difficult to see why a window-frame should be better than
a bush.

Influence of Temperature

The very obvious suggestion that Zilla x-notata requires
a higher temperature for its comfort is negatived by the
fact that it as often spins outside the window as inside, and
as often in unwarmed sheds as in our houses. Yet the

1 88 THE BIOLOGY OF SPIDERS

actual temperature may not have so great an influence as
the variations to which it is liable.

Exposure to winds and to changes in humidity must be
much more severe on the bushes than in the comparative
shelter of the side of a house, and the range of temperature,
or difference between the daily maximum and nightly
minimum, is well known to be very much less in the former
situation.

It may be assumed, then, that spiders are very sensitive
to changes in the physical conditions of their environment,
that there is an optimum, from which any departure is
most unwelcome. The malacologist would say the same
in explanation of the distribution of molluscs on the shore.

There is ample support for the belief that change in the
physical conditions is more potent than the actual con-
dition itself. The occurrence of spiders on mountains
affords convincing evidence. We know, too, that com-
paratively small changes in concentration of hydrogen ions
in a fresh-water pond produce remarkable and seemingly
disproportionate changes in the animal and plant life.

Response to Physical Changes

Experience in collecting spiders tells the same story, for
many species are localised within exceedingly narrow
boundaries. It can only be sensitiveness to change in the
physical condition which is responsible for such confined
stations.

For example, in a large wood near Malvern, where
the writer often collects, the beautiful Epeira pyramidaia
(Fig. 76) is to be found. At the right time of year a couple
of dozen may be seen in half an hour — all within a space of
a hundred yards. Here the spider is abundant, yet nowhere
else in the country round and nowhere else in the same wood
has a single specimen ever been seen.

A very striking instance is reported from Litchfield by
Carr. The spider Agyneta ramosa is common under a
clump of bushes a few square yards in extent : it has

DISTRIBUTION

189

never yet been found elsewhere in the whole world, not
even under the apparently similar clumps which are
plentiful in the immediate neighbourhood.

The sudden disappearance of spiders from a haunt
confirms what may perhaps be called the individuality of
distribution. Many jumping-spiders, for example, are but
fleeting inhabitants of their neighbourhood. It is possible
to find ten or twelve individuals within an hour at a place
where, a week later, a day's search may be quite unrewarded.

Our belief is, then, that although some spiders are
ubiquitous, there are many others which react strongly to
change in the physical environment.
This must imply susceptibility of
internal organisation and need not
necessarily be expressed in marked
external features. It is, therefore,
possible to find, within the limits of
a single genus, such striking differ-
ences as that of the two Zillas con-
sidered above. These two stand at
extremes of the scale and it is only
reasonable to look for instances where
a gradation of habits occurs — show-
ing us, perhaps, the steps by which
the process has come about. It is
very easy to find examples which
illustrate this.

Four species of the genus Tegenaria are common in
Great Britain, occurring in the situations mentioned
below :

Fig. 76. — Epeira pyra-
midata. The abdomen
is bright yellow with
brown marks.

1. Tegenaria derhamii. Nearly always indoors.

2. Tegenaria parietina. Usually indoors, sometimes
outside.

3. Tegenaria atrica. Sometimes indoors, very often
outside.

4. Tegenaria silvestris. Nearly always outside.

There are here, therefore, what may be described as

190 THE BIOLOGY OF SPIDERS

four consecutive terms of a series, an illustration of a
gradual transition from an outdoor life of comparative
variability to an indoor life of comparative constancy of
physical conditions.

Another example is provided by the genus Lycosa of
the wolf-spiders, eighteen of which are found in Britain.
Eight of these are widely distributed, and of these eight
only one is arboreal and is always to be found on the
branches of trees or shrubs ; one is riparian, living among
river shingle, and one is sylvan, and prefers the shade of
the woods.

The fact is that the system of classification which we
use stresses architectural similarity which is only an
external, and therefore a partial, expression of the relations
between species. Thus they may conceal differences in
the manner of life which are essential characteristics of the
animal as a living organism.

We have to realise that while we can perceive these
structural details, we remain ignorant of their active utility.
As mammals, we are provided with a regulating system
which tends to stabilise our internal environment and make
us in some measure indifferent to external change. We
have only begun to realise that, for the cold-blooded
invertebrate, changes in temperature, alkalinity, humidity,
and electrical state may have a very different significance.

Ritter has lately pointed out that what is truly charac-
teristic of a species is the way it behaves. This exceedingly
significant statement exactly summarises the foregoing
considerations of the relation between the spider and its
environment. We may look upon it, as an analogy, by
comparing the life of a spider in its environment to the
turning of a key in its lock. Each ward of the lock represents
a physical condition, temperature, humidity, wind velocity,
and so on. If a ward is altered, the key no longer turns ;
and similarly if a condition changes, a species no longer
inhabits a particular environment, or at least will not be
able to do so as successfully as before. But clearly, a
variety of the species might be better able to survive under

DISTRIBUTION

191

the changed conditions, and here is the raw material for
producing a step in the evolution of the spider-race.

Geographical Distribution

Let us pass from the parochial to the continental dis-
tribution— the geography of spiders. This subject may be
looked at in two differing yet complementary ways, by
considering either the localities favoured by the species of
certain distinct groups or the spider population of different
types of environment.

It is only in a comparatively small number of cases
that the distribution of any group has been worked out in
detail. Chief among these stands out the sub-order
Mygalomorphae, the subject of a masterly paper by Pocock.
Trap- door spiders lend themselves particularly well to the
study of distribution, for they seldom migrate on gossamer-
threads. Many of their newly-hatched young are as heavy
as the adults of most other spiders and are too big for this
mode of transport.

Pocock points out that in very early Tertiary times the
primitive trap-door spiders arose in Eastern Asia and
spread thence in four directions :

1. South-east to Australia and New Zealand, where a
very primitive type, Hexathele, still survives. The ancestor
of its near ally, Scotinoecus, crossed from here to South
America.

2. South-west to India, Madagascar, and tropical
Africa ; from here to South America.

3. North-west to the Mediterranean.

4. North-east to North America.

The later forms have arisen from these four centres and
spread all over the world, except into the cold northern
region. The only genus reaching temperate climates is
Atypus, the representative found along the south coast of
England and Wales.

The chief peculiarity of the distribution of existing
Mygalomorphae is the persistence of a distinct Mediter-

iQ2 THE BIOLOGY OF SPIDERS

ranean region, north of the Ethiopian and south of the
great mountain ranges of Europe. In 1903 twenty- two
genera were known from this region, more than half of
them being peculiar to it.

The Distribution of Liphistiomorphae

These results are in striking contrast to the distribution
of the sub-order Liphistiomorphae, which in Tertiary
times was the dominant type of spider throughout the world.
To-day these spiders have no survivors in America, North
or South. The small number of species which have
managed to persist are almost entirely confined to Penang
and Sumatra, and, since their unusual form would attract
the attention of any naturalist, it is most probable that they
occur nowhere else. This surprising fact suggests that in
the East Indies alone of the habitable world, Liphistius and
its allies have found an environment in which they could
persist unchanged for geological ages. It is quite in
accordance with this that Sumatran fauna is very distinct
from that of Java, across the narrow Straits of Sunda. For
example, a species of elephant found in Sumatra does not
occur in Java, while an ape, one of the Gibbons (Siamanga
syndactyld), is peculiar to that island.

The Distribution of Arachnomorphae

The sub-order Arachnomorphae is too widely spread
to yield valuable results when taken as a whole. The
Peckhams published, about twenty years ago, a table show-
ing the distribution of the families of spiders among the
six regions defined by Alfred Russel Wallace — Ethiopian,
Oriental, Palaearctic, Australian, Nearactic, and Neo-
tropical. Nineteen of the 35 Arachnomorph families then
recognised are represented in all of these regions. At the
other extreme are five families represented in but one
region only — Psechridae in the Oriental, Hadrotarsidae in
the Australian, Platoridae and Senoculidae in the Neo-

DISTRIBUTION

i93

tropical, and Ammoxenidae in the Ethiopian. The explana-
tion of this is probably similar to that given for the Liphistio-
morphae. The number of genera from the widespread
families having a discontinuous distribution forms an
extremely small proportion of the whole, and may well be
supposed to be the survivors of a more general type whose
intermediate species have become extinct.

Spiders on Mountains

The adaptability of spiders, combined with that in-
surgence which characterises all living creatures, explains
their representation in all situations except in the depths
of the sea. We may select for short considerations the
following four localities :

1. Mountains.

2. The Polar Regions.

3. Oceanic Islands.

4. The Sea-shore.

Of special interest are the spiders which are found at
great altitudes, for they have not only reached places which
the majority of their kind never attain, but they have also
to withstand exposure to temperatures and winds which
never affect their relatives in the plain. It is therefore
unfortunate that few mountaineers are arachnologists, and
few arachnologists mountaineers.

Prominent among the exceptions is Dr. Jackson, who
has collected many rare species from the mountains of
both Wales and Scotland. The main characteristic, which
seems to be shared by all the British mountain species, is
small size. Nearly all of them belong to the family Liny-
phiidae. Their habitat is generally one that will afford as
much protection as is possible in the circumstances, and
their usual dwelling-place is under a stone, almost embedded
in the earth.

A number of related species of spiders have been
collected from the mountains of central Europe, and

194 THE BIOLOGY OF SPIDERS

recently attention has been directed to the subject by the
discovery of spiders on Mount Everest itself.

Far above the highest plant, which grew at an altitude
of 18,000 feet, small black spiders belonging to the family
of jumping-spiders were found, hopping among the rocks
and hiding under the stones in such places as were swept
bare of snow by the wind. They reached a height of
22,000 feet, at which altitude they were not only in the
proud position of being the highest permanent inhabitants
of the earth, but seemed to be alone in their isolation. No
other living thing has been found to share their loneliness.
There is nothing but rock, snow, and ice. What they get
to feed on is a mystery.

Some very interesting observations made by Hingston
on Mount Everest in 1924 throw light on the conditions
in which these spiders have to live. He compared the
temperature of the air with that under a stone at a height
of 17,000 feet on 2 1 st May. The results were :

Under stone. In air.

Maximum temp. . 39° F. 56° F.

Minimum temp. . . 27° F. 12° F.

Range of temp. . . 12° F. 44° F.

This shows that by seeking the shelter afforded by a stone,
the spider obtains far more uniform conditions than it
would experience elsewhere. It is also important to
realise that the temperature of the air does not vary nearly
as much as that of the surface of the sand in exposed
places. This is shown by a set of observations taken at
the Base Camp at 16,500 feet on 20th May.

Temp, of sand. Temp, of air.

Maximum temp. . . 960 F. 55° F.

Minimum temp. . . 20 F. n° F.

Range of temp. . . 940 F. 44° F.

It is clear that the spiders are seeking the most uniform
set of conditions available. They may be found in April,
dormant inside small snail shells, but it is noteworthy that
as summer comes they are among the first to shake off their
winter's sleep and may be seen running about on the
moist earth at the very edge of the retreating snows.

DISTRIBUTION

195

Spiders of the Polar Regions

The hardy spiders from great heights naturally suggest
comparison with those from the polar regions where
conditions are of somewhat the same degree of severity.

No spider has yet been found in the Antarctic Continent.
A trawl, recorded in Scott's Last Expedition (vol. ii,
p. 94), was made by Capt. Campbell off Cape Adare, and is
reported to have yielded " one sea-louse, one sea-slug, and
one spider," but this must refer to one of the Pycnogonids,
which are often called sea-spiders.

From the sub-antarctic islands, however, a number of
very interesting spiders have been recorded. The islands
of Macquarie, Auckland, Snares, Camp-
bell, and Bounty lie between latitudes
470 S. and 540 S., and may be supposed / 0 0 \ A
to represent the remains of an ancient
connection between South America,
Australia, and South Africa. The
present distribution of other animals

suggests very strongly that such a con- — ,. .

nection must have existed in the past ; I o • • o j 5
hence the value of a study of all the q 0
fauna of these islands.

All of these sub-antarctic spiders Fl% ?7- ~ Antarctic

. 1 . Eye-Pattern. A,

resemble the mountain species in being Myro hamiltoni. B,
of comparatively small size, simple ^^^O^mmosos'
form, and sober colours. The bright
hues and highly evolved bodies, common in the hotter
lands where food is plentiful, are altogether lacking.

Orb-spinners, wolf-spiders, and jumping-spiders, which
are found all over the world, are represented among the
sub-antarctic species, but in addition to this a single group,
the Cyboeeae, of the house-spider family, Agelenidae,
stands out pre-eminently as definitely Antarctic. A quite
disproportionate number of the island spiders belong to
this group, which is represented over the whole distance
between South America and South Africa. There seems

i96 THE BIOLOGY OF SPIDERS

also to be an Antarctic eye-pattern. In northern and
tropical forms it is rare to find the direct eyes smaller than
the first indirect eyes, but such an arrangement (Fig. 77) is
comparatively common in spiders of more than one family
from the far south.

The Arctic regions are in every way different from the
Antarctic. For the South Polar Continent is a land mass,
mostly of great altitude, isolated from the rest of the world
by immense stretches of storm-swept ocean, while in the
north there is no continent, only a frozen sea-basin, almost
surrounded by land. The conditions at corresponding
latitudes are therefore far less severe in the north than in
the south, and the pole- ward spread of animal life is there-
fore greatly facilitated.

Thus, within the Arctic circle are lands of comparative
fertility, supporting the Esquimaux and the Samoyeds,
with their herds, and producing flowering plants. In these
circumstances it is not surprising that Arctic spiders are
plentiful and have long been known.

Thorell had described spiders from Siberia and north
Norway more than sixty years ago. Most of the Arctic
expeditions from those that sought the North-West Passage
to the recent parties of scientists who set out from Oxford,
have brought back collections of spiders.

The predominant Arctic type belongs to the Liny-
phiidae, the same family of midgets as that represented on
the highest mountains of Britain. Many other families,
however, include Arctic representatives — there are, for
example, about a score of Arctic jumping-spiders. This is
not surprising, since access to Arctic regions is com-
paratively easy. All share the general features which we
have already seen to characterise the spiders of a cold
environment — small size, simple form, and sober colour.

Spiders of Oceanic Islands

The spiders of oceanic islands form two groups. These
are the endemic or original inhabitants and the later

DISTRIBUTION

197

immigrants ; and nearly every island includes both
kinds.

Madeira is probably the oceanic island whose spider
fauna is best known. In 1892 Warburton compiled a list
of 64 species known from the Madeiras, over half of which
were taken to be endemic. Most of the rest probably
arrived on gossamer threads, and some, such as Argiope
trifasciata and Pholcus phalangioides , were probably intro-
duced by man. A few may have made the journey on
floating objects.

Some spiders of the Falkland Islands and of the Monte-
bello Islands have been described by Hogg. In both
instances a big proportion of the collection consisted of
members of the orb- weaving family Epeiridae, which is
spread throughout the world, and most of the remainder
belonged to families whose members are well known to be
conveyed by wind. It is thus clear that spiders are not
suitable subjects for providing evidence as to the past
history of oceanic islands.

Spiders of the Sea-shore

The littoral region, so prolific in other forms of life, is
only rarely inhabited by spiders ; but the spiders which
are found there are, necessarily, of great interest.

The first to be discovered was Desis martensi, found by
Dr. Martens at Singapore in 1861. He described its habit
of concealing itself in a retreat impermeable to water at
high tide, and of coming out at low water to hunt Isopods
and other small creatures.

In 1877 a fuller account was given by Pi ckard- Cambridge
of an allied species, Desis {Robsonia) marina, caught in the
tidal pools off Cape Campbell, New Zealand. The rocks
of Cape Campbell are full of holes bored by molluscs, and
in these the spiders make their retreats and spin their
cocoons of eggs. They close the mouth of the hole with a
web, which is water-tight, the rocks being covered by the
sea at high tide. The spider swims in the water of the pool,

198 THE BIOLOGY OF SPIDERS

just as our English water-spider swims in ponds, and there
catches its food, which consists of small fish and crustaceans.
The original account says : " When a small fish is placed
in a bottle of water with one of these spiders, the latter will
attack it at once, driving its long sharp fangs into the fish
near the head, and killing it instantly."

Since 1877 s^x otner species of the same genus have
been discovered from Samoa, Victoria, and South Africa.
The distribution of this genus is of particular interest,
because its restriction to the shores of Africa, Australia, and
Eastern Asia furnishes another example of the similarity
between the fauna of the Australian and Ethiopian regions,
and supplies another item of evidence in favour of a former
land connection between the two continents.

Three of these remaining species are worth noticing :
the first, Desis Kenyonae, of Victoria, has a blue abdomen
and a red cephalothorax — an unusual selection of colours ;
the second, Desis tubicola, lives deep down in rocky holes
or in the calcareous masses made by a marine worm
Tubicola. It is a soft and delicate creature, unable to dive
and unable to live long in a dry box. How it survives
among the breaking waves or how it feeds is a mystery.
The third, Desis crosslandi, is a species from Zanzibar.
As a rule the African forms are somewhat distinct from the
Malayan, and the Australian ones are intermediate, but this
species is of the Malayan type. This would imply that
north-east Africa got its species of Desis from the same
source as Malay, and that the southern forms are the
results of a later modification.

The family Agelenidae, to which Desis belongs, con-
tains some other semi-marine species, such as Muizenbergia
abrahami of Muizenberg, South Africa, and Desidiopsis
racovitzai of the Mediterranean. But the other families
are not without their littoral representatives.

In 1894 a semi-marine spider was discovered in England,
and described under the name Lycosa purbeckensis. It
belongs to the family of wolf-spiders, and quite lately
Bristowe has described its habits. The spider has been

DISTRIBUTION

199

found at several places on our coasts, where it lives among
the plants that grow between the tide marks. At low tide
it hunts for food — any of the insects or other small creatures
which abound in such haunts. As the tide rises, the
spiders crawl down the stems of plants, carrying with them
a bubble of air, entangled in the long hairs with which
they are covered. At the roots, they rest in security.
Experiment has shown that the air which accompanies
them will last for quite ten hours. Although they can run
on the surface, they seldom do so, being more comfortable
below it. They are, however, unable to dive, but must
crawl down stems of plants if they are to break the water
surface.

It is a far cry from the Lycosidae to the tiny black
Linyphiidae, yet, different as are the habits of typical
members of the two families, there are a few of these
midgets that live in the same littoral region. Bristowe
noticed three of them in the Isle of Wight accompanying
his wolf-spiders ; others have occurred on the Irish coast,
and the writer has found yet more in Pwllheli harbour.

There, among the seaweed and coarse green vegetation,
the little spiders are plentiful, spinning delicate webs close
to the ground. When taken home and dropped into a
tumbler of sea water, the spiders float on the surface. If
pushed under, they slowly sank, upside down, the lungs
covered with an air bubble, the legs outstretched. With
the hind legs, they held on to any object capable of affording
anchorage, and so remained content for several hours.

To complete our catalogue we must include Amauro-
bioides of New Zealand and Uliodon of Madagascar, which
are both members of the family Clubionidae, and two
Malayan coast spiders recently discovered by Abraham.
One of these, Diplocanthopoda marina, is a jumping-spider ;
the other, which feeds on marine worms, is Idioctis littoralis,
the first known marine Mygalomorph spider.

The spiders of the sea are not, therefore, members of a
single pelagic family. Like the spiders of mountains and
caves they are wanderers from beaten paths, derived from

200 THE BIOLOGY OF SPIDERS

several parent stocks ; originally-minded spiders, who have
colonised a new environment. They illustrate the in-
surgence of life ; that universal will to live which seems to
inspire all creatures. As Goethe said : " Animals are
always attempting the almost impossible — and achieving
it," and spiders have not hesitated to go up to the hills
or down to the sea and seek their livelihood on the edge
of its waters.

CHAPTER X

THE COURTSHIP OF SPIDERS

Activities of courtship, or preliminaries before mating, are
well known to biologists, and have been described by
observers of nearly every kind of creature from mankind
downwards. Spiders supply many examples of these
performances, and also provide good material for the dis-
cussion of their significance. Indeed, it is probable that
on this line the study of spiders may make a very real
contribution to the study of animal behaviour.

The Courtship of Jumping-Spiders

In this matter of courtship one family of spiders stands
supreme. This is the family of jumping-spiders, or Salti-
cidae. Our knowledge of their " dances " is due almost
entirely to the patience and enthusiasm of Dr. and Mrs.
Peckham, who published their well-known papers on the
subject nearly forty years ago. With a few isolated excep-
tions, it is only within recent years that courtship among
spiders has again attracted attention, and lately work on
the subject has been done by Gerhardt in Germany and by
Locket and Bristowe in this country. Much of this
chapter is indebted to the papers of the latter.

It has been said in an earlier chapter that jumping-
spiders are the possessors of keen sight, which enables
them to recognise objects at a distance of nearly a foot.
Many of the males bear decorations on their legs or palpi,
or on both, and sometimes also on their abdomen ; the
decorations consisting of tufts of hair or of coloured or

20 1

202 THE BIOLOGY OF SPIDERS

black patches. When a male jumping-spider approaches a
female, he seems to recognise her by sight. He then per-
forms a kind of dance before her. He raises his front legs
and waves them about, or he holds out the adorned legs of
one side and walks round in a circle, or he raises his abdomen
into the air. An example may be quoted to give an idea
of the complexity of the dance with some species. The
classical instance, that of the species Saitis pulex, wh ch
circled before its mate in times, has been quoted so often
in zoological literature, that another example, that of a
species of Habrocestum, is chosen here.

Fig. 78. — Courtship of Icius mitratus. After Peckham.

" He begins to move from side to side, with his hand-
some first legs pointed downward and somewhat outward,
his palpi extended parallel with them and his third legs
raised above the first and second, in such a way as to show
the apophyses on the patellae. Frequently, in these pre-
liminary movements, he bends the ends of the legs inward,
so as to put them into the form of a diamond, meanwhile
moving the palpi rapidly up and down. As he approaches
the female, he raises the first pair of legs swaying them
backward and forward, still keeping the third pair well up,
seeming as eager to display them as the first pair. When

COURTSHIP 203

he gets to within an inch of her, he lifts the first legs nearly
at right angles with the body, giving them a bowed position,
with the tips approaching each other, so that each leg
describes a semicircle, while the palpi are held firmly
together in front. Up to this time he has held the body

Fig. 79. — Courting attitude of Astia vittata. After Peckham.

well above the ground, but now he lowers it by spreading
out the second and fourth pairs, at the same time bringing
the tips of the third pair nearer the body, and arching the
legs over the cephalothorax so that the proximal ends of
the tibae nearly meet. Now he approaches her very

2o4 THE BIOLOGY^ OF SPIDERS

slowly, with a sort of creeping movement. When almost
near enough to touch her he begins a very complicated
movement with the first pair of legs. Directing them
obliquely forward, he again and again rotates each leg
around an imaginary point just beyond the tip ; when they
are at the lowest point of the circle, he suddenly snaps the
tarsus and metatarsus upward, stiffening and raising the
leg, and thus exposing more completely its under surface.
While this is going on with the first pair, he is continually
jerking the third pair up higher over his back."

Whatever a jumping-spider does, he is performing a
dance which is peculiar to his own species, and other
species of spiders will dance in a different way. It is note-
worthy that the movements he makes are always such as
will best display his decorations. Even if he were conscious
of the exact nature of his beauty, as he almost certainly is
not, and aware of his precise objects in courting, which is
at least questionable, he could scarcely improve upon his
display. He behaves just as if he were determined to
exhibit himself as conspicuously as possible. The female
for her part takes an obvious interest in the proceedings.
There is no doubt that she sees the charms that are dis-
played before her, and watches them intently, for she turns
herself so as always to keep the male in full view. Some-
times she brings the business to an end by joining in the
dance, the two spiders whirling round together.

The Courtship of Wolf- Spiders

It is clear that a complicated dance of this sort is of
interest only to a spider which possesses good eyesight.
The only spiders whose eyesight is comparable to that
of the jumping-spiders are the wolf-spiders or Lycosidae.
Some of the male wolf-spiders have decorations on their
legs or palpi, in the form of a brush of black hairs on one
or more of their joints. With these ornaments a wide
range of courting attitudes is possible.

At the outset, however, it is necessary to point out that

COURTSHIP

205

some wolf-spiders show no courtship at all. If a pair of
the species Lycosa pullata are introduced to one another in
a cage, the male usually leaps at the female and mating
begins immediately, without any preliminaries whatever.

With other species, however, things do not move so
fast. The courtship may consist, as with Lycosa amentata
or Lycosa nigriceps, in waving the
palpi in a semaphore-like fashion.
Locket thus describes the be-
haviour of the former species :
" The male, on sighting the fe-
male, started his usual antics. He
raised himself as high as possible
on his legs, extended his palpi as
indicated above (Fig. 80), with-
drew them, and extended them
again, the positions reversed. Each
time he did this he (usually) took
a pace towards the female, and
his abdomen quivered now and
then. He would often work his
way round the female, leaning over
in the direction he was going."

In other species the male may
have legs, and not palpi, to dis-
play. The common species, Tro-
chosa ruricola, raises and lowers its
first pair of legs alternately, quiver-
ing as they rise, and with the tarsus pIG< 80# — Courtship of Ly-
and metatarsus gracefully and cosa amentata. After
gently waved up and down as they Locket-
fall. An even more elaborate courtship is that of Tarentula
barbipes (Fig. 81), in which the cephalothorax is raised by
the second pair of legs, while both palpi and first legs
are raised into the air together. The legs, in a bent
position, are jerked as high as possible and then, trem-
bling violently, are lowered to the ground. Then a step
or two may be taken and the process repeated again and

2o6 THE BIOLOGY OF SPIDERS

again, until the female ceases to rush at him when he
approaches.

The family Pisauridae is not very distinctly related to
the true wolf-spiders, and one of its species, Pisdura
mirabilis, is very common in England. The sense of sight
is not quite so well developed, and the male possesses no
decoration. His courtship is a far more material business
than any of the dances which have just been described, for
he wraps up a fly and presents it to the female for her
acceptance. If he is given a fly in the complete absence

Fig. 8i. — Male Tarantula barbipes displaying legs before female.
After Locket.

of a female, he eats it at once, without attempting to wrap
it up, but if she is present, the fly is swathed in silk and
held out for her to feel with her palpi. It is remarkable
that the carnivorous male should be willing to refrain from
eating his gift himself, and Locket has given his description
a humorous touch by adding the record of a male which
offered a fly it had itself previously sucked.

The Courtship of Crab- Spiders

There are the other families of spiders which hunt their
prey, chief among which are the crab-spiders, or Thomi-
sidae. These include several species in which the male

COURTSHIP

207

has a different pattern from the female or is to some extent
decorative, and hence, though the sense of sight may not
be very keen, we might expect to find acts of courtship in
this family.

But this is not the case. When a male encounters a
female, he climbs upon her back with no sort of preliminary.
If she tries to escape he seizes one of her legs roughly in
his jaws, to avoid so lamentable a loss. They may roll
over and over together, but as soon as she ceases to struggle,
he climbs upon her back again. The only sort of courtship
is the tactile stimulation to which he subjects her, tickling
her with his feet as he crawls about her back. In some
species the male, before mating, ties the female to the
ground with such a quantity of silk that she ultimately has
some difficulty in tearing herself free.

Very few observations seem to have been made on the
simple wandering spiders of the families Drassidae and
Clubionidae. In some species the male finds the female
resting in a silk cocoon. He taps upon it with his forelegs
for some time, then tears it open and enters. Some males,
such as that of the British species Clubiona trivialis, con-
struct a mating nest next to the rest-cocoon in which the
female is confined, and tap upon the partition between them,
sometimes for days together. Other species have been seen
to mate forcibly, the male seizing the female and showing her
no consideration. In others, again, the male and the female
tap each other with their front legs for a few minutes.

The courtship of the comparatively primitive spider,
Dysdera erythrina, was described by Berland in 1912, but
his account seems to have been overlooked by British
workers. When the two animals came face to face, the
male immediately placed his two forelegs over the female,
with his claws on her abdomen, seeking to hold her still
while with his second pair of legs he gently caressed her
sides and the under surface of her abdomen. Both spiders
had their jaws wide open, but as the male continued stroking
the female, her aggressiveness vanished and she fell into a
sort of hypnotic condition ,

2o8 THE BIOLOGY OF SPIDERS

The Courtship of Web- Spiders — Agelenidae

The spiders which spin webs form a group somewhat
apart from the active jumping species, since their sight is
in general less keen and their sense of touch more delicate.
The courtship of the spiders which spin the familiar tubular
web is a very easy process to witness and has long been
known.

If a male house-spider is put upon the web of a female,
he at once begins a performance which is seen in no other
circumstances. With his two palpi he vigorously drums
upon the sheet of the web. The female, waiting in the
tubular part of the web, is aroused. She feels the web
shaking and behaves as if she was aware that this disturbance
is not produced by any fly or blundering intruder. She
waits expectantly and lets the vibrations play all round her.
The male gradually approaches until he can touch her
with his forelegs. The female of Agelena labyrinthica falls
into a cataleptic trance as a result of this courtship. The
male carries her about, by a leg grasped in his jaws, and she
does not awake until mating is over.

A similar but more complicated courtship is exhibited
by the spinners of the calamistrated bluish-looking webs,
described in Chapter VII. Locket has given an account of
it for the species Dictyna latens and Amaurobius similis, and
Berland for Filistata insidiatrix. Berland's account is
translated as follows : " There was established between the
two animals a curious and complicated kind of telegraphy.
The male advances on to the web and with his anterior
claws, pulls strongly at the threads ; he taps impatiently,
proceeds, retreats, circles round the female's retreat. One
sees that he is delivering ' une veritable supplication
amoureuse.' And the female replies, pulling the threads,
in such a way that it is evident that a communication is
established between the two, a real exchange of sentiments,
but of a purely tactile nature. At last, after half an hour,
the female decides to come out, and advances a little from
her retreat. But she must be made to come out on to the

COURTSHIP

209

web, and the male goes to seek her. He caresses her with
his front legs, he takes her by the hand, if I may use such
an expression, which is, however, very exact. I have often
seen him take up her fore-claws in his, and drag her gently
towards him. Sometimes she is afraid, and escapes back
to her retreat. Then he begins again."

The Courtship of Web- Spiders — Linyphiidae

This complex behaviour of Filistata is of great interest,
for it more closely resembles the actions of the higher
families of web-spinners than the lower ones. Nothing so
elaborate seems to have been observed among the Liny-
phiidae— the spinners of the sheet- webs. For example,
Bristowe thus describes the courtship of Linyphia clathrata :
" He gently touched the web, first with his palps, then his
legs ; these actions became more rapid, and very slowly he
began to advance with quivering abdomen and palpi.
Performing these motions he circled round the female, who
remained motionless in the centre of the web. . . . Then
a new set of motions were noticed. He stretched his front
legs out in front of him and alternately bent them inwards,
the tips of the legs remaining fixed to the web ; then,
letting go with his front legs he began to rock up and down
in the web, at first gently and then more rapidly ; finally,
with some twitches of the abdomen and movements of the
palpi he came to a stands till/ '

Other Linyphiidae which have been watched at court-
ship perform somewhat similar actions. It is important to
realise, however, that many members of this family are the
possessors of stridulating organs. These have been already
described. They exist in the male only, usually between
the chelicerae and the palpi, sometimes between lung-books
and the fourth legs. It is particularly unfortunate that the
courtship of such species seems not as yet to have been
witnessed.

The character of the courtship is changing as we move
about the scale of spider families. Dancing gave place to

210 THE BIOLOGY OF SPIDERS

tickling, and this has now been followed by shaking or
drumming on the web. The hostility of the female has
also been decreasing, and in the next group has not only
disappeared, but is replaced by eagerness.

The Courtship of Web-Spiders— Theridiidae

The courtship of Theridiidae in some ways resembles
that of the Linyphia described above — that is to say, the
male plucks at the threads of the web. But there is often
this difference, that the male's importunities coax the
female out from her customary retreat to a place in the
web which the male has prepared for mating. Locket
writes thus of Theridion pallens : " A male on being
introduced to a small case where a female had built her
web, began crawling upwards, his abdomen pulsating
slightly from time to time. Having found the female, who
up to now had made no movement, he began walking about
in her vicinity biting away threads and spinning new ones.
He then hung inverted, his legs slightly flexed, and with
the second pair began a series of rapid pluckings on the
web, otherwise remaining quite still. The female, as
though attracted by these movements, came slowly towards
him, her front legs outstretched and waving. She stopped
whenever the male stopped his movements (which were
intermittent) and came on again when he recommenced.
When she was quite close the male stopped."

The males of Theridiidae do not often live for long, and
it may be because of the shortness of the breeding season
that the females are generally less hostile than those of
other families. In several descriptions of the mating of
species of this family, emphasis has been laid on the ardent
behaviour of the female, who sometimes takes the lead in
the courting, and sometimes appears to be quite insatiable.

Again, in this family males are known which possess
stridulating organs. The common brown British spider,
Steatoda bipunctata, is the most familiar of these, but,
though both Bristowe and Locket have described its court-

COURTSHIP 211

ship and mating, there is no reference to any movement
which could bring the two halves of the organ into play.
Bristowe, however, says elsewhere that he has seen such
movements, without describing them. It would almost
seem as if the possession of the organ were but an extra
protection granted to the wandering males, who use it in
the same way as do the trap-door spiders. This, however,
is only speculation.

The Courtship of Orb- Spiders — Epeiridae

Finally we reach the head of the spider family, and
come to the familiar species, whose pronounced ferocity to
their mates has helped to give all spiders a reputation for
cruelty.

Courtship in the common species, Zilla x-notata, is thus
described by Locket : " The male climbs to the centre of
the female's web, and usually seizes the line communicating
with the female's hiding-place with his four front legs.
With his back legs he seizes one of the adjacent radii at the
centre, and starts a series of jerking and plucking move-
ments on the communicating line, using himself as a sort
of spring at the angle of the radii. If the female does not
respond he then usually climbs to her retreat, but returns
again after an interplay of legs. Eventually the female
comes out, also making plucking movements."

An essentially similar procedure is described for the
little green spider, Epeira cucurbitinay and the resemblance
of that of the Theridiidae is obvious.

A sufficient number of instances of courtship have now
been described to give a general impression of the pro-
ceeding, which must now be considered with the object of
determining, if possible, its biological significance. It
seems that the acts of courtship among spiders are more
favourable for this purpose than those of any other sort of
creature, for it is possible to compare the behaviour of the
spiders which see with that of the spiders which feel (or
" hear "). It becomes apparent not that some spiders

2i2 THE BIOLOGY OF SPIDERS

indulge in courtship, but that in all families the act of
mating is preceded by various kinds of preliminaries,
which appeal to the particular sense that is most highly
developed.

Earlier Theories of Courtship

Three theories at least have been put forward in explana-
tion of the courtship of animals.

Darwin saw in courtship an opportunity for a choice of
a mate, an acceptance or refusal which, embodying a
process of sexual selection, explained also the vivid colouring,
ornamentation, or whatever secondary character the animals
bore.

Wallace regarded such secondary sexual characters as
recognition marks, which enabled the female to recognise
the male of her own species. Thus their display tended
to prevent the uneconomical act of an unfertile cross.

The third theory, due also to Wallace, regards the
secondary character as a mere expression of, and the
activities of courtship as a result of, the more vigorous
metabolism of the male organism, without offering any
further explanation of either.

These theories were put forward at a time in the history
of Biology when Natural Selection was considered all but
omnipotent. They make demands on the female's powers
of discrimination which it is difficult to justify. Moreover,
if they imply a direct connection between acts of courtship
and secondary sexual differences, they ought also to deny
the possibility of courtship where such marked differences
do not exist. We have seen that this is not so. Again,
secondary differences may exist, as in the spider Microm-
mata virescens, whose female is uniformly green, while the
male has a vivid yellow and scarlet abdomen, without a
corresponding utilisation in courtship. The third theory
seems to imply that there is no necessary connection
between the courtship of the male and the subsequent
mating ; that both courtship and decoration have a merely

COURTSHIP

213

bio-chemical origin and may be devoid of purpose or result.
Further, as Peckham has shown, there is some reason for
doubting whether the female spider is a less vigorous and
active organism than the male.

It seems that the process of courtship is more intelligible
if it is considered in its relation to the individuals concerned
than if it is considered racially. For there is some certainty
as to the physiology of the individual, but there is still a
very considerable doubt as to the true way or ways in which
the evolution of the race has taken place. This is the chief
point in favour of Montgomery's and Berland's modified
acceptance of Wallace's views. Montgomery interpreted
the courtship as a mixture of the actions of excitement and
self-defence ; while Berland, who had seen male jumping-
spiders courting nothing, that is to say, dancing when
alone, attributed their activities entirely to physiological
excitement.

The same concern with the individual rather than with
the race, is a feature of the more recent theory of Bristowe
and Locket. These authors interpret their observations
thus. Since the male spider runs the risk of being killed
and eaten by the female, the first use of his courtship antics
is to enable her to recognise him as a male, and not to
regard him as something to be eaten. When he has begun
his courtship, the male spider is practically safe, but it
takes a varying amount of continued solicitation to stimulate
the female so effectively that she submits herself to him.
Recognition and stimulation are therefore both necessary
before mating can take place, and the essential characteristic
of Bristowe's and Locket's hypothesis is that it for the
first time includes a supposed necessity for preliminary
" recognition," and so places a dual responsibility upon the
actions of courtship. All these theories will be recon-
sidered later, when the behaviour of the two spiders them-
selves has been summarised and brought into perspective.

2i4 THE BIOLOGY OF SPIDERS

Behaviour of the Male

When the courtship of American jumping-spiders was
the only known instance of these activities, it was natural
enough to suppose that the sight of the female was the
instigating cause of the male's dance. Berland, however,
saw Saitis barbipes courting in the absence of a female, and
Bristowe and Locket showed that the smell of the female
would also stimulate male wolf-spiders to go through their
courting actions. They describe the behaviour of Trochosa
picta thus : " When a male of this species has come upon
the trail of a female, he reminds one of a hound following
up a scent. He becomes very excited, and appears to
advance in a zigzag fashion along the trail, feeling the
ground with his palps and the tips of his legs, often touching
the ground two or three times with the latter before actually
putting them down."

It was proved conclusively that sight was not used, for
males of several species were seen to go through their
performance when placed in a box which had previously
contained a female. Water which had been shaken round
her cage or particles of sand over which she had crawled
or threads she had spun were found to be equally effective
in exciting him to action, but threads dried and then baked
would not do so.

However, this is not a specific reaction of the male
spider to the scent of the mature female of his own species.
It is possible to learn more by the study of a few abnormal
cases than by much repetition of the ordinary, as psycho-
therapists know well, and many occasions of curious
behaviour on the part of the male spider have been recorded.

Male spiders have been incited to begin their courtship
actions before other males, both mature and immature, of
their own species or even of another species. Peckham
saw a male Phidippus mccookii court a female Phidippus
clarus, while Locket saw a male Tarentula barbipes per-
forming in front of a male Trochosa ruricola. These
spiders, which were separated by a glass partition, were not

COURTSHIP

215

even of the same genus. Male spiders frequently court
immature females, and Montgomery saw a male Prosthesima
atra seize two young females at once. Again, Locket saw
a Tarentula barbipes start his performance in a box which
had previously contained a male, while males have been
known to embrace the cast-off skin of a female, and to
become excited on being placed in the empty web of a
female or even of another male. It is clear, therefore, that
the stimulus which initiates the male's performance is
vague, rather than definite and specific. It may act upon
the sense of sight, of smell, or of touch, but the appearance
or the scent of the female does not seem to be readily
distinguishable from that of the male.

Two curious actions are often exhibited by spiders
during their courtship. One is a sharp twitching of the
abdomen, which is sometimes violent enough to cause a
distinct tapping sound as the ground is struck. This
action, which was described by Campbell long ago, is
probably due to extreme excitement or self-stimulation.
The other is more difficult to understand. The spider
stops its courting actions and rapidly rubs its legs together.
On at least one occasion a female spider has also been seen
to do this. It may be due to intense stimulation, or, since
the legs contain sense organs, Bristowe suggests that it
" may have the effect of sharpening the senses and be the
equivalent to blowing one's nose or taking off one's gloves."

A final action which seems to mark the end of court-
ship in practically all spiders is a rapid thrust-and-parry or
interplay of the forelegs of both sexes. The tactile spines
are no doubt concerned here, so that whether the courtship
was originated by sight or by scent, it is concluded by
touch. As Montgomery says, " There is a language of
touch," and doubtless all spiders can speak it well.

Behaviour of the Female

The part played by the female during the courtship of
the male is usually much more passive, unless she happens

2i6 THE BIOLOGY OF SPIDERS

to be in no mood for wooing. It is very rarely that she
actually kills a courting male ; more often she chases him
away. She may content herself with a particular menacing
attitude ; for instance, Xysticus cristatus " raised her front
legs threateningly, giving a little jerk forwards every few
seconds, whenever he approached. Although the male
appeared to be quite ardent, he seemed to recognise this
as a danger signal and retreated." Again, the female may
gently but firmly push the male away with her front legs.

A male who is not performing the acts of courtship does
indeed run a risk of being killed. Bristowe has recorded
instances of this, including one of a Pisaura mirabilis who
was killed because he had no fly to wrap up and present.

Some females, particularly those of the genus Theridion y
respond almost immediately to the presence of the male.
Locket tried the interesting experiment of putting males of
Theridion varians into the webs of the very similar Theridion
denticulatum. Some of the males were stimulated thereby,
but the females invariably attacked them without the least
hesitation, although they never attack males of their own
species.

As courtship proceeds, the females become more
stimulated. That this is so is not merely a hypothesis to
explain the facts of courtship, but is borne out by evidence.
The female Leptyphantes leprosus has a large downwardly-
directed vulva and Locket has observed that this " was
extended in a curious manner during the male's advances,
while after mating it was found to be in its normal position
again." The same thing was seen to a less marked extent
in Epeira cucurbitina.

By this time the female is taking a more active share in
the courtship. If she is a web-spider she may be giving
jerks to the web, which help the male to locate her and
which also stimulate him. Other spiders have been seen
to reciprocate the leg- movements of the dancing male.

COURTSHIP

217

Relation between Male and Female

The popular notion that the female spider eats the male
may now be considered more precisely. Such cannibalism
is, as has been said, rare before mating and practically never
occurs if the male is carrying out his courtship actions
normally. The ordinary hunger of the one and the ordinary
fear of the other are both swamped by the ardour of the
sexual impulse — a fact which is true of many other animals
besides spiders. As will be noticed later, male and
female spiders of several different species may often be
found living in the same retreat.

As opposed to monogamy, polygamy and polyandry may
readily occur if the male escapes successfully. He may then
mate with any other female he may meet, just as he may
mate with the same female again and again, and just as
the female may mate with other males who discover her.
Locket has seen males of Lycosa pallata mating with
females which were already the owners of egg-cocoons ; but
an even better example, observed by Abraham in Taiping,
was recorded by Hogg. A web of the large orb-spider,
Nephilia maculata, contained a female and three males, all
three of which were seen to mate with her in a short interval
of time.

The Significance of Spider Courtship

What is the real significance of spider courtship, con-
sidered as a whole ? It must be realised at the outset that
even yet the observations which have been made are not
sufficiently numerous to yield conclusions which are more
than tentative. No certainty, no dogmatism is possible in
the existing state of our knowledge. The theories which
have been put forward by previous workers have already
been mentioned, and the objections to some of them have
been stated.

The latest theory, that of Bristowe and Locket, seems
to err in being needlessly complex and in attributing mental

218 THE BIOLOGY OF SPIDERS

powers to the spider which it probably does not possess.
The idea that the female must first recognise the male so
as to distinguish him from edible prey is superficially
attractive, but it is open to two very serious objections. In
the first place, " recognition " is a psychological term which
presupposes a state of awareness or consciousness in the
spider, and it therefore offends against the canon, stated in
the chapter on behaviour, that all actions should be inter-
preted in their lowest possible terms, rather than in their
highest. It will be shown later that a simpler interpretation
is possible in the instance of courtship.

In the second place, " recognition " is clearly not the
right word to use, since a virgin female cannot recognise
that of which she has had no previous experience. " Realisa-
tion " might better express the female's seeming ability to
distinguish mate from prey, but even so, it is too strong a
term.

Such realisation as does exist occurs first when the male
sees, smells, or feels the female, and so begins his court-
ship, whether it be dancing, semaphoring, or plucking the
web, and whether she is actually there or not. The " recog-
nition " theory seems to imply that the male is better able
to recognise the female than she is to recognise him. Other-
wise he would run away. The theory neglects the fact
that the male has to suppress his natural fear of a bigger
spider just as much as the female has to suppress her
normal instinct to feed. It cannot be supposed that the
male can see or smell the female before the female can see
or smell the male, for the fact that a spider would begin its
courtship in a box which had previously contained a male,
shows that males, no less than females, can be smelt by
other spiders.

Even if we grant that this realisation is a part of the
courtship, we must assume that it results from the effect of
courtship upon the female. Courtship produces physio-
logical changes in the female, which begin by resulting in
" recognition " and ultimately result in stimulation. Where
does the distinction commence ? It is clear that, looked at

COURTSHIP

219

from the point of view of female physiology, the two
processes are inseparable. All courtship, of whatever
character, is nothing more than an appeal to the " mind "
of the female, and nothing is gained by dividing that appeal
into indistinguishable stages. Looked at critically, the
" recognition plus stimulation " theory fails to establish its
claim.

It fails to do so because it demands too high a degree
of mental development in the participants. If the actions
involved in courtship be compared to those described in
the chapter on behaviour, it is seen at once to what category
they belong. They are instinctive actions of the chain-
instinct type, and it is as such that they may best be
interpreted.

The origin of the whole business is the maturation of
the testes of the male spider. When his final moult has
been accomplished, the whole character of his actions
changes. He ceases to spin a web and becomes a wanderer.
It is possible that a hormone, such as is known to exist in
vertebrate animals, is responsible for his changed attitude
towards life, and that the male rapidly reaches a condition
in which the sight or the scent of another similar spider,
not necessarily the mature female of his own species, is
sufficient to initiate the first of his series of instinctive
actions. He begins his courtship.

It has already been pointed out that actions of the
chain-instinct type require some definite stimulus to set
them in motion. One is reminded of Ogilvie's observation
that young partridges reared under a hen never squat when
danger threatens, as the young birds always do in natural
conditions when they hear the parental signal. " The
necessary stimulus is absent, and that stimulus is supplied
by one particular cry of the parents and nothing else."

After courtship has proceeded for some time, there
always comes an occasion of contact between the two spiders.
The common " interplay of legs " has already been
mentioned : in some spiders it is a slower touching of the
forelegs, or an actual " shaking of the hand," claw to claw,

220 THE BIOLOGY OF SPIDERS

as in Filistata, or a meeting of some other part, as in the
case of Pachygnatha listen, where the male seizes the cheli-
cerae of the female with his own. Whatever it may be,
the moment of actual contact always occurs. I interpret
this partly as a test of conspecificity : males which have
been courting empty boxes or their own mirror-image or
another male or an immature female proceed no further
with their activities when this test cannot be made or when
it reveals the wrong spider. When, however, a positive
answer is made to this tentative, further results follow.

It has often been noticed that the male himself becomes
more stimulated as courtship proceeds. This may be due
to the continued presence of the female, or to the repeated
contact with the threads of her web or with her legs. It is
clear, however, that the final touching of the female leads
to the next and last link in the chain, when the male climbs
upon the female's back or otherwise takes up the correct
position for copulation. The male is now sufficiently
stimulated to be able to exert the very considerable effort
which is necessary to the ejaculation of the spermatozoa.

The " appeal to the mind of the female " produces
results which are generally less conspicuous but not less
important. The first effects of the male's presence must
be an inhibition of the female's desire to feed. It is clear
that an internally produced hormone cannot do this, or
otherwise female spiders would have to fast. Hence the
female refrains from attacking the courting male. During
the whole of the courtship she is receiving impressions by
the eyes, or the scent organs or the organs of touch. It is
reasonable to conclude that when the central nervous
system of the female spider receives notice of the court-
ship, from one sense organ or another, it reacts to the
impulse and directs activities in other parts of the body.
Actual change in the position of the vulva has already been
mentioned, and there may be other changes which, being
internal, are not manifest from without, but may none the less
be essential if the mating is to be successfully consummated.
Only the central nervous system can induce such changes.

COURTSHIP

221

and only when stimulated by the receipt of the appropriate
intimation of so great a change in the environment as the
arrival of a mate.

If we may venture to summarise in a few words the
results of so complex an activity as courtship, we may say
that courtship is a chain of related instinctive actions, in
which the reproductive urge suppresses the normal habits
of self-protection and self-nourishment, and is accompanied
internally by the physiological changes necessary to make
the subsequent union possible.

CHAPTER XI

THE MATING AND PARENTHOOD OF SPIDERS

The duties of parenthood are very unequally divided among
spiders, for they fall entirely upon the mother. Although
some male spiders continue to live in company with the
female after mating, there seems to be no instance on record
of a male spider performing any act likely to benefit the
coming generation. As he lives on the female's web he is
little more than a dependant, taking his share of the captures
and doing nothing in return.

Sperm Induction

There is, however, one important act which the male
spider must perform in preparation for fatherhood, and
that is the charging of his palpi with sperm. It has already
been stated that the spider is one of the few animals in
which the intromittent organ is separated from the testes,
and the consequence of this separation is seen in the act
we are about to describe.

The process was first observed and explained by Menge
in 1843, but very few other zoologists during the nineteenth
century offered confirmatory accounts. Some failed to
witness it at all and concluded that it could not be of general
occurrence. But the number of descriptions is now suffi-
cient to give us a good idea of the nature of the act, which
is certainly not one that can be very readily observed.

There seems to be considerable constancy among the
different families in their carrying out of this process. The
male spider spins a small sheet-web of very fine silk, some-

22a

PLATE VIII

Banana Spider {Heteropoda venatoria) with Eggs and Young.
To face p. 222.] [E. A. Robins, photo.

MATING AND PARENTHOOD

times upon the ground, sometimes among the branches of
the plant upon which it

is living. For many Si *

species the making of
this web is the only spin-
ning activity exhibited by
the mature male. The
length of this sperm- web
is about half the length
of the spider itself. The
spider, standing over the
sheet, deposits a minute
drop of seminal fluid
upon it, a drop so small
that it is not easily seen.
The palpi are then ap-
plied to the drop, alter-
nately and repeatedly.
Often they are applied
to its under side and the
fluid is absorbed through
the web : sometimes one palpus is slowly waved in the air
while the other one is
being applied to the
drop.

Some spiders, like
Xysticus cristatus,
whose sperm - web is
shown in Fig. 82, place
the drop on the lower
surface of the web and
apply the palpi to the
upper surface. Others
again do not employ a
web at all. They may
use a few threads in-
stead, as does Linyphia clathrata (Fig. 83), while Hull has
seen Linyphia montana deposit the droplet on a leaf of

Fig. 82. — Sperm- web of Xysticus
cristatus. After Bristowe.

Fig. 83. — Sperm-web of Linyphia
clathrata. After Locket.

224 THE BIOLOGY OF SPIDERS

the bush and Lycosa amentata on a dead leaf on the
ground.

In these examples, mentioned by Hull, courtship and
mating immediately followed the transference of the sperm
to the palpi, and it would seem that sometimes the process
is withheld until the female has been found. On the other
hand, most of the occasions witnessed by Montgomery
immediately followed the mating. Locket has recorded
the most interesting case, in which a male of Theridion
sisyphium recharged his palpi with sperm after each applica-
tion to the female, approaching and retiring from her and
then approaching again several times within an hour and a
half.

Copulation

The relative positions taken up by spiders when in
copula are diverse, but within the limits of each genus
seem to be almost constant. There is also a degree of
constancy within the limits of each family. Individual
eccentricities, however, are found.

The position is dependent on the relative sizes of the
sexes and on whether the meeting occurs on the ground or
on a web. In the former instance, the male most usually
mounts upon the back of the female, his head pointing in
the opposite direction from hers. The female generally
maintains a normal position, but may be partially pulled
over to one side or even bound down with silk. Occasionally
the smaller male is compelled to creep underneath the
female's abdomen before he can reach the epigyne, and then
their heads are, of course, pointing in the same direction.
Alternatively, the male and female may be merely facing
each other, their bodies in one line, or the male may creep
right under the female and turn over so that their ventral
surfaces are next to one another.

When the spiders meet in a web, the position is usually
one in which the ventral surfaces are opposed to one
another. They may be facing in the same or in exactly

MATING AND PARENTHOOD 225

opposite directions and may or may not be in close contact
or embrace.

Whatever the position may be, it seems to be constant
for every species, and this is no doubt due to the fact that
the male palp is, as has been mentioned, a very complicated
organ. It is possible that in one and only in one position
is it capable of being inserted at all. This implies the
impossibility of cross-breeding between two different
species, and it is noteworthy that, while male spiders have
several times been seen courting the females of other
species, no single instance of an actual copulation between
different species has been recorded.

All the possible variations in the mode of palpal insertion
have been observed. In some instances the two palpi are
inserted simultaneously. There is a group of families of
spiders, designated Haplogynae by Simon, characterised by
having a symmetrical epigyne divided into two similar
halves, and in these families this method of insertion seems
to be the usual one. It occurs, however, in exceptional
species of other families.

In other cases one palpus and only one is used. Gene-
rally the palpi are used alternately. Each may be used
once in this way, or several insertions of one palp may be
followed by several insertions of the other. The total
number of insertions during one mating varies from one to
over a hundred. There is no doubt that this detail is
influenced to some degree by the condition of the spider,
and probably also by such physical conditions as tempera-
ture. Furthermore, the time taken in mating varies from
but a single second to several hours.

The behaviour of the female during mating is also
variable. She may be bound up tightly, and generally she
is completely passive, falling in some instances into a trance-
like cataleptic state. On the other hand, the females of
some species seem to be quite undisturbed by the process
and may be seen running about in the ordinary way with
the males clasping their abdomens.

The male's activities during mating are more complex.

226 THE BIOLOGY OF SPIDERS

He has often to raise the abdomen of the female and may
experience considerable difficulty in so doing, so that he
must try and try again before succeeding. He may find
insertion of the palp difficult, particularly if he has only
recently moulted. In an extremely interesting observation
of Bristowe's, a male Micrommata virescens, less than a
week past his final moult, was found to be unable to copulate
successfully until after an hour's fruitless efforts. This
species bears a small spur or apophysis on the penultimate
joint of the palpus, and this spur has to fit into a special
groove in the epigyne (Fig. 84). In this case the pressure

Fig. 84. — Male Palp and Female Epigyne of Micrommata virescens.
A, Tibial apophysis. B, Groove into which apophysis fits.

exerted by the swelling of the haematodocha forced the
rather soft spur out of place.

The male often pauses during the mating to pass his
palpi through his jaws. Blackwell recorded this in 1873.
Locket has watched the process through a microscope and
has seen that it is actually the style of the palpal organ
which is being passed through the chelicerae. It is probable
that the style thus receives a necessary lubrication from the
fluids of the mouth or of the maxillary glands.

Another very interesting observation of Locket's is
concerned with the time occupied by the insertion of the
palpi of the little spider Theridion varians. The first
application of each palp lasted about a minute, but there-

MATING AND PARENTHOOD 227

after (each palp being applied forty-five times) the time
taken dropped to six or seven and later to three seconds.
Locket's conclusion is, " It seems probable that only the
first two or three long applications of the palp are really
effective and that innumerable short subsequent applica-
tions are not really functional at all, but only take place
because they are pleasurable to the male, who in the intervals
between the applications keeps the female stimulated by
his taps on her sternum." To bring this conclusion of the
pleasure-loving, self-indulgent male into line with the view
we have taken of the instinctive nature of all these actions
would require a discussion — obviously irrelevant here — of
what is implied by the word " pleasure," both for man
and for the lower organisms. It is possible to supplement
Locket's conclusion by the suggestion that there is a similar
" pleasure " felt by the females of some species, who,
apparently insatiable, continue to signal to the males by
the jerks on the web long after the males have ceased to
respond.

The Cannibal Female

The widespread belief, promulgated from book to book,
that the female spider devours the male after mating, is
very far from being justified by the facts. Perhaps the too
facile acceptance of the generalisation may be condoned in
some measure since the garden-spider, Epeira diademata,
the best known of all British spiders, and one which to
many represents the whole order, is a particularly fierce
species and undeniably addicted to cannibal practices.

It is a fact that the females of several different species
have been seen to kill and eat the males after mating.
Much more rarely it happens that the murder is com-
mitted before mating. A male spider in the neighbourhood
of a female is stimulated to begin his acts of courtship, and
it seems that when he is performing these he is com-
paratively immune from attack. It has already been
suggested that his courtship stimulates the female's repro-
ductive instincts so that for a time they dominate her

228 THE BIOLOGY OF SPIDERS

pugnacious habits. When mating has been accomplished,
a very different state of affairs obtains. The sexual impulse
has died down and normal reactions return. It is now
that the male is in the greatest danger, and not infrequently
he makes off at his best speed. A certain proportion, how-
ever, undoubtedly perish at this time, especially, as Bristowe
points out, towards the end of the mating season, when the
vigour of the males is decreasing and their power to escape
rapidly is consequently lessening. Locket thus describes
the behaviour of a mated Phyllonethis lineata : " The
female now suddenly started to attack the male by throwing
viscid lines on to him, and he was removed. He had
already mated with another female who had treated him in
exactly the same way, and he would certainly have perished
had I not removed him." A " pregnant " female will often
attack a male, almost at sight : his courtship makes no
appeal to her.

The relative security of the male before mating is
against Montgomery's theory that the male's courtship
activities are but an exaggeration of the usual expression of
fear, and so is the fact that many of the courting actions
are quite unlike those exhibited on any other occasion.
The post-nuptial risk admits of the possibility of competition
between males, which would result in a kind of sexual
selection, for those males that escaped would have a chance
of mating again with other females. It is therefore probably
true that the males whose appearance or whose courting
actions are the most pronounced are the most likely to leave
descendants, because, as Montgomery has said and Bristowe,
following him, has emphasised, they " most quickly and
surely announce themselves to be males." Thus they
secure the pre-marital immunity, but the theory does not
take account of the second danger period, after mating.

The males that run the greatest risks are those of the
species whose mating period is prolonged. When males
are likely to arrive at any time between September and
April, as is the case with Amaurobius ferox, for example, the
females are not so ready to " love, cherish, and to obey."

MATING AND PARENTHOOD 229

A meal may be preferable, and there is also a greater chance
that the female is already " pregnant." It must be remem-
bered that her actions are governed more by her internal
physiological condition than by her " state of mind."

In other cases, when the mature male has only a tran-
sient existence, the females are seldom hostile and often
eager. In such instances the risk to the male before mating
is negligible, and it is much less afterwards, although
accidents may happen at any time. Quite often it happens
that male and female live together in the web, not only
before mating but even afterwards, and sometimes for a
considerable period. Males of Linyphia triangularis are
generally found in August in the female's web, and I have
found both Epeira quadrata and Epeira cornuta living in
pairs in the same nest. I have known a pair of Pholcus
phalangioides to continue to share the same web until after
the hatching and dispersal of the family ; but this is probably
exceptional. In a few extreme cases the partners are
sufficiently tolerant of one another to share their food, as
Locket has described for Dictyna uncinata and we for
Agelena. It is, however, always probable that such
partnerships depend for their continuance on a sufficient
supply of insect food, when the predatoriness of the spider
tends to be subdued.

Egg-laying and Cocoon-making

The mother's share of the duties of parenthood begins
when she lays the eggs and spins the cocoon round them.
The eggs are never laid singly, but it is said that the cocoon
of the common species Oonops pulcher contains only two.
Most spiders make only a single cocoon, but there are many
that spin two or more. Probably the actual number of
cocoons made in such cases is more dependent on the
conditions of life, and the fortunes of the spider than on
the spider's specific identity. For example, the house-
spider, Tegenaria atrica, usually makes three cocoons, but
well-fed captive species have been known to make twelve.

23o THE BIOLOGY OF SPIDERS

The cocoon is much more than a mere egg-bag. It
usually includes some protection for the eggs within, and
in not a few cases its finished appearance is as characteristic
of the species as is the form of the spider itself. Generally,
however, it is spherical or lenticular in shape.

The process of laying the eggs and spinning the cocoon
around them is not nearly so difficult to observe as the
process of sperm-induction, partly because female spiders
are easier to keep in captivity than males, partly because it
takes much longer to accomplish, and partly because its
approach is indicated beforehand by the actions of the
mother. It has the disadvantage that it usually takes place
in the evening and may keep the watcher from his bed
until the small hours.

If one may judge from the numerous published descrip-
tions, there seems to be considerable similarity in all the
processes of cocoon-making and it may be more useful to
give a general outline of the process, rather than descrip-
tions of what occurs in a few selected species. Nearly-
all the original descriptions are in readily accessible
papers.

The first stage is generally the spinning of a small sheet
of closely woven silk, upon which the eggs are to be laid.
Sometimes, however, as in the case of Agelena labyrinthicay
the egg-cocoon is contained in a silk chamber of its own,
and then the making of this chamber is the first care. It
may occupy the whole of the previous day and only shortly
before midnight is the little sheet placed inside it. The
size of this sheet roughly corresponds to the length of the
spider's body.

In the simple cocoons, the eggs are now laid directly
upon this sheet, but in a great many species, a flocculent
layer of downy silk intervenes between the sheet and the
eggs. This beautifully soft material is jerked out of the
spinnerets, which are themselves working like scissor-blades
during its production, and it is to these movements that the
downy consistency of the substance is due It has been
mentioned already that this protective layer is the product

MATING AND PARENTHOOD 231

of a special set of silk-glands, and that it is often yellow or
brown in colour.

The eggs are laid upon this cushion. It is only rarely
that they are laid so as to be separately visible. Generally
a drop of fluid is exuded from the mouth of the spider's
oviduct, comes in contact with the sheet, and then increases
greatly in size. The drop remains, however, connecting
the sheet with the oviduct, and the eggs pass gradually
into it. This fluid is probably in part a lubricant, but it
seems also to have another function.

It is slightly alkaline, syrupy in consistency, and sus-
pended in it are numerous small round particles. When it
evaporates, these particles are deposited on the surfaces of
the eggs, giving them a bloom like that on grapes. This
layer prevents the eggs from sticking together into a solid
mass, as they would otherwise do, with fatal consequences.
It also strengthens the outer covering of the egg, which,
instead of being very delicate, becomes firm and elastic.

The eggs of hunting-spiders, which have spun the first
sheet near the ground, are laid downwards upon the upper
surface. Web-spinners, working at higher levels on the
vegetation, generally lay their eggs upwards upon the lower
surface of the sheet. In many individual cases, such as
that of Palystes described by Warren, it is far from obvious
why the eggs do not at once fall from their correct
position.

The eggs are then covered with the intervening padding,
when this is used ; and lastly, another sheet is spun over
all. The lower sheet is then generally freed from the
ground so that the whole cocoon may be picked up and
finished by turning it round and round by the legs while
the spinnerets cover it with more threads of silk. This
rounds it off and seals up the equatorial joint.

In many cases the cocoon is now finished. It may be
retained in the mother's possession, or fastened to a stone,
or to a fence, or it may be suspended on a stalk, as in the
examples shown in Fig. 85. Again, it may be covered with
a protecting coat of mud or of small pieces of wood or of

232

THE BIOLOGY OF SPIDERS

tiny stones, which make it less conspicuous and also help
to render it immune from the attacks of Ichneumons.

The size of the spider's abdomen is always much
reduced by the laying of the eggs. In some spiders the
reduction is so marked that the abdomen is con-
spicuously wrinkled even before the actual laying is com-
pleted.

The Cocooning Instinct

Mistakes are sometimes made in the placing of the eggs,
and these mistakes are never corrected. The empty cocoon
is carefully finished, while the eggs remain exposed beside
it or lie on the ground below. This illustrates the nature
of the actions which the spider performs in cocoon-making ;
they form yet another series of instinctive acts of the chain-
instinct type. Virgin spiders generally follow the same
course as do those that have been fertilised, and construct
with equal care cocoons of infertile eggs. Several spiders
have been known to devour their infertile eggs as soon as
they were laid, but it is not certain whether this is due to
the unnatural circumstances of captivity and to some
disturbance occasioned by the observer, or whether the
spider " knew " that the eggs could not hatch. However,
the fact that virgin spiders behave like this shows that the
series of instinctive actions is initiated by the maturation of
the eggs within. Probably external sensations of touch
decide the choice of the actual spot where the cocoon is
made : for example, Montgomery noticed that a large
proportion of his captives began the first sheet on or near
a drop of water which was lying in the cage.

It would be difficult to find a more beautiful instance
of the complementary nature of the male and female
characters, than this comparison between the sexes of
spiders. Maturity in the male impels it to give up web-
spinning, to take to a wandering life and to commence
courtship when a suitable opportunity occurs, while
maturity in the female impels it in due course to perform

MATING AND PARENTHOOD

in the correct order all the complex actions necessary for
making a cocoon.

Forms of Cocoon

It is not surprising that, since it is possible to trace an
evolutionary series of web-forms, something of the same
kind can be done for cocoons. It is not quite so satis-
factory a succession, because there is only a general and
not a complete resemblance between the cocoons of all the
species of any one family, while some of the most striking

Fig. 85. — Spiders' Cocoons.

and complex forms of cocoons appear at comparatively
low levels.

It seems fair to assume that if the primitive nest was no
more than the lining to a cranny, the primitive spiders
merely laid their eggs against the side of the nest. The
first step in the production of a cocoon came when the egg-

234 THE BIOLOGY OF SPIDERS

mass was provided with a protective cover. This condition
probably remains with the Liphistiomorphae and some of
the simpler Mygalomorphae. The next stage is the
provision of a special base on which to lay the eggs, which
are then covered simply, as before. This condition is
general among the wandering Drassidae and Clubionidae and
the jumping Salticidae, spiders which only spin chambers
for mating, moulting, egg-laying, and wintering.

Among the Clubionidae, however, some of the most
wonderful of the cocoons are found. The best-known
examples are those of the common British species of the
genus Agroeca, whose cocoons resemble miniature wine-
glasses, coated with a thin layer of mud (Fig. 85).

In the next stage the cocoon, consisting still of base and
cover, is spun away from any nest. These are represented
by the lenticular cocoons which the wolf-spiders carry
about with them, as well as by the small flat cocoons, fixed
to stones and the bark of trees, which are produced by
many of the smaller Linyphiidae.

In the last stage the cocoon differs from those just
mentioned only in the addition of a middle layer of soft
down, or an outside wrapping of protective substance.
These are the cocoons of the Theridiidae and Epeiridae.
Some of these may be suspended on stalks, like those of
Theridion varians or Me ta menardii, but the majority are
plain spheres or hemispheres, either hung in the web or
attached to some solid surface.

The outer layer of protecting substances may be com-
posed of anything which lies accidentally at hand, as in the
case of ordinary house-spiders, or of material actually
determined and sought for, as in the case of Agroeca.

Care of the Cocoon

Many spiders, perhaps the majority, pay no heed to
their cocoons after they are finished, and die sooner or
later after the labour of completing them. This is true of
practically all the Linyphiidae and most of the Epeiridae,

MATING AND PARENTHOOD 235

the exceptions among the latter family being those which
so closely resemble their own cocoons that they acquire a
degree of protection by continuing to live among them. It
is also true of many of the simple wandering spiders, but
some of those who spin a silk chamber all round themselves
and make their cocoon inside it do not forsake their eggs,
remaining in the nursery on guard for some time.

Among wolf-spiders, and Theridiidae and several others,
however, personal concern for the cocoon is the general
rule. The possession of a cocoon changes the mother's
entire outlook on life, and her regular reactions to certain
stimuli are very different after the eggs have been laid.

Most of the Theridiidae hang up their cocoons near the
little bell-like retreat in which they themselves rest, but
one common British species, the small brown Theridion
bimaculatum, always clasps hers in her legs and carries it
about. These spiders vigorously attack anything which
ventures to approach or threaten their cocoons, but there
are exceptions to this. Montgomery has recorded that
Theridion tepidariorum often hangs up enshrouded flies close
to her cocoon. When she has finished feeding, she cuts
the fly loose and lets it fall ; sometimes the cocoons fall
with it, and in such circumstances the cocoon is not raised
into the web again.

Crab-spiders generally mount guard over their cocoons
with some tenacity. Montgomery observed that Xysticus
stomachosus after completing her cocoon would not leave it
for ten days, even to secure food. After ten days she would
leave it to chase prey, but always returned to her charge.
Bristowe described Diaea dorsata as sitting on her egg-
cocoon, catching such small insects as came her way. She
bit fiercely at larger ones to drive them away, stretching
out her front legs and jerking her body in a way which
seems to be a recognised sign of hostility. Similarly
Ctenus malvernensis when threatened falls on her back,
spreading wide her legs and opening her chelicerae.
Palystes natalius, the African Sparassid, is equally deter-
mined. The female will not feed while she is guarding the

236 THE BIOLOGY OF SPIDERS

cocoon, though sometimes she will take a little water. If
an insect approaches, she seizes it with her chelicerae and
throws it down with very manifest purpose. As a rule,
when she is not hungry and has no cocoon, she simply
moves away from any insect that may touch her, without
attempting to bite it. A member of another family, Drassus
fieglectus, carries her cocoon about with her, and refuses to
feed while so occupied.

But care of the cocoon, as distinct from care of the
newly-hatched young, reaches its climax in the families of
Pholcidae, Pisauridae, and Lycosidae.

It is well known that Pholcus phalangioides , a common
species in the south of England, carries her cocoon in her
chelicerae. The cocoon in this instance is so flimsy that
the eggs are easily visible — indeed it is only after the young
have hatched that one can see, from the thin silk case that
is left, that a real cocoon has been surrounding them at
all. Generally the mother retains her hold upon the cocoon
until the eggs hatch, but occasionally she has been seen to
hang it up while she cleans herself or feeds. With some
difficulty, even with the help of her second and third legs,
she frees her jaws from the cocoon, touches it with her
spinnerets, and suspends it from a few threads of the web.
When she has finished she returns and takes up the cocoon
again.

The Pisauridae, a family of hunters related to the wolf-
spiders, include a species, Pisaura mirabilis, which is very
common in England. The cocoon is a large cream-coloured
sphere, which the mother carries about under her sternum.
When the young spiders are nearly ready to emerge, she
fixes it to the end of a branch of a shrub, and all round
and about it spins a beautiful silk nursery. Outside this
she mounts guard for the rest of her life.

Female Lycosidae carry their cocoon, as is well known,
attached to their spinnerets, and guard it with great tenacity.
If it is forcibly taken away, the spider seems at first to be
stupefied, she moves slowly, as though dazed, with none of the
rapid precision which usually characterises her movements.

MATING AND PARENTHOOD 237

It is evident that her organisation at this time of her
life demands that there be something in contact with her
spinnerets. If the cocoon is taken away and she is pre-
sented with it again, so that she can feel it, for she is unable
to recognise it by sight, she immediately fastens it to her
spinnerets and regains all her former activity. Peckham
showed that the spider generally retains her response to the
restored cocoon for sixteen or seventeen hours, seldom as
long as twenty-four hours, and in no case for forty- eight.
It is tempting to ascribe this apparent desire of the spider
for her cocoon to maternal affection, but in reality her
actions are nearer being automatic. She does not dis-
criminate between , her own cocoon and that of another
species, and accepts with equal readiness a pith ball or a
pellet of cotton wool. Locket has recorded an instance of
a Lycosa palustris found running about in natural circum-
stances with a small snail-shell attached to her spinnerets.
Evidently the spider is impelled from within to carry some-
thing, and it is not essential that this something shall be
her own cocoon.

In this respect wolf-spiders are in interesting contrast
to the African Palystes natalins. These females, when
offered their own cocoon and that of another spider, have
no hesitation in choosing their own. They decline to
attend to another cocoon if their own is available, and if
the two cocoons are put into the cage and the spider is
placed on the wrong one she will desert it and go to her
own. It is probably by smell that the spider detects her
own cocoon, but sight may also help. On one occasion a
spider deserted her own badly misshapen cocoon in favour
of another properly made one ; and again another's cocoon
was preferred to her own by a spider whose cocoon was
stained with aniline dye.

Spiders of the family Theridiidae, which live in close
association with their cocoons, will also refuse substitutes.
In no case, however, would true associative memory seem
to be involved. The spider's actions are instinctive
responses to a particular stimulus.

238 THE BIOLOGY OF SPIDERS

Hatching : Care of the Young

As a general rule the young spiders escape from the
cocoon without any help. They may be able to bite
through the imprisoning threads, but it probably more
frequently occurs that the cocoon simply splits at its weakest
part, when the pressure of the youngsters within becomes
great enough. Many cocoons, as has been stated, are
made of a base and a cover, and the equatorial seam where
these meet is more readily torn. Fabre has described the
almost explosive rupture of the cocoon of Epeira fasciata
when brought into the warmth of the sunshine. Several
of the spiders which live close to their cocoons and guard
them from intruders, take some share in the emergence of
the young. It seems to be the general rule that such
Theridiidae, Pholcidae, and Thomisidae cut open the
cocoon when the moment has arrived ; and Fabre, in a
sentimental mood, describes this action as the last act in
the life of the crab-spider, Thomisus onustus.

Generally, however, the mother survives and a sort of
family life may follow. Co-operation of this kind is rare
among spiders, and its occasional occurrence is therefore
interesting. It emphasises the wide diversity of habits in
the order.

Wolf-spiders give their newly-hatched young more
attention than do most other spiders. As soon as the
spiderling has scrambled from the cocoon, it climbs upon
its mother's back, where with its numerous brothers, it
maintains a precarious foothold until it is strong enough
to fend for itself. The mother presents a very curious
appearance with the crowd of young ones all over her
abdomen and part of her cephalothorax. It has been said
that the young refrain from crowding upon the mother's
eye-region, but the truth is that, if any should venture too
far forward, the mother gently but firmly sweeps them off
with her leg. They are often scattered by accidents, but
do not voluntarily descend, except when the mother is
drinking, when a few have been seen to scramble down to

PLATE IX

Cocoon of Epeira fasciata. x i.

To face p. 238.] [H. Main, photo.

MATING AND PARENTHOOD 239

the water's surface and back again after assuaging their
thirst.

The habits of the mother-spider do not seem to be so
strongly influenced by the possession of the hatched brood
as they previously were by the presence of the cocoon.
The loss of half her family does not seem to be regarded as
a catastrophe, and conversely the mother-spider raises no
objection to taking on the additional burden of another
spider's offspring, should any happen to come aboard.
Warburton gives an account of a fight between two mother
wolf-spiders, after which the scattered broods climbed upon
the victor as she ate her victim, and Fabre says that three
families may be accommodated on the same spider.

No other kind of spider carries her young about with
her so solicitously as the wolf-spider. The nearest approach
is among the Pholcidae, whose young immediately after
hatching cling to the chelicerae of their mother. They do
not as a rule stop very long in this position.

The brood of some web-spiders continue to live for a
short time in the protection of the parent- web. Young
trap-door spiders are in no immediate hurry to leave their
burrow. The most striking developments of a family life
have been described by Locket among some of the Theri-
diidae, particularly Theridion sisyphium. The mother and
all her offspring live in the same web. When a fly is
entangled the mother attacks and kills it ; she then bites
its body in several places. The young ones make their
way to the fly and, crawling over it, feel it with their palpi.
They stop at the soft spots, particularly at the holes made
by the mother, and rhythmical movements of their body
then follow, showing that they are sucking vigorously.
Locket's most striking discovery is thus described in his
own words : " On several occasions I found two or three
young spiders collected round the mother when she was
not feeding, and on examining them with a microscope
found that their mouths were applied to hers. Presumably,
then, she was feeding them. I have never heard of another
instance of this habit among spiders."

240 THE BIOLOGY OF SPIDERS

Fertility

The fertility of spiders varies very greatly. It is least
among the species that care for their young or are well
protected, by coloration or by specialised habits, from their
natural enemies. It is greatest among those that leave
their cocoons to chance and that lead lives exposed to the
attacks of wasps and ichneumons.

We may take Dictyna uncinata as an example of the
small family type ; it produces something under thirty-five
eggs a year, but some rarer species have far fewer. Thus
Oonops pulcher makes several cocoons each containing but
two eggs ; Synageles picata lays three eggs.

The large British spiders, Epeira quadrata and Epeira
dtademata, lay about six hundred eggs, and the wolf-spiders
have about the same number. The African Palystes
natalius reaches about eight hundred. The cocoons of the
large American Epeirids contain from fifteen hundred to
more than two thousand eggs, while some of the large trap-
door spiders lay as many as three thousand eggs.

When the population of spiders remains approximately
constant in numbers there must be a relation between the
fertility of the species and the risks to which it is exposed,
so that of the progeny of a pair of spiders, a pair survives.
At present our knowledge of the details of the life of spiders
is inadequate to explain the great differences in fertility that
are known to exist.

CHAPTER Xll

THE DEVELOPMENT OF SPIDERS

Biological theory looks upon the animal or plant as an
assemblage of a vast number of units known as cells. Each
cell is, to a certain limited extent, an independent unit,
bounded by its own cell wall (when one is present) and
controlled by its own nucleus. Each cell has originated
from the division of some pre-existing cell and can, by
division, itself produce more cells. Thus the whole of an
animal's body has in the course of its development and
growth arisen from a single cell. Indeed, the whole animal
and plant population may be regarded as the outcome of
an enormous number of generations of cells, stretching
back into remote antiquity to their origin in the first speck
of primordial living matter.

Cell-division

The individual animal normally comes into being when
the egg-cell or ovum of the female parent is " fertilised " by
the spermatozoon of the male. The product is a zygote, a
single cell capable of a development which neither of its
producing gametes can bring about alone. This chapter
is concerned with the origins of the gametes in the gonads
of the parents, their fusion and the subsequent develop-
ment of the zygote. It is necessary first to understand
something of the process by which cells divide, the process
called mitosis or karyokinesis.

The nucleus, in which the control of the cell's activities
is evidently vested, consists of a special protoplasm called

241 R

242 THE BIOLOGY OF SPIDERS

nucleoplasm, in which lies a mesh of darkly-staining threads,
the chromatin network. The whole is surrounded by a
nuclear membrane, outside which lies the centrosphere, a
star-like body, whose nature is something of a mystery.

In the process of cell-division, the nuclear membrane
disappears, putting the nucleoplasm into continuity with
the cytoplasm of the rest of the cell, and the chromatin
network is rearranged, forming a continuous thread or
skein. This skein breaks into a definite number of short
pieces, the chromosomes. Meanwhile, the centrosphere
has divided and the two halves have moved apart, still,
however, connected with one another by a number of very
delicate rays. To the equator of these rays the chromo-
somes become attached and lie in one plane across the middle
of a spindle-like figure. The chromosomes are split
longitudinally and the split half-chromosomes are borne on
the ends of the rays of the now separated centrospheres.
Skeins are now reformed, chromatin networks and nuclear
membranes follow, and the segregation of the protoplasm
round the two daughter nuclei completes the formation of
two cells from the original one.

In this process of typical mitosis it is to be noticed that
the cytoplasm of the cell plays no part. Further, the
number of chromosomes produced is a fixed and definite
one for each species, and is known as the species number.
In man the species number is 48, in many spiders it is 14,
in others 24 or 54. The chromosomes are split longi-
tudinally and not transversely, which means that if a chromo-
some be (as it probably is) a linear aggregate of smaller
units not necessarily all alike, the two daughter chromo-
somes resemble each other exactly. They would not do so
if the division were transverse. According to most cytolo-
gists all the inheritable characteristics are represented
somehow in the chromosome ; hence the interest which
attaches to these bodies arises from the fact that in studying
them we are studying, as nearly as is yet possible, the
actual carriers of inherited traits. Chromosomes will be
referred to again in this chapter.

DEVELOPMENT

243

Oogenesis

In spiders the first signs of the developing ovary appear
in the embryo some days after the egg has been laid, as
two narrow longitudinal strands of tissue, ventral and
parallel to the developing gut. These strands contain
many large nuclei, most of which will ultimately be con-
tained in egg-cells, but their anterior ends develop into the
oviduct leading to the epigyne. The distinction becomes
evident a few days later when the future eggs or oogonia
come to occupy the centre of the strand and possess larger
nuclei than the peripheral cells.

The next change in the oogonia, the formation of
primary oocytes, is one of great importance. The division
differs from ordinary mitosis in that the chromosomes
appear at the equator of the spindle-rays in pairs instead of
separately, and disposed at right angles to the equatorial
plane instead of lying on it. When the oocytes in their
turn divide to form secondary oocytes, these pairs of
chromosomes separate instead of splitting. Thus the
secondary oocytes have but half the original chromosome
number, seven in spiders, instead of fourteen. This
reducing division or meiosis is a characteristic stage in the
gametogenesis of both sexes of animals and plants.

There is, however, another important feature to be
noticed in the production of the secondary oocytes. The
egg differs from the sperm in being essentially passive
while the sperm is active. Thus the sperm consists almost
solely of nucleus with the minimum quantity of investing
protoplasm, of which the egg has a plentiful supply. To
secure this supply, the division which produces the
secondary oocyte is unequal. When the pairs of chromo-
somes have separated, almost all the protoplasm remains in
association with one of the nuclei, the other nucleus is
extruded as the " first polar body."

The secondary oocyte now divides by a normal mitosis,
but again the protoplasm is unequally distributed and the
second polar body is cast out. The other product is the

244 THE BIOLOGY OF SPIDERS

mature ovum or egg-cell. In some animals the first polar
body divides into two cells by ordinary mitosis, so we may
sum up by saying that the oogonium gives rise to the egg-
cell plus three ineffective cells or polar bodies.

A large proportion of the cytoplasm in the ovum is used
as a basis for the yolk, whose function is the nourishment
of the developing embryo. Yolk is formed in different
animals by different methods and nuclear matter is some-
times concerned in its production. It appears, however,
that in spiders the yolk is purely cytoplasmic in origin,
though the nutritive material must be originally derived
from the haemolymph or " blood " of the spider, and,
further back still, from the food. As the ovum grows,
small droplets or yolk globules gradually appear, at first
near the surface and later inwards. They have a tendency
to be formed in radiating lines. The core of unchanged
rather granular protoplasm containing the egg-nucleus
occupies a more or less central position, and as the egg
increases in size, the yolk spheres grow by fusing with one
another. During this time the ova are being nourished by
copious supplies of surrounding lymph, rich in nutritive
substances. These are eventually traceable to globules of
reserve protein in the caeca of the food-canal.

As the eggs grow, the abdomen of the spider swells
considerably, and now, in some spiders at least, a very
remarkable feature appears. The pedicles which attached
the eggs to the original ovarian strand disappear, so that
the eggs lose their connection with the ovary and are, in
fact, lying in the haemocoelic cavity between the intestine
and the silk-glands. How, then, can the eggs be laid ? It
is found that each oviduct becomes perforated, close to its
junction with the uterus, and through this small aperture
the eggs squeeze themselves in single file on their way to
the exterior.

Spermatogenesis

Typical spermatogenesis resembles typical oogenesis
in the pairing and halving of the chromosomes. Each

DEVELOPMENT

245

spermatogonium gives rise to spermatocytes, and the final
spermatocytes have half the normal number of chromosomes.

There is an important difference between the two sexes
in the number of chromosomes. When the spermatogonia
divide there is seen to be an extra chromosome, making the
total fifteen, in place of fourteen. It must therefore happen
that in the pairing of the chromosomes which precedes the
reducing division, this extra chromosome must be un-
matched, with the further consequence that the final
spermatocytes and the spermatozoa are not all alike. Half
of them possess seven chromosomes, the others eight. This
extra chromosome is known as the X- chromosome or the
Sex-chromosome, because it seems to determine the sex of
the offspring. The ova are all alike with seven chromo-
somes : an ovum fertilised by a sperm with seven chromo-
somes produces a female with fourteen chromosomes in all
the cells, an ovum fertilised by a sperm of eight chromo-
somes produces a male with fifteen chromosomes in its
cells. This same difference has been noticed in some
insects and in some mammals, including man. The fact
that the spermatozoa are produced exactly similarly and in
equal numbers destroys many, if not all, of the attractive
theories of sex- determination of the Middle Ages — and
later.

Spermatogenesis in spiders seems to vary sometimes
from the typical sequence, at least in certain species.
Professor Warren of Pietermaritzburg, has observed in the
spermatogenesis of Palystes natalius frequent divisions of
the spermatogonia by mere fragmentation of the nuclei, or
division by amitosis. But if amitosis is general in spiders,
the belief that the several chromosomes are the individual
vehicles of particular hereditary characters would have to
be modified. At the moment, the situation is further com-
plicated by the description of quite typical spermatogenesis
for other spiders. It appears certain, however, that there
are two sorts of spermatozoa, some formed typically, and
the others smaller and produced by atypical changes. This
phenomenon is not unknown in other animals. Abnormal

246 THE BIOLOGY OF SPIDERS

spermatids have been found in many insects and molluscs
and even occasionally in mammals. In all cases, however,
there is a proportion of normal spermatozoa which effect
fertilisation. Both types may be found in the spermathecae
of female spiders, having been placed there by the methods
described in an earlier chapter.

Fertilisation

The soft and delicate eggs are laid, as already described,
in a quantity of syrupy lubricating fluid. Since the polar
bodies are formed within half an hour or so of the oviposi-
tion, and since ova do not usually attract sperms until
after the polar bodies are formed, it is most likely that the
spermatozoa are discharged from the spermathecae into the
lubricating fluid at the time that the eggs are laid and that
fertilisation occurs almost immediately afterwards.

There is no aperture in the outer egg-membrane or
chorion, but at the time of laying this is so soft that it would
offer no resistance to the passage of the spermatozoon.
The latter, therefore, penetrates the egg at any point, and
in eggs laid only half an hour before fixation there can be
found a small nucleus between the yolk globules, which is
no doubt the sperm-nucleus travelling towards the ovum-
nucleus.

Parthenogenesis

The exact significance and value of the nearly universal
phenomenon of the conjugation of the gametes is an old
problem and one which has not even to-day been satis-
factorily solved. There has never been any doubt that, in
the majority of cases, fertilisation is an essential preliminary,
without which development of the egg cannot occur. The
problem is complicated by our ignorance of what, precisely,
the ovum owes to the sperm, and also by the existence in
some animals of both parthenogenesis and polyspermy.

Polyspermy, or the entry of two or more spermatozoa
into an ovum, has not been observed in spiders, but there

DEVELOPMENT

247

are several records of parthenogenesis. If such records are
to be regarded as trustworthy, one condition must be
fulfilled. Since the female spider can store in her sperma-
thecae all the sperm required to fertilise three or four
cocoons of eggs, proof must be forthcoming that the spider
has not been mated before capture. The only proof of
this is that she shall undergo at least two moults, and so
become sexually mature, when in captivity.

The first record of parthenogenesis in spiders was made
by Campbell in 1884, on the not uncommon British spider
Tegenaria parietina. His spider spent most of her life in a
bottle and was apparently given no opportunity of meeting
a male. She laid a cocoon of eggs, as many virgin spiders
will do, and two of these eggs developed into young spiders.
These interesting little creatures, however, did not survive
for very long. Six years later a second case was recorded,
by Damin. His spider was Filistata testacea, the females
of which are said to be very common in the South of Europe,
while the males are much rarer. She underwent two
moults while in captivity, never met a male, but laid a
cocoon of eggs from which sixty-seven healthy young
hatched.

Montgomery, in 1908, kept two females of the famous
Black Widow, Latrodectus mactans, in circumstances which
would test the possibility of parthenogenesis, but none of
the eggs hatched. This result was in accordance with the
more extensive tests carried out by Blackwall fifty years
previously, in which no parthenogenetic young were
produced.

An important contribution to the subject has been made
by Warren in his recent work on Palystes natalius. Of
eight females caught and kept by him, four laid eggs which
all developed in a perfectly normal way, while the eggs of
the other four developed only partially and very slowly.
It is suggested that these eggs exhibited a parthenogenetic
tendency which varies in intensity in different individuals.
This is supported by the fact that a female which Warren
reared from the egg, of whose virginity there could there-

248 THE BIOLOGY OF SPIDERS

fore be no question, laid eggs which were able to undergo
the early stages of segmentation.

The only conclusion justifiable at present seems to be
that parthenogenesis in spiders is rare, but possible, at
least for some species.

Development

The fertilised egg is a spherical mass of protoplasm, the
zygote nucleus within but not necessarily at the centre,
surrounded by the yolk globules already mentioned,
arranged radially around it. Enclosing the whole are two
membranes, the vitelline membrane inside and the chorion
outside. A thin layer of protoplasm underlies the vitelline
membrane and is doubtless in continuity with the central
protoplasmic mass containing the nucleus, being joined to
it by the fine foam-like protoplasm through which the yolk
globules are dispersed.

The first division of the nucleus is meridional and
produces anterior and posterior cells ; at the same time the
two-celled embryo acquires a bilateral symmetry by the
flattening of the future ventral surface. The second
division is also meridional, but it is at right angles to the
first, and the third is equatorial. The eight-celled stage
thus consists of dorsal and ventral layers of four cells each,
and is reached in about ten hours from the time of laying.
After this the cell-division becomes irregular, and although
some workers have been able to recognise a sixteen-cell
stage, and even a thirty-two-celled stage, it is generally
agreed that irregularity begins after the third division. The
small cells travel between the yolk spheres in an outward
direction, and when about twenty-eight hours old the egg
possesses an approximately complete layer of perhaps a
hundred peripheral cells, surrounding the yolk within.

This condition forms a stage which is common to the
development of most animals and is known as the blasto-
sphere. In an egg like that of Amphioxus, not complicated
by large masses of yolk, the blastosphere is made by a very

DEVELOPMENT

249

similar separation of cells as they are produced, and takes
the form of a hollow sphere, bounded by a single layer of
cells. The formation of the blastosphere is usually taken
as marking the end of the simple process called segmen-
tation.

The next stage is one of great importance. The blasto-
sphere consists of a single layer of cells, whereas the bodies
of all higher animals consist of cells derived from three
embryonic layers. These germinal layers, as they are
called, are the epiblast outside, the hypoblast inside, and
the intermediate mesoblast separating them. The forma-
tion of the layers themselves is of interest because of the
importance attaching to them. Adult organs or parts
produced from different embryonic layers cannot be con-
sidered homologous, even if they have the same function,
and must not be taken as evidence of relationship. The
Malpighian tubules have already been mentioned in
illustration of this. Hence the three germinal layers form
a court of appeal from which we may learn much concerning
the relationships of different classes of animals.

In a simple hollow blastosphere the next stage consists
of a tucking-in of one side until it touches and is surrounded
by the other, just as a hollow ball might be pushed in with
the thumb. In this way epiblast and hypoblast are formed.
But this simple invagination is not possible when the
segmentation cavity is filled with yolk, and other methods
must therefore be used.

In spiders, the cells which form the ventral surface
multiply rapidly at a point near the anterior end, forming
an opaque white mass which ultimately projects a little
above the surface of the egg. This is called the anterior
cumulus. Its cells multiply rapidly, absorb nourishment
from the yolk and form first the mesoblast, then the hypo-
blast. A similar posterior cumulus arises behind the first
and ultimately comes into contact with it (Fig. 86). The
meeting-point of the two cumuli marks for the first time
the division between the cephalothorax and abdomen. At
this stage, which is reached after about three days, the egg

250 THE BIOLOGY OF SPIDERS

is still approximately spherical and the mesoblast is a single
layer of cells internal to the ventral surface.

There now appear almost simultaneously four segments
of the cephalothorax, and later a fifth segment. Meanwhile

the mesoblast within
has split into two
layers, the space be-
tween them constitut-
ing the coelom or
primitive body-cavity,
but this is ultimately
obliterated except in
the coxal glands and
the stercoral pocket.

Appendages now
begin to appear on the
cephalothoracic seg-
ments, at first as small
knobs and later elon-

FiG. 86. — Development. An early stage in
development of the egg. After Mont-
gomery. A, Anterior cumulus. P, Pos-
terior cumulus.

gating until they become obvious cylindrical limbs (Fig. 87).
After their appearance, the abdomen, previously represented

pIGi 87. — Development. Stage Fig. 88. — Development. Stage

snowing beginning of limbs. showing abdominal segments

After Montgomery. i, Che- and limbs. After Montgomery,
licerae ; ii, Palpi ; iii-vi, Legs.

only by the posterior cumulus, begins to elongate rapidly,
spreading from beneath round the egg until caudal and
cephalic regions almost meet. It also acquires a temporary

DEVELOPMENT

but very definite segmentation, consisting of from eight to
twelve segments. The foremost of these segments dis-
appears very early and never bears a sign of appendages,
but on all the others rudimentary limbs appear in the form
of small knobs (Fig. 88). Those of the second and third
segments become invaginated and form lung-books ; those
of the fourth and fifth persist as spinnerets ; the rest
disappear with the segments. Heart, intestine, and nervous
system have meanwhile been formed within, and all the
other internal structures are gradually established.

If the preceding account has been followed, it will be
realised that the embryo spider is formed on the outside of
the egg and that it is now bent round it with its ventral
surface outside and convex (Fig. 88). This extraordinary
position is altered before hatching by a process not generally

Fig. 89. — Embryology. After reversion. From Balfour.

seen in the embryological development of other animals
and called reversion. The mechanical forces which bring
about reversion have been variously described and the
most likely course of events seems to be as follows. The

252

THE BIOLOGY OF SPIDERS

' sternum widens and therefore shortens, so dragging the
abdomen down. Simultaneously the elongating legs,
pressing against the harder chorion, force the cephalo-
thorax upwards, so that the bending of the spider is reversed
and it becomes convex above and concave below. It is
now ready to hatch (Fig. 89).

Hatching

Not less than a fortnight after the egg was laid the
embryo bursts the vitelline membrane and chorion by the
forward growth and stretching of the cephalothorax. The
period varies, however, as might be expected, with the
same species in different climates, and with different species
everywhere according to their life-history. Eggs laid in the
spring or early summer become small independent spiders
in the course of a few weeks, while those laid in the autumn
do not appear until the next spring. Hatching from the egg
by the rupture of its membrane is, however, not the same
thing as escape from the egg-cocoon, inside which the small
spiders remain for a similarly variable time. At this
period of their lives there is some justification for following
the practice of the few authors who refer to them as larvae,
for they differ in several ways from the adult or even the
free-living young spider. Larva is, however, a word with
an exact technical meaning and should strictly be applied
only to those instances of development in which there
occurs a metamorphosis or complete change of outward
form and often of habits as well. The newly-hatched
spider in the cocoon is not entirely or even conspicuously
different from the adult ; it is merely incomplete ; more-
over, its subsequent changes are introduced by an ordinary
moulting which differs in no essential from those that
follow. The development, in fact, is " direct " at all times
and, for these reasons, the word " larva " is not admissible.
When it is necessary to distinguish the newly-hatched
spider from the spider outside the cocoon, the word
" spiderling " might well be used.

DEVELOPMENT

253

The Spiderling

The spiderling, while still within the cocoon, is a
particularly interesting creature. At first it is quiescent,
but in a few days it begins to move about inside its silk
nursery. Warren has described the curious fact that
during all this time, even when the spiderling was not
moving about, a constant up-and-down movement of all
the limbs is to be seen, quite slow but quite continuous.
He suggests that these movements have probably a physio-
logical function promoting the circulation of the blood
during the development of the vascular system.

By far the most interesting thing about the outwardly
normal spiderling is its incompleteness. The spinning
glands have as yet scarcely begun to form, so that the young
creatures do not waste their substance in the production of
silk. If threads were spun at this time, they would merely
tend to choke up the cocoon and impede the movements of
the occupants. They would be doubly purposeless, for there
is no prey to be caught and, even if there were, the spider-
ling would be unable to eat it. The spiderling cannot
feed, for its mouth-parts are still incomplete. For some
days, until by moulting it ends its pseudo-larval life, it
depends for nourishment on the remnants of yolk which
are still present in the gut-caeca. All the spiderling's
energy is due to the retention of the yolk, which can easily
be seen under a microscope, even as its disappearance from
the abdomen can be followed in the gradual thinning of
the fat little creature.

The young spiderling is almost entirely devoid of pig-
ment and is therefore nearly transparent ; under a micro-
scope the stomach and the diverticula filled with yolk can
easily be seen. The proportions are not those of the
adult. Most interesting results are being obtained by a
sufficiently close study of these spiderlings, which are
easily mounted for examination. Spiderlings of different
families, including the most specialised, usually show con-
siderable resemblance at this time, and they recall the

254 THE BIOLOGY OF SPIDERS

adult forms of more primitive types. For example, the
coxae of the fourth legs are usually widely separated, and
the end of the sternum is produced between them. All the
coxae are longer, when compared with the other leg-joints,
than in full-grown spiders. In the adult Epeira the palpi
are quite short and inconspicuous, but in the spiderling
from the cocoon they are about two-thirds as long as the
legs of the first pair. The result is that at first glance the
spiderling seems to have ten legs, in fact, exactly the same
appearance as have the Mygalomorphae.

The arrangement of the eyes, which, as already
mentioned, is a feature used in the separation of the families
and genera, illustrates the same early resemblance of
divergent types. For example, the Lycosidae and the
Pisauridae are two allied families of hunting-spiders, the
Lycosidae being later arrivals in the history of the spider
race than the Pisauridae. Their eye-patterns are distinct,
but the spiderling Lycosid has the eyes of the Pisaurid.

All the limbs are smooth and colourless, for the spider-
ling has no hairs or spines. The claws on its tarsi are
smooth and devoid of teeth. On the abdomen, the anterior
spinnerets are somewhat in front of their final positions.
The anal tubercle is prominent, and above it traces of
segmentation are still perceptible. A large proportion of
the little creature is soluble in caustic potash, showing that
chitin is not as yet abundantly present — in fact, the tiny
fangs of the chelicerae are almost all that can be recognised
after treatment with this reagent.

This stage of the spider's development is brought to an
end by its first moult, which usually but slightly precedes
the escape of the spiderling from the cocoon. As a result
of this first moult, the legs lengthen and a certain degree of
colouring appears, but not that of the adult pattern. The
silk glands commence to secrete and silk can be spun for
the first time, though the alimentary canal is generally still
incomplete. Often, too, the eyes only appear at this stage.

DEVELOPMENT

255

Recapitulation

It is obvious that to a very marked extent the developing
spider illustrates the important biological fact known as
recapitulation. In the embryonic development of most
animals, certain features appear which have only a transient
existence and vanish before the creature hatches. Thus in
spiders, the appearance of both thoracic and abdominal
segments has been noted, and of abdominal appendages
which are not present when the spider has grown up. The
whole of embryology is full of similar instances, but the
most striking examples are found among the Vertebrates.
The developing vertebrate has at one time a simple tubular
heart, pharyngeal apertures like gill-clefts, a notochord,
segmented muscles, and so on. All these features are
known in the adult states of lower Vertebrates, and their
temporary appearance in the life-history of higher Verte-
brates can scarcely be explained by any other hypothesis
save that of recapitulation. Based upon the theory of
evolution, this explanation suggests that their retention is
due to the fact that these structures were once possessed by
the ancestors of the race, but that they have been lost or
repressed in the evolutionary changes which followed. In
other words, the embryonic development of an animal is a
much abbreviated recapitulation of the historical evolution
of its race, or, in Haeckel's form of statement, ontogeny
repeats phylogeny.

The recapitulation theory has had a great attraction
for some writers, who have extended it beyond justifiable
limits. As long as it is confined to the embryonic per-
sistence of important structures, known to have been
possessed in primitive ancestors, but disappearing in the
later development of the type in question, the theory is on
firm ground, but it is hopeless to extend it to include every
embryonic character, and to interpret all as inheritances
from ancestral conditions. A slavish adherence to the
recapitulation theory in its extreme form would lead one
to postulate the existence of an ancestral spider which
could neither see nor eat.

256 THE BIOLOGY OF SPIDERS

Moulting or Ecdysis : Regeneration

The young spider, after its escape from the cocoon,
becomes an independent individual, and, as explained in a
previous chapter, its first care is migration. It is worth
noticing that at this time the outstanding feature of the
spider's character is its apparent bravery. Apart from the
recklessness with which it launches itself upon its first
aerial voyage, it exhibits an unhesitating boldness in
attacking its prey. These young spiders may be kept in
cages and fed on gnats and other small insects. The delicate
webs which they spin are all but invisible, but when the
gnat intrudes, the spider rushes upon it without hesitation.
Sometimes the spider bites the insect before it succeeds in
disentangling itself, and then gets carried bodily round the
cage, still holding fast. Its whole behaviour suggests
vigour and that quality of insurgence which characterises
all life.

As the spider feeds it grows, with the result that the
rigid chitinous exo-skeleton becomes too tight for its
expansion. Since the chitin is not only hard but non-
living, it must be cast before an increase in size can take
place. This discontinuous growing is not, of course,
peculiar to young spiders : it is characteristic of Arthropoda
in general, and is necessitated by the non-expansible non-
cellular, non-living cuticle. Even at lower levels, as in
nematode worms, there is a somewhat similar punctuation,
associated with cuticular moulting.

The process of moulting or ecdysis in spiders has been
several times described, and indeed it is not difficult to
observe it. It is only necessary to keep a sufficient number
of immature spiders in cages and to look at them often
enough. It is probable that in natural circumstances
ecdysis most generally occurs at night, but in captivity it
is often performed at a more convenient time.

Ecdysis does not occur without warning. For some
days before it is due, the spider refuses food and the colour
of the legs darkens until they are almost black. From all

DEVELOPMENT

257

the published accounts and from my own observations, it
seems that the position which the spider occupies when
moulting is similar in all families, and that, broadly speaking,
the process is always more or less the same.

For some time before any visible changes occur, the
spider suspends itself upside down, its feet close together
and its abdomen supported by a thread from the spinnerets.
Its first activity is a raising and lowering of its cephalo-
thorax by bending the legs, and a broadening of the abdomen.
This causes the cuticle of the abdomen to split along the
middle of the back, and the split gradually extends round
the sides of the cephalothorax until it reaches the chelicerae.
It usually stops here. The old cuticle soon shrivels off the
abdomen and the carapace of the cephalothorax soon falls
away. The most tedious part of the operation is the
simultaneous extraction of the legs and palpi. The cuticle
here does not split, so that the limbs have to be slowly
pulled out. This is achieved by a series of heaving move-
ments, assisted by the weight of the spider's body, which
gradually extracts them from their old coverings. During
this time the spinnerets are still attached by the silk threads,
and it is important that the now empty tarsi remain fixed
in their original positions. If one of them come adrift, the
spider has great difficulty in freeing that limb.

As many as six hundred pulls may be required to
remove the legs, and the time occupied by the whole casting
of the cuticle varies from fifteen to forty minutes. After
the moult the spider is paler in colour and softer in con-
sistency than usual ; it is exhausted and rests motionless
for some time, but before the new cuticle has hardened it
combs itself, particularly its jaws, mouth parts, and under
surface with its metatarsi. Possibly this sets the setae in
their proper directions.

The period of moulting is a critical time in the spider's
life, during which it is quite unprotected. It is therefore
not surprising that some species spin a silk chamber all
round themselves and cast their cuticle within its shelter.
Internal changes begin a comparatively long time before

258 THE BIOLOGY OF SPIDERS

the actual casting, before, during, and after which the
creature is temporarily deprived of several of its faculties —
sight, touch, movement, and even for a moment respiration.
Wagner, who described the course of the moult as long ago
as 1888, stated that a lubricating fluid is secreted to help
the process. This seems to have been an error, for under
the most favourable conditions no drops of fluid are visible
and the limbs seem to be perfectly dry when extracted.

At the time of moulting the spider's power of regenera-
tion is often in evidence. It is a common character of
most of the lower animals that they can reproduce lost
parts. Higher in the animal kingdom this regenerative
power becomes less, until in mammals there is little more
than the ability to heal a wound. It has already been
mentioned that the spider often escapes from its captors by
throwing off a limb. The lost parts grow again beneath
the exo-skeleton and at the time of moulting become
visible and functional. If the loss occurs shortly before
moulting is due, a rudiment only may be produced, but if
there is a subsequent moult, a perfect limb results. This
accounts for spiders with an apparently asymmetrical set
of legs.

Size

Owing to the difficulty of rearing young spiders, there
are few records of the number of moults that occur before
the spider reaches maturity. It is probable that not less
than three and not more than ten changes of integument
take place, but the number may depend on the size of the
adult and on the circumstances of growth.

The size of the adults of the various kinds of spiders
differs within unusually wide limits. The smallest known
spiders are probably the members of the Amazonian
species, Ogulnius obtectus (Fig. 90) of the family Epeiridae.
The female of this spider is only one millimetre long of
an inch). The British spiders of the genus Tapinocyba
are little more than a millimetre long, and the type specimen
of the male of Tapinocyba praecox is under a millimetre.

DEVELOPMENT

259

Male spiders, as has been noted, are nearly always smaller
than the females. On the other hand, the body of the
trap-door spider, Theraphosa
leblondii, is nearly 90 mm.
(about 3 \ inches) long : and
several other members of
this sub-order are over sixty
millimetres.

It should also be noted
that individuals of the same
species are not all of the
same size. The species of
Tegenaria, for example,
found in sheltered situations FlG- Ogulnius obtectus. x 40.

After Pickard- Cambridge.

in Cornwall are very much

bigger than those which live in the north of England. It
is frequently noted in reports on collections from certain
localities that the particular spiders are larger or smaller
than the general run of their kind, and no doubt local
conditions alone are responsible for this. I have been
told of a Pholcus phalangioides caught in England whose
legs spanned six inches, an excess of nearly fifty per cent,
over the usual size.

It seems also to be quite well established that spiders
may sometimes increase in size, even after sexual maturity
has been attained, to such an extent that another moulting
may be necessary. Thus it may come about that a spider
which has been fertilised and has laid her eggs in their
cocoon, may afterwards moult. It has even been suggested
that in spiders whose mature life occupies more than one
year, an annual moult may be a normal occurrence, but
there is as yet no definite information on this point.
Moulting after egg-laying would seem to be exceptional
rather than usual.

26o THE BIOLOGY OF SPIDERS

Alternatives in Development — Dimorphism

The normal development of the individual spider is a
repetition of that of its parents and is similar to that of its
brothers, but there are a few species in which alternative
types may arise.

One instance of this is the female of a spider already
mentioned (p. 159), Misumena vatia, which sometimes has
reddish streaks on its abdomen and sometimes has not.
A much commoner British spider, which is to be found
almost everywhere in summer months, is one of the Theri-
diidae, Phyllonethis lineata (Fig. 91). Four or five varieties
of this species exist. The typical form has a uniformly
yellow abdomen, with a characteristic arrangement of black
dots. A common variety, originally described as a distinct

Fig. 91. — Phyllonethis lineata. Variations of pattern.

species, Theridion redimitum, has a crimson red loop
surrounding the central mark, while in another, rather less
common and at first called Theridion ovatum, the crimson
forms a continuous shield over the whole of the upper side
of the abdomen. More rarely still pure white specimens
may be found and very occasionally uniformly pink examples
occur.

This spider is richer in well-marked varieties than any
other, but several possess varieties, often of the familiar
melanic type. The spider Drapetisca socialis in particular
is a species often found on the bark of trees, and specimens
vary from a light shade with well-marked pattern to a
uniform jet black, on which no pattern is visible.

DEVELOPMENT

261

The problem of the origin and relations of the different
varieties of Phyllonethis lineata does not seem to have been
worked out as yet. All the three commoner types may
usually be taken in the same neighbourhood, but it is not
known whether the pigmentation is influenced by the
surroundings or whether it is an unalterable inborn
character.

Among male spiders the phenomenon of dimorphism is
in a few species much more pronounced. The best-known
case among British spiders is in the little species Troxochrus
scabriculus. This was described in 1862, and in 1870
another, Troxochrus cirrifrons, was discovered and believed
to be its close ally. Some authorities maintain that the
two are distinct species, others regard them as varieties of
one, differing only in the extra tufts of " hair " on the
head of cirrifrons.

That this view is at least probable is supported by
another well-known instance of a similar dimorphism in the
American jumping-spider Maevia vittata. In this case
there is no doubt that there is but a single species, with one
type of female and two types of male. The two males are
found in equal numbers, and together are about as numerous
as the females. One male is uniformly grey and only a
little darker than the female, the other is pitch black with
yellow legs and carries on the frontal region three tufts of
" hairs " projecting forwards. In this respect, therefore,
there is a striking resemblance between the two instances
of dimorphic species.

The constitution of Maevia vittata has been carefully
studied by Painter, who finds that the varieties are accom-
panied by particular chromosomes. The cells of the
female spider possess two sex-chromosomes, represented
in Fig. 92 by the letter X, and one other chromosome-like
body, represented by the letter C. The ova are thus of
two kinds, those which carry XC and those carrying X
alone. The cells of the grey male possess one X chromo-
some and one C. Half of its spermatozoa, therefore, carry
neither X nor C, one- quarter carry X and C, and one-

262 THE BIOLOGY OF SPIDERS

quarter X only. The cells of the tufted male carry one X
chromosome only, so that half its spermatozoa carry X and
half nothing. Their possible unions, producing viable or
living zygotes, are shown in Fig. 92.

Fig. 92. — Scheme showing relation between dimorphic forms of
male Maevia vittata and the chromosomes of the gametes. Circles,
gametes ; squares, zygotes.

This work of Painter's is of particular interest since
it illustrates, for the first time among spiders, that the
chromosomes influence the sex and appearance of the
individual and its offspring.

Abnormalities in Development— Gynandry

It is a familiar fact that the customary distinction
between male and female organisms is absent from some
animals, such as earth worms and snails. These are
hermaphrodites, and are able to produce both ova and
spermatozoa. Hermaphroditism is unknown among spiders,
but the term is sometimes misapplied to abnormal specimens
which unite in their bodies some of the characters of both
sexes. Such freaks are properly described as gynandro-
morphs, the distinction being that hermaphrodites are
normal and functional members of their race, while

DEVELOPMENT

263

gynandromorphs are rarities, incapable of functioning as
either sex.

Gynandromorphs are well known among ants and in
the fly Drosophila. In the latter case it has been shown
that the cause of gynandry is the failure of an X chromo-
some to keep pace with the others, so that in an early
division of the egg it is dropped from one of the cells.
This cell and all its descendants have thus one X chromo-
some fewer than the others ; they show male characters,
while the rest show female characters. Thus the resultant
insect is a mosaic of male and female features.

The subject of gynandry in spiders was treated in a
paper by Hull in 19 19. The instances which are there
described may be classified in three groups, as follows :

1. One side male, the other female (Fig. 93).

Fig. 93 . — Gynandro-
morph Oedothorax
fuscus. Left side
male, right side fe-
male. From Hull,
after Kulczynski.

Fig. 94. — Gynandromorph Lophomma her-
bigradum. Cephalothorax female on left,
male on right. Abdomen male on left,
female on right. The smaller diagram
shows the genital area. After Hull.

2. The same, but one side imperfectly developed
before, the other behind.

264 THE BIOLOGY OF SPIDERS

3. One side male before and female behind, the other
side female before and male behind (Fig. 94).

Spiders with these peculiarities are very rare indeed,
and probably less than a score have ever been found. It
is clear that they are all of a mosaic type, probably due to
abnormalities in the behaviour of the X chromosome.

CHAPTER XIII

FOSSIL AND PRIMITIVE SPIDERS

There is always an intrinsic interest attaching to the early
history of a race, whether it be mankind or some group of
animals. The interest is due partly to our natural curiosity
about the beginnings of things, and partly to the fact that
our attempts to read these early histories are necessarily
mixtures of deduction and conjecture, and thus have the
appeal which the solving of a puzzle must always possess.

In Biology the early histories of the different classes of
animals gain an additional importance from the light they
throw on our interpretation of evolution. This is obvious,
because it is only from a study of the bodies and skeletons
of animals which died in far-off days that we can hope to
obtain an undeniable proof of the fact of evolution itself,
as well as an indication of the path it has taken in the group
we happen to be studying.

The Geological Record

These bodies and bones which the rocks have preserved
for us in the form of fossils, are as words on the pages which
make up the geological record of animal life. It is when
we remember how small a proportion of the animals of the
past can have died in circumstances suitable for the produc-
tion of fossils, and how small a proportion of the existing
fossils have as yet been unearthed and examined, that we
realise that the geological record must be very incomplete.
Ideally, it would be a story of surpassing interest and pro-
found value ; in practice we cannot hope for more than a

265

266 THE BIOLOGY OF SPIDERS

few hints. These, however painfully, we must try to piece
together.

In seeking to determine the geological history of the
order of spiders, we are faced with this incompleteness in
an extreme degree. Spiders' bodies are too soft to provide
good material for forming fossils among the stratified rocks,
with the result that in such situations the preservation of
spiders has occurred but rarely. There is, however, another
way in which not only spiders but also insects and other
invertebrates have been preserved for us, and this is in
amber. Amber or succinite is a compound of carbon,
hydrogen, and oxygen, but is not quite homogeneous in
character. It is a fossil resin, exuded from trees of the
Eocene and earlier Oligocene periods, and is found on the
shores of a large part of the Baltic and the North Sea.

The spiders preserved in amber belong to a much later
period of the world's history than those found in rocks,
and, as it is necessary to understand this, the following
table is given as a guide : —

Primary or Paleozoic Epoch.
Cambrian Era.
Ordovician Era.
Silurian Era.
Devonian Era.
Carboniferous Era.
Permian Era.

Secondary or Mesozoic Epoch.
Triassic Era.
Jurassic Era.
Cretaceous Era.

Tertiary or Cainozoic Epoch.
Eocene Era.
Oligocene Era.
Miocene Era.
Pliocene Era.
Pleistocene Era.

Earliest fossils.

Fishes.

Amphibia.
Reptiles.

Birds.

Mammals.

Man.

FOSSIL AND PRIMITIVE SPIDERS 267

It will be seen that the world's past is divided into three
major epochs, each of which is subdivided into a number
of eras, corresponding to defined systems of rocks. The
length of time, measured in years, occupied by these epochs
is a somewhat controversial subject on which it is difficult
to secure agreement. In any case the total age is so
enormous that the mind does not really appreciate it. It
may be said that life has existed on the earth for five hundred
million years, but in reality all that this conveys is " a very
long time."

Paleozoic Spiders

In the Paleozoic rocks, spiders occur in the Carboniferous
system. The first known fossil spider was discovered in
1866 in the argillaceous shale of coal formations at Katto-
witz, in Upper Silesia, and has been named Protolycosa
anthrocophila. It is a wonderfully fine and almost entire
specimen, its dark body well defined against the greyish
background of the shale. The separate joints of the legs
and palpi are clearly to be seen and even the setae which
covered them, while there is no mistaking its most striking
feature — the segmentation of its abdomen. The name
Protolycosa was a somewhat unfortunate choice, due to a
superficial resemblance of this unique spider to the modern
Lycosidae. Its segmented abdomen proclaims what the
rest of its visible structure supports — the fact that it is not
a distant relation of those primitive spiders which have
persisted till to-day as the Liphistiidae. For instance, its
legs have the same relative lengths as have the legs of the
Liphistiidae, and the close approximation of its eyes is
another primitive feature.

Another spider, similar in many ways to Protolycosa,
was discovered in Carboniferous strata in Illinois in 1874.
This was called Arthrolycosa antiqua, as it was regarded as
belonging to a different genus. Thirty-seven years later,
in 191 1, three fossil spiders were described from Dudley,
Worcestershire. One of these evidently belonged to the
same genus, which was thereby shown to have had a

268 THE BIOLOGY OF SPIDERS

distribution embracing the northern halves of both hemi-
spheres. A third species, Arthrolycosa danielsi, was added
to the genus in 191 3, also from Illinois. Five other fossil
spiders have been described as species of Arthrolycosa, but
they have been transferred by Petrunkevitch to a new family,
Arthromygalidae. Four other genera, each at present
consisting of a single species, complete the list of Paleozoic
members of the primitive sub-order Liphistiomorphae.

1 . Arthrolycosa antiqua Harger. 1874. Illinois.

2. Arthrolycosa danielsi Petrunkevitch. 191 3 . Illinois.

It is clearly of great interest to notice that this sub-order,
at present confined to the East Indies and Japan, was
evidently the dominant type of aranead population in
Paleozoic days. It possesses, so far as we know, at least
two genera in America and five in Europe.

No Paleozoic remains of the Mygalomorphae have been
discovered in either continent, and until lately none of the
most specialised sub-order, the Arachnomorphae, had been
discovered. This led to the assumption that these sub-
orders arose during the secondary or Mesozoic epoch, in
which case they might have been nearly coeval with
mammals. In 1904, however, several fossil spiders were
discovered in the coal measures of Nyran, Bohemia, and
two of these are Arachnomorphae. The names by which
they are now known are Eopholcus pedatus and Pyritaranea
tubifera. These are extinct species, whose descendants
to-day have become so modified that they are placed in
different genera, and they are of particular interest as
showing that spiders, of even the highest sub-order, were
already in existence in the Paleozoic epoch. For thirty-
eight years it had been believed that only spiders of the

3. Protolycosa anthracophyla Romer.

4. Eocteniza silvicola Pocock.

5. Arthromygale carbonaria Kusta.

6. Arthromygale fortis Fritsch.

7. Arthromygale beecheri Fritsch.

8. Arthromygale lorenzi Kusta.

9. Arthromygale palaranea Fritsch.

10. Racovnicia antiqua Kusta.

11. Geralycosa fritschii Kusta.

12. Perneria salticoides Fritsch.

1888. Bohemia.

1904. Bohemia.

1888. Bohemia.

1904. Bohemia.

1888. Bohemia.

1904. Bohemia.

1866. Silesia.
1 9 1 1 . Worcestershire .

FOSSIL AND PRIMITIVE SPIDERS 269

Liphistiomorph type were in existence at that early period
of the earth's history.

Another fossil Arachnomorph spider, which came to
confirm this discovery, was the third of the fossils from
Dudley. This was another extinct genus, and the spider
was called Archeometa nephilina. Its most characteristic
feature is the fact that its second pair of legs are longer than
the fourth pair.

Existing knowledge of Paleozoic spiders may therefore
be summarised by saying that the dominant types were in
every essential similar to the Liphistiomorphae of to-day,
and that they were apparently widely distributed over the
land. In saying this, it must be remembered that there is
as yet no information of the contemporary spiders from
the southern parts of the world. Spiders of the Arachno-
morph type were perhaps fewer in number, perhaps more
limited in distribution, but our present knowledge of them
is not sufficient to warrant any definite conclusions.

The Paleozoic Arachnomorphs may be tabulated thus :

1. Eopholcus pedatus Fritsch. 1904. Nyran.

2. Pyritaranea tubifera Fritsch. 1904. Nyran.

3. Archeometa nephilina Pocock. 191 1. Dudley.

No Mygalomorph spiders have as yet been discovered
in either Paleozoic or Mesozoic strata. It is therefore
necessary either to suspend judgment on these or to make
the assumption that they did not arise until Tertiary times.
This is unlikely, for the Mygalomorphae of to-day possess
a primitive type of structure which allies them more closely
to the Liphistiomorphae than to the Arachnomorphae, and
if primitive Arachnomorphae were existent in Paleozoic
times, probably Mygalomorphae were in existence too.

Mesozoic Spiders

Knowledge of the spiders of the Mesozoic epoch is not
so full, and indeed for many years no Mesozoic spider was
known. The Oolitic limestones of Pappenheim, Bavaria,
are famous both for the fineness of grain, which makes

270 THE BIOLOGY OF SPIDERS

them valuable for lithography, as well as for the number
and beauty of the fossils they contain. These include many
insects, among other animals, and four species of spiders
have also been discovered.

This scarcity of records from the Mesozoic rocks is
unfortunate. That spiders were numerous at this time
may be deduced both from their relative plentifulness in
the other two epochs, and from the number of insects and
other remains which indicate an environment quite suit-
able for the spider's mode of life. Circumstances, however,
were perhaps not favourable to fossilisation, and at present
the scarcity of Secondary spiders must be attributed to the
same Chance which renders all geological records so
imperfect.

Of the Cainozoic or Tertiary epoch there is, however, a
very different story to relate. Tertiary formations have
yielded comparatively large numbers of fossilised spiders,
from the following chief localities : —

It will be seen that all these places lie north of the equator
and that our knowledge of southern forms remains a blank.

An examination of the fossils found shows that Tertiary
strata have yielded nearly three hundred species of Arach-
nida, of which over two hundred and twenty are spiders,
the remainder being scorpions and other orders.

The Carboniferous type of Liphistiomorph spider is
seen to have persisted in Europe until the Oligocene era.
Mygalomorphae have been found in the Tertiary rocks of
both America and Europe, the latter including a species,
Eoatypus woodwardii, from the Eocene of Garnet Bay, Isle
of Wight.

Altogether, at least 222 species of Tertiary spiders are

Cainozoic Spiders

1. Germany

2. Switzerland.

3. Provence.

4. Isle of Wight.

5. Colorado.

Rott.

Aringen.

Aix.

Cowes.

Florisant.

Miocene.
Miocene.

Eocene marl.
Eocene limestone.
Eocene.

PLATE XI

Tube of Atypus affinis at Hastings x

To face p. 270.] [E. A. Robins, phct<

'0.

FOSSIL AND PRIMITIVE SPIDERS 271

known, included in seventy-one genera. Sixty-six of these
genera have been found in Europe and thirteen in America,
eight being therefore common to both. Thirty-five Euro-
pean and two American genera are extinct, but the remaining
thirty-four genera have living representatives, unaltered
from those remote times. Of the European species 168
have been found in amber and forty-one in stratified rocks.

When the prehistoric faunas of Europe and America
are compared, it is found that in Paleozoic times Europe
was apparently the richer in Arachnomorphae. To-day
this sub-order is far more numerous in America than in
Europe. By Tertiary times, a balance was to some degree
maintained. A multitude of forms, including many which
have undergone but slight modification since that date, had
a widespread distribution over the northern hemisphere.
There was then, as there is now, a general correspondence
between the fauna of America and Europe, for the same
families are represented in the stratified rocks, and, to some
extent, among the amber species.

The antiquity of the spider race, even in its present
form, is therefore very great. Its pedigree stretches back
to the time when our present-day coal was growing in the
forests as fern-like trees, long before mammals or birds or
even the majority of the reptiles had appeared on the earth.

Primitive Spiders

In this chapter, and in various other places, the Liphistio-
morphae have been referred to as primitive spiders, without
further describing them or stating the evidence on which
their claim to a primitive position is based.

A primitive animal is biologically of greater interest
than another because it represents a " missing link," or
because it is a present reminder of a bygone age. The
structure of a primitive animal differs from that of its
nearest living relatives in a number of features which, for
various reasons, are considered to be of an earlier origin,
and hence it furnishes living evidence of the course that

272 THE BIOLOGY OF SPIDERS

evolution has taken in the group to which it belongs.
Moreover, the material providing the evidence is usually
obtainable in a fresh state and in quantity, so that it can be
dissected, and these are properties which are not shared
by the fossil remains on which the geological record rests,
These are the reasons for the emphasis laid on the descrip-
tions of the structure of such familiar primitive animals as
Scyllium the dogfish, Amphioxus the lancelet, and Peripatus.
The well-remembered " worst journey in the world," the
five-weeks' expedition of Dr. Wilson, Bowers, and Cherry-
Garrard from Cape Evans to Cape Crozier during the
Antarctic winter of 191 1, was made for the purpose of
securing embryos of the Emperor Penguin, the nearest
living approach to the primitive bird.

Two difficulties attend the consideration of the biological
significance of a primitive animal. The first of these is
generally our comparative ignorance of the directions in
which evolution has travelled. It is not as though the past
history of any race were a ladder-like ascent of types, or
linear progress in which the more specialised examples
of one group ultimately gave rise to the less specialised
examples of the next. It is more probable that the
generalised examples of a group have produced, on the one
hand, the specialised examples of that group, and on the
other, the primitive members of the next higher group.
When a sufficient number of the primitive types have
become extinct, the survivors get more or less isolated and
the task of discovering their origins and relationship becomes
proportionately harder.

The second difficulty is to distinguish between the
primitive and the specialised characters of the same animal.
Rarely can a type exist for geological ages without
acquiring specialisation in one way or another, which, as
it were, compensates for its simplicity elsewhere. In other
words, it evolves, responding to the impress of environment
upon its innate tendency to variation, and it is therefore
important to realise that a primitive animal is seldom found
to be primitive, lock, stock, and barrel. Further, while an

FOSSIL AND PRIMITIVE SPIDERS 273

organ or a part may have all the appearance of simplicity, a
study of its development may show that, instead of being
primitive, it has retrogressed from some more elaborate
condition.

History of the Liphistiidae

Primitive spiders constitute a sub-order with a single
family, the Liphistiidae. The first species was described
under the name of Liphistius desultor by Schiodte in 1849,
from a mutilated specimen, whose abdomen had been slit
open and stuffed with cotton wool. Pickard- Cambridge in
1875 gave a description of an uninjured example and believed
it to be a different species, since Schiodte had been unable
to discern the spinnerets of his specimen. Another descrip-
tion of a perfect example was given by van Hasselt in 1879,
under the name of L. desultor. In 1890 Thorell, of Upsala,
pointed out that van Hasselt's species was different from
Schiodte 's original L. desultor, while Cambridge's L. mam-
millanus was identical with it. He proposed the name of
Liphistius sumatranus for van Hasselt's spider. In 1897
Thorell described a third species of the same genus, named
Liphistius birmanicus.

In the first volume of the Histoire Naturelle des
Araignees, Simon pointed out that the specimen in his
own collection differed in several ways from all of these,
and in the supplement to the second volume, founded upon
it a new genus, Anadiastothele.

Within recent years, two species have been added to
the genus Liphistius. These were described by Abraham.
Yet another species was discovered in Japan and was
referred to a new genus, Heptathela. There are, therefore,
at the present time seven species of this sub-order, included
in three genera. This elaboration of the original species
into several closely allied genera is precisely what has
occurred in the histories of both Amphioxus and Peripatus,
and does not in any way detract from their general signi-
ficance. Indeed, this separation is of value because it
emphasises the fact, already referred to, that the surviving

274 THE BIOLOGY OF SPIDERS

primitive animals are not necessarily without elaboration of
their own.

Characters of the Liphistiidae

In many ways these spiders recall those of the family
of Ctenizidae or trap- door spiders. This is particularly
evident in the general outline, in the structure of the
cephalothorax and chelicerae, and in the form of the mouth
parts, palpi, and legs. At the same time the appearance of
the abdomen and spinnerets proclaims the family to be
obviously different from all others.

The external features in which Liphistius shows its
primitive nature most plainly are :

1. The position and number of its spinnerets.

2. The segmentation of its abdomen.

3. The grouping of its eyes.

4. The shape of its sternum.

5. The lengths of its legs.

The usual position for the spinnerets is, of course, at
the end of the abdomen, close to the anal tubercle. In
Liphistius the spinnerets are placed in the middle of the
lower surface, a position which more clearly indicates their
analogy to the abdominal appendages of other Arthropoda.
All other spiders have six or fewer spinnerets, while
Liphistius alone has eight, arranged in four pairs, con-
stituting the endopodites and exopodites of the fourth and
fifth abdominal segments. In the Japanese species, Hepta-
thela kimuraiy the two inner spinnerets of the posterior
group fuse into one, so that there are apparently seven
spinnerets.

The segmentation of the abdomen is equally striking.
In Chapter I it was stated that this part of the body of
Arachnida consists, or originally consisted, of twelve
segments, of which the first is the waist or pedicle. In
Heptathela all twelve segments are visible and each is
covered above by a distinct shield or tergite, composed of

FOSSIL AND PRIMITIVE SPIDERS 275

chitin and of a leathery consistency. In the descriptions
of the other Liphistiidae, nine or ten tergites are mentioned.
The first one, above the pedicle, is either overlooked or not
included in this count, and these six species seem not to
have the large twelfth tergite over the anal tubercle. Simon
suggests that these plates may not represent segmentation,
but that they result from the division of a dorsal shield
similar to that possessed by the genera Tetrablemma and
Hexablemma, and some members of the family Oonopidae.

This is a point which cannot easily be decided, but
there is much in favour of the segmental nature of these
tergites. A segmented abdomen would ally Liphistius to
Protolycosa, the primitive spider of Carboniferous strata,
described above. It would also ally spiders as a whole to
the Pedipalpi, another order of Arachnida, an alliance
which the Dudley fossil spider Archeometa nephilina to
some extent supports. Moreover, since the abdomen of
all spiders whose embryonic development has been studied
passes through a segmented stage, it is reasonable to
suppose that the segmented state is a primitive one, and
that the dorsal shield of the Oonopidae is a survival
which has lost its metamerism, like the rest of the
abdomen.

The shape of the abdomen of most of the Liphistiidae
tends to become almost spherical, and this is certainly not
a primitive form. In all living spiders, the more primi-
tive types have a low cylindrical abdomen, while the
spherical form is characteristic of the highest families, the
Linyphiidae, Theridiidae, and Epeiridae. It is, perhaps,
unwise to stress this point, because of the difference in the
constitution of the abdomen in the two sub-orders. The
spinnerets of the Arachnomorph spiders appear to belong
to one of the later segments, but as a matter of fact they
still belong to the fourth and fifth segments. The sixth to
the twelfth segments which form the posterior half of the
abdomen of the Liphistiidae are much reduced in the
Arachnomorphae and form no more than the small anal
tubercle. In any case the spherical abdomen of Liphistius

276 THE BIOLOGY OF SPIDERS

is a character in which it shows a specialisation of its own
and a departure from the primitive type.

The taxonomic value of the grouping of spiders' eyes
has already been mentioned. The course of evolution
seems, roughly speaking, to have been a gradual separation
of the eyes from a close approximation around and upon
the ocular tubercle, so that they become spread over a
larger area of the cephalothorax. The retention and
elaboration of the ocular tubercle in some of the male
Linyphiidae (Fig. 3) is a secondary specialisation, and the
reduction of the number of eyes to six, four, two, or none
in a few other families seems to be a degenerate rather than
a primitive condition. The eyes of Liphistius, eight in
number, are all situated upon a small
pinnacle, and it is probably reasonable
to regard this as a primitive condition
(Fig. 95). It is interesting to perceive
that the median anterior eyes are
much smaller than the others. This
unusual occurrence has been referred
to in a previous chapter ; it is an
arrangement which is much more
common in the southern hemisphere
than in the northern, and might perhaps be taken to indicate
one of the centres of origin of the spider race.

The sternum of the Liphistiidae is long and narrow.
This is a very unusual shape among living spiders : a few
six-eyed spiders show somewhat the same shape, but the
elongation is not so marked. The nearest approach to the
Liphistiid shape is probably that of the Australian trap-door
spiders of the genus Dolicosternum (Fig. 96), but until
more is known of the genealogy of the order of trap- door
spiders it is difficult to estimate the significance of this
resemblance. It is, however, probably justifiable to assume
that a long narrow sternum is more closely allied to a type
with a series of segments than is a shorter form.

Liphistius is very unusual in the relative lengths of its
legs. In all seven species the fourth pair are the longest

Fig. 95. — Eyes of Li-
phistius malayanus.
After Abraham.

FOSSIL AND PRIMITIVE SPIDERS 277

and the first pair are the shortest. The second pair are
sometimes shorter and sometimes longer than the third
pair. In this respect, as in its segmented abdomen,
Liphistius recalls Protolycosa, in which the relative lengths
are 4, 3=2, 1.

The underside of the abdomen of the Liphistiidae is
characterised by two very large segmental plates of chitin.

Fig. 96. — Sternum of Dolicho-
sternum. After Rainbow.

Fig. 97. — Heptathela kimurai.
Underside of abdomen. After
Kishida.

The later segments are not so large nor conspicuous (Fig. 97).
The two large plates cover the two pairs of lung-books and
the genital opening. The possession of two pairs of lung-
books and the absence of spiracular tracheae constitute a
primitive feature, shared by the Liphistiomorphae and the
Mygalomorphae.

The female genital aperture has no trace of the outer
epigynum, described in a previous chapter, which occurs in
all other spiders. All that is visible is a pair of spermathecal
apertures at the sides of the hind edge of the plate covering
the second segment.

The palpal organ of the male is, naturally, a feature to
which one turns in expectancy, for the multitudinous forms
which this organ takes throw much light, as we have already
noted, on the relationship of the different families.

The most remarkable condition is that shown by the

278 THE BIOLOGY OF SPIDERS

Japanese species Heptathela kimurai. Here the bulb-like
receptaculum seminis is completely absent. The tarsal
joint of the palp is somewhat swollen, and has very much
the appearance of the organ of other male spiders during
their penultimate moult. The inner side of this joint is
provided with two rows of spines, six or seven spines in
each row (Fig. 98), surrounding a space in which the drop
of semen is conveyed. Anything more primitive than this
literally spoon-like arrangement it would be hard to imagine :
indeed, in several ways the Japanese species seems to be
even more primitive than those of the Malay Peninsula.
The males of both Liphistius birmanicus and Liphistius
batuensis, however, possess palpal organs which, though
simple, are more reminiscent of the ordinary types. The

Fig. 98. — Heptathela kimurai. Male palp. After Kishida.

organ projects as a stout blunt point from the very position
it would be expected to occupy if it be supposed to have
been derived from the palpal claw. This terminal position
of the palpal organ is found in most of the trap-door spiders,
but in practically none of the highest sub-order, the Arachno-
morphae. The retention of a terminal claw by the mature
male of Heptathela is unique and is not the least remarkable
feature of that spider.

Internal Structure of the Liphistiidae

The only described dissections of the Liphistiid spider
are those of Buxton, who, in 1923, cut sections of four
specimens of Liphistius batuensis. Petrunkevitch has also
cut sections of the same species, but has given no account
of his results. The description given above of the external
features might lead one to suppose that further evidence of

FOSSIL AND PRIMITIVE SPIDERS 279

the primitive character of the Liphistiidae would be obtained
from its internal structure. It is remarkable that this is
not the case, yet the negative results are valuable from a
biological point of view.

Buxton was particularly interested in the coxal glands,
which show, more than any other internal organ, an evolu-
tion of form among the different families. He found that
the coxal glands of the Liphistiidae resemble those of the
Mygalomorphae or trap-door spiders in every respect.
They are not in any way more primitive.

Again, in a very young specimen of a trap-door spider,
Chilobrachys , from Sumatra, Buxton discovered five pairs
of transient abdominal ganglia, a temporary vestige of the
vanishing abdominal nerve-chain. One might expect to
find these ganglia persisting in the Liphistiidae, but there
is no trace of them ; and at present there is no evidence that
they persist any longer in Liphistins than in any other
spider.

The other organs of Liphistius show no peculiarities
indicative of a more primitive character than the Mygalo-
morphae.

These results are of great interest because they show
that the Liphistiomorphae are much more closely related
to the Mygalomorphae than these are to the Arachno-
morphae. They tend to correct the impression, which a
study of the external characters alone might give, that
Liphistius and its allies are very primitive spiders indeed.
Clearly they are not : they are very important spiders to
the zoologist, but they are some way removed from the
Archearanead.

Habits of the Liphistiidae

All the earlier species of the Liphistiidae were described
from dead specimens, and even Kishida, who apparently
finds Heptathela kimurai common enough from South
Kinshiu to the Loochoo Archipelago, has published no
information as to its habits. Abraham, the discoverer of

28o THE BIOLOGY OF SPIDERS

Liphistius bataensisy has told us more ; but it should be
remembered that his species lives in the Batu Caves,
Selangor, and that its mode of life may not be shared by
its allies, which presumably live in the open jungle.

Abraham's spider spins a silk tube, three or four centi-
metres long upon the vertical sides of the cave. At the
bottom of the tube the egg-cocoons are laid, in a cavity
which is separated from the tube above by a fine sheet web.
A trap-door, consisting of a simple flap of silk, closes the
tube, which is fixed to the wall by a number of radiating
threads. The trap-door and the tube are covered with
particles of sand so that they come to resemble a piece of
rock on the side of the cave. This resemblance, if it be

Fig. 99. — Heptathela kimurai. After Kishida.

protective, by making the tube inconspicuous, is rather
remarkable since the spiders live some way from the cave-
mouth, in the dark. Perhaps the sand masks the feeling
of the silk, and thus deceives predatory wanderers.

The remains found in the nests indicate that this spider
feeds chiefly on grasshoppers. These it would obtain by
hunting along the cave walls, and it apparently takes them
back to the nest to devour them in safety. From this fact,
together with the coating of the tube with sand, its closure
by a trap-door and the nervous behaviour of the spider, it
is quite evident that, even in the darkness of the caves,
there is some enemy against whom the spider must be
perpetually on guard.

When captured by Abraham, the spiders were all

PLATE XII

A Trap-door open and closed, illustrating Perfect
Concealment, x

To face p. 280.]

[H. M ain, photo.

FOSSIL AND PRIMITIVE SPIDERS 281

crouching in their tubes, with the doors just ajar, as if they
had been driven home in fear on the approach of the
intruders. If the hand was brought near the tube, the
door was at once closed tightly and held down from within
— the spider's last hope of escape.

It is much to be hoped that the Liphistiidae will one
day receive the close attention they deserve. Their own
interrelations might teach us much, for the Japanese form
is clearly more primitive in some ways, and yet in the
degeneration of its median spinnerets and the elevation of
the cephalic region it has undergone specialisations peculiar
to itself. The internal structure, the habits, and the
development are all well worth investigation : at present
our knowledge is scanty and is scattered over a number of
years and a wide range of publications.

In conclusion, the following complete classification of
both recent and fossil forms may be not without interest,
and will serve as a summary of the chapter.

Sub-order LIPHISTIMORPHAE Petrunkevitch

(=Arthrarachnae Haase, =Mesothelae Pocock, =Verticu-
latae Dahl.)

Abdomen segmented. Not much more than two
posterior abdominal segments lost. Anal tubercle separated
by a considerable space from the spinnerets.

Family LIPHISTIIDAE

Recent. Tarsi with three claws, the superior claws
with 2 or 3 teeth.

Sub-Family LIPHISTIINAE

Four lateral spinnerets, each consisting of two segments ;
the distal segment with a number of false articulations.

Group Liphistiiae
Two pairs of median spinnerets.

282 THE BIOLOGY OF SPIDERS

Genus Liphistius. Schiodte

1. L. desultor Schiodte (=L. mamillanus Camb.).

2. L. sumatranus Thorell (=L. desultor v. Hass.).

3. L. birmanicus Thorell.

4. L. batuensis Abraham.

5. L. malayanus Abraham.

Group Heptatheleae
Three median spinnerets.

Genus Heptathela. Kishida

6. H. kimurai Kishida.

Sub-Family ANADIASTOTHELINAE

Four pairs of spinnerets, each consisting of a single
segment only.

Genus Anadiastothele. Simon

7. A. thorelli Simon.

Family ARTHROLYCOSIDAE
Carboniferous. Eyes on a tubercle. Claws unknown.

Genus Arthrolycosa. Harger

8. A. antiqua Harger.

9. A. danielsi Petrunkevitch.

Genus Protolycosa. Romer

10. P. anthracophyla Romer.

Genus Eocteniza. Pocock

11. E. silvicola Pocock.

FOSSIL AND PRIMITIVE SPIDERS 283

Family ARTHROMYGALIDAE

Carboniferous. Eyes in two rows. Claws two, without
teeth.

Genus Arthromygale. Petrunkevitch

12. A. carbonaria Kusta.

13. A. fortis Fritsch.

14. A. beecheri Fritsch.

15. A. lorenzi Kusta.

16. A. palaranea Fritsch.

Genus Racovnicia. Kusta

17. R. antiqua Kusta.

Genus Geralycosa. Kusta
18 G. fritschii Kusta.

Genus Perneria. Fritsch
19. P. salticoides Fritsch.

CHAPTER XIV

THE TRAP-DOOR SPIDERS

Trap-door spiders were discovered by Patrick Browne in
Jamaica nearly two hundred years ago, and have since been
found to be a numerous group, including about a thousand
species, widely distributed throughout tropical and sub-
tropical countries. Their structure is so different from
that of other spiders that as long ago as 1802 Walckenaer
separated them as a " tribe " which he called les Thera-
phoses. He included, however, the family Filistatidae in
the same group. Thorell, in 1869, included them in a
sub-order which bore the same name, Territelariae, as the
corresponding family of Latreille. The Territelariae
included a family Theraphosidae and a family Liphistioidae.
Simon's corresponding group in his great Histoire
Naturelle of 1892 was the sub-order Araneae Thera-
phosae, in which he placed also the Liphistiidae. Dahl,
in 1913, followed Latreille in distinguishing the group by
its possession of four lung-books, and in his sub-order
Tetrapneumones therefore included the family Hypo-
chilidae, which in other ways does not resemble the rest
very closely. In the most recent classification, Petrunke-
vitch has removed both the Liphistiidae and the Hypo-
chilidae to more suitable positions, and called the sub-order
by Pocock's name, Mygalomorphae.

Features of the Mygalomorphae

The cephalothorax of these spiders is nearer a square
shape than that of others, with little narrowing in the

384

THE TRAP-DOOR SPIDERS 285

cephalic region. The median groove or fovea is transverse
and is either procurved, with the concavity forwards, or
recurved, with the concavity backwards. The eyes are
usually closely grouped upon a small ocular prominence
and are eight in number in nearly all genera.

The chelicerae afford the readiest means of recognising
the sub-order (Fig. 100). Their basal joints project forwards
and are able to move sideways only to a slight extent. Their
normal action is to strike downwards, so that the fangs
pierce the prey from above and move through it in parallel
directions. This is in direct contrast to the chelicerae of
other spiders, which pierce sideways, and meet in the
middle of the transfixed prey. The distal end of the first
joint of the chelicerae is in
many species provided with
a number of teeth forming
an efficient rake or rastellus.
This is used in excavating
the burrow.

The palpi are very like
legs in appearance, and are
much longer in proportion
than is common among
spiders. The male organs Fig. 100.
are terminal in position and
simple in structure. The
first, or coxal joint of the palp is not provided with the
endite or maxilla which forms an important part of the
mouth in other spiders. The lung-books, as already
mentioned, are four in number. There are also four
spinnerets, instead of six. The persistent spinnerets are
those of the anterior and median pairs ; the posterior pair
being absent, save in the family Atypidae and in a few
isolated genera.

The abdomen differs slightly in appearance from that
of other spiders, for it lacks the colulus, or small tubercle
in front of the spinnerets. It is also different in constitu-
tion. The heart of the Mygalomorphae possesses four

Chelicera of a Mygalo-
morph Spider, dissected to show
poison-gland. After Pawlowsky.

286

THE BIOLOGY OF SPIDERS

pairs of lateral ostia instead of three, and is held in position
by eight ligaments instead of six.

This makes it probable that one more segment is per-
sistent in the abdomen of the Mygalomorphae than in the
Arachnomorphae, that there are six in the former and five
in the latter. There is, at present, no embryological
evidence which affords definite proof of this view, but
other facts are in its favour. If it be accepted, it makes the
three modern sub-orders of spiders much more distinct
and, moreover, much more naturally separated than in any
earlier classification.

Sub-order Liphistiomorphae, 10-12 abdominal segments.
Sub-order Mygalomorphae, 6 „ „
Sub-order Arachnomorphae, 5 „ „

Habits of the Mygalomorphae

The habits of these spiders are far from being completely
known, partly because many of them are active only at
night, and are unusually well concealed during the day.
The habits which are known are of great importance,
because there is a close connection between them and the
structure of the legs, the mouth-parts, and the spinnerets.
Habits may thus be taken into account, both in classifying
and in considering the evolution of spiders. This will
become more evident in the next chapter.

Among the Mygalomorphae there are wandering species,
who hunt their prey in the open and take their rest in any
chance shelter, under stones or the fallen branches of trees ;
while others make very simple excavations, lined with but
little silk, or even unlined. More skilled diggers excavate
deeper holes in the ground, which contain a silk tube and
which may or may not be closed with a trap-door, while a
few do not burrow at all, but spin their tubes entirely
above the ground or weave a web which closely resembles
the tube-and-sheet web of the Agelenidae.

These habits have probably arisen by divergence in two

THE TRAP-DOOR SPIDERS 287

directions from the habits of a primitive ancestor. Some
of the descendants specialised in digging and in making
trap-door nests. These species possess the rake or rastellus
on the chelicerae, with which the digging is done ; they
have but a slight covering of hairy setae and retain three
claws on their tarsi. The most typical family of this tribe
is the Ctenizidae. The Migidae represent a further develop-
ment, and the Atypidae form a family acclimatised to colder
regions. The Paratropididae also belong to this group,
but nothing is known of their habits.

Other descendants took to hunting. They lost their
median tarsal claw and acquired more setae on their legs
and bodies. The family Barychelidae includes the species
which are in a transitional stage between the burrowers and
the vagrants. The Theraphosidae is the typical family of
this group. These two families are the only ones which
possess claw-tufts, and for this reason they are grouped
together, and separately for the other six. The Dipluridae
and the Pycnothelidae, which were originally one of their
sub-families, are two families which stand apart in several
ways from the rest. They spin tubular webs.

There are, therefore, eight families of the sub-order
Mygalomorphae, whose chief characters are expressed in
the following table : —

Number of
claws.

Number of
spinnerets.

Rastellus.
Present.
Absent.
Absent.
Absent.
Absent.
Present.
Absent.
Absent.

1. Ctenizidae

2. Migidae .

3. Atypidae .

3
3
3

4 or 6

4
6

4 or 6
4

4 or 2
4 or 6
4

4. Paratropididae .

5. Theraphosidae .

6. Barychelidae

7. Dipluridae

8. Pycnothelidae .

2
2

3
2

The Paratropididae from the Amazon, and the Pycno-
thelidae from Brazil, are small families of relatively little
importance. The rest deserve fuller consideration.

288 THE BIOLOGY OF SPIDERS

The Makers of Trap-doors

These are the spiders which owe their popularity to the
perfection of their architectural skill, and include the most
practised diggers and makers of trap-doors.

The digging is carried out solely by the chelicerae,
which, as already noted, are provided with a rake. With
this rake small particles of the earth are dislodged, and
worked into a ball. This may be carried in the spider's
jaws and dropped outside the burrow, or it may be cast up
by the strong hind legs, which are sometimes armed with
rows of spines adapted to this function (Fig. 101). The
sides of the burrow are coated with a plaster, made of
earth and saliva, firm enough to isolate it completely from

the surrounding earth and
able to stop water from soak-
ing in. Within this is a silk
lining. The lining is gene-
rally fixed to the sides of the
burrow, but is sometimes
found lying quite freely, and
sometimes it does not reach
to the bottom.

Several of these spiders

Fig. ici.-TheRastellus. IefVe their burr0WS °Pen'

This is the rule in the genus

Leptopelma, where the lining is extended above the ground,

in the form of a hollow cone of clean white silk. One

species, Cyrtauchenius inops, surmounts the burrow with a

small rampart of earth ; others, of the genera Phaeoclita

and Celidotopus, roughly protect it by a few leaves dragged

together and attached to the silk.

But the normal burrow is closed by a door, continuous
across a short hinge with the silk lining. When, as is
usually the case, the burrow is dug in a bank, the hinge is
placed at the highest point of the door, so that the latter
shuts by its own weight.

The two different types of door are known as the cork

THE TRAP-DOOR SPIDERS 289

door and the wafer door. The cork door is hard and thick,
with bevelled edges which fit closely into the mouth of the
tube. It is made of alternate layers of silk and earth. The
spider usually covers the outer surface, consisting of earth,
with leaves, moss plants, and so on, gathered from its
immediate surroundings, and these have the effect of
making the closed door almost indistinguishable. Its inner
surface is of smooth white silk and is nearly always pierced
on the side opposite the hinge with two or more small
holes. Into these the spider, when attacked, fixes its
claws and holds down the door from within. The wafer
door is less perfect, and consists only of a thin flap of silk
overlapping the edges of the burrow. It is, as a rule,
softer and less perfectly concealed than a cork door, and it
has no holes inside for the spider to grasp. In some nests,
however, a loose network of stout threads serves the same
purpose. Both kinds of door are made of earth and silk,
and Moggridge dissected a cork door into fourteen separate
discs of silk.

The burrow is generally deep and cylindrical with a
uniform diameter from top to bottom. In one rather
interesting nest, that of Cyrtanchenius vittatus, the lower
end is a narrow cul-de-sac, which serves as the spider's
dust-bin. Into it are dropped the remains of the insects
which the spider has eaten. Burrows are sometimes
unb ranched, but often side tubes diverge from them.
These side tubes do not usually reach the surface of the
ground, but in some nests they do, and provide a way of
escape.

The different types of burrows are shown diagram-
matically in Fig. 102. In several nests, as is shown, the
branch tube is closed by an extra door of its own. These
inner doors are usually stouter than the wafer doors which
close the burrows, and in some cases are of an elongated
oval shape. They are generally so hung that they can be
used to close either the main or the side tube. One spider
at least, Nemesia eleanora, makes an unbranched tube with
a second door a little way below the first.

THE BIOLOGY OF SPIDERS

Particularly interesting nests are made by the spiders
Rhytidicolus structor in Venezuela and Cyrtaachenius artifex
in Algeria. The former is composed of three successive
chambers, communicating with one another by hinged
doors. The first is pear-shaped, though somewhat narrowed
at its ends, the second is cylindrical and ends blindly. The
third opens from the side of the second and is also pear-
shaped, but rounded below. The whole is lined with soft
white silk. The three doors are similar and are quite
thick, fitting closely into the bevelled spaces which receive
them.

The other species makes an unbranched burrow with
an oval chamber at a depth of a few centimetres, in which

Fig. i 02. — Types of trap-door nests.

the second door is hung. This door is a hemisphere of
hard, fine earth coated with silk. To its inner surface is
attached a tube of elastic silk. In its normal position the
door exactly fits one half of the chamber, while the tube
leads into the other and allows the spider to pass in and
out. When the spider wishes to shut up its home, it pulls
the door round, so that it rests on a small rim made to
receive it and closes the burrow. In this position the tube
is flattened against the side of the tube, ready to spring
back and resume its ordinary position as soon as the spider
releases the door.

Another member of the same genus, Cyrtauchenins
elongatus, found in Morocco, spins a very unusual and

THE TRAP-DOOR SPIDERS 291

conspicuous nest. It has no door, the silk lining is pro-
longed about three inches above the surface of the ground
and is enlarged in the shape of a funnel. This aerial
portion is snow-white, and is a very conspicuous object
among the plants to which it is attached.

All the spiders of this trap-door group are of nocturnal
habits, and spend the day resting in closed burrows. Some
of them mount, in the evening, to the top of the tube,
raise the door with their heads till it is just ajar, allowing
them to peep out. Thus they await the chance arrival of
some insect upon which they quickly leap. Others, such as
Cyrtocarenum cunicularium from the Isle of Tinos, in the
Greek Archipelago, have been seen to fasten back their
doors and to spin a web about six inches long and half an
inch high. This web entraps low-flying insects, which the
spider sucks dry, carrying away the carcase when finished.
Before morning the web is removed and apparently added
to the trap-door, which is then closed down for the day.

Under observation, these spiders show themselves very
unwilling to leave their burrows. It is probable that in
natural circumstances they very seldom do so. The young
spiders for a time all share the nest with their mother, but
as they grow up, they scatter and dig burrows for them-
selves. These are at first quite small — as Moggridge
expresses it, " no larger than a crowquill " — but they seem
to enlarge both burrow and door, instead of deserting them
and making others.

The Migidae

The spiders of this small but interesting family are
found in South Africa, Madagascar, and New Zealand.
They are distinct from the burrowing spiders just described,
having shorter chelicerae, not provided with teeth for
excavating. The spiders, in fact, do not dig in the ground
at all. They spin a short tubular nest, about two inches
long, in the corky bark of certain trees, such as the " Kaffir
Boom " tree, or species of oak. The bark is not dug

THE BIOLOGY OF SPIDERS

away ; the spider makes use of natural crevices to which
it fits the tube.

At one or both ends the tube is closed with a hinged
door, which combines the characters of both the cork and
the wafer types of the previous section. That is to say, the
central part is thickened, bevelled, and fits closely into the
tube, while the edge of the door is thin, and overlaps
the bark outside. Both the door and the exposed parts of
the tube are covered with small pieces of bark and lichen,
which serve to conceal it. So perfect is the result that
Pickard-Cambridge, writing of a piece of bark containing a
nest, which had been sent to him from Grahamstown,
said, " I had to search very minutely for ten minutes, and
test every part of the pieces of bark with the point of a
needle, to find out the lids of the nests."

The Atypidae

The spiders of this family have been able to establish
themselves in colder regions than those inhabited by the
other Mygalomorph families. They have been recognised
as a separate group since Latreille, in 1802, separated the
genus Atypus from the true Mygales, as they were then
called, and all subsequent authors have maintained the
distinction.

The chief structural features which distinguish the
family are the possession of six spinnerets, and the position
of the anal tubercle, which is some distance above the
spinnerets instead of being close to them. In some species
the first joints of the palpi have maxillary lobes which are
similar to those of Arachnomorph spiders.

The family includes less than thirty species, found in
Asia, Europe, and North and South America. Their
habits are quite different from those of the Mygalomorph
families which have been described above. There are two
rather different types of web.

In America, the " purse-web spider," Atypus abbottii,
occurs chiefly in the southern states. It lives in a burrow,

THE TRAP-DOOR SPIDERS 293

nearly always dug at the foot of a tree. The silk tube,
which, as in other Mygalomorph nests, lines the burrow, is
in this family extended outwards and by the purse-web
species is carried vertically upwards against the side of the
tree, as a tube about a foot long and three-quarters of an
inch wide.

This tube is protected to some extent by pieces of moss,
lichen, bark, and grains of sand, which the spider gathers
and attaches to the outside. The final colour of the tube
varies considerably from a light gray to a very dark brown,
and to a great degree depends on the colour of the tree to
which it is fixed. In spite of this, the tubes are not difficult
to see, when one has learnt their appearance, for they are
quite straight and of a uniform diameter. The tube is
slightly flattened at the top, and attached so firmly to the
tree that between this point and the ground it is very
tightly stretched. It therefore responds to the tread of an
insect by vibrating, and the spider, waiting below, rushes
to the spot. It bites the insect through the web, slits the
latter, and pulls the insect inside. After the prey has been
sucked dry and the remains thrown away, the slit is repaired.

Only occasionally is more than one adult spider found
on a tree, but six or seven tubes belonging to young ones
may be found side by side

The European Atypus, Atypus affinis, which is also found
in several localities in the south of England and Wales,
shows a somewhat similar mode of life. The upper part
of the silk tube, however, is neither raised nor attached to
a tree ; it merely rests along the ground. The nest is
generally made in a bank, in a dry situation, and is not at
all easy to distinguish. The outer side of the tube is
covered with small particles of earth and sand, which, as
Enock has shown, the spider obtains from the inside of the
burrow, and not from the surroundings. Sometimes,
however, the spider has been seen to push its fangs through
the silk and drag a piece of earth into its meshes.

The British Atypus is an attractive little spider, about
half an inch long, with a brownish abdomen and a yellow

294 THE BIOLOGY OF SPIDERS

cephalothorax, but with no pattern on either. It is a very
interesting creature to keep in captivity, and to any one
who is fortunate enough to find it, it well repays the trouble
necessary to give it a congenial home. This is best done
by Main's method, using an inverted deflagrating jar, as

WIRE
FLY TKAF.

KTH.

'AMF
AND.

Fig. 103. — Tube of Atypus in deflagrating jar. After Main.

shown in Fig. 103 The lower end is closed by a per-
forated cork, which is covered by about two inches of damp
sand. Clean sifted earth, slightly damp, is added above
the sand, and rammed down moderately hard. During
the addition of the earth a glass tube, about one-third of

THE TRAP-DOOR SPIDERS

295

an inch in diameter, is held against the glass, thus making
a cylindrical hole. The spider's tube is carefully lowered
into this with about two inches lying along the surface.
The free end must be held in position for a day or two by
a pin, stuck through it into the earth. It is necessary to
avoid dryness. Therefore the corked end should be
occasionally immersed in water, which rises by capillary
attraction. It is not possible to keep the earth satisfactorily
moist by adding water from above ; in Nature the lower
layers are always the source of the water supply.

In cages of this sort, all trap-door spiders will live in
comfort. They will feed on earwigs, beetles, flies, and all
such creatures, and do not suffer in any way from monotony
or lack of exercise. The remarkable feature of their natural
mode of life is that they remain constantly inside the nest,
while the part of the tube which lies on the ground takes
the place of the ordinary spider's web. The spider inside
the tube rushes to the spot touched by a passing insect and
catches it just as do the American Atypidae, which spin the
purse-web. Enock discovered a curious habit which the
spider shows when it is not hungry. If an insect touches
the tube, the spider gives it a sharp pull, which drags a
portion into the burrow. It may be imagined that this
startles the intruder and prevents it from damaging the
tube. The underground portion of the tube is sometimes
invaded by earthworms, and it seems that the spider
attacks them when they do so, for partly-eaten remains have
often been found in the tube.

The male Atypus digs a burrow similar to that of the
female, but not, as a rule, quite so deep, and he leaves it,
when mature, to seek the home of a female. When he
finds one, he drums on it with his palpi, an action which
has already been described for other spiders. After a few
moments, he tears open the tube and enters. The female
then comes up and repairs the hole ; she pulls the edges
together with her jaws and secures them with a few threads
from her spinnerets. The male and female may live
together in the tube for nearly a year.

296 THE BIOLOGY OF SPIDERS

The eggs, which are about a hundred and fifty in
number, are laid in the autumn, and remain in the nest
during the winter. When suitable weather returns in the
spring, a small hole, perhaps made by the mother, appears
at the end of the tube and the young spiders squeeze them-
selves through it. They at once disperse and begin life on
their own account. Sometimes it happens that the weather
changes suddenly, before all the young spiders have dis-
persed. The mother then seals up the hole, and it is to
be feared that she sometimes eats the young ones that
remain behind.

The Bird-eating Spiders

The family Theraphosidae, to which the name bird-
eating spider properly belongs, includes the largest members
of all the Araneae. They are the spiders originally called
My gale by Walcknaer in 1802, but the name was pre-
occupied by a genus of mammals, founded by Cuvier in
1800. Americans usually refer to these large spiders as
tarantulas, but the true tarantula is a small Lycosid of
South Europe, in no way related to the present family.

Their ability to overcome the small humming birds of
South America was discovered many years ago by Mme.
Merian. Doubt was cast upon the accuracy of her observa-
tions and was fostered by the very foolish " experiment "
of pushing a dead bird near a spider, which, probably
frightened and certainly unaccustomed to any but living
food, naturally took no notice of it. Bates, however, in his
" Naturalist on the Amazons," gave an account of his
discovery of a large spider which had captured a pair of
small birds. He thus verified the original observation.

It is not to be supposed that these spiders eat birds
instead of insects, but merely that many of them have the
strength to overcome the tiny birds which occasionally may
fall into their power. Their usual victims are insects.

This family includes the typical hunters of the Mygalo-
morph sub-order. Their chelicerae have not the rake of
strong teeth which characterise the burro wers, and their

THE TRAP-DOOR SPIDERS 297

feet are provided with conspicuous claw tufts. These
claw tufts, or ungual tufts, are distinct from the scopula
mentioned in Chapter II. A scopula is a group of stout
spines on the lower side of the tarsus or metatarsus. A
claw tuft consists of longer and less rigid setae, and is often
so large that it projects beyond the actual claw and quite
conceals it. In some spiders the tuft is divided so that
the extremity of the leg has a bifid appearance. The bodies
of these spiders are usually more " hairy " than those of
the burrowing species.

The bird-eating spiders live in any chance shelter.
They line the cavity with a light web, which is but seldom
prolonged to any extent, and is never shaped within into
the tubular retreat characteristic of so many true webs.
During the day the spiders are quiescent in their retreats,
and it is only towards evening that they awake and go in
search of prey. They wander over the ground and also up
the trunks and branches of trees, their claw tufts being well
adapted for climbing — and it is here that they find the
opportunity to capture small birds.

These spiders enclose their eggs in a white cocoon,
which some of them carry in their jaws until the young
ones hatch.

Among the many genera which the family includes
there are a few which deserve special mention. One of the
most interesting species is Orphnoecus pellitus, which lives
in caves in the Philippine Islands. The spider is charac-
terised by the smallness of its eyes, a feature which may be
interpreted as the result of disuse in the course of the many
generations during which its ancestors have lived in the
dark. The spider is popularly credited with a poisonous
bite, and it is so numerous that the natives are afraid to
enter the caves on account of its presence.

The spiders of the genus Phlogius, although they have
no rake on the chelicerae, dig deep burrows which they
line with a silk tube. The burrow, however, is never
closed with a trap-door, and some species extend the lining
in the form of a white silk funnel, similar to that made by

298 THE BIOLOGY OF SPIDERS

Cyrtauchenins. It is very interesting to find these two
genera, Cyrtauchenins and Phloghis, differing from the
majority of their true allies and resembling one another as
regards the type of web they spin. They thus afford a
good illustration of convergent evolution.

The genus Theraphosa was founded for the great spider
TherapJiosa leblondi, the giant of the whole order, whose
body length approaches 9 cms. This spider was described
by Latreille in 1804, and the name has been several times
misapplied to large spiders found in the Antilles, in Brazil,
and even in Java. The true Theraphosa leblondi was found
in Guinea, where it is a rare species with a limited dis-
tribution. The genera Eurypelma and Avicularia, the
latter the original " bird-eater," are peculiar to America,
and are second in size only to Theraphosa.

The Barychelidae and Dipluridae

The Barychelidae are an interesting family of spiders,
intermediate in character between the burrowing and the
hunting types. They have the two tarsal claws and long
bifid ungual tufts of the hunters, combined with the
rastellus, pubescent appearance and habits of the burrowers.
The rake on the chelicerae is made of much finer teeth
than in the Ctenizidae, and is, in fact, better described as
a row of stout spines. However, the spiders dig very
typical burrows lined with silk and closed by thin but
rigid trap-doors, almost circular in shape. The burrow is
sometimes single, with an enlarged round chamber at the
bottom, sometimes branched a little way below the door,
the branch having a second door of its own.

A rather unusual type of burrow is dug by Stothis
astuta in Venezuela ; it curves downwards and then turns
upwards, forming a complete semicircle, and the two ends
are each provided with a door (Fig. 102). Some species
leave their burrows open and others close them with leaves,
drawn together with threads of silk.

Other genera of this family, such as Sason in Ceylon,

THE TRAP-DOOR SPIDERS

Rianus in Penang, and the species Sipalolasma aedijicatrix,
recently discovered by Abraham in Singapore, resemble
the Migidae in their habit of making their burrows in the
bark of trees. These burrows are generally short and are
closed by two doors. Abraham mentions that, if attacked
at one door, the spider will escape at the other, but that
if this door is prevented from opening, the spider will hold
down the first so strongly that considerable force is needed
to open it.

The marine Idioctis littoralis, mentioned in Chapter IX,
is a member of this family, as also is the curious Diplothele,
an Indian spider which has only
the two superior spinnerets
(Fig. 104).

The Dipluridae differ in
several ways from all other
members of the Mygalomorph
sub-order. They have no
rastellus and no ungual tufts ;
they have three claws of which
the superior paired claws have
numerous teeth ; and their posterior spinnerets are long
and three-jointed. In this respect they resemble the family
Agelenidae, and the web they spin is of the same type.
They thus provide another striking example of parallel
evolution, having produced, from the beginnings of a lined
retreat, exactly the same web as have certain of the Arach-
nomorphae, whose webs, we believe, arose from a similar
origin. They never live underground ; their large webs,
which are of light transparent silk, ending in a tube which
is open behind to permit escape, are found both among
rocks and between the roots of trees. The family is widely
represented in Central and South America, in Central Asia,
reaching the Eastern Mediterranean, in Madagascar, Aus-
tralia, and in New Zealand.

Fig. 104. — Spinnerets of
Diplothele.

CHAPTER XV

THE EVOLUTION OF SPIDERS

In an early chapter of this book a longish passage was
devoted to a discussion of the method by which scientific
progress is made. The length of that passage was justified
both by its own importance and by its application to the
present chapter ; for here it is to be seen that the advance
of the biological sciences does not differ in character from
the advance of the physical sciences. The same methods
are used in both.

The Evolution Theory

The nature of a scientific hypothesis has already been
indicated. It is a tentative formulation, based on the
recorded facts of the science, with the intention of so
expressing the relationship between them as to render
them intelligible. A hypothesis is an attempt at an explana-
tion, born of the innate desire of the human mind to
rationalise the data set before it, that perchance it may
find an answer to man's eternal " Why ? "

The test of a good hypothesis is its utility, its living
spirit. If it assimilates new facts, points the way to new
discoveries and corrects past errors, it is justifying itself.
It is a good hypothesis. But it is not necessarily true.
Many a useful hypothesis is a conscious fiction, perhaps
little more than a vague analogy ; yet it is clear that even
conscious fiction has its part to play in the advancement of
learning.

When, however, a hypothesis retains its value for many

300

EVOLUTION

301

years, and especially when it maintains it without additions,
modifications, or loss of fertility, then man becomes more
and more inclined to believe in its truth, to trust it
unquestioningly, to teach it dogmatically to the next
generation.

If this scientific use of hypothesis is understood, the
theory of Organic Evolution is less likely to be misunder-
stood. It is the underlying hypothesis of all biological
progress. All the facts of biology demonstrate one
supremely important truth, that of the adaptation of the
organism to its environment. The shape, size, and colour
of an animal, its habits, its internal structure, its physio-
logical balance or correlation of parts, all are such that the
individual is able successfully to carry out the competitive
activities which constitute its life. This major fact of
adaptation must find first place in all biological theory.
The geographical distribution must also be kept in mind.
Some creatures are numerous, others rare ; some range
the world, others are found only within confined limits ;
some are independent, others parasitic.

The history of biology has seen two hypotheses which
aim at formulating these facts of adaptation and distribution.
There is the hypothesis of Special Creation and the hypo-
thesis of Evolution, or Descent with Modification. The
first theory cannot pretend to be a scientific account of the
facts, and is rather an interpretation than a description.
The second theory, the Evolution theory, is the only
scientific attempt to describe how living creatures have
come to be what they are.

It is outside our present scope to discuss the rivalry
between these theories. At present all biologists are agreed
that evolution of animal and plant life has indeed occurred
and is still occurring. The problem which remains a
matter of uncertainty and discussion is the method by
which this evolution has taken place. The contributions
to this aspect of biology which Lamarck, Darwin, Weismann,
de Vries, and Mendel have made will not be appraised here,
but it may perhaps be pointed out that their several theories

302 THE BIOLOGY OF SPIDERS

are not necessarily in conflict with one another. Because
Mutation may make good its claim to be considered as a
potent factor in evolution, it is not necessary to deny the
truth of Natural Selection or of the effects of use and
disuse. Evolution is a mighty progressive force in the
world of living organisms, certain to make use of every
available channel for achieving results. It is not to be
limited to a formula and confined to acting by one method
only.

Spiders as Evidence of Evolution

Our present purpose is to try to show that the spider
may claim to provide support for what may be termed the
Neo-Lamarckian school. Kammerer's important experi-
ments on toads and salamanders provide the facts on which
these ideas are based. Kammerer showed that changes in
the colour of the surroundings, as from black to yellow,
provoked corresponding changes in the body colour of
Salamandra atra and Salamandra maculosa , changes which
were sufficiently deep-seated to be represented in the next
generation. In the same way, the change from a moist to
a dry environment altered not only the number of young
produced at a birth, but also the stage of development at
which they were born.

It is this response of one generation to a new environ-
ment, and the acquisition of new habits of life which shall
be impressed on the next generation, that spiders also show
when the history of their race is studied. For the purpose
of tracing the working of an evolutionary tendency, spiders
are particularly suitable, for various reasons.

In the first place, the order of spiders, like the order of
birds, possesses a large number of species, approaching
twenty thousand, within the limits of a comparatively small
range of structural diversity. This means that there is a
dense population within narrow limits, and in consequence
there is a better chance of our being able to follow the
course which Evolution has taken. There is less likelihood

EVOLUTION

303

of breaks in the chain, with the search for missing links and
the suggestion of imaginary intermediate forms which such
gaps produce. Yet, although the structure is uniform the
habits are widely different, as the whole of this book has
shown. Now that the importance of habit as a factor in
evolution has been realised, spiders deserve serious con-
sideration from phylogenists, who in the past have been
wont to base their hypotheses on the facts of morphology
alone. Yet more than thirty years ago F. Pickard-
Camb ridge wrote, " Now it would seem that either habit
produces variation in structure, or slight variations in
structure give rise at length to peculiar habits, or they both
arise simultaneously with mutual influence, and whether
the habit has resulted from a modification of the structure,
or the structure from the habit, or each acted and reacted
upon the other, certain it is that we cannot now (in the
case of spiders at all events) well conceive of, or deal with
the one apart from the other, and that, therefore, they must
both perforce be taken into consideration in schemes of
classification, a conclusion to which Dr. Thorell has long
since come."

The correlation between habits and structure is in
spiders most conspicuous in the legs and spinnerets. The
question as to whether habit or structure made the first
appearance still remains, but a growing body of evidence
seems to point to the habit as the initiator of change. For
example, Elliot Smith, in describing the evolution of the
human brain, has shown how change of habit and change
of structure have gone hand in hand ; he has stated that,
in this instance at least, the only tenable hypothesis is that
the change of habit had come first and that the change of
structure had followed.

Another feature of the order of spiders is that there is
no doubt about the starting point. The primitive nature
of the Liphistiidae has already been fully described, and
with the help of the suggestions as to the nature of the
primaeval spiders which have been made in earlier chapters,
it is possible to compose a satisfying description of the

304 THE BIOLOGY OF SPIDERS

hypothetical creature which may be regarded as the ancestor

Our Archearanead (Fig. 105) was therefore probably a
hunter of insect prey. It had eight eyes quite close
together and its cephalothorax was joined to its abdomen
by a broader waist than that of recent spiders. This waist
was the first of twelve visible segments of which the
abdomen was composed. Below, the abdomen had four
lung-books on the second and third segments, and eight
spinnerets on the fourth and fifth. Its first pair of legs
was the shortest, and each tarsus had three claws, un-
provided with teeth. Its home was at first a chance cavity,
and the appearance inside this of the tubular silk lining,

Fig. 105. — The Archearanead. A hypothetical ancestral spider.

diverging at the mouth, has already been described in
Chapter VII.

From this beginning evolution has proceeded on three
different lines, expressed in the three sub-orders of our
modern classification.

The first and shortest of these ends in the Liphistiidae,
which differ from the Archearanead in having a narrow
waist and one or two teeth on their tarsal claws. They
close their nests with a trap-door. In the other two lines,
the posterior abdominal segments have been lost and only
the anal tubercle remains to recall their existence. The
spinnerets therefore seem to have shifted backwards, but
in reality they occupy their original situations, modified

of all spiders.

Ancestral Spiders

EVOLUTION

305

only by an increase in the length of the third segment,
which has occurred in some species.

The second line is occupied by our present order of
Mygalomorphae, described in the last chapter. They more
closely resemble the Liphistiomorphae than the Arachno-
morphae, but very early in their racial history diverged
into two groups. These were the hunters and the
burrowers already described, and in this sub-order in
particular it is difficult to suggest any alternative to the
idea that these changes of habit preceded changes of
structure.

The third line led to the type of spider dominant
throughout the world to-day, the sub-order Arachno-
morphae. In tracing the evolution of the numerous forms
which this sub-order contains, we make use of the significant
fact that there exists a web precisely similar to that of the
modern Liphistiidae, with the exception that it has no
trap- door. This is the web of Sege stria, described in
Chapter VII. The Dysderidae, the family to which this
genus belongs, are divisible into two sub-families, Dysde-
rinae and Segestriinae, of which the former are the more
active, the latter more sedentary. These have accordingly
retained a type of nest which comes very near to that of
the ancestral spider. For some reason they have never
closed the tube with a trap-door, and this may be because
the radiating threads gave sufficient warning of the approach
of intruders, or because the spiders adopted the habit of
turning the third legs forwards, thus having six limbs
available for attack and defence in the mouth of the tube.

Anatomically the nearest allies to the Dysderidae are
the Oonopidae. Some of the spiders of this family carry a
dorsal shield on the abdomen which cannot fail to recall
the segmented plates which characterise the Liphistiidae.
It may one day be possible for embryological research to
prove that this shield of the Oonopidae is homologous with
the plates of the Liphistiidae, but that the former, in
persisting, has lost its segmental character.

If these views be accepted, these families and their

3o6 THE BIOLOGY OF SPIDERS

allies will form the most direct line from the primitive
ancestor and must be considered as the founders of the
Arachnomorph sub-order. In modern classification, there
are seven families in this early group, which afford material
for more detailed consideration.

Methods of Respiration

In the first place, it is interesting, and perhaps not with-
out significance, to notice that three families, Dysderidae,
Oonopidae, and Caponiidae include species that have only
six eyes.

There is also a most significant diversity in the respira-
tory organs possessed by these families. It has already
been said that all Liphistiidae and Mygalomorphae have
two pairs of lung-books, while the vast majority of Arachno-
morphae have a single pair of lung-books and one median
tracheal aperture. However, five families, all included in
the present group, are exceptional. The Hypochilidae
have two pairs of lung-books, the Dysderidae and Oono-
pidae have a pair of lung-books and a pair of tracheal
apertures, while the Caponiidae and Telemidae have no
lungs, but two pairs of tracheal apertures. Thus there
seems to be, among the spiders of this stage in evolutionary
history, an instability of the respiratory system, with the
result that different methods have been produced and
some of the results of each experiment have survived.

The Hypochilidae, because of their four lung-books,
were something of a problem when the number of lungs
was made the distinguishing feature between the trap- door
and other spiders. They have been placed in both sub-
orders by different authorities, and some reasons for
uncertainty still exist. A study of their circulatory system
or of their coxal glands, would, as Petrunkevitch has pointed
out, probably settle the question without doubt, but no
such study has yet been made. If they are placed among
the Mygalomorphae, they will be quite isolated there, for
they have a cribellum and calamistrum, which no Mygalo-

EVOLUTION

307

morph spider possesses. They have more affinities with
Arachnomorphae, and the existence of diverse types of
respiratory systems in this sub-group shows that these
organs cannot be regarded as of great systematic value.
Their position among the Arachnomorphae may be justified
if it be merely admitted that they alone have retained the
primitive means of breathing. The genus Nebalia occupies
a very similar position among the Crustacea, and is placed
among the higher Malacostraca with the same reservations.

The tracheal system of the other families has replaced
the second pair of lung-books, opening at first at a pair of
spiracles. Later these joined. A transitional stage is seen
in the Filistatidae, where the groove uniting the two
tracheal openings is already shorter and deeper.

This family is another which is in some ways a puzzle.
They are cribellate spiders which live in a web very similar
to that of our common Amdurobius. Their coxal gland
system was studied by Buxton and found to be of the
simplified type, like that possessed by the Epeiridae.
Buxton therefore suggests that the true position of this
family is near the top of the spider kingdom, and that they
have descended to protected situations nearer the ground
for spinning their webs. In favour of this idea there is the
fact that there is a family of spiders, the Uloboridae, closely
related to the Epeiridae, and occupying, as will be seen
presently, some such situation as that from which the
Filistatidae might be supposed to have come. If the
Filistatidae are the descendants of the Uloboridae, they
form an exact parallel to that section of the Linyphiidae
which, as already noted in Chapter VII, took the sheet- web
back to the shelter of crevices in the ground. Against the
theory there is the fact that the external structure of the
Filistatidae does not suggest an alliance with the Uloboridae
or with the Epeiridae. This is especially true of the palpal
organ of the males, which is of a very primitive type, and
points to their nearer relationship to the Dysderidae and
other families of the lowest group. However, their mouth
parts and chelicerae are very similar to those of the Sicariidae,

308 THE BIOLOGY OF SPIDERS

and their courtship is also allied to that of the higher
families.

The family has always been a puzzle, ever since Walcke-
naer and Koch classed it with the Mygalomorphae. There
are good arguments in favour of both positions and as yet
no apparent way of reconciling the two sets of opposing
views.

The Cribellum

The significance of the supernumerary spinning organ
or cribellum and the accompanying comb or calamistrum
on the metatarsus has long been discussed. Many spiders
of similar structure and habits are readily distinguished by
the presence or absence of these organs, and Simon used
this character for splitting his Araneae verae (a division
corresponding to the Arachnomorphae) into two sections,
Cribellatae and Ecribellatae. If our classifications are to
deserve the adjective " natural," this is equivalent to
implying that these two sections represent different routes
in the history of the spider race, in which the cribellum
made a very early appearance. The numerous instances
of resemblance between cribellate and ecribellate genera
would then have to be ascribed to a rather astonishing
amount of " convergence." Petrunkevitch, who goes into
the matter in great detail, has come to the conclusion that
the cribellum is indeed an ancestral possession. From the
first cribellate spiders, some, also cribellate, have arisen,
but in others the cribellum has become the colulus, and an
ecribellate spider has thus resulted. And, of course, such
spiders have given rise to other ecribellate forms.

It is thus impossible to look upon the presence or
absence of this organ as splitting all spiders into two
fundamentally separate groups. It might even be justifiable
in some cases to unite both cribellate and ecribellate genera
into the same family. Whether or not this is to be done
is of small importance, and is largely a question of individual
opinion. Probably it is of greater practical convenience to
separate them.

EVOLUTION

309

The Tarsal Claws

The remaining families of spiders, whether cribellate or
not, which all breathe by two lung-books and a single
tracheal spiracle, divide themselves broadly into those with
three tarsal claws and those with two. This recalls the
similar division of the Mygalomorphae and depends on the
same difference in the mode of life. Like that division, too,
it is not complete, for there are a few families, such as the
Zodariidae and Palpimanidae, which include both two and
three-clawed genera. On the whole, however, it is a
convenient and probably a natural separation.

The two-clawed group consists of one fossil family, the
Parattidae, and fourteen recent ones, with some differences
in their general modes of life. The
most important families, the numerous
Clubionidae and Drassidae, contain the
spiders that merely wander, usually at
night, without great power of speed or
conspicuous ability to leap and so prey
upon what they may chance to en-
counter. Indeed, among the Clubio-
niidae there are genera, such as Corinna,
which spin the primitive form of diverg- Fig. 106. — Tarsus of

ine tube-web Clubiona spiderling,

ni& LUUC wcu' showing transitory

The two other chief modes of life third claw. From a
in this division are obvious elaborations Rh^™arneyaph ^
of simple wandering. The crab-
spiders, or the family Thomisidae, often hidden by the
protective colourings which have been already described,
lie in wait for their prey and leap, perhaps sideways, upon
it. The large Sparasside are flattened crab-like spiders,
which generally conceal themselves in narrow crevices.
The jumping-spiders or Salticidae have developed the habit
of leaping upon their prey instead of chasing it, a method
which, if one may judge from the multitude of species and
world-wide distribution of this family, has certainly been
very successful.

3io THE BIOLOGY OF SPIDERS

The most interesting feature about the two-clawed
spiders is that on the tarsi of the spiderling in the cocoon
the full complement of three claws is present. Fig. 106,
which illustrates this, is drawn from a photomicrograph,
originally published in Nature in 1926, of the leg of a
spiderling of the species Clubiona inter jecta. The tiny
median claw, plainly visible between the paired claws, is
lost very early in the spider's life, but its transient appearance
shows that the possession of three claws is the ancestral
condition.

House- Spiders and Wolf- Spiders

By far the greater number of living spiders possess
three claws throughout their lives, and form a group
divisible into four sections.

The lowest of these is certainly the group of seven
families which includes the Agelenidae and the cribellate
Amaurobiidae. The common bluish webs of the latter are
undoubtedly the cribellate analogue of the primitive diverging
tube. The extension by the Agelenidae of the lower edge
of the tube mouth into a hammock-like sheet has already
been described. The Psechridae are obviously allied to
the Amaurobiidae and the long spinnerets of the Hersiliidae
are among the features which relate this family to the
Agelenidae.

Secondly, there is a group of nine families which are
best regarded as a specialised offshoot from the group just
considered. Like the two-clawed division, most of these
spiders have taken to hunting their prey, which they over-
come by sheer speed. The wolf-spiders, Lycosidae, and
the Pisauridae are the best known of these families. The
latter are actually the more primitive, but the resemblance
between the Lycosidae and the Agelenidae are very striking.
The most significant from the point of view of this chapter
is the fact that some genera of the Lycosidae, such as
Hippasa, spin large sheet- webs of the same form as the
webs of the Agelenidae. It was indeed the form of these

PLATE XIV

B. Zebra-Spider (Salticus scenicus). X 6.
Tc face p. 310.] [E. A. Robins, photo.

EVOLUTION

webs which first suggested to Simon that the Lycosidae and
the Agelenidae might prove on examination to be related —
a relationship which, as he says, in speaking of the advantage
he gained from foreign travel, " nous aurait sans doute
tourjours echappe si nous avions restreint nos recherches
a la faune de France."

Of the other families in this group, the Senoculidae
form an American family obviously allied to the Pisauridae,
as are the Oxyopidae to the Lycosidae. The Palpimanidae
and the Zodariidae are rather primitive and in some ways
resemble the Drassidae, but some of their species have
three tarsal claws. The exact position of the last family,
the Eresidae, has always been something of a puzzle, for
they show a superficial resemblance to the Salticidae. It
is probable that this is due to convergence and their true
position is to be found among the hunting-spiders.

Web-spinning Spiders

Our hypothesis concerning the origin of the last two
groups, as the sheet- web was modified on being taken into
arboreal situations, has already been stated in Chapter VII.

The group which contains the sheet-webs of the Liny-
phiidae and the simple tangles of the Theridiidae consists
of five families. The Pholcidae have from the first been
recognised as closely allied to the Theridiidae, and the
Archaeidae are similarly related to the Linyphiidae. The
last family, the Dictynidae, are a cribellate group, which
may reasonably be regarded as the arboreal descendants of
the Amaurobiidae. Indeed, it is only lately that Petrunke-
vitch has separated these two families, which were previously
united.

The last group of all is much the hardest to place
satisfactorily. It contains four families, the Epeiridae,
Mimetidae, Dinopidae, and Uloboridae, and it seems
impossible to derive it directly from any family in the
Agelenidae group. It may be represented as an early
offshoot of the third or Linyphiidae group, with whose

3i2 THE BIOLOGY OF SPIDERS

families its own are closely parallel. There are obvious
similarities between the Dictynidae and the Uloboridae,
two cribellate families which both have claims to a genus

Fig. 107. — The Spiders' Genealogical Tree.

Mbutina. The Mimetidae recall the Theridiidae in several
respects, including the form of their webs, while the
relation between the Epeiridae and the Linyphiidae, the

EVOLUTION

3i3

supreme families of the two groups, is so close that Simon
united them into one huge family, Argiopidae.

These ideas are summarised by the diagrammatic
Evolutionary Tree in Fig. 107.

All the foregoing derivation of one set of families of
spiders from one another is, like the early part of
Chapter VII, of very recent date and includes the spider's
chief claim to consideration as an animal able to make
serious contribution to the theory of biology. The first
suggestion of an evolutionary relationship between the
different families was made by Thorell in 1869. In a plate
in his book, On European Spiders, he gives a diagram-
matic representation of the tracks of evolutionary progress,
in which he makes the Tubitellariae the lowest group,
containing the families Drassidae, Dysderidae, Agelenidae,
and others with the " Liphistioidae " as one of several
offshoots therefrom. It seems, however, quite clear that
the Liphistiomorphae must be the starting point.

In the authoritative Histoire Naturelle des Araignees,
Simon puts forward the views both of himself and others as
to the relations of each family in turn. If one takes stock
of all these statements, one gets the impression of a direct
linear ascent from the lowest to the highest forms, with
many convenient intermediates, but with plenty of room
for divergence of opinion.

The most important contributions to the subject are
two recent papers by Petrunkevitch. The former, On
Families of Spiders, appeared in 1923 and was generally
recognised as one of the most striking contributions to
the systematic study of any group of animals that has
ever been seen. The latter, Systema Aranearum, an in-
valuable monograph of nearly three hundred pages, appeared
in January, 1928, and brings together, for the first time in
the history of arachnology, the whole of the 2,144 genera
established to date.

3 14 THE BIOLOGY OF SPIDERS

The Classification of Spiders

Zoologists regard the subject of classification from at
least three different points of view. There are some who
affect to despise taxonomy as the Cinderella of natural
history, and there are those who, almost grudgingly, recog-
nise that animals must be grouped into orders, families,
and genera, but who sternly repress any attempt to push
the division to finer intermediate stages. Finally, there
are the few who realise that our classificatory schemes not
only summarise the results of the labours of embryologists,
morphologists, and others, but that, when reasonably
complete, they will tell the whole history of animal life,
recording age-long experiment, success, and failure in the
ever-present problems of self-preservation and race-
propagation. To the last class taxonomy becomes a valuable
aid in the study of zoology, for, instead of remaining bound
by convention, it confers its greatest benefits by becoming
a live branch of the science, elastic where elasticity is
desirable, and not bound down to arbitrary and probably
artificial limitations. The classification of spiders, in
particular, responds to such a mode of treatment.

It is not so very long since the subject of spider classi-
fication was in a state of chaos and confusion. The diffi-
culties with which earlier workers had to contend were due
in part to their ignorance of the fauna of many distant
quarters of the earth, so that fresh discoveries failed to
find a place in their schemes. Partly because of this, many
systematists went to work on fundamentally the wrong
lines, endeavouring to arrange the order in a few large
divisions, instead of a greater number of almost equivalent
groups. Thus C. A. Walckenaer, in 1805, divided spiders
into " les Theraphoses," and " les Araignees," which were
further split into " les Binoculees," " les Senocutees," and
" les Octocutees." P. A. Latreille, in 1809, adopted two
sub-orders — " Quadripumonaires " and " Bipumonaires,"
— but sixteen years later produced a new scheme of division
into tribes, based on the habits of their members. There

EVOLUTION

3i5

were the Orbitelariae, Retitelariae, Citigradae, Laterigradae,
Territelariae, and Saltigradae. The method was followed
by many naturalists, by some quite closely — as by Menge
in his " Preussische Spinnen " — by others with slight
modifications, such as the interpolation of the groups
Vagabundae and Sedentariae. In fact, it had more to
recommend it than some of the systems which followed.

Daylight began to break over the families of spiders
when the amazing industry and genius of the late Eugene
Simon produced the second edition of the Histoire
Naturelle des Araignees between 1892 and 1903. It can-
not, however, be said that Simon's grouping of his forty-
one families was altogether fortunate. His major divisions
were as follows : —

Sub-order. Araneae theraphosae. (3 families.)
Sub-order. Araneae verae.

Section Cribellatae. (8 families.)
Section Ecribellatae.

Sub-section Haplogynae. (6 families.)
Sub-section Entelegynae. (24 families.)

The validity of the two sections has already been criticised.
The last two sub-sections depend on whether the epigyne
of the female is medially divided into right and left halves,
or not. This is not a character of a very fundamental
nature, and the six families of the Haplogynae do not form
the whole of a natural group in the scheme outlined below.

It is not difficult to see why a method of sub-division
such as this should have recommended itself to one in
Simon's position. It must be remembered that he did all
the pioneer work of modern arachnology ; that he collected
spiders himself in every part of the world, and that later,
as the unchallenged and unchallengeable head of the
devotees of these creatures, he received specimens in almost
overwhelming numbers. At the time of his death in 1924
his collection contained some twenty-six thousand tubes
with about a quarter of a million specimens.

The task of surveying such a multitude might well have

316 THE BIOLOGY OF SPIDERS

dismayed a lesser man, and it seems only reasonable to
suppose that the system he adopted was favoured because
of its practical advantages in classifying specimens. It is
easy to see if a spider has a cribellum or not, or whether its
epigyne is divided or not. At the time, this was of greater
value than the establishment of a wholly natural scheme.
Even now, an artificial rather than a natural " key " is the
most convenient method to use, when it is necessary to
determine the family of a given spider.

The aim of taxonomists, however, is to give a natural
classification, in which the relation between the different
groups shall be the same as their actual and historical
origins. For instance, there are, as we have seen, three
distinct groups of hunting-spiders and at least five distinct
groups of web-spinners among the Arachnomorphae alone.
All these represent different lines of development of the
spider race, and, as our classification stands at present,
exist as nameless and all but unrecognised stages inter-
mediate between the sub-order and the family. It is, of
course, possible to leave them unnamed, and many will
wish to do so, partly from innate conservatism, partly from
an apparent horror of admitting any new division between
family and sub-order. But if we do so, our scheme of
classification is at once becoming stereotyped, ceasing to be
natural, ceasing to express racial history, and losing its
most valuable function of summarising existent knowledge.
It becomes a dead index, in which alphabetical order would
be as good as, or better than, any other.

The possible alternative is, of course, to make the
family a larger body, including a greater number of genera.
There are many to whom such a course would appeal —
those who possess an " inclusive " type of mind, and who
delight in obliterating boundaries wherever " intermediate
forms " make it possible. In this way the Insecta and
Myriapoda have become the Antennata ; the Annelida and
Arthropoda have become the Appendiculata, and so on.
An obvious criticism of this process is that, carried by
increase of knowledge to its logical conclusion, the whole

EVOLUTION

3*7

animal kingdom becomes one phylum (or one genus), and
taxonomy has disappeared. This is perhaps an idealist
absurdity ; the real drawback is a practical one — the
unwieldy character of the groups it produces.

It has to be realised that there is not, in the present
state of our knowledge, any stage in the separation of
organisms where, by fixed rule, one family or genus ends
and the next begins. Our classifications are made to be
of use to us, and at present workers have little hesitation
in splitting a family or genus into several parts when the
number of contained genera or species exceeds a useful
limit. This is the antithesis of the inclusive mind — it is
a mind which delights in finer and finer subdivisions, in
more and more precise analysis. It has this obvious
justification, that its schemes become of increasing utility
without losing their claims to be considered natural, while
at the same time they avoid that appearance of a linear
ascent through all units of the series, which is just the way
by which evolution has not travelled.

For the Evolutionary Power was never an Urge which
at any time decreed, " Here and now shall a new family
(or genus) be created." Our division into families and
genera are devices of our own subsequent invention and
for our own convenience. We have to try to make them as
natural, as true, as possible, and not to try to force the
facts of nature into our schemes. There is always the
risk of our treating our classifications with more reverence
than they deserve, for families and genera, and perhaps
species too, are inventions of man and not creations of
Nature.

The present chapter ends with a classification which
differs from that of Petrunkevitch only in emphasising the
varied direction in which Evolution has proceeded. Thus
each separate experiment of the past is represented by a
named group of families. This has necessitated the
introduction of stages between the sub-order and family,
which I have called divisions, tribes, and grades. Each of
these is named, and as far as possible, the names suggested

3*8 THE BIOLOGY OF SPIDERS

for them are resurrections of the proposals of other writers,
which would otherwise be forgotten. These are not now
used with necessarily the same significance as that which
they originally possessed, but it seems more reasonable to
use them than to invent an entirely new series of names for
expressing very much the same ideas.

Order ARANEAE
I. Sub-order LIPHISTIOMORPHAE

1. Family Liphistiidae . . (2)

2. Family Arthrolycosidae . . (1)

3. Family Arthromygalidae . . (1)

II. Sub-order MYGALOMORPHAE
Tribe NELIPODA

4. Family Ctenizidae . . (3)

5. Family Atypidae . . (1)

6. Family Migidae . . . (3)

7. Family Dipluridae . . (5)

8. Family Paratropididae . . . (1)

9. Family Pycnothelidae . . . (1)

Tribe HYPODEMATA

10. Family Barychelidae . . (4)

11. Family Theraphosidae . . (7)

III. Sub-order ARACHNOMORPHAE

A. Division TETRASTICTA

Tribe TUBITELLARIAE

Grade Tetrapneumones
12. Family Hypochilidae . . . (1)

EVOLUTION

Grade Dipneumones

13. Family Filistatidae

14. Family Dysderidae

15. Family Oonopidae

16. Family Hadrotarsidae .

Grade Apneumones

17. Family Telemidae

18. Family Caponiidae

B. Division DIONYCHA

Tribe VAGABUNDAE
Grade Oligotrichiae

19. Family Zoropsidae

20. Family Acanthoctenidae

21. Family Ctenidae

22. Family Drassidae

23. Family Ammoxenidae .

24. Family Prodidomidae .

25. Family Homalonychidae

26. Family Selenopidae

27. Family Clubionidae

28. Family Platoridae

Grade Latepjgradae

29. Family Thomisidae

30. Family Aphanthochilidae

31. Family Sparassidae

Grade Saltigradae

32. Family Salticidae

33. Family Parattidae

320 THE BIOLOGY OF SPIDERS

C. Division TRIONYCHA
Tribe STICHOTRICHIAE

34. Family OEcobiidae . . (1)

35. Family Urocteidae . . (1)

36. Family Psechridae . . . (3)

37. Family Tengellidae . . (2)

38. Family Amaurobiidae . . . (1)

39. Family Agelenidae . . (4)

40. Family Hersiliidae . (1)

Tribe CITIGRADAE

41. Family Palpimanidae . . (3)

42. Family Zodariidae . . (6)

43. Family Eresidae . . (2)

44. Family Pisauridae . . (3)

45. Family Lycosidae . , (5)

46. Family Senoculidae . . (1)

47. Family Oxyopidae . . . (1)

48. Family Leptonetidae . . (2)

49. Family Sicariidae . . (7)

Tribe RETITELARIAE

50. Family Dictynidae . . (2)

51. Family Theridiidae . . . (11)

52. Family Pholcidae . . (6)

53. Family Linyphiidae . . (6)

54. Family Archaeidae . . (2)

Tribe ORBITELARIAE

55. Family Uloboridae . . (3)

56. Family Dinopidae . . (1)

57. Family Mimetidae . . . (1)

58. Family Epeiridae . . (7)

Note. — The numbers in parentheses after each family refers to the
number of sub-families into which the family is divided by Petrunke-

vitch in his latest work. The number of genera is as yet too uncertain
to be usefully included.

PLATE XV

To face p 320.]

B Harvester.

[E. A. Robins, photo.

CHAPTER XVI

SOME OTHER ARACHNIDA

Besides spiders, there are other orders of Arachnida, whose
more interesting features may be considered in a final
chapter. Thus will the arachnid corner of the animal
kingdom be surveyed, and a comparison made between
spiders and their nearest allies.

The King- Crab

The king-crabs form a genus, formerly known as
Limulus, of primitive Arachnida of an extraordinary type,
differing in several ways from all other members of the
Class. They are marine creatures, living in waters less than
ten fathoms deep on the Atlantic coast of America and in
a few localities near Japan, Malaysia, and India. About
half a dozen living species are known.

In appearance the king-crab (Fig. 108) may be roughly
compared to a semicircle linked to a hexagon. The semi-
circle is the outline of the sloping carapace which is rounded
in front. The abdomen is a broad hexagon, its anterior
margin fitting into a re-entrant behind the cephalothorax,
its posterior margin edged with spines and bearing in the
middle a long unjointed spine-like telson. The colour
varies from dark green to black, and the creature has a
clean-looking, burnished appearance. The only other
feature visible from above are the eyes, of which there are
two pairs, one median, the other lateral.

The lower aspect of the king-crab is a deep hollow, in

321 y

322 THE BIOLOGY OF SPIDERS

which the appendages lie. Of these there are seven pairs
belonging to the prosoma.

The chelicerae, which mark the third segment of the
animal's body, lie just in front of the mouth. They are
very short and consist of three joints only. The third joint
is chelate, ending in a delicate pair of points like those

Fig. 108— The King-crab.

of fine forceps. The pedipalpi have six joints. In the
females of some species the last joint is chelate, in others
it ends only in a claw. In the mature males the pedipalpi
end always in a claw, and the organ is thicker and heavier
than in the female. The legs are also composed of six
joints. The first three pairs are chelate. The fourth pair
end in a number of fan-like plates, which can be separated

SOME OTHER ARACHNIDA

or brought close together. These are used in burrowing.
The last pair of appendages on the prosoma are the chilaria.

The coxal joints of the pedipalpi and of all the legs have
inwardly directed processes covered with spines and
furnished with crushing teeth. They assist in masticating
the food before it enters the mouth.

The appendage of the first abdominal segment is the
median genital operculum, through which the female
deposits the eggs. The next five segments carry paired
gill-books (Fig. 109). These respiratory organs are very
different from anything possessed by the land Arachnida.
The gill-book itself is borne
on the hind surface of the
expodite or outer branch of
the appendage. It consists
of a hundred and fifty to
two hundred leaves within
each of which the blood is
flowing, while the oxygen-
ated water circulates be-
tween the leaves. In this
possession of breathing
organs visible from outside
the body, Limulus resembles
the extinct Eurypterida.

The king-crab spends
the greater part of its life
burrowing in the sand under shallow water. It is probable
that in this comparatively unpopulated environment it enjoys
a freedom from competition with the more active creatures,
and that this has enabled it to persist in its relatively primi-
tive form since the Silurian era. It makes its way through
the mud with astonishing facility. Bending its body
upwards, it urges the front edge of its carapace downwards
and forwards, while the sharply-pointed spine is pressed
into the mud behind. At the same time, the extensible
fan-like organs which terminate the fourth pair of legs are
thrust backwards, so that the lobes are opened by the

Fig. 109.
crab.

-Gill-book of the King-
Partly after Shipley.

324 THE BIOLOGY OF SPIDERS

resistance of the sand, a load of which is pushed out behind
the shell. This process is rapidly repeated and the clearing
action is probably assisted by the fanning action of the
plates bearing the gill-books, the current from which helps
to wash the sand particles away.

At night the king-crab leaves the sand and swims by
means of its gill-bearing appendages, helped by the spine
on which it balances between the flights. Its mode of
progression is therefore a kind of combination of swimming
and hopping. The food of Limulus consists of softish
molluscs and marine worms such as Nereis, which it
encounters as it burrows in the sand. It seizes them with
its chelicerae and holds them under its mouth, in such a
position that they can be reached by the gnathobases of
the legs. Opposing movements of the gnathobases shred
the food into particles small enough to pass into the mouth.

The sexes are separate, the male, as is common among
Arachnida, being smaller than the female. Fertilisation is
external. The creatures come into shallow water for
pairing and spawning during the months of May, June, and
July, and the male grasps the hinder edge of the carapace
of the female with the chelae of the second pair of legs.
At intervals the couple stop for a few moments, and at each
of these stopping-places, a nest of eggs may be found,
buried under about two inches of sand. It thus seems
probable that the female thrusts her genital plate into the
sand and that at the moment that she lays the eggs, the
male discharges sperms into the water. Each nest contains
about a thousand eggs. Some species of king-crab do not
bury their eggs but carry them about attached to their
under surface in a quantity which may amount to as much
as half a pint. In this condition they are valued as food
for pigs and poultry.

Each egg is protected by a leathery coat. From it there
emerges an interesting little creature known as the trilobite
larva, because of its superficial resemblance to that fossil.
The larva is very active, burrowing in the sand like its
parents and also swimming freely by means of its posterior

SOME OTHER ARACHNID A 325

limbs. It soon moults, when the segments of the abdomen,
which had at first been free, become more closely united.
The spine is absent from the larva, but makes its appearance
at the first moult, and increases in size at subsequent
changes of the cuticle.

Thus the king-crab grows like other arachnids. There
are five or six moults in the first year of its life. In moulting,
the old cuticle splits along the lower side of the front edge
of the shield, and through this slit the body and legs of the
animal emerge. The increase of size is rapid and an
individual may reach a width of nine or ten inches. The
time required to reach this size is estimated at about eight
years.

Scorpions

Scorpions are the largest of the land-living Arachnida,
and are interesting because their structure combines parts
which indicate a state of
high specialisation with
parts which show a primi-
tive nature. They are
essentially dwellers in hot
countries and are found
widely distributed to the
south of the 45th parallel
of latitude in the northern
hemisphere. They do not
occur in New Zealand or
in the Antarctic Islands.

The body of the scor-
pion (Fig. no) is divided
into three parts, each of six
segments. The first part,
or prosoma, is covered
above with an unsegmented Fig. no. — A Scorpion. From a

1 • photograph by C. Milton Adcock.

carapace, bearing two me- p B F y

dian eyes and two lateral groups of from two to five eyes.

All the eyes are simple, like those of spiders. Beneath the

326 THE BIOLOGY OF SPIDERS

prosoma is a very small sternum, surrounded by the six
pairs of appendages. These are the same as those of the
spider, namely, the chelicerae, pedipalpi, and four pairs of
legs. The chelicerae are three-jointed ; the third, joint is
articulated on the outer side of the second, forming a strong
" finger " armed with teeth. The palpi are six-jointed,
and also end in a movable finger-like chela. The legs are
seven-jointed ; the last joint terminates in a pair of stout
claws, with a vestigial third claw beneath them. The
teeth of the chelicerae, the last joint of the palpi, and the
last three joints of the legs exhibit differences in detail
which make them useful guides in classification.

The segments of the mesosoma are separate from one
another, and are protected by hard tergal and sternal
plates, joined at the sides by softer chitin. The second
mesosomatic segment bears a pair of remarkable comb-like
organs, the pectines. These seem to be special organs of
touch, a sense which is highly developed in scorpions, and
they are apparently in constant use determining the nature
of the ground over which the scorpion is walking. Thus
Pocock has seen a scorpion walk over a cockroach until the
pectines came into contact with it, when it immediately
backed and ate the insect.

The segments of the metasoma or abdomen are enclosed
in complete chitinous rings. The last or post-anal segment
has a globular base known as the vesicle and terminates in
a fine curved point along which runs the poison duct.
This point is usually directed downwards, but in the
attitude of attack or defence the " tail " or abdomen is
curved over the back and the sting points forwards.

Scorpions are nocturnal in activity and rapacious in
habits. During the day they rest in hiding under logs of
wood, under stones, or in holes in the sand. These holes
are dug by the scorpion itself, using the second and third
pairs of legs as scoops, while it supports its body on its
chelicerae, abdomen, and other legs. At night they awake
and hunt their prey, which consists almost entirely of
insects and spiders. Their power of vision is feebly

SOME OTHER ARACHNIDA 327

developed and they seem to be quite deaf. There is no
evidence that they possess any sense of taste. The prey is
seized in the pedipalpi and torn to pieces by the chelicerae.
If the victim is a formidable one, the poison-bearing sting
in the tail is used to paralyse it. Like spiders, scorpions
are slow eaters, and will generally spend more than an hour
in eating a single beetle.

The food of scorpions seems to supply them with all
the moisture that their bodies need, for they apparently
never drink. They are in this respect well adapted to live
in the dry sandy localities in which they are generally
found, and, like other Arachnida, they can undergo pro-
longed fasts without fatal consequences. They are solitary
animals and Warburton remarks that the only occasion on
which two may be found together is when one is engaged
in eating the other.

As is well known, the poison they secrete is much more
virulent than that of spiders, and is instantaneously fatal
to insects, spiders, and centipedes. A scorpion's own
poison is, however, without effect upon itself, an interesting
fact which contradicts the fable that a scorpion will commit
suicide when in danger from fire. Their ferocity has been
much exaggerated. They never attack without consider-
able provocation, and generally exhibit a much greater desire
to avoid notice or to escape unostentatiously.

Their mating habits have been described by Fabre, who
kept numbers of scorpions in his garden. They indulge in
courtship, which is strongly reminiscent of the courtship of
spiders. In a preliminary dance together their tails are
entwined, and later the male takes the chelicerae of the
female in his own and leads her to the neighbourhood of
a suitable stone, where, without letting go, he digs a hole
into which both scorpions retire. After mating the female
sometimes eats the male.

All scorpions are viviparous. The newly-born young
are carried on the mother's back, where they remain for a
week. During this time they do not feed, and in this
respect they resemble young wolf-spiders. They then

328 THE BIOLOGY OF SPIDERS

moult, after which they leave their mother and fend for
themselves.

Subsequent growth takes place, as in spiders, by casting
the cuticle. The size of an adult scorpion is very different
in different species, some are over eight inches long, others
are barely a quarter of an inch. Fab re estimates the
normal length of a scorpion's life at five years.

The number of different species of scorpions known is
about three hundred, and they are divided into six families :

Buthidae Scorpionidae Chaerilidae

Chactidae Vejovidae Bothriuridae

Solifugae

The Solifugae form an order of about two hundred
species, interesting because of their primitive structure.

There is in fact a remarkable re-
semblance between the general ap-
pearance of these creatures and that
of the hypothetical Archearanead
described in the last chapter, a re-
semblance which cannot be wholly
due to chance. There is, however,
so much difficulty in determining the
relationship between the different
orders of Arachnida that it would
not, as yet, be justifiable to stress
this resemblance further.

Solifugae are confined to hot
countries. No species is found in
England and in Europe they are
limited to Spain, Greece, and South

Russia. They abound in Africa,
Fig. hi. — Galeodes .,»• * i« •

arabs. From a photo- tropical Asia, and central America,
graph by C. Milton DUt are absent from Australia and

Adcock. _ _ t

Madagascar.

In general appearance they are very spider-like, but
they have a segmented body and no spinning organs

SOME OTHER ARACHNIDA 329

(Fig. 111). The cephalothorax consists of six segments, of
which the first three are fused together to form a head,
while the posterior three are quite separate. The abdomen
consists of ten clearly defined segments. It is a little
harder than the abdomen of a spider, but not nearly so
hard as the body of a scorpion. The whole body and the
limbs of the animal are thickly covered with hair-like setae.

The appendages of the cephalothorax are the same as
those of spiders. The chelicerae, however, are greatly
developed and the muscles which move them produce
large " cephalic lobes " in the front of the cephalothorax.
They are two-jointed chelate limbs ; the basal joint bears
in the male a curious flagellum composed of modified hairs
and believed to have a sensory function. The pedipalpi
are leg-like and consist of six joints. The last joint is knob-
like, and contains a remarkable extensible sac, believed to
be an olfactory organ. There are four pairs of legs. The
first have a single small claw, the others have two large
claws. Sensory organs are also present on the legs. The
first pair of legs is not used for walking, but is carried like
the palpi and used for feeling.

A pair of large simple eyes occupies a prominent
position on the cephalic lobes, and in addition one or two
pairs of lateral eyes may be present.

Most Solifugae are nocturnal, but a few are lovers of
sunshine ; many of them are very active, and so rapid in
their movements that they are difficult to catch. Their
normal diet consists of insects. In spite of the widespread
belief that Solifugae are venomous, it has been shown
conclusively that there are no poison glands. Bacteria,
however, may of course be introduced into the wound
made by the bite. The strong chelicerae can inflict such a
serious wound that poison is unnecessary.

Solifugae became familiar during the War to our troops
in Egypt and the near East, where Galeodes arabs is very
common. The soldiers named them " jerrymanders, " and
admired them on account of their extreme ferocity. At
one time the men stationed at Aboukir kept pet Solifugae

330 THE BIOLOGY OF SPIDERS

and fought them against each other, like fighting cocks.
Each company had its champion, and bets were freely laid
on the results of the fights.

Size is not always the decisive factor when Galeodes
fights. Although a large one may catch a small one behind
the head and not let go until the head is severed, it some-
times happens that a smaller individual seizes its opponent
between its too widely-opened jaws and conquers by
holding on in a position in which the big creature is quite
helpless.

False-Scorpions

The false-scorpions form one of the most interesting
orders of the lesser Arachnida. They are widely spread
over the whole of the habitable world, being represented in
small numbers even in cold countries. But the largest
known species, Garypus litoralis of the Mediterranean, is
barely a quarter of an inch long, and no British species
exceeds a sixteenth of an inch in length, so that, partly
because of their small size, and partly because of their
retiring habits, they are comparatively little known, for
they are seldom found unless specially sought.

Many of them hide under stones, under the bark of
trees, among moss, and in collections of vegetable debris.
A few live in houses, where they may be found in cellars
and among books. The " book-scorpion " is Cheiridium
museorwn, a member of this order, and has been known
since the time of Aristotle. In stables and sheds false-
scorpions often occur, living in cracks in the woodwork and
in neglected heaps of hay or straw. Some species are
partial to heaps of manure, and one or two cling to the legs
of flies as a means of dispersal. A few others live on the
seashore, below high- tide mark in deep rock-crevices and
under large stones.

These little creatures have a superficial resemblance to
a scorpion, enhanced by their large claw-like pedipalpi
(Fig. 112). The body consists of a cephalothorax and an
abdomen of twelve segments. The segments are protected

PLATE XVI

SOME OTHER ARACHNIDA 331

by dorsal and ventral plates, but, since the plates covering
the eleventh and twelfth segments are fused together, only
eleven segments can be seen from above. In the same way
the last four ventral plates are joined, so that only nine can
be seen from below. The dorsal plates are often divided
by a median line of soft membrane.

The cephalothorax has no trace of segmentation beyond
a few transverse striae, present in some species. The eyes

Fig. 112. — Obisium muscorum. A common British false-scorpion.
After Kew.

are two or four in number, save in some species which are
blind, and are placed in the usual position near the front
of the cephalothorax. They are pearly white in colour and
are never much raised above the level of the carapace.
The ventral surface of the cephalothorax is formed by the
coxal joints of the legs and palpi ; only in Garypus is there
any trace of a sternum.

The abdomen, unlike that of the true scorpion, bears no

332 THE BIOLOGY OF SPIDERS

" tail." The chitinous plates are separated by intervals of
membrane, and this membrane is very extensible. The
result is that when the abdomen is distended, as it is before
the female lays her eggs, the plates are some distance apart,
while after the eggs have been laid, they may even overlap.

The respiratory tracheae open at the sides of the
abdomen, on a level with the hind edges of the first and
second segments. The first ventral plate bears the genital
orifice and also a pair of other apertures from the " abdominal
glands."

The appendages of the cephalothorax are the chelicerae,
pedipalpi, and four pairs of legs. The chelicerae are two-
jointed, and the second joint moves up and down against
the prolongation of the first to form a grasping chelate
organ. Near the top of the second joint there is the opening
of the silk glands. False-scorpions produce a secretion
similar to the silk of spiders, but use it only for nest-
making.

The large pedipalpi are six-jointed, the last joint being
a movable one. They form the only effective weapons of
the creature. Unlike the palpi of spiders, their coxae bear
no maxillary lobes ; they are, however, very close together
and are enlarged and flattened, so that they probably assist
in mastication.

The legs are by comparison short and weak ; they are
composed of five to eight joints, of which the first, or coxae,
are large and form a substitute for a sternum. The tarsus
ends in two smooth claws, between which is a conical
adhering pad or sucker.

False-scorpions are carnivorous, and their food consists
of insects and mites even smaller than themselves. Thirty
years ago, when Pickard- Cambridge published his mono-
graph on the false-scorpions of Britain, very little was known
of the habits of these small animals and some of the published
information was erroneous. Since then, however, they
have been the subject of study by With of Copenhagen and
Wallis Kew in this country, with the result that our know-
ledge has grown both in accuracy and extent. In particular

SOME OTHER ARACHNIDA

their silk-producing organs and the nests they spin have
received attention, and form one of their most interesting
features.

All false-scorpions make nests of silk. In such nests
they moult, and so are protected during the time of help-
lessness which both precedes and follows the casting of the
cuticle. Female false-scorpions also make brood nests to
shelter them while they are distended with eggs, and also
to protect the brood pouch when laid. Finally, some
species make hibernation nests in which they pass the
winter.

In all species the nests, whatever be their use, are
essentially similar in character. They are more or less
circular in outline and rounded or globular in shape,
according to the space available where they are made.
They are completely enclosed and are just large enough to
contain the animal in comfort without cramping. The
outside is in many cases coated with small particles of
earthy or vegetable debris, but from the nests of some
species these are invariably absent. The nest is then
glistening white, made of a material of tissue-paper-like
consistency.

The silk is secreted by glands situated in the cephalo-
thorax and passes out through ducts which open on the
chelicerae. In some genera the ducts, six or ten in number,
travel along a small almost transparent projecting structure
known as the galea ; in others there is no galea and the
ducts open at a small tubercle which occupies the same
place. On the tubercle there are several orifices from
which the silk issues, and the presence or absence of a
galea does not seem to make any difference to the way in
which the creature works, or to the structure which it
produces.

Wallis Kew has given the only full description of the
making of nests. When a false-scorpion is about to start
spinning, it may first be seen moving actively about as if
seeking a suitable spot. When this is chosen, it begins by
collecting a number of the small particles with which to

334 THE BIOLOGY OF SPIDERS

cover the outside, and these it arranges in a circle. The
particles are picked up in the palpi, and then transferred
to and carried by the chelicerae. They are built up, one
upon another, by brushing the chelicerae against them and
thus attaching threads of silk which hold them in place.
The particles are never overspun from the outside. At
first, when the circular rampart is still quite low, the animal
can pick up solid particles lying near by simply reaching
over ; later it must climb over the wall and make longer
journeys to fetch more. The silk rapidly hardens and the
wall is so firm that it is not injured by the frequent climbing
in and out. In this way the animal gradually encloses
itself in the outer framework of its cell. When this is
complete, however, its labours are by no means over. It
continues to lay down silk on the inside of the walls until
the paper-like consistency is attained. The threads lie in
all directions, but leave no interspaces, so densely are they
applied. The energy expended in this part of the work is
remarkable ; Wallis Kew records an instance of one false-
scorpion which continued for six weeks energetically
strengthening the wall of its cell.

The eggs are laid in such a cell and the story of the
development of the young is a remarkable one. In the
early spring about thirty eggs are laid, but they do not lose
their connection with the mother. They are contained in
a small egg sac which remains attached to the genital area.
The abdominal glands, whose ducts open in this neighbour-
hood, probably have an important part to play in supplying
the adhesive secretion which fixes the sac, the interior of
which is still in communication with the mother's abdomen.
Nutritive material is thus passed from the mother into the
egg-sac throughout the period of its attachment.

The eggs themselves lie towards the sides of the sac.
The embryos which develop from these eggs become true
larvae, for they do not continue their development at the
expense of internal yolk. Instead of that they develop a
temporary stomach and a large sucking organ, with which
they imbibe the fluids from the centre of the sac. These

SOME OTHER ARACHNIDA 335

larvae undergo a kind of metamorphosis shedding the lower
half of their cuticle and entering on a stage in which the
sucking organ is lost and the albuminous fluid which has
been taken in is absorbed as if it were the original yolk of
the egg.

During this development two moults occur, and after
the second, the mother bites a hole in the silken cell and the
brood escapes.

Twenty-four species of false-scorpions are known in
Great Britain and rather less than a hundred in Europe.
The order is split into two divisions, Panctenodactyli and
Hemictenodactyli, based on the character of the chelicerae.
Each division includes several families.

Harvesters

Unlike the false-scorpions, the harvesters, harvestmen,
or harvest-spiders, which form the order Opiliones, are
well known to all who are interested in Natural History.
They are distributed over almost the whole of the world.
But a curious feature of their distribution is that each
family has a range in which it is greatly predominant and
outside which its representatives are comparatively few.
There are many different kinds, and species from tropical
countries have sometimes a very remarkable appearance,
unlike any of our native examples.

Despite one of their popular names, harvesters are very
clearly distinguished from true spiders in having the
abdomen and cephalothorax joined across their whole
breadth, there being no waist or pedicle (Fig. 113). Further,
the abdomen is clearly segmented, and there are no lung-
books or spinnerets. In fact, the structure of a harvester
more closely resembles that of some of the mites ; but a
clear distinction is to be found in the anal aperture, which
is transverse or circular in harvesters, and always longitudinal
in mites.

Although harvesters are never brightly coloured but
always of varying shades of yellow and brown or black,

336 THE BIOLOGY OF SPIDERS

their bodies are beautifully sculptured and well worthy of
examination. The cephalothorax bears two large eyes
placed back to back on a tubercle so that they look sideways.
This eye tubercle is usually decorated with spines, and the
black eyes are sometimes surrounded by a white ring. The
position and shape of the ocularium
and the character of its spines are
important features in classification.
A group of spines is also situated in
front of the eyes of many species.

Fig. 113. — Body of a
Harvester. After
Pickard- Cambridge .

Fig.

114. — Chelicera of
Harvester.

The segments of the abdomen are marked by transverse
rows of small tubercles. The abdomen has seldom any
pattern, but a broad regular black band or vitta frequently
marks the middle of the upper surface.

The appendages are the chelicerae, palpi, and legs.

The chelicerae are in no way striking. They are com-
posed of three joints and are chelate (Fig. 114). The palpi
are purely organs of touch. They have six joints and are
leg-like in appearance, terminating in a single claw.

The legs are characterised by their great length and
delicacy (Fig. 115). They have the same joints as the legs
of spiders, but the tarsus has a number of rings or false
articulations which give it an appearance different from
any joint of a spider's leg. The legs of the first pair are
always the shortest and those of the second pair are always
the longest. Despite their clumsy appearance, the creature

SOME OTHER ARACHNIDA 337

is able to move with a fair turn of speed. The legs are very
readily cast off if they are seized, and a harvester can only

Fig. 115. — Leg of a Harvester.

be caught by grasping two or three legs at once. The legs
seem to be well endowed with tactile organs, like the legs
of spiders, and in this respect must prove very valuable to
the animal. A harvester may often be seen at rest on the
trunk of a tree with its long legs spread out symmetrically
round it, covering a large area. A slight touch on any
part of one leg immediately causes the creature to drop to
the ground.

The arrangement of the mouth parts of harvesters is
very characteristic (Fig. 116). The mouth lies between an
epistome in front and a labium be-
hind, and is furnished at its sides -\ \r\f j F
with three pairs of maxillary lobes J ^
from the coxal joints of the palpi CZ^Cb'^d^r^
and the first and second legs. In a CZDC?

few species the second legs have no J

maxillae. Although the chelicerae £^3 / \
are weak, the creature does not f 1 *
limit itself to liquid food as do FlG Il6._Mouth of a
spiders. Harvesters are essentially Harvester. P, Palp ;
carnivorous and eat mites, centi- 1-1V' legs*
pedes, caterpillars, and spiders as well as each other. I
have seen one carrying a butterfly in its jaws, but was not
fortunate enough to see the capture, which must have
been interesting. They do not scorn to eat the bodies of
any of these creatures if they are already dead, but reject
them if they are not fresh. They are thirsty animals and
may often be seen drinking drops of dew when this is the

338 THE BIOLOGY OF SPIDERS

only available water. In extreme cases they obtain moisture
from juicy plants.

It seems probable that the harvestmen are helped to
escape from their enemies by giving out an odour. A pair
of odoriferous glands lie in the forepart of the cephalo-
thorax and their orifices are usually very conspicuous on
the upper surface near the coxae of the second pair of legs.
Simon compares the odour of the secretion produced by
Phalangium opilio to the smell of walnuts, but it does not
seem to be generally noticeable to our olfactory sense. So
far I have never been able to detect it.

The sexes of harvesters do not as a rule differ much in
external form. The males are usually smaller in the body
and longer in the legs than the females, and their spines
are often longer and more numerous. Sometimes they are
more brightly coloured. They fight vigorously with each
other during the breeding season. The sexual organs are
ordinarily concealed, but if one gently squeezes the sides of
a living harvester between finger and thumb the long
ovipositor of the female or the intromittent organ of the
male will be extruded. These are remarkable for their
great length, which often exceeds that of the creature's
body. In mating, the two harvesters stand face to face and
the long penis of the male reaches forwards to the genital
opening of the female. The female lays twenty or more
eggs, in holes in the ground, under stones and under the
bark of trees, unprotected by any cocoon. From the eggs
there hatch out small but in most cases fully formed
harvesters which have at first a uniform dull cream colour.
At the first moult they acquire the normal markings. They
moult five to nine times before reaching maturity. Only
in a few cases is the mature harvester markedly different
from the immature individual.

The Order, which should be called Opiliones and not
Phalangidea, is divided into three sub-orders :

i. Cyphophthalmi.

2 Mecostethi or Laniatores.

3. Plagiostethi or Palpatores.

SOME OTHER ARACHNIDA 339

The first two sub-orders consist mainly of tropical
species, and have no British and only a few European
representatives.

Mites

Mites form an order of Arachnida which in numbers, in
their economic importance, and in the complexity of their
life-histories far surpass spiders, harvesters, and all the
other orders. Their distribution is world-wide, for they
extend from the arctic regions to at least the South Orkneys
in the sub-antarctic ocean. Their diversity of habits is
very great and their mode of life often remarkable in the
extreme.

Mites are the smallest of the Arachnida, the majority
of them being less than a millimetre long. The division
between the cephalothorax and abdomen is marked by a
transverse groove, but this is not visible in water-mites.
The number of eyes is not constant, and many mites are
blind. The appendages are the usual six pairs.

The chelicerae and palpi are subject to a great degree
of modification in the different families. The former may
be chelate or not, and sometimes they terminate in a single
blade. In Ticks they form two long piercing weapons,
with teeth on their outer edges. The palpi are scarcely
noticeable in some forms. In the majority they are leg-
like feeling organs and in the snout-mites are very long and
antenniform. On the other hand, the palpi of some mites
can seize their prey while the water-mites anchor themselves
by their means. Maxillary plates are always developed
from their coxae. The legs have six or seven joints, and
end in one, two, or three claws, or in a sucking disk, or
simply in a long bristle.

Owing to the great diversity of habits among mites and
the correlated differences of structure it is most convenient
to subdivide the order first and then to survey the groups
in turn. The study of mites has progressed so rapidly in
recent years that the earlier schemes of classification have
been found to be inadequate, and agreement has not yet

340 THE BIOLOGY OF SPIDERS

been reached as to a trustworthy scheme. The arrange-
ment adopted in this chapter is not intended to be more
than a convenient one for the present purpose.

Nathan Banks, in 191 5, divided the order of mites into
eight groups called super-families, as follows :

Eupodoidea. Snout-mites.
Trombidoidea.

Hydrachnoidea. Water-mites.
Ixodoidea. Ticks.

5. Gamasoidea.

6. Oribatoidea. Beetle-mites.

7. Sarcoptoidea.

8. Demodicoidea.

The Eupodoidea are soft-skinned mites, generally
found free-living in cold and damp places under moss,

leaves, and decayed wood. One of
the genera, Linopodes (Fig. 117), is
characterised by the extraordinary
length of its front legs, which are
more than four times the length of
its body. Clearly, such legs could
not be used for walking ; they are
held out in front as feelers. One
family of this division is the Bdelli-
dae, known as snout-mites on ac-
count of a prominent forwardly
directed false head or capitulum.

The Trombidoidea are distinctly
coloured mites which include the
popular " red-spider," Tetranychus
telarius. The Tetranychidae are
also known as spinning-mites, for
they have the power of producing
silk from glands which open into
the mouth and are probably modi-
fied salivary glands. Masses of vegetation are occasionally
covered with their webs, under which the females lay their

Fig. 117. — Linopodes, a
Mite. After Soar.

SOME OTHER ARACHNIDA

eggs. These mites eat vegetable matter, and by sucking
the sap of plants injure the leaves and give them a blistered
appearance.

The most remarkable of the mites of this group belong
to the family Cheyletinae. The normal members of this
family have very large palpi, which are formidable weapons
of attack. Unlike most mites they do not run or creep,
but hop. A curious degenerate genus of the family is
Syringophilus , which is parasitic in the interior of birds'
feathers, where it is frequently to be found, and has a wide
distribution. These mites enter the feather by the
" superior umbilicus " (a minute slit at the junction of
quill and vane) and live in the quill, feeding upon the pith
until the feather is moulted or the bird dies. They then
escape by the " inferior umbilicus " (a minute hole by
which the pulp enters the base of the young feather) and
seek a new host.

The " harvest-bugs " which often attack the hands and
arms of labourers working in the fields belong to the genus
Trombidium. The trouble is due to the larvae (perhaps of
special species), which are particularly numerous in late
summer and autumn. They attack any small mammal —
rabbits, hares, and moles are frequent victims — forcing
their mouth parts into the skin, which hardens round the
pharynx in a cylinder, the so-called proboscis. The
amount of trouble they cause varies greatly in different
people. At its worst the skin swells and an intense irritation
is set up. The natural scratching which follows often
induces a rash, which may spread rapidly and be accom-
panied by a degree of fever. No disease, however, is known
to be conveyed by these mites.

The Hydrachnoidea are aquatic mites consisting of two
families. The Halacaridae are mostly marine mites, but
some of them inhabit fresh water. They have hard bodies
and a prominent capitulum, recalling that of the Bdellidae.
Their legs are not adapted to swimming ; they crawl upon
the seaweed and burrow in the mud. The Hydracarina or
fresh-water mites are when alive among the most beautiful

342 THE BIOLOGY OF SPIDERS

of all the mites, having a very rich and varied colouring.
They also exhibit a great diversity of shape. Their legs
are provided with long hairs and by their means the water-
mites swim rapidly. They are predaceous, and their young
stages are often parasitic upon other aquatic animals. They
form a large group, with about two hundred and fifty
species in Great Britain.

The Ixodoidea or Ticks are the largest of the mites.
They are all parasites, which suck the blood of their hosts
and thereby become enormously distended. When starved
they are generally flattened in form. Their chelicerae are
their cutting organs, with which they pierce the skin of
their hosts, and behind the mouth there is always a hypo-
stome set with backwardly directed teeth, which gives it
an extremely firm hold of the skin into which it is thrust
(Fig. 118). "

Not many ticks are found in Britain, but from Africa
and America come species which cause untold damage to
cattle and crops. They have therefore
been extensively studied.

The group consists of two families,
Argasidae and Ixodidae. The former
are parasitic on warm-blooded animals
only and are responsible for the spread-
ing of some rather uncommon maladies
of men and animals in the Tropics.
The trouble caused by ticks may be
due to two reasons. Their bites may
be irritating wounds, which extraneous

FIG. u8. Chelicerae bacteria on the foul-mouthed append-

and hypostome of ages may enter, producing sores and
ulcers. More important, however, is
the fact that parasitic within the tick there are often
Protozoa capable of producing diseases in man and other
animals. The very remarkable feature of these Protozoa
is that they can remain alive in the body of the tick,
even if the latter is unfed, for months or years. They
may even be present in its eggs and in the larvae which

SOME OTHER ARACHNIDA 343

hatch from those eggs, so that the next generation of ticks
is as dangerous as the first.

In the Argasidae, both sexes are capable of distension
on feeding. The two most important genera of this family
are Argas and Ornithodorus. A well-known species, Argas
persicuSy also known as the " teigne de miana " is a brownish
Asiatic tick about five millimetres long. It is mainly a
parasite of fowls, to which it conveys a disease called
spirochaetosis. A similar disease of men in South Africa
has been traced to Ornithodorus moubata, which contains
the bacterium Spirochaeta duttoni. Another form, Argas
reflexusy is a yellow and white tick, common near dove-
cotes and pigeon houses, which also attacks man. Its bite
is very irritating, and at one time it was unpleasantly
common in Canterbury Cathedral. The " Garapata " of
Mexico, Ornithodorus megnini, attacks horses, oxen, and
sometimes men about the ears ; Ornithodorus turicata, the
" Turicata," is often fatal to poultry.

In the larger family, the Ixodidae, the whole of the
back of the male is covered with a hard scutum and in
consequence little distension is possible in this sex. In the
female, the scutum forms only a small patch in front. The
most familiar of all ticks is Ixodes ricinus, the common
sheep-tick, specimens of which are often to be found on
dogs if they have entered fields where sheep are pasturing.
Fig. 119 was drawn from a tick collected in this way by the
writer's springer.

The life-history of ticks is of great interest. The eggs,
some thousands in number, are laid in a crack in the soil,
where they hatch after an interval which varies from days
to months and is dependent on the temperature. A larva
emerges from each egg, like a small tick but possessing only
six legs. These larvae climb the grass and wait in patient
expectation until an animal brushes past. At the approach
of an animal the young tick manifests great excitement,
and, if possible, seizes its hair as it passes. Once secure,
the larva plunges its rostrum into the skin and sucks the
creature's blood until it is gorged. It then unhooks its

344 THE BIOLOGY OF SPIDERS

claws, withdraws its rostrum and drops to the ground
again. Here it secretes itself in a crevice and rests while
its huge meal is absorbed and other changes take place
within. When these are complete, it casts its cuticle and
becomes a nymph, with eight legs, but sexually immature.
The nymph climbs the grass and repeats the actions of the
larva. The moult which follows this second gorging
produces a mature male or female tick which again seeks
a host. Fertilisation takes place on the third host, the
female being often the active member of the pair during

mating. Finally, the well-fed and fertilised female drops
to the ground again and lays her eggs.

Although in some species of ticks, all the changes from
larva to adult may be passed through without leaving the
first host, it is a more general rule that three hosts are
visited. It is a remarkable feature of ticks that they are
well adapted to this extraordinary life-history, for they are
able to undergo prolonged fasts without dying, and they
seldom let slip a chance of attacking a host. Yet thousands
must perish before an animal comes into their neighbour-

Fig. 119. — Ixodes ricinus. The sheep tick.

SOME OTHER ARACHNIDA

hood ; as Shipley remarks, "it is terrible to think of the
amount of unsatisfied desire which must be going on in
the tick world."

At least one genus of ticks, Aponoma, confines its
attention to reptiles and is therefore of little economic
importance, but nearly all the other genera include species
known or suspected to be transmitters of disease. The
following are a few of the more important diseases
propagated by ticks :

1. Texas fever or redwater, in cattle, by Boophilus spp.

2. Rhodesian fever, in cattle, by Rhipicephalns appen-

diculatus.

3. Carceag, in sheep, by Phipicephalus bursa.

4. Heartwater, in sheep and goats, by Amblyomma

hebraeum.

5. Canine piroplasmosis, by Rhipicephalus sanguineus

and by Haemaphysalis leachi.

The Gamasoidea, also known as the Parasitoidea, form
a numerically large group, whose British species have not
yet been fully studied. They
are pale-coloured carnivorous
mites, both free-living and
parasitic. The mites which are
found as parasites on bats be-
long to this group (Fig. 120),
and so do the mites often found
attached to beetles and other
insects. One genus, Hala-
rachne, lives in the bronchial
passage of seals, and another,
Pneumonyssus, in the lungs of
old-world monkeys — good in-
stances of the extraordinary
haunts chosen by mites. The members of the sub-family
Dermanyssinae are found on poultry and cage-birds.

The curious beetle parasites , of the sub-family Uropo-

Fig. 120. — Spincturnix sp.
from a bat. Partly after Soar.

346 THE BIOLOGY OF SPIDERS

dinae, are attached to their hosts solely for transport, and
not as true parasites. They are fixed by a thread, which
the mite can sever at will, and which consists of consolidated
excrement.

The Oribatoidea owe their popular name of beetle-mites
to their hard cuticle. They are all blind, all under a
millimetre long, and are free-living. They are vegetable
feeders and are found in dead wood, under bark, and
amongst moss or lichen. Although blind, they are sensitive
to bright light and always move away from it. Many of
them have the curious habit of collecting dust and dirt on
their backs, and this quite masks their true shape.

The Sarcoptoidea form a numerous group of mites,
some of which are familiar. The typical genus, Sar copies,
includes Sarcoptes scabiei, which is popularly known as the
itch-mite. These mites are only a little longer than broad
and look like extremely diminutive pearly- grey tortoises,
with four legs directed forwards and four backwards.
Their cuticle is translucent and is strengthened by trans-
verse folds, which also occur on the legs. The legs end in
suckers or hairs. The male and female meet on the skin
of the host and after pairing the male dies. The female
begins to burrow in the skin laying eggs behind her as she
goes, and may continue this for two or three months, by
which time she has laid about a hundred eggs. She cannot
retreat from this burrow because of the spines with which
her body is covered, and she cannot turn round in it, for it
is too narrow. Thus she digs her own grave. The eggs
hatch within a week and are mature within a month, so
that infection soon spreads upon the body of the host.
The mature mites, when seeking each other on the surface,
may be transferred by contact to other persons or to horses,
cattle, dogs, cats, and even camels and lions.

Another species, Sarcoptes mutans, causes the " leg
scab " of poultry.

The smooth soft-bodied mites of the family Tyro-
glyphidae, also belong to this group. They include
Tyroglyphus siro and Tyroglyphas longior, which are the

SOME OTHER ARACHNIDA 347

familiar cheese mites. Some of them are very destructive
to stored roots and bulbs.

The smallest of all known mites are also members of
the same group. The best-known example is Acarapis or
Tarsonemus zvoodt, which lives in large numbers in the
tracheal tubes of the honey bee, and causes " Isle of Wight
disease."

The Demodicoidea include two families, of which the
first contains but one genus, Demodex. These are micro-
scopic skin parasites, living in the hair
follicles of mammals. They are the
cause of follicular mange. A common
species, Demodex folliculorum, infests
the skin of man and is so widespread
that Guiart says " nous en sommes
presque tous porteurs." They are in
themselves quite harmless.

All these " worm-like " mites have a
very long annulated abdomen (Fig. 121).
The other family of the group, Erio-
phyidae or Phytoptidae, are known as
gall mites and are vegetable feeders
only. They are unique in possessing
only two pairs of legs, and are the
cause of some of the curious growths
which occur on the leaves and buds of plants. Sometimes
they do no great damage, but at least one of them, Eriophyes
ribis, which feeds on the buds of the black currant, has
been a serious pest to fruit-growers.

Mites make a good conclusion to a book on Arachnida
because they remind us once more of the varied forms that
Life may take. Within the limits of a single Class we find
a wide diversity of habit and a remarkable choice of haunt,
emphasising better than anything else the intensity of the
struggle for existence. To this struggle many of the
phenomena of biology may be traced.

Fig. 121. — Demodex.
From a dog.

BIBLIOGRAPHY

§ i. Alimentary System.
§ ii. Vascular System.
§ iii. Respiratory System.
§ iv. Nervous System.
§ v. Excretory System.
§ vi. Reproductive System.
§ vii. Silk, Silk Glands, and Spinning-Organs.
§ viii. Poison and Poison Glands.
§ ix. Eyes and Sight.
§ x. Taste and Smell.
§ xi. Spines and Lyriform Organs.
§ xii. Stridulation.
§ xiii. Instinct.

§ xiv. General Habits and Behaviour.
§ xv. Regeneration and Autotomy.
§ xvi. Mimicry and Protective Resemblance.
§ xvii. Courtship and Mating.

§ xviii. Parthenogenesis, Gynandry, and Dimorphism.

§ xix. Gametogenesis, Embryology, Growth.

§ xx. Geographical Distribution.

§ xxi. Classification and Evolution.
§ xxii. Historical.
§ xxiii. General Works.

i. Alimentary System

877. F. Plateau. Recherches sur la structure de l'appareil
digestif et sur les phenomenes de la digestion chez
les araneides dipneumones. Bull. Acad. R. Belg.,
2, xliv. No. 8.

880. F. M. Campbell. On Certain Glands in the Maxillae of
Tegenaria domestica. Journ. Linn. Soc, xv. 155-
158.

910. C. Hamburger. Die Entwicklung des Darmkanals der
Argyroneta aquatica. Verh. nathist. Ver., x. 351—
355-

349

350

THE BIOLOGY OF SPIDERS

1916. C. Hamburger. Zur. Kenntnis des Mitteldarmes der
Spinnen. Zool. Anz., xlviii. 39-46.

1 91 2. E. Oetcke. Histologische Beitrage zur Kenntnis der

Verdauungsvorgange bei den Araneiden. Zool.
Jahrb., xxxi. 245-276.

1905. M. A. Lecaillon. Sur le pouvoir qu'ont les araign^es

de rester pendants de longues periodes sans prendre
aucun nourriture. C. R. Soc. Biol., lviii. 1062-
1063.

1906. R. Shelford. Note on a Feeding Experiment on the

Spider Nephilia maculata. Trans. Ent. Soc. Lond.,
Ixiii. Proc., 63-66.

1913. E. C. Chubb. Fish-eating Habits of a Spider. Nature,

xci. 136.

1914. G. Clagget. A Spider swathing Mice. Ent. News,

Philad., xxv. 230.

1914. A. Krausse. Milchtrinkende Spinnen. Arch. Naturg.,

lxxix. A, 118.

191 5. J. H. Lovell. Insects Captured by the Thomisidae.

Canad. Entomol., xlvii. 115-116.

1920. S. W. Bilsing. Quantitative Studies in the Food of

Spiders. Ohio J. Sci. Columb., xx. 215-260.

1921. T. Barbour. Spiders Feeding on Small Cyprinodonts.

Psyche., xxviii. 1 31-132.

1922. I. H. Burkill. The Irregularity of a Spider's Feeding.

J. Straits Asiatic Soc, lxxxvi. 270.

1923. E. Warren. Note on a Lizard-eating South African

Spider. Ann. Natal. Mus., v. 95-100.
1925. S. D. Kirkham. A Spider traps a Humming-bird.

N.Y. State Mus. Bull., 260. 34-36.
1925. E. W. Gudger. Spiders as Fishermen and Huntsmen.

Nat. Hist. New York, xxv. 261-275.

ii. Vascular System

J. Causard. The Circulation of the Blood in Young

Spiders. Ann. Mag. Nat. Hist., 6. xii. 65-68.
A. Petrunkevitch. Uber die Circulationsorgane von

Lycosa carolinensis. Zool. Jahrb., xxxi. 161-170.
A. Petrunkevitch. The Circulatory System and

Segmentation in Arachnida. Journ. Morphol.

Philad., xxxvi. 157-185.
V. Willem. Essais description des pulsations cardi-

aques chez une araignee. Haarlem Arch. Neerl. Sci.

Soc. Holl., 3. ii. 285-289.

1893.
1910.
1922.

1917.

BIBLIOGRAPHY

35i

1917. V. Willem. Observations sur la circulation sanguine
et la respiration pulmonaire chez les araignees.
Haarlem Arch. Neerl. Sci. Soc. Holl., 1. i. 226-256.

iii. Respiratory System

1872. P. Bertkau. Uber die Respirationsorgane der Araneen.

Arch. Naturg., xxxviii. 208-233.
1909. R. Janeck. Die Entwickelung der Blattertracheen und

der Tracheen bei den Spinnen. Zeits. Natur., xliv.

587-646.

1909. W.F. Purcell. Development and Origin of the Respira-

tory Organs of Araneae. Quart. Journ. Micr. Sci.,
liv. 1. 1-110.

1910. W. F. Purcell. The Phylogeny of the Tracheae in

Araneae. Quart. Journ. Micr. Sci., liv. 4. 519-563.
1 9 14. Schollmeyer. Argyroneta aquatica : Biologie mit be-

sondere Berucksichtigung der Atmung. Ann. Biol.

lacustre Brux., vi. 4. 314-338.
1 9 14. B. Haller. Das zweite Fachertracheenpaar der mygalo-

morphen Spinnen. Arch. Mier. Anat., lxxxiv. 1.

438-445-

1921. L. Fage. Sur quelques araignees apneumones. C. R.
Acad. Sci., clxxii. 10. 620-622.

1923. S. Weiss. Untersuchungen iiber die Lunge und die

Atmung der Spinnen. Zool. Jahrb., Abt. Allg.
Zool., xxxix. 535-545.

1924. A. Kastner. Die vergleichend-anatomische Bedeutung

der Interpulmonarfaite der Araneen. Zool. Anz.,
lviii. 97-102.

iv. Nervous System

1912. B. Haller. Uber das Zentralnervensystem des Scorpions
und der Spinnen. Arch. Micr. Anat., lxxix. (1),
504-524.

1912. W. A. Hilton. A Preliminary Study of the Central

Nervous System of Spiders. Pomona Coll. Jour.
Ent. Claremont, iv. 832-836.

191 3. W. A. Hilton. Nerve Cells of Tarantula. Pomona

Coll. Jour. Ent. Claremont, v. 93-95.
191 6. G. Brites. Sur les terminaisions des nerfs moteurs des
les muscles cephalothoraciques des Araneides dipneu-
mones. Lisbonne Bull. soc. Port. sci. nat., vii.

352

THE BIOLOGY OF SPIDERS

1921. B. Hanstrom. Uber die Histologic und vergleichende

Anatomie der Sehganglien und Globuli der Araneen.

K. Svenska Vet. Akad. Handl., lxi. 1-39.
1923. B. Hanstrom. Further Notes on the Central Nervous

System of Arachnids. Journ. Comp. Neur. Philad.,

xxxv. 249-274.

v. Excretory System

1885. P. Bertkau. Uber den Verdauungsapparat der Spinnen.

Arch. Mikrosk. Anat., xxiv.
1885. P. Pelseneer. On the Coxal Glands of Mygale. Proc

Zool. Soc, 3-6.

1913. B.H.Buxton. The Coxal Glands of Arachnids. Zool.

Jahrb. Abt. Anat., xiv. 231-282.
1 9 17. B. H. Buxton. Notes on the Anatomy of Arachnids.

Jour. Morphol., xxix. 1-25.
1925. J. Millot. L 'excretion chez les araignees. C. R. Soc.

Biol., xciii. 1598-1600.

vi. Reproductive System

1875. P« Bertkau. Uber den Generationsapparat der
Araneiden. Arch. Naturg., xli. (1), 235-262.

1875. J- H. Emerton. On the Structure of Palpal Organs of
Male Spiders. Proc. Boston Nat. Hist. Soc.

1908. T. H. Jarvi. Uber die Vaginalsysteme der Lycosiden.
Zool. Ans., xxxii. 754-758.

1908. T. H. Jarvi. Zur Morphologie der Vaginal Organe

einiger Lycosiden. Festschr. fur Palmen, vi. 1 and 36.
1 912. T. H. Jarvi. Das Vaginalsystem der Sparassiden.
Helsinki Ann. Acad. Sci. Fenn., iv. A, 1.

1909. J. A. Nelson. Evolution and Adaptation in the Palpus

of Male Spiders. Ann. Soc. Ent. Amer., ii. 60-64.

1910. J. H. Comstok. The Palpi of Male Spiders. Ann. Soc.

Ent. Amer., iii. 161-185.

1921. U. Gerhardt. Vergleichende Studien uber die Mor-

phologie des mannlichen Tasters und die Biologie
der Kopulation der Spinnen. Arch. Naturg., 87. A,
(4), 78-247.

1922. U. Gerhardt. Neues uber Bau und Funktion des

Tasters der mannlichen Spinnen. Verh. D. Zool.
Ges., xxvi. 56-58.
1922. U. Gerhardt. Uber die Samentaschen einiger weiblicher
Spinnen. Verh. D. Zool. Ges., xxvii. 65-67.

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cxix. 326-418.

1925. A. Petrunkevitch. External Reproductive Organs of
Agelena naevia. Journ. Morphol. Phys., xl. 559-573.

vii. Silk, Silk Glands, and Spinning-organs

1839. J- Blackwall. On the Number and Structure of Mam-
mulae employed by Spiders. Trans. Linn. Soc,
xviii.

1882. P. Bertkau. Uber das Cribellum und Calamistrum.
Arch. Naturg.

1889. C. Apstein. Bau und Funktion der Spinndrusen der

Araneidea. Arch. Naturg., lv. 29-74.

1890. C. Warburton. The Spinning Apparatus of Geometric

Spiders. Quart. Journ. Micr. Sci.

1906. J. H. Comstock. The Hackled Band in the Webs of

Certain Spiders. Science, N.Y., xxiv. 297.

1907. J. R. Benton. The Strength and Elasticity of Spiders'

Thread. Amer. Journ. Sci., xxiv. 75.
1907. E. Fischer. Uber Spinnenseide. Zeits. physiol. Chem.,

liii. 126. Sitz. Ber. Ak. Wiss., 440-450.
1909. T. H. Montgomery. On the Spinnerets, Cribellum,

Colulus, Tracheae, and Lung-books of Araneae.

Proc. Acad. Nat. Sci. Philad., lxi. 299-320.

1912. F. Dahl. Seidenspinne und Spinnenseide. Berlin,

Mitt. Zool. Mus., vi. 1-90.

1913. J. Berland. Note preliminaire sur le cribellum et le

colulus des araignees cribellates et sur les mceurs de
ces araignees. Arch. Zool. Exp. et Gen., li. 23-41.

1914. B. Johansson. Zur Kenntnis der Spinndrusen der

Araneina. Lund. Univ. Arsskr, N.F. 10. Afd 2. 5.

viii. Poison and Poison Glands

1855. J. Blackwall. Experiments and Observations on the
Poison of Animals of the Order Araneida. Journ.
Linn. Soc, xxi. 31-37.

1905. C. A. Mitchell. The Venom of Spiders. Knowledge,

298-299.

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1912. Mme, Phisalix. Effets physiologiques du venin de la
Mygale de Corse et d'une grande Mygale de Haiti.
Bull. Mus. Paris, 1912, 132-138.

2 A

354

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1 91 5. L. Drenski. Le venin des araignees et leur action sur
l'organisme animal. Trav. Soc. Bulg. Sci. Nat.,
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1915. V. L. Kellog. Spider Poison. Journ. Parasitol.

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1916. R. Levy. Sur les toxines des araignees. C. R. Acad.

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1916. R. Levy. Contribution a 1 'etude des toxines cher les

araignees. Ann. Sci. Nat., 10. i. 161-399.
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1916. L. Hutcheson. Effects of Spider Bite on Man. Ent.

News, Philad., xxvii. 464.
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xx. 58-74.

1921. E. Rabaud. L'instinct paralyseur des araignee. C. R.
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1921. A. M. Reese. Venomous Spiders. Science, N.Y.,

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1922. J. R. Watson. Bite of Latrodectus mactans. Science,

N.Y., lv. 539.

1922. B. A. Houssay and J. Negrete. Estudios experimentales

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ix. Eyes and Sight

P. Bertkau. Die Augen der Spinnen. Arch. micr.

Anat., xxvii. 589-631.
K. Graber. Uber das unicorneale Tracheaten-Auge.

Arch. micr. Anat., xvii. 58-92.
W. Peckham. The Sense of Sight in Spiders, with
some Observations on the Colour Sense. Trans.
Wise. Acad. Sci., v. 10.
K. Kishinouye. On the Lateral Eyes of the Spider.

Journ. Coll. Sci., Imp. Univ. Jap.
A. Petrunkevitch. The Sense of Sight in Spiders.

Journ. Exp. Zool., v. 275-309.
E. Widmann. Der feinere Bau der Augen einiger

Spinnen. Zool. Anz., xxxi. 755-762.
E. Widmann. Uber den feineren Bau der Augen
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1886.
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1916. T. S. Painter. Spermatogenesis in Spiders. Zool.

Jahrb. Abt. f. Anat., xxxviii. 509-576.
1916. M. L. Moles. Growth and Colour Patterns in Spiders.

Journ. Ent. Zool. Claremont, viii. 129-157.
1920. W. W. Smith. Parasitism in New Zealand Spiders.

N.Z. Journ. Sci. and Tech., hi. 13-15.
1920. C.Morley. Ichneumons parasitic on Spiders. Entom.,

1920, 53-68.

1925. E. Warren. Note on the Ecdysis of a Spider. Ann.

Natal Mus., v. 231.
1925. E. Warren. Spermatogenesis in Spiders. Nature,

cxvi. 395.

1925. S. D. King. Spermatogenesis in Spiders. Nature,
cxvi. 574.

xx. Geographical Distribution

1877. J. H. Emerton. A Comparison of the Spiders of

Europe and North America. Proc. Boston. Nat.
Hist. Soc.

1878. H. C. McCook. Note on the Probable Distribution of

a Spider by the Trade Winds. Proc. Acad. Nat.
Sci. Philad.

G. W. and E. G. Peckham. On the Family Attidae from
South Africa. Trans. Wise. Acad. Sci., xiv. 173-
278.

1903. R. I. Pocock. Geographical Distribution of Spiders of
the Order Mygalomorphae. Proc. Zool. Soc, i.
340-368.

1907. F. Dahl. Ein Versuch den Bau der Spinnen physiolo-
gisch-ethologisch zu erklaren. Zool. Jahrb. Abt. f
Syst., xxv. 339-352.

366

THE BIOLOGY OF SPIDERS

1914. J. Ritchie. The Fauna of a Coal-pit at Great Depths.

Scott. Nat., 1914, 181-188.
1922. T. H. Gillespie. Animal Stowaways. Scott. Nat.,

1922, 167.

xxi. Classification and Evolution
(a) Liphistiidae

1849. J* C. Schiodte. Om en afvigende Slaegt af Spindlernes

Orden. Kr0yer. Naturh. Tijdskrift, 2. ii. 621.
1875. O. Cambridge. On a New Species of Liphistius. Ann.

Mag. Nat. Hist., 4. xv. 249.
1879. M. van Hasselt. Bijdrage tot de Kennis van den

Liphistius desultor. Vers. Med. K. Akad. Wetensch.,

A. Naturk., 2. xv. 186.
1890. T. H. Thorell. Studi sui Ragni Malesi e Papuani. iv.

26-31.

1892. R. I. Pocock. Liphistius and its bearing on the Classi-
fication of Spiders. A.M.N.H., 6. x. 306-314.

1900. R. I. Pocock. Fauna of British India. Arachnida, 156.

1892. E. Simon. Histoire Naturelle des Araignees, i. 63-67.

1903. E.Simon. Histoire Naturelle des Araignees, ii. 873-5.

1908. E. Simon. Etudes sur les Arachnides du Tonkin.
Bull. Sci. Fr. Belg., xlii. 69-147.

1922. T. H. Savory. The Spider Liphistius : a Study in the

Biology of a Primitive Animal. Ann. Mag. Nat.
Hist., 9. x. 444-449.
1924. T. H. Savory. New Evidence of the Relationship
between the Spiders Liphistius and Segestria. Ann.
Mag. Nat. Hist., 9. xiii. 472-473.

1923. H.C.Abraham. A New Spider of the Genus Liphistius.

Journal Malayan Branch R. Asiatic Soc, i. 13-21.
1923. H.C.Abraham. A New Spider of the Genus Liphistius
from the Malay Peninsula, and some Observations
on its Habits. Proc. Zool. Soc, 1923, 769-774.

1923. K. Kishida. Heptathela, a New Genus of Liphistiid

Spiders. Annot. Zool. Jap., x. 235-242.

1924. B. H. Buxton. Notes on the Internal Anatomy of

Liphistius batuensis. Journal Malayan Branch R.
Asiatic Soc, ii. 85-86.

(b) Classification

1837. C. L. Koch. Ubersicht des Arachniden-Systems.
1878. P. Bertkau. Versuch einer natiirlichen Anordnung der
Spinnen. Arch. Naturg., xliv. 351-410.

BIBLIOGRAPHY

367

1886. T. Thorell. Bertkau's Classification of the Araneae.

Ann. Mag. Nat. Hist., xvii. 301-326.
1904. F. Dahl. Uber das System der Spinnen. S.B. Ges.

naturf. Fr. Berlin, 93-120.

1906. F. Dahl. Das System der Araneen. Zool. Anz., xxix.

614-619.

1907. F. Dahl. Zur Systematic der Spinnen. Zool. Anz.,

xxxii. 121-126.

1907. E. Strand. Zur Systematic der Spinnen. Zool. Anz.,
xxxi. 851-861.

1926. L. Giltay. Remarques sur la classification et la

phylogenie des families d'Araignees. Ann. Bull.

Soc. Ent. Belg., lxvi. 115-131.
1926. T. H. Savory. The Classification of Spiders : some

Comments and a Suggestion. Ann. Mag. Nat. Hist.,

9. xviii. 377-381-
1928. A. Petrunkevitch. Systema Aranearum. Trans. Conn.

Acad. A. Sci., xxix. 1-270.

1909. A. Petrunkevitch. Contributions to our Knowledge of

the Anatomy and Relationships of Spiders. Ann.

Ent. Soc. Amer., ii. 11-20.
1924. A. Petrunkevitch. On Families of Spiders. Ann.

Acad. Sci. N.Y., xxix. 145-180.
1912. J. H. Comstock. The Evolution of the Webs of Spiders.

Ann. Soc. Ent. Amer., v. 1-10.
1916. F. H. Gravely. Evolution and Distribution of Indian

Aviculariinae. Journ. As. Soc. Bengal, x. 411-420.
1924. M. Monier. Observations sur les moeurs des araignees

comme contribution a l'etude des lois de revolution.

Ann. Soc. Linn. Lyon., lxx. 186-188.
1926. T. H. Savory. Evolution in Spiders. Sci. Prog., xx.

475-480.

xxii. Historical

1 88 1. O. Pickard-Cambridge. John Blackwall, F.L.S.
Entomologist, xiv. 145.

1920. E. B. Poulton. Obituary Notice of O. Pickard-
Cambridge. Proc. Roy. Soc, B, xci. 49-53.

1924. L. Fage. Eugene Simon. Bull. Soc. Zool., xlix. 550-

554-

1925. L« Berland. Notice Necrologique sur E. Simon.

Ann. Soc. Ent. Fr., xciv. 73-100.

368 THE BIOLOGY OF SPIDERS

xxiii. General Works

1678. Lister, M. Historiae Animalium Anglicae.
1736. Albin, E. A Natural History of Spiders.
1757. Clerck, C. Svenska Spindlar.
1793. Martyn, T. Aranei.

1806-8. Walckenaer, C. A. Histoire Naturelle des Araneides.
1 817. Latreille, P. A. Arachnides du Regne Animal.
1825. Audouin, V. and de Savigny, J. C. Description de
l'Egypte.

1830. Sundevall, C. J. Svenska Spindelarnes.

1831-48. Hahn, C, and Koch, C. L. Die Araclmiden.

1834. Blackwall, J. Researches in Zoology.

1856. Thorell, T. Recensio Critica Aranearum Suecicamm.

1861-4. Blackwall, J. Spiders of Great Britain and Ireland.

1862. Westring, N. Aranei Suecicae Descriptae.

1862. Claparede, E. Recherches sur Involution des Araignees.

1863. Vinson, A. Araneides de la Reunion, Maurice et

Madagascar,
1866-9. Menge, A. Preussische Spinnen.

1866. Staveley, E. F. British Spiders.

1867. Ohlert, E. Die Araneiden der Provinz Preussen.
1869. Canestrini, G. Araneidi Italiani.

1869. Thorell, T. On European Spiders.
1870-3. Thorell, T. Synonyma of European Spiders.
1873. Blackwall, J. Researches in Zoology (2nd edn.).
1873. Moggridge, J. T. Harvesting Ants and Trap-door
Spiders.

1875. Hentz, N. M. Spiders of the United States.

1 878- 1 926. Simon, E. Les Arachnides de France.

1879- 81. Cambridge, O. P.- The Spiders of Dorset.

1883. Emerton, J. H. The Structure and Habits of Spiders.

1891- 8. Chyzer, C, and Kulczynski, L. Araneae Hungariae.

1892- 1903. Simon, E. Histoire Naturelle des Araignees.

1 901. Cambridge, O. P.- List of British and Irish Spiders.
1 901-3. Bosenberg, W. Die Spinnen Deutschlands.

1902. Emerton, J. Common Spiders of the United States.
1904-5. Cambridge, F. O. P.- Biologia Centrali Americana.

Araneida.

1905. Planet, L. Histoire Naturelle de la France. i4epartie,
Araignees.

1909. Warburton, C. Cambridge Natural History, vol. iv.

1912. Warburton, C. Spiders.

1912. Ellis, R. A. Spiderland.

1912. Fabre, J. H. The Life of the Spider.

BIBLIOGRAPHY

369

1912. Comstock, J. H. The Spider Book.

1913. Dahl, F. Vergleichende Physiologie und Morphologie

der Spinnentiere.
1917. Fraganillo, P. Las Aranas.

1926. Dahl, F. Die Tierwelt Deutschlands. Dritter Teil.
Springspinnen.

1926. Savory, T. H. British Spiders, their Haunts and

Habits.

1927. Dahl, F. Die Tierwelt Deutschlands. 5te Teil.

Wolfspinnen.

2 B

INDEX

Abdomen, 18, 286
Abraham, H. C, 217, 273, 279, 2
Accessory claws, 40
Acetabula, 24
Acoustic setae, 87
Agelena labyrinthica, 103, 117, 1
230

Agelenidae, 97, 139, 207, 310
Agroeca, 234
Agyneta ramosa, 188
Akerman, C, 120
Alae, 23

Alimentary canal, 51
Alveolus, 29

Amaurobius atrox, 44, 80

— similis, 208
Amauiobiidae, 138, 310
Amcioca forticeps, 1 67
Ammoxenus, 29
Anadiastothele, 273
Anal tubercle, 24
Ancestral spiders, 304
Ants, association with, 174
— , mimicry of, 27, 165
Apodemes, 50
Apophysis, radial, 29
Apus, 5

Arachnida, characters of, 2-6
— , classification of, 6
Arachnidism, 129
Araneus, 9
Archaeidae, 27
Archearanead, 304
Argiope pulchella, 154

— catenulata, 155
Ariamnes simulans, 164
Arteries, 57
Arthromygalidae, 283
Asagena phalerata, 94, 174
Association with ants, 174
Attidae, see Salticidae
Attus volans, 85
Atypidae, 292
Atypus abbottii, 292

— affinis, 293
Autotomy, 173

Barrois, J., 108
Barrows, W. M., 91
Barychelidae, 298
Bateson, W., 81
Bathyphantes concolor, 80
, Behaviour, 104
Berland, L., 87, 170
Bertkau, P., 126
Black Widow, 128
Blackwall, J., 79, 80, 126, 133, 226
Blastosphere, 248
Blood, 59
Body-wall, 46
Bogen, E., 129
Bon, M., 135
Book-lungs, 60
Boys, C. V., 102
Brain, 66

Bristowe, W. S., 87, 98, 101, 159,

199, 209, 214, 226
Browne, P., 284
Buxton, B. H., 62, 278

Caeca, 54

Cainozoic spiders, 270
Calamistrum, 44
Cambridgea antipodiana, 97
Campbell, F. M., 117, 131, 247
Caponiidae, 306
Catalepsis, 105, 172, 226
Causard, J., 59
Celidotopus, 288
Cell-division, 241
Cephalothorax, 16
Ceratinella, 27
Chain-instincts, 111
Chelicerae, 25, 285
Chilobrachys stridulans, 95
Chitin, 46
Chromosomes, 242
Cladomelea akermani, 121, 161
Classification, 314

— of arachnida, 6

— of mites, 340

— of spiders, 318
I Clavus, 23

371

372

INDEX

Claw tufts, 297
Claws, 39, 309
Clubiona interjecta, 309

— trivialis, 207
Clubionidae, 122, 309
Cocoons, 230
Coelotes, 139

Coenoptychus pulchellus, 167
Colour vision, 85
Colours, flash, 160

— of spiders, 158
— , warning, 161
Colulus, 24

Compound reflexes, 107
Conductor, 31
Condyles, 26
Copulation, 224
Cornea, 81
Courtship, 201
Coxal glands, 62
Cribellum, 43, 308
Crochet, 23
Cryptothele, 41
Ctenizidae, 287
Ctenus, 235

Cyclosa centrifaciens, 156

— cornea, 115, 152
Cymbium, 31
Cyrtauchenius artifex, 289

— elongatus, 290

— inops, 288, 298

— vittatus, 289
Cyrtocarenum cunicularum, 291

Dahl, F., 91, 92, 99,
Damin, N., 247
de Morgan, 14
Demodicoidea, 347
Desis, 197
Development, 241
Diaea dorsata, 235
Dichrosticus magnificus, 121
Dictyna latens, 208

— uncinata, 229, 240
Dictynidae, 311
Digestion, 55
Dimorphism, 260
Diplothele, 299
Dipluridae, 298
Dislike of spiders, 11
Distribution, 191

— of Arachnomorphae, 192

— of Liphistiomorphae, 192

— of Mygalomorphae, 191
Dolomedes neptunus, 84
Doors of nests, 288
Drapetisca socialis, 260

Drassidae, 24, 171, 309
Drassus neglectus, 236
Drink, 130
Dysdera erythrina, 87
Dysderidae, 73, 305

Eboria caliginosa, 97
Ecdysis, 256
Educability, 114
Egg-laying, 229
Eggs, 240, 243, 248
Embolus, 31
Embryology, 248
Empodium, 39
Endosternite, 48
Enemies, 176
Enoch, F., 295
Entelecara broccha, 97
Environment, 186
Epeira cornuta, 229

— cucurbitina, 211, 216

— diadema, 90, 107, 117, 227, 240,

255

— pyramidata, 189

— quadrata, 229, 240

— sclopetaria, 148
Epeiralysin, 130
Epeira toxin, 130
Epeira trypsin, 130

Epeiridae, 40, 42, 71, 141, 168, 210,

234, 3ii
Epigastrium, 22
Epigyne, 22
Epipharynx, 51
Ero, 38

Euctimena tibialis, 129
Euophrys frontalis, 98
Eupodoidea, 340
Eurypelma hentzii, 179
Eurypterida, 359
Everest, 194

Evolution of spiders, 302

— of webs, 137

— theory, 334
Excretion, 62
Exoskeleton, 46
Eyes, 77

Fabre, H., 103, 107, 124, 126, 132,

145, 238
Falces, 25
Falconer, W., 79
False-scorpions, 330
Fat, 56

Fear of spiders, 11
Fertilisation, 246
Fertility, 240

INDEX 373

Filistata insidiatrix, 205
Filistatidae, 307
Flash-colours, 160
Folium, 18
Food, 116
Forbes, H. O., 123
Fossils, 266
Fundus, 30
Fusulae, 41

Gabritschevsky, E., 159
Galeodes, 328
Gamasoidea, 345
Ganglia, 67
Gaubert, E., 95
Geological record, 265
Geotropism, 107
Glands —

abdominal, 368

aciniform, 71

aggregate, 74

ampullaceal, 72

coxal, 62

cribellum, 75

cylindrical, 74

digestive, 53

lobed, 74

maxillary, 69

odoriferous, 374

pharyngeal, 52

poison, 68

pyriform, 72

spermathecal, 66
Glycosamine, 47
Gnaphosidae, see Drassidae
Gossamer, 181
Grammonota inornata, 107
Gynandry, 262

Habit, 302
Habrocestum, 202
Haemocoel, 45
Haemocyanin, 59
Hahniidae, 40
Haplogynae, 225
Harpactes hombergii, 174
Harvesters, 335
Hatching, 252
Hearing, 89
Heart, 56
Heliotropism, 107
Heptathela kimurai, 277
Hewitt, J., 101
Hexablemma, 77
Hilaira excisa, 80

Hingston, R. W. G., 88, 102, 106,
112, 149, 151, 152, 194

Hippasa olivacea, 88
Horhaare, 91
Hormones, 75
Hudson, W. H., 172
Hull, J. E., 224, 263
Hydrachnoidea, 341
Hy dropsy che, 10
Hypochilidae, 306
Hypodermis, 47
Hypopharynx, 51
Hypothesis, 14, 300
Hyptiotes, 119

Ichneumons, 176
Idioctis littoralis, 299
Instinct, 108
Intelligence, 114
Islands, 196
Ixodoidea, 342

Jackson, A. R., 193
Joints of legs, 33
Jumping, 123

Kammerer, 302
Karyokinesis, 241
Katipo, 128
Kew, H. W., 333
King-crab, 321

Labium, 25
Laches, 27
Lacunae, 59

Lamella characteristica, 33
Latrodectus, 128
Legs, 33

Leptyphantes leprosus, 216

— minutus, 86, 94
Limulus, 6, 62, 321
Linyphia clathrata, 209, 223

— furtiva, 166, 175

— montana, 223

— triangularis, 172, 229
Linyphiidae, 71, 94, 97, 140, 158,

209, 307, 311
Lip, 25

Liphistiomorphae, 19, 40, 137, 273
et seq.

Locket, G. H., 170, 206, 208, 211,

213, 223, 226, 229, 239
Longevity, 180
Lorum, 18
Lung-books, 60
Lycosa amentata, 223

— godeffroyi, 84

— kochii, 98

— narbonnensis, no, 126, 180

374

INDEX

Lycosa purbeckensis, 198
Lycosidae, 122, 204, 236, 238, 310
Lyra, 95

Lyriform organs, 99

Madeira, 197
Maevia vittata, 261
Malmignatte, 128
Malpighian tubes, 55
Mandibles, 25
Mastidion, 26
Maxilla, 28
Maxillary gland, 69
McCook, H. C, 84, 91, 140, 182
Mclndoo, N. E., 101
Menge, A., 222
Menneus camelus, 120, 161
Mesenteron, 53
Mesozoic spiders, 269
Meta segmentate!, 70, 80
Miagrammopinae, 24
Micaria scintillans, 166
Micrommata virescens, 212, 226
Micryphantes beatus, 166, 175
Mid-gut, 53
Migidae, 291
Mimetidae, 311
Mimicry, 163
Miswnena vatia, 123, 159
Mites, 376
Mitosis, 241
Moggridge, J. T., no
Montgomery, T. H., 107, 148, 179,
213, 224, 228, 232, 235, 247, 250
Moulting, 256
Mountain spiders, 193
Muscle, 48
Mygale, 296

Mygalomorphae, 24, 26, 31, 51, 57,

68, 95, 125, 138, 284
Myrmarachne, 166
Myrmecium, 166
Myrmecophiles, 174

Nebalia, 307
Neglect of spiders, 10
Nemesia eleanora, 289
Nephilia maculata, 217
Neriene bituberculata, 80
Nervous system, 66
Nests of false scorpions, 333
Newtonian method, 14
Nops, 78

Oogenesis, 243
Oonopidae, 20, 305
Oonops pulcher, 229, 240

Orb-web, 143, 145
Oribatoidea, 346
Orphnoecus pellitus, 297
Ovary, 65
Oviduct, 66
Ovipositor, 24

Pachygnatha listen, 220
Painter, T. S., 261
Paleozoic spiders, 267
Palpi, 28

Palystes natalius, 113, 231, 235, 237,
245

Paracymbium, 32
Paraplectana, 164
Paratropididae, 287
Parattidae, 309
Parmula, 24
Parthenogenesis, 246
Paturon, 26

Peckham, W. G., 85, 98, 115, 192,

201
Pecten, 95
Pedicle, 17
Peripatus, 2
Petiole, 31

Petrunkevitch, A., 78, 278, 284, 306,

313, 3i7
Phaeoclita, 288
Pharyngeal gland, 52
Pharynx, 51
Phlogius, 297
Pholcidae, 311

Pholcus phalangioides , 27, 229, 236,

239, 259
Phrynarachne, 123
Phyllonethis lineata, 260
Physical conditions, 188
Pickard- Cambridge, F., 303
Pickard- Cambridge, O., 28, 33, 83,

126, 292
Pisaura mirabilis, 85, 206, 236
Pisauridae, 125, 205, 254, 310
Plagula, 18

Pocock, R. I., 117, 165, 171, 191,

268, 284
Poecilotheria, 161
Poison glands, 68

— of spiders, 125

— of scorpions, 327
Polar body, 242

— regions, 195
Postabdomen, 24
Praetarsus, 39
Preening, 169

— comb, 171
Primitive spiders, 271

INDEX

Pritchett, A., 99
Proctodaeum, 51
Prosthomeres, 2
Protective coloration, 158
Protolycosa, 267, 275
Pseudoscorpions, 330
Purposiveness, 13
Purse-web spider, 292
Pycnothelidae, 287

Radial apophysis, 29
Rainbow, W. J., 84, 85, 102
Rake, 26

Rastellus, 26, 288
Rayleigh, Lord, 14
Recapitulation, 255
Receptaculum seminis, 30
Reese, A. M., 129
Reflex actions, 105
Regeneration, 256
Respiration, 60
Retina, 81
Reversion, 251
Romanes, 111
Rostrum, 51

Salticidae, 73, 122, 201
Salticus scenicus, 122
— volans, 85
Sarcoptoidea, 346
Scape, 22
Scent, 98
Scopula, 28, 37
Scopus, 33
Scorpions, 325
— , false, 330

Scotophoeus blackwallii, 122
Sea shore, 197
Secretion, 75

Segestria, 26, 126, 138, 160, 180
Segmentation, 2, 24
Selenogyrus, 97
Seothyra schreineri, 167
Setae, 36, 86
Shape, 161
Sight, 83
Silk, 134

Simon, E., 225, 273, 3", 3i3> 3*5
Sinus, 59

Sipaloplasma aedificatrix, 299
Size, 258
Smell, 98
Social spiders, 175
Solifugae, 328
Sperm-induction, 222
Spermathecae, 22, 66
Spermatogenesis, 244

Spigots, 42
Spines, 37, 86
Spinnerets, 40
Spinning a web, 142
Spools, 41

Stasimopus, 101, 171
Steatoda bipunctata, 94, 133
Stegodyphus, 175
Stercoral pocket, 55
Sternum, 24
Stomach, 52
Stomodaeum, 51
Stridulation, 93
Sucking stomach, 52

Tapetum, 82
Tarantula, 127
Tarentida barbipes, 205

— pulverulenta, 98
Taste, 102

Tegenaria atrica, 118, 132, 229

— derhamii, 189

— parietina, 247
Tegulum, 32

Temperature, influence of, 187
Tenent hairs, 37
Tertiary spiders, 270
Testis, 65

Tetrablemma, 19, 77
Tetrapneumones, 284
Thalassius spencert, 125
Theraphosidae, 296
Theridiidae, 38, 71, 74, 94, 118

140, 210, 237, 239, 312
Theridion lunatum, 172

— pallens, 210

— sisyphium, 224, 239

— tepidariorum, 235

— varians, 80, 216, 226
Thomisidae, 123, 206, 309
Thorell, T. H., 273, 284, 303,
Thyreothenius biovatus, 174
Tibellus, 160

Tibia of palp, 29
Ticks, 342
Tige, 26
Tiso vagans, 80
Touch, 88
Tracheae, 60
Trap-doors, 288
Trichogen, 47
Trochosa leopardus, 80

— picta, 158

— ruricola, 158, 205
Trombidoidea, 340
Tropisms, 106
Troxochrus, 261

376 6 3 2 Q 2 7

Uloboridae, 311
Uloborus republicans i 176
Uloborus scutifaciens , 152
Ungual tufts, 297
Unguis, 26
Uric acid, 63

Vagina, 66
Vancho, 128
Vas deferens, 22, 65
Venom of scorpions, 327
— of spiders, 125
Vibro taxis, 91, 108
Vision, 83
Vogal, H., 101

Walckenaera acuminata, 80
Walking, 34
Warburton, C, 197

INDEX

Warning colours, 161

Warren, E., 113, 247

Wasps, 178

Web-
evolution of, 137
of young spiders, 148
origin of, 137
spinning of, 142

Westring, N., 94

White, G., 183

Xysticus cristatus, 80, 216, 223
Young spiders, 148, 253

Zelotes subterraneuSy 171
Zilla, 90, 136, 150, 186, 211
Zora, 38

PRINTED IN GREAT BRITAIN BY WILLIAM CLOWES AND SONS, LIMITED,
LONDON AND BECCLES.

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