flit

D.

GDIFT OF
DEWITT BISHOP

COLLEGE OF AGRICULTURE
DAVIS, CALIFORNIA

MB' LIBRARY

~

OUR INSECT FRIENDS AND ENEMIES

I

y «*.

',< V .

10

11

1. The oriental roach or " black beetle " : male.

2. The oriental roach or " black beetle " : female.

3. The German roach or " croton bug " : male.

4. The German roach or " croton bug " : female, with egg case.

5. Egg of bed-bug.

6. Bed-bug.

7. Caterpillar of a " clothes-moth " in its case.

8. One of the common " clothes-moths."

9. The " buffalo moth " or " bug."

10. The parent beetle of the " buffalo moth."
it. Egg of a flea.

12. A flea larva.

13. The common dog flea.

14. The little red house-ant.

All of the figures are very much enlarged and most of them were re-drawn
from the Bulletins and Reports of the Division of Entomology, U. S. Department
of Agriculture.

OUR INSECT FRIENDS
AND ENEMIES

THE RELATION OF INSECTS TO MAN, TO OTHER
ANIMALS, TO ONE ANOTHER, AND TO PLANTS

WITH A CHAPTER ON

THE WAR AGAINST INSECTS

BY
JOHN B. SMITH, Sc.D.

PROFESSOR OF ENTOMOLOGY IN RUTGERS COLLEGE; ENTOMOLOGIST TO THR
NEW JERSEY AGRICULTURAL EXPERIMENT STATIONS; NEW JERSEY

STATE ENTOMOLOGIST; MEMBER AND FELLOW OF A. A. A. s.;

N. Y. ACADEMY OF SCIENCES; ENTOMOLOGICAL
SOCIETY OF AMERICA ; ETC., ETC.

PHILADELPHIA &• LONDON

J. B. LIPPINCOTT COMPANY
1909

COPYRIGHT, 1909
BY J. B. LIPPINCOTT COMPANY

Published April, 1909

Electrotyped and printed by J. B. Lippincott Company
The Washington Square Press, Philadelphia, U. S. A.

FOREWORD

NOTHING in this world of ours exists to, for or by
itself alone. Every living creature depends upon some
other form of life, or upon inorganic matter and is, in
turn, the dependence of others that find it useful or
essential for continued existence. And as inorganic
matter is, after all, the base of organic matter as we
know it, plus the addition that makes it organic and
whose nature we do not yet know, so in due course all
organised forms again return to their lifeless constituents.

Every living thing, then, has relations to many
other living things and some of these relations, so far
as insects are concerned, it is my object to present.
I need hardly disclaim any attempt at completeness;
but so far as the presentation goes it claims accuracy.
A large proportion of the facts have been personally
observed or verified, others are common knowledge
and all are based upon the observations or records of
scientific investigators.

Some of these relations of insects to the welfare of
man have been but recently worked out and are imper-
fectly known; yet enough has come to the general
information to arouse a decided interest in these long
despised creatures. Their presence or absence from our
midst may make all the difference between sickness
and health, irritation and comfort, poverty or wealth,
or, on the other hand, wealth and poverty. They make
some regions uninhabitable that would otherwise be
attractive as sites for homes and, altogether, their
influence upon humanity, directly and indirectly, is
vastly greater than is generally realized.

5

72685

ACKNOWLEDGMENTS

Of the figures illustrating this work, the following
were drawn for me by Mr. John A. Grossbeck, my as-
sistant, from originals or modified from published
sources: i, 4, 5, 6, 7, 8, 10, n, 13, 18, 19, 20, 22, 24,
34, 41, 61, 64, 65, 66, 67, 68, 70, 71, 80, 81, 87, 89, 92,
93> 94, 95' 96, 104, 107.

From the publications of the Entomological Division
of the U. S. Department of Agriculture the following
were obtained, either as electrotypes or as copies from
the prints: 9, 49, 63, 77, 91, 98, 100, 101, 103, no, 112,

113-

From the New Jersey Agricultural College Experi-
ment Station I obtained blocks for figures 48 and 99.

The other blocks are by courtesy of the J. B. Lip-
pincott Company from my "Economic Entomology,"
where their original source is stated; but a number of
them have been somewhat reduced in size.

CONTENTS

I. INSECTS IN THEIR RELATION TO THE ANIMAL KING-
DOM 9

II. INSECTS IN THEIR RELATION TO PLANTS AS BENE-
FACTORS 21

III. INSECTS IN THEIR RELATION TO PLANTS AS DE-

STROYERS 40

IV. INSECTS IN THEIR RELATION TO EACH OTHER 84

V. INSECTS IN THEIR RELATION TO THE ANIMALS THAT

FEED ON THEM 130

VI. INSECTS IN THEIR RELATION TO WEATHER AND DIS-
EASES THAT AFFECT THEM 138

VII. INSECTS IN THEIR RELATION TO OTHER ANIMALS. ... 1 53

VIII. INSECTS IN THEIR RELATION TO MAN: AS BENEFAC-
TORS .... , 185

IX. INSECTS IN THEIR RELATION TO MAN: AS CARRIERS

OF DISEASES *99

X. INSECTS IN THEIR RELATION TO THE HOUSEHOLD.. . 217

XI. INSECTS IN THEIR RELATION TO THE FARMER AND

FRUIT-GROWER 249

XII. THE WAR ON INSECTS 271

INDEX 309

OUR INSECT FRIENDS
AND ENEMIES

CHAPTER I

THEIR RELATION TO THE ANIMAL KINGDOM

IF we examine any insect, large or small, in any
save the egg stage, we note at once that it has its skeleton
on the outside of the body. Not much of a skeleton in
some cases, e.g., a caterpillar, a slug or a maggot; a
very resistant and rigid shell or body wall in others, as
in some beetles which may be run over by a heavy
wagon wheel without being any the worse, or may pass
unchanged through the digestive system of a toad.
In any event it serves for the attachment of the muscles
on the inside, and they are thus protected, instead of
sheltering and protecting an inside bony framework as
in man and other vertebrate animals.

It will be further seen, especially in the simpler
forms, that the body is made up of successive rings or
joints, more or less similar in the primitive types, often
very unlike in the higher orders, and that the legs also
are made up of a number of parts or segments. These
characters place the insects with that great section of
the animal kingdom known as Articulata, which includes
everything from an earthworm to a lobster, and more
narrowly restricts them to the Arthropods, which have
jointed legs, and thus exclude the worms; but still
leaves the lobster as a relative.

9

io INSECTS

Matters now become a little more difficult; but if
we continue our examinations by comparing a lobster,
a spider and a beetle, we find that the latter has a
distinct head, separate from the rest of the body, while
in the others the head and middle section of the body
form a single mass known as a " cephalothorax. " Our
beetle also will be found to be breathing from the sides
of the body through a series of ringed tubes known as
trachea and this makes it a Tracheate — an honor that it
shares with centipedes or myriapods. Finally, if we
persist in our policy of exclusion, we leave as true
insects only those forms that have no more than three
pairs of jointed legs, attached to the thorax or middle
region of the body, the body itself made up of no more
than thirteen obvious rings or segments, grouped into
three regions, the head, thorax, and abdomen, contain-
ing respectively one, three and nine segments.

We are now ready to define an insect as an articulate,
arthropod, tracheate hexapod; but it will be equally
correct and much easier to say that it is a ringed ani-
mal, with six jointed legs, breathing by means of air
tubes or tracheae; this definition applying more particu-
larly to the adult stage, and only to the adult stage of
many of those having a complete metamorphosis.
. This method of breathing, by the bye, carries with
it a modification of the circulating system. The air
being carried in tubes to all parts of the body, there is
no need for lungs nor for any system of veins or arteries.
The blood simply flows about in the interstices of the
body cavity, kept in motion by a tube-like heart, divided
into chambers, which lies just under the back or dorsal
surface, and oxygen is taken up from the tracheae any-
where in its course, while the products of digestion are
taken up from the specialized cells about the digestive
system. And, after all, the process of maintaining life

RELATION TO ANIMAL KINGDOM

ii

..-

12 INSECTS

and activity is much the same among insects as it is
in the higher animals, although the method is some-
what different. The blood is equally the agent for
transporting nutritious material to whatever point it
may be needed, and the oxygen to burn out waste
products is as essential.

Under the microscope, insect muscle is not so very
different from that of man: it has similar transverse
striations, and contracts and extends in a similar
manner, but, nevertheless, there is no chance of con-
fusing insect with vertebrate muscle. This muscular
system is under the control of a nervous system which
is very highly developed in detail, but consists essen-
tially of a double cord extending from one end of the
body to the other, lying just above the under or ventral
surface and furnished with a series of enlargements or
ganglia, of which that lying in the head and termed the
brain is the largest, although it exercises no such dominant
influence as does that organ in the higher vertebrates.

There is quite a difference, of course, among insects,
in the amount of specialization in this nervous system.
In some and especially in larval forms all the ganglia
are similar in size and appearance, and there is one for
every segment; in others the tendency to centraliza-
tion is marked, all the thoracic ganglia being united into
one, while in the abdomen two or three of the posterior
ganglia join in the control of the reproductive system
and the various accessory parts connected with it. The
thoracic centre controls the organs of locomotion and a
paralysis that is practical death results immediately
when this ganglion is cut, whereas we can cut off the
head and abdomen, of a house-fly for instance, without
interfering with its power to use legs or wings. This
fact was known to the digger wasps long before the
entomologist knew it, for when such a digger wishes to

RELATION TO ANIMAL KINGDOM 13

quiet its prey ^before carting it home, the sting is aimed
at this very ganglion with instantaneous results.

As to senses, the insects have all those of other
animals and perhaps more, too; but developed in an
altogether different way and to a very diverse extent.
Insects see and have the most complicated kinds of
eyes known, as well as almost the simplest in existence.
Some species are sensitive to rays of light which man
cannot see at all and some species certainly seem to
see better at night than during the day. But, on the
other hand, it is doubtful whether they see at all dis-
tinctly or can recognize form and color when not directly
connected with their life-needs. So they can hear;
some of them very acutely, and ears are by no means
confined to the head: they may be on the feet, the body,
the abdomen or on the antennae, and it is believed that
they hear sounds so high in pitch that they are beyond
the reach of our senses. Nevertheless it is almost equally
certain that they are probably incapable of discriminat-
ing between sounds, and of really recognizing any but
those connected with the sexual calls of their mates or
perhaps the noises made by their prey and possibly
their enemies. Insects certainly have the sense of taste
and some of the most elaborate taste organs are found
in species feeding on the vilest excrementitious material.
Perhaps the less we say on this point the better,
unless it is to suggest that there are gustatory possi-
bilities that man is utterly incapable of appreciating.
Insects smell, and this sense is most acutely developed.
The male seeks and finds the female almost entirely
by this sense even when she is carefully and intentionally
hidden from sight, and both sexes find their food by
this sense more often than by sight: and that is particu-
larly true of those forms that feed on fermenting or
decaying matter. Insects feel, no doubt, and the tac-

i4 INSECTS

tile sense is popularly and probably with _, ,'tice located
chiefly in the antennae; but the mouth feelers or palpi
are also organs of touch and tactile hairs may occur on
any part of the body or its appendages. No one insect
species has all these senses equally well developed, and
few have more than one or two really so specialized as
to be conspicuous. There are more, indeed, which have
none of them more than rudimentarily present and
probably a fairly well-developed general sense of per-
ception is enough for the majority. Such a sense enables
the insect to recognize the vibrations that mean food,
a mate and a place to oviposit and that is all that is
really necessary to enable it to fill its place in life. As
to that tactile sense that implies a recognition of what
we know as pain, I believe it to be very feebly developed.
I do not indeed assert that insects are insensible to pain ;
but all observations indicate that they appreciate it
very little and very temporarily: real suffering I do
not believe them capable of at all.

An interesting question that is often raised in this
connection is whether insects reason or whether all
their actions are instinctive. I do not believe that
any one can study insects at all closely without crediting
them with a certain amount of reasoning power. Some
species do such incredibly stupid things occasionally
that it would be a libel on instinct to charge it with such
actions, and often specimens of the same species will
do things so differently that individuality and ratio-
cination must be accepted as accounting for the differ-
ence. To be sure it is not a very high grade of intelli-
gence that is manifested, using our own attainments as
a standard; but it is such a grade as brings out the
difference between individuals and species and enables
one to do well what the other fails in, habitually. It is
in the Hymenoptera and especially among the social forms

RELATION TO ANIMAL KINGDOM 15

that this intelligence is best manifested ; but I have noted
it in the majority of the species that I have observed at
all carefully in the open, under natural conditions rather
than in the laboratory in artificial surroundings.

Insects are as a rule prolific breeders, although
there is a great difference between them in this respect:
some multiply only ten-fold in the course of the season,
while in others the capacity is 1,000,000,000 descendants
in the same period. No one has actually counted that
number, of course, but we have counted the number
born to a single pair and determined the number of
broods to the season; so it is a mathematical certainty,
even if, as a matter of fact, probably no one pair ever
matured all its offspring for as many successive genera-
tions as are required to produce such a result.

In their development there is considerable variety,
but as a rule they pass through four more or less distinct
stages: this being called transformation or metamor-
phosis, while the various stages are also called instars.

The first, or egg-stage, is usually quiescent and gen-
erally passed outside the insect body ; but in some cases
it hatches within the ovary of the mother and young are
born alive, as in many plant lice and scale insects. Spe-
cies may therefore be oviparous (egg-bearing), or vivip-
arous (live-bearing), the latter also termed larviparous.

The second, or larval stage, is that which hatches
from the egg, and it may or may not be like the parent.
In the grasshopper, for instance, we can recognize it
as such, no matter how recently hatched; but in the
minute caterpillar, just out of the shell, no resemblance
to the butterfly can be traced. The larval stage is the
period of growth: the insect feeds to the limit of the
elasticity of its integument or outer skeleton, then
sheds this skin or "moults," and repeats this process
until it has reached its limit of size.

i6

INSECTS

It may be well to say just a few words as to this
outer skin which forms so important a feature in the
insect structure. It is soft yet resistant, and may
become so resistant that it is almost impenetrable to
corrosives or oils and with difficulty to be punctured
with needle or knife. It all depends upon the amount
of chitin deposited in the tissue and chitin is a secre-
tion from the lower layers of the cuticle, resembling
horn in texture and somewhat in qualities. No matter

FIG. 2. — Moulting of a grasshopper: a, nymph ready to change ; b, the skin
split along the back and the adult emerging; c, continues the process, and at d,
the insect is drying out.

how soft the body wall it contains some chitin and as
this is not elastic, there is a limit beyond which it cannot
be stretched. When this limit is reached a new skin
forms beneath the old one which, thereupon becoming
lifeless, splits and permits the larger next stage to escape.
This sort of change is found also in the crustaceans,
and in some of the reptiles.

The third, or pupal stage, may be a period of rest
or of continued activity, depending upon whether the
species has a "complete" or an "incomplete" meta-
morphosis. Returning again to our young grasshopper,

RELATION TO ANIMAL KINGDOM 17

usually called a "nymph" rather than a larva, when
this has become ripe, it develops wing pads or rudimen-
tary wings ; but continues its feeding as in the preceding
stages until the period when it moults for the last time
and changes to the adult or fourth stage. It thus
develops continuously, without conspicuous change of
form, and the metamorphosis is incomplete. Our
caterpillar, however, after moulting as often as needed
to obtain full size, changes into a
nondescript creature bearing no close
resemblance to its former nor to its
future stage and remains in this
"pupal" or "chrysalis" form while FlG.3._Sectionthrough
the caterpillar structures are disin- insect crust showing iay-

-...-. ers of chitin at c, the cel-

tegrated and re-formed into butter- luiar layer at h, and the
fly parts. This is a complete trans-
formation, in which almost no part
of the larval structure remains unchanged, and even
the method of feeding may become completely reversed:
indeed, in some cases the adults never feed at all,
depending entirely upon«the supply stored by the larva
to mature the reproductive cells or eggs.

Among themselves insects differ as much in appear-
ance and habits as they do from their more remote
relations. They are found wherever life is capable of
existing at all, and there is no organic substance known
which, in one stage or another, is not food for some
insect. They are moderately numerous, some 200,000
different kinds being already known and described,
with the reasonable certainty that we have not yet
discovered much more than one-half of those that exist.

There are some that never become winged; that are
soft -bodied in all stages, live usually in damp places
and are simply organized: these are the Thysanura, in
which the mouth structure is not well developed.

1 8 INSECTS

A very decided advance is found in those insects
that gain their food by sucking it through a jointed
beak by means of slender, bristle-like lancets in all
stages; and these are the Hemiptera or true bugs.

Grasshoppers, roaches, crickets and the like have
the hind wings folded in longitudinal plaits, laid straight
under the covering primaries, and are hence called
Orthoptera. They chew their food and are often trouble-
some to the agriculturist.

Another large series has the wings thin, transparent,
usually of good size, with numerous longitudinal and
transverse veins like a net or reticule and hence called
Neuroptera. This is the most primitive of the winged
orders of biting insects, and shows a great diversity of
forms and grades of development. The dragon flies
serve as a well-known illustration of one type. The
very general definition of the order here given covers a
series of remnants that are elsewhere more particularly
specified. It was in the Neuropterous or net-winged
type that the great break-up among the mandibulate
insects occurred and variation ran in many directions.
Some of the lines flourished for a little time only; they
proved ill adapted to their surroundings and survive
only by a few families and genera in which the species
are usually well fixed and easily distinguished. Others,
well suited to live, proved barren when it came to adapt-
ing themselves to new or a variety of conditions. These
are fairly numerous even now in families, genera and
species; but their limit of adaptation is reached and
they are shoots from which no further branches may
be expected. From the other lines the modern domi-
nant orders developed which, rich in forms, show
species capable of living under the greatest conceivable
variety of conditions.

The Coleoptera or beetles are known by the hard

RELATION TO ANIMAL KINGDOM 19

FIG. 4.— The orders of insects: i, a bristle tail and 2, a spring tail, are Thysa-
nura; 3, a dragon fly and 4, a Psocid, illustrating Neuroptera; 5, a grasshopper
illustrating Orthoptera; 6, a shield bug represents Hemiptera; 7, a ground
beetle shows Coleoptera; 8, a butterfly, illustrating Lepidoptera; 9, a horse-fly
represents the Diptera, and 10, a bumble-bee, the Hymenoptera.

20 INSECTS

or leathery fore-wings, beneath which the membranous
secondaries are transversely folded. They gain their
food by chewing, in all stages, although the early or
larval forms are usually altogether unlike the adults.

The Lepidoptera include the butterflies and moths,
known by the scaly covering of the wings. The scales
appear as fine, dust-like particles that are easily rubbed
off; but under the microscope show great differences
in form and color. In this order the mouth parts of the
adult are modified into a coiled tongue capable of sipping
liquids only ; but in the larval stage the caterpillars are
voracious devourers of plant and other tissue.

Bees, ants, wasps and the like belong to the order
Hymenoptera, in which the wings are transparent, with
few and often no veins; never reticulated. Many of
the species are of extreme interest because of their
social habits and organizations, and the honey bee is of
direct benefit to man in. more ways than one.

Finally come the flies ; differing from all other insects
by having only one pair of wings, whence their ordinal
name Diptera. We shall have more to say concerning
some of their species and development elsewhere.

The insects as a whole are at the top of the line of
development in the Articulata: they diverged early
from the worm-like ancestors and their remains, already
well developed, are found in the earliest fossil-bearing
strata. At the present time there are more species of
insects than there are of all other species of animals
taken together, and in number of individuals they are
unapproachable. The class as a whole is yet a growing
one and both genera and species are in some orders
unfixed and in process of formation. There is no better
field for the study of animal variation, and the problems
imposed upon us by them have scarcely begun to be
appreciated.

CHAPTER II

THEIR RELATION TO PLANTS AS BENEFACTORS

WHILE, in a general way, insects frequent plants
merely to feed on them, yet this feeding is not neces-
sarily destructive and may even contain an element of
advantage. Hence we find that, far from developing
structures to repel, many plants produce attractive
flowers and secrete nectar as an invitation to insects to
call upon or visit them.

Flowering plants as a rule have two kinds of sexual
organs: the pistil connected with the seed or female
element, and the stamens, producing the pollen or male
element. Fertilization takes place when the pollen or
male element is brought into contact with the receptive
surface of the pistil, and this pollination may be produced
in many different ways. Sometimes the same flower
has both pistil and stamens, and the pollen from the
latter may be discharged so as to come into immediate
or direct contact with the former. But this is not
always the case, for the pistil may not reach the recep-
tive condition until after all the pollen has been removed
from the stamens and, on the other hand, the pistil
may become receptive before the pollen on the same
flower is mature. In such cases there must be polli-
nation by some outside agency. Many flowers are of
one sex only, i.e., either pistillate, bearing female
organs only, or staminate, bearing male organs only:
and sometimes an entire tree or plant may bear flowers
of one sex only. Here again pollination by some carrier
is necessary and among the carriers the most active
agents are the wind and insects.

22

INSECTS

Plants which depend upon the wind for pollination
usually produce a light pollen in great quantity, so that
at times the air may be full of it. Plants which depend
upon insects for pollination may produce much or little ;
but it is usually somewhat sticky so as to adhere readily
to the body or vestiture of the visitor. And as insects are
not altruistic enough to call on the flowers merely to
benefit them, some sort of attraction must be offered

FIG. 5. — Section through a flower, illustrating the reproductive parts.

to invite the visits. This attraction may be in the shape
of honey or nectar for those species who seek for them-
selves alone, or for their progeny; or in the shape of
pollen suitable for use as food directly or in preparing
food for the young of the visitor.

Where nectar alone is relied upon to attract, it is
usually stored so as to compel the insects to come into
contact with the reproductive organs in their efforts to
reach it; and in such cases, not infrequently, the flowers
are modified to invite special kinds of insects only.

THEIR RELATION TO PLANTS 23

For instance, the clovers are especially adapted to
attract long-tongued bees; flowers like the Petunia,
the evening primrose or the jimpson weed attract the
hawk-moths, whose long, flexible tongues reach to the
nectar cups at the very bottom of the deep florets.

FIG. 6. — a, Yucca flower with moth in position, ovipositing; &, Pronuba gath-
ering its pollen mass; c, head of Pronuba from side showing the maxillary
tentacle; d, tip of the ovipositor.

So far as the insects are concerned the pollination
is a mere incident in most cases: it occurs because the
flower is so built that it must occur when the pollen or
nectar is gathered. But there is at least one case in
which it appears almost as if the insect acted intel-
ligently, with a definite purpose in view, and the
demonstration of this case we owe to the careful obser-

24 INSECTS

vations of Dr. C. V. Riley, erstwhile Entomologist to
the U. S. Department of Agriculture.

The flowers of the species of Yucca are absolutely
incapable of self- or wind-pollination, and the stigma is
so situated that no ordinary insect visitor can reach it
in a casual search for food. In some localities, it was
observed that the common Yucca or soap-weed never
produced seed and that wherever seed was produced,
almost every pod was infested by a little caterpillar
that destroyed a greater or less percentage of the seeds.
The parent of this caterpillar is a small white moth,
the Pronuba ynccasella of Riley, in which the mouth-
parts are curiously modified and utterly unlike those of
any other moth species that we know. At the sides of
the ordinary tongue there are developed a pair of flex-
ible processes set with little pegs and spines, and capable
of being coiled like the tongue itself. When the female,
which alone has these processes, is ready to lay an egg,
she enters a Yucca blossom, gathers a little mass of
pollen, rolls it into a ball, carries it by means of the
coiled processes to the pistil, and rams it down so as
to bring it into direct contact with the receptive surface.
Not until this has been completed does she turn and
then, into the ovary or embyro seed pod, she forces an
egg by means of a slender, sharp-pointed ovipositor.
She is now ready to repeat the process on another flower
and she does repeat it until her stock of eggs is exhausted.
Here we have a deliberate pollination preceding ovi-
position, as if the insect knew that it would be useless
to lay an egg until the possibility of development in
the seed pod was assured.

This peculiarity, though confined so far as we know
to the genus Pronuba, is not confined to one species
only. There are a number of Yuccas in the country,
including the giant or tree Yuccas of the southwest,

THEIR RELATION TO PLANTS 25

and for every species of Yucca there is a species of Pro-
nuba. Surely a most wonderful adaptation of insect and
plant, neither of which can now exist without the other.

And yet, while the adaptation is not so specific, nor
the evidence of design so apparent, the dependence of
red clover upon long-tongued bees is not less absolute.
Australia has no native bumble-bee, and red clover was
unknown there until the colonists began to cultivate it.
There was no difficulty in making crops of forage; but
it would not seed. Importing seed annually was expen-
sive and, naturally, the Australians were anxious to
raise their own. This led to a study, of the reasons for
the failure, in the course of which the dependence of the
plant upon bumble-bees was established. The remedy
was obvious, and now European bumble-bees disport
themselves among the Australian red clover, seed is
plentiful, and interference with bumble-bees is a crime —
as it should be rated everywhere.

Bees, by the way, are the most universal pollenizers,
and are highly specialized for that purpose. All bees
are more or less hairy: sometimes conspicuously so, a
dense woolly clothing appearing all over the body;
sometimes sparsely, the hair being often localized. But
whatever the bee, and however scant its clothing, the
hair is always compound: spurred, branched or even
plumose. In some series it is so strikingly characteristic,
that from the hair alone, the genus to which a bee
belongs can be determined with reasonable certainty.
In all modifications and adaptations, be they small or
great, the pollen-gathering function is always attained:
for bees need pollen in their domestic economy. Most
insect mothers have no more care for their offspring
than to place the egg in some position where the larva,
when hatched, will find food. In the Hymenoptera, to
which the bees belong, storing food upon which the

26 INSECTS

larva feeds is a common occurrence, and the larva,
when hatched, finds surrounding it sufficient nourish-
ment to bring it to maturity. In the social forms,
matters have developed yet further, and the larva does
not even feed itself: it is fed by the mother or a nurse,
and its food is prepared beforehand; either a mixture
of pollen and honey, or fragments of insects mixed
with salivary secretions of the adult. And so bees need
pollen as food for their larvae, and upon the mothers or
females falls the burden of gathering and storing it.
For convenience we consider as females those sexually
undeveloped forms in the social species which we know
as workers, and in that sense all the female bees are
supplied, not only with gathering hairs, but with some
sort of structures to carry the pollen. In the common
hive-bee the inside of the first joint of the hind foot or
tarsus is modified into a curry-comb-like structure for
cleaning the pollen grains out of the hair, and the out-
side of the hind tibia is provided with a fringe of long
hair forming a basket into which the pollen is packed
for transportation. In other bees other parts of the
legs, of the breast, or even of the abdomen are provided
with means of transporting pollen loads, and so after
a visit to the first flower the bee is fitted for its mission
of fructification, which occurs as a mere incident in the
gathering.

There is no group among the insects that is more
interesting as a subject for study than that containing
the bees. Not only are the structures of adaptation
very beautifully developed for their purpose; but their
life history is often of intense interest. On the honey
bee alone we have not only the vestiture, the pollen
carrier and the brushes that clean out the pollen from
the hair; we have, in addition, the antenna-cleaner
on the fore leg and the complicated mouth parts. The

THEIR RELATION TO PLANTS

27

PIG ^ — Bee structures: a, honey bee, pollen loaded; b, mouth parts of a long-
tongued bee; c, hind leg of bee showing pollen carrier; d, wax cutter and curry-
comb of ist joint of hind tarsus; e, antenna-cleaner of fore leg; f, hair of bumble-
bee; g, hair of Melissodes; h, hair of Megachile; i, hair of Xylocopa.

28 INSECTS

antenna-cleaner is a little notch on the inner side of the
basal joint of the front tarsus, set with fine teeth and
closed by a spur from the end of the fore tibia. When
the bee desires to comb out the vestiture of one of the
feelers, the fore leg is brought up, the notch is hooked
over the stem at base, the spur is brought to the lock,
and at a single sweep the entire series of joints is brought
into condition. It is all very simple and very neat,
and could not 'be better adapted for its purpose if
designed by man himself. The mouth structures which
are also kept in condition with this apparatus merit a
little further attention.

I have already alluded to "long-tongued" bees and
this has carried with it the suggestion that there was a
difference in that respect. As a matter of fact there is
every intermediate form between the tongue of the
bumble-bee, more than half as long as the insect itself,
and the little digger bee, whose labium or lower lip does
not extend beyond the edge of the moutii. It is not
always easy for the novice to recognize to which division
a bee under observation belongs, because the long tongue
is usually hinged, and may be drawn back against the
breast in such a way as to be protected from danger of
injury. When fully extended the mouth has, laterally,
a pair of very well-developed mandibles, which usually
serve more as tools in building homes than as organs
for securing food. Between these mandibles, and com-
pletely separated from them, is a pair of sheath-like
structures which are generally pointed at the tip. These
are the maxillae, which are not of much active use,
though they are the organs by means of which ripe
grapes and other fruits are occasionally punctured
when normal supplies are scarce. In the very centre is
the flexible tongue itself, ringed in structure, with series
of hairs round about it, and a little button of hair at the

THEIR RELATION TO PLANTS 29

tip. This is the structure that is forced down into the
very heart of the flower and forms a lapping organ, by
means of which every particle of nectar may be secured.
The bee is not really a sucking insect at all; but gets its
food by lapping somewhat after the manner in which
a dog laps water.

Only the honey gatherers have tongues of this type.
Bees and honey are usually associated, but as a matter
of fact many kinds gather no honey at all, and very
few of them store it. In the species in which there is no
elongated central tongue, this is replaced by a short
bladder-like organ, also set with more or less spatulate
hair, suited for lapping, but not for getting down into
deep flowers. Bees of this sort we find on our shallow
flowers like those of the strawberry, blackberry and
other Rosace®, and many of these gather no honey at all.

It is a delightful pastime, although not always easy,
to investigate the domestic economy of the various
bees. Some of them make nests or cells of mud gathered
from road-side puddles; some bore into twigs, branches
or even boards and in the tunnels so chewed out form
the cells in which a brood is raised; some make cells of
wax in cavities of trees; others seek a cavity under the
turf, and in a mass of pollen raise their brood with little
attempt at making cells of any kind; and yet others
dig down deep underground, five or six feet below the
surface and, far from the light, build the homes in which
their young are developed. And when we find a bee-
home, we can always recognize it by the character of
its store. It may be a cake of solid pollen, packed hard
in a definite, loaf- like form, or it may be a semi-liquid
mass of mixed pollen and honey, so arranged that the
larva may feed on, without being imbedded in, it. But
always there is pollen, and the, pollen gatherer is always
also a plant fructifier.

INSECTS

There are many others among the Hymenoptera
that are useful in the work of pollination because of
their habit of feeding among the flowers, even if not on
them; but all this is based on the same visits which the
flower encourages and of which it takes advantage;

but no account of this sort
of relationship could be con-
sidered even passably com-
plete, without some reference
to the complicated relation-
ship existing between the
Smyrna fig and the minute
little Blastophaga, a species
whose life relations have been
beautifully worked out by the
Entomologists of the United
States Department of Agri-
culture.

The Smyrna fig of com-
merce depends for its edible
quality upon the ripened
seeds that it contains. The
fig is not really a true fruit
as that term is generally
defined, but is a thick fleshy
envelope within which the
flowers are contained. In
the Smyrna fig these flowers

are all female and no pollen is produced anywhere on
the tree. Left to themselves, such trees could never
produce ripe fruit, and that was the condition of the
Smyrna fig orchards in California, prior to 1900. In the
Mediterranean countries, whence our commercial sup-
ply is generally derived, there are found beside the culti-
vated also several varieties of wild or caprifigs, which

FIG. 8.— a, cell of Augochlorawith
egg laid on pollen mass; b, cell of
Andrenid with egg resting on mix-
ture of pollen and honey; c, cells of
carpenter bee in wood; d, mud cells
of mason bee in burrow — c and d,
after Packard.

THEIR RELATION TO PLANTS 31

produce three crops of fruit during the season. These
fruits contain male flowers, producing an abundance of
pollen; but this pollen is never naturally discharged
from the envelope containing the florets.

FIG. 9. — Blastophaga pollenizer of fig: a, female; b, c, male in two positions.

Yet it was recognized by the fig-growers in the
Orient that to obtain fruit of the commercial edible
varieties, it was necessary to bring to them when in
bloom, branches containing fruit of the caprifig, which

32 INSECTS

were usually hung up in the tree which it was intended
to fructify. This work of pollination is accomplished
by the Blastophaga already referred to, although, far
from benefiting itself in the process, the insect dies
without even being able to continue its kind.

In the caprifigs the female flowers are replaced by
little gall-like swellings in which the larvae of the Blasto-
phaga develop. One generation of figs, the so-called
"mammae," remain on the trees during the winter and
by the time they are ready to drop, there is already on
the trees a new or spring crop of fruit, known as the
"profichi. " By the time that this crop is in proper
condition, the insects that have hibernated in the
"mammae," are fully developed, the wingless and almost
blind male Blastophaga has fertilized the female before
she is even out of her cell, and the latter, leaving the
dried-up fig by the small anterior opening, makes its
way into the new figs, to provide for a new generation.
In the "profichi" this generation matures at the time
the commercial Smyrna fig is in proper condition and
the females, emerging pollen covered from the "pro-
. fichi," enter the small opening of this true female flower
receptacle, if they find themselves in a tree bearing them.
But in this Smyrna covering all the female florets are
fully developed, and the gall-like swellings that replace
them in the caprifigs are absent. The insect therefore
moves about over the entire interior surface of the
pouch, seeking a place to oviposit, and in the process
distributes its load of pollen everywhere. It event-
ually dies without reproducing, and usually without
even being able to make its way out again. But
though the insect has lost its life, the tree has gained
and the seed pouch that we know as the fig, comes to
maturity and ripens seed.

THEIR RELATION TO PLANTS 33

At the same time that the Smyrna fig which produces
the edible commercial fruit is in bloom, there is also
another crop developing on the caprifigs, and these are
known as "mammoni. " The Blastophaga issuing from
the "profichi" on the same tree, naturally enter these
fruits which are of the same character as the preceding
crops, and are able to continue their kind, coming to
maturity when the third crop is ready for their reception.
This third crop represents the "mammae" or over-
wintering form, from which the "profichi" of the fol-
lowing season are again entered by the Blastophaga.

Here we have an extremely complicated relation-
ship which, reduced to its simplest terms, means that
in order to produce the commercial Smyrna fig there
must be suitable caprifigs producing "profichi" infested
by Blastophaga, at a period corresponding to the develop-
ment of the female flower capsule. And as the insects
are very small and very frail, the caprifigs must be
either well distributed among the Smyrna trees, or the
infested "profichi" must be gathered and distributed
among the trees to be pollenized.

The accounts, published by Dr. L. O. Howard in the
Bulletins and Reports of the U. S. Department of
Agriculture, make interesting reading and show how,
after many trials and much painstaking investigation,
the Blastophaga and the necessary caprifigs were finally
introduced into the fig-growing districts of California,
and how a new industry, absolutely depending for its
continuance upon a minute hymenopterous insect, was
finally established upon a firm and scientific basis.

How many cases of this kind exist among plants
having no present economic value it would be difficult
to estimate, and how so complicated a relationship ever
became established is not yet explainable even by a
theory.
3

34 INSECTS

The Lepidoptera have been already incidentally
referred to as pollenizers and they rank, as an order,
next to the Hymenoptera in importance. Butterflies
and moths, when they feed at all, feed only on liquids
and most of them on prepared plant juices or nectar.
The butterfly hovering over a flower and sipping honey,
is a familiar figure, and the visits of hawk-moths to the
flowers that open at dusk are fairly well known; but
that busy life that stirs among the flowers after night
falls, is unknown except to the naturalist who prowls
about in wood and field, among the hedges and along
the road, often with a bulls-eye lantern like a thief;
seeking indeed to surprise some of nature's secrets by
artificial light, his organs of sight being far inferior to
those of the creatures whom he seeks to study.

That many flowers are most fragrant at night, and
that many fragrant, night-blooming flowers are white
•or without striking colors, is a commonplace to one
who knows the country at all; but that this penetrating,
fragrance is to attract insect visitors at a time when sight
does not suffice for an invitation is not so well known.
And yet it is at night that the most abundant, albeit
almost noiseless, life can be observed on such flowers,
and here we will find owlet and other moths busily
engaged in probing every floret and incidentally accom-
plishing nature's aim of reproduction. I say "inci-
dentally" with intent in this case, because neither
moth nor butterfly has any use for the pollen that it
dislocates and relocates as it moves. It is after food,
purely and simply, and that food is nectar: if in reaching
that nectar the tongue, pollen laden, is brought into
contact with the stigma, that is merely because the
insect could not help itself, any more than it could pre-
vent the adhesion of a few grains of pollen from
another flower.

THEIR RELATION TO PLANTS

35

Exceptions occur always and that of Pronuba in its re-
lation to Yucca has been related ; but in general the Lepi-
doptera pollenize as a mere incident and with the tongue,
while feeding. And this tongue is a really interesting bit
of structure. It is coiled like a watch spring when at rest
between the mouth feelers, and no one would suspect. its
presence or size from an ordinary dried specimen; but
when uncoiled it is often as long and sometimes much
longer than its bearer, and here
again we have that beautiful
ringed structure that adapts it-
self to so many purposes among
the insects. There is no flower
so deep that its nectaries are
beyond the reach of all insects
but there are many flowers so
deep that only a single long-
tongued species is invited. And
therefore we have an abun-
dance of species with tongues
of less than an inch in length,
quite a number that have them
from two to four inches and
a very few where ten or even
twelve inches are attained.

The butterfly tongue really consists of two separate
parts or halves, the modified maxillae, held together
by specially developed structures; and the space be-
tween them forms the tube through which the liquids
are carried into the mouth. Each half contains its
own supply of muscles, a large tracheal tube extends
to the very end, and there is an excellent supply of
nerve-fibres to guide the insect in its operations in the
depths of the florets.

Most of the tongue is bare or set with scanty stiff

FIG. 10. — a, tip of butterfly
tongue showing the sensory pits
and taste cups ; b, section through
tongue showing division into two
halves.

36 INSECTS

hair only; but at the tips in the different species, are
found a great variety of tactile structures, taste cups
and gathering processes, by means of which our moth
not only recognizes the presence of something good to
eat, but manages to get it all, as well. In the adult stage
as moths or butterflies, the Lepidoptera have few bad
and many good qualities; but in the larval or cater-
pillar stage the reverse is the case. As pollenizers the
Lepidoptera could be missed much more readily than the
bees; none of our cultural plants depending upon
them for their continued existence.

Among the Coleoptera or beetles there are many
that frequent flowers for one purpose or another and
many of these are more or less pubescent or covered
with hair, so that they may be and often really are
much covered by pollen as they move about. And
as they move about they do without question add
their share to plant fruitfulness ; but they are also very
often feeders upon them or upon the pollen. In so
far as they are pollen-feeders merely, this does little
harm, because that is usually produced in great ex-
cess; but some feed on the pollen in such a way as to
rob the plant of all possible chance of benefit. For
instance the strawberry-weevil in the larval stage
subsists altogether upon pollen. But the parent beetle
punctures the unopened bud, lays the egg in the mass
of forming pollen and then punctures the stalk below
the bud, so that the latter may never open. This is
sheer robbery without corresponding benefit and, on the
whole, flowers pay pretty heavily for such incidental
advantages as they derive from the visits of beetles. In
any case the pollination is purely incidental, for the
beetles gather neither pollen nor honey, and the hairy
covering is not modified to make it especially serviceable
as a carrier.

THEIR RELATION TO PLANTS 37

Diptera or flies are often intimately associated
with flowers, and many of these are hairy, some even
with spurred or compound hair; but none with modi-
fications that adapt them especially or peculiarly as
pollenizers. We have one family, the BombyliidtB or
bee-flies, resembling bumble-bees somewhat in appear-
ance and quite as hairy, many of which also have a
long tongue rivalling some of the Lepidoptera. But
their habits are quite different. One
never sees them buried in a flower
or rolling about among the blos-
soms, pollen-covered. On the con-
trary they usually hover daintily over
bare, sandy areas or, if over flowers,
then very delicately and resting
lightly when at all. That they are
of some use to the plants is prob-
able; but they have no important
function. And the same is true of FIG. n.— chrysanthe-

c^ j . j . -i f ., mum fly ; Eristalis tenax.

the Syrphida that are found so

often resting on or about blooms:

the majority of these are bare, or have only a thin soft

vestiture and slender hairless legs to which pollen

could not adhere if it would.

An exception to this general statement is found in
the chrysanthemum or "drone fly," a burly bustling
species that becomes conspicuous late in the season
and resembles in size, color and general appearance a
honey bee, for which indeed it is often mistaken. A
little experience, however, shows that it has no sting,
and therefore the term " drone fly " is not so
inappropriate.

Growers of chrysanthemums believe this fly of
great importance in the pollination of that plant and
they may be correct; but on other plants or flowers

38 INSECTS

they are of little use. Their habits in the early stages
are about as unlike those of the adults as it is easily
possible to imagine. The larvae live in all sorts of semi-
liquid excrementitious matter and are known as rat-
tailed maggots, because of the long anal process by
means of which they obtain air from above the surface
of the filthy mess in which they live.

The number of flies known to us is already very
great, and the number that still remains to be studied
is probably even greater; while as to their habits we
know them in the most general way only. There may,
therefore, be groups more decidedly beneficial to
plants than anything that I have mentioned; but
there can be nothing comparable with the bees, since
none of the flies store food for their progeny.

The fact is, then, that many plants depend for their
reproduction entirely upon insect visitors. Some flowers
are so constructed that only very specialized forms can
accomplish the function of pollination and there is in
many such cases a mutual dependence: the insect can-
not exist without the plant nor can the plant continue
its kind without the insect. Other flowers issue a general
invitation by bright colors, wide open parts, abundant
pollen or filled nectaries, readily accessible to anything
that may come along. Yet others depend upon nectaries
that are attractive, but are so situated that any insect
that succeeds in gaining access to them must of necessity
pay in pollenizing. And here we come to a subject on
which the botanist has his say, and shows how ingenious
are some of these plant structures and how well adapted
to their end, so that pollination may even be accom-
plished without the necessity for bringing the pollen
into contact with the insect at all, the latter merely
releasing the trigger that restrains the distribution of
the fructifying material.

THEIR RELATION TO PLANTS

39

There is one other method in which insects are
useful to plants, and that is as food. A very few plants
are "carnivorous" or feed upon animal food, and that
animal food consists mostly of insects; but that is a
relation which is extremely simple in character al-
though the plant habit is exceptional.

CHAPTER III

THEIR RELATION TO PLANTS AS DESTROYERS

WHILE, as has just been shown, there is a mutual
interdependence of plants and insects in which both
may be benefited, or if one is harmed, the benefit
derived is so far in excess of the injury suffered that it
does not count against the value of the relation, there
is also a kind of dependence in which the insect gets
all the benefit, and the plant all the injury.

A vast number of insects depend absolutely upon
plants for their very life and give nothing at all in re-
turn: they are destroyers pure and simple, using the
plant tissue as food, as material to supply protection,
or as a habitation. But the amount and character of
the injury vary enormously and may either be a neg-
ligible incident in the life of the plant, or form the
principal check to its growth or cultivation.

We may dismiss with no more than a mere mention
that vast horde of insects that gets into plants when
they are dead and begin to disintegrate. Nature dis-
likes dead organic matter, and when a tree or plant
is dead or dying, or when decay begins in a sappy fruit
or fungus, there are insects among other agents ready
to reduce it to that inorganic condition from which it
originated. While the actual death of a diseased or
weakened tree is often hastened by such insects, they
can hardly be said to be enemies in the direct sense ; but
scavengers, ever ready to begin their office and fostering
the condition in which it becomes their legitimate prey.

Beginning with the simplest order, the Thysanura,
we find few plant destroyers among them. Originating

40

THEIR RELATION TO PLANTS 41

as they did in primitive times when dampness, mud
and ooze were prevailing conditions and vegetable
life just established, they were fitted to live and gain
their subsistence in disorganized tissue: they were
simple forms of scavengers, and so they are to-day in
most cases. They are always found where there is
moist vegetable decay and sometimes, in manure beds,
they occur in countless numbers. In fermenting sap,
under bark of trees undergoing moist decay, in masses
of leaves and similar localities, these species may gen-
erally be sought. Their direct influence upon growing
vegetation is extremely small.

In the Neuroptera there has been an advance, al-
though, as these were also primitive species and largely
adapted to aquatic or semi-aquatic life, the vegetable
feeders are in the minority. Almost everywhere the
larval life is more or less predatory in tendency and
in some, like the Odonata or dragon flies, this predatory
character is carried into the adult stage. The feeders
on vegetable matter, like Psocids and Termites, usually
attack dry or dead tissue or feed upon Lichens and
similar material. None of them rank as destroyers of
the higher forms of plant life, although Termites do in
some instances attack growing vegetation.

In the Hemiptera we have a well-developed series
of terrestrial species, the vast majority of which are
feeders on plant life or on plant juices drawn from
living plants. The mouth structure of the insects is
such that they can feed only on the liquid which they
draw from a punctured tissue, whether vegetable or
animal, and therefore, primarily, the injury is due to
a withdrawal of sap, severe in proportion to the amount
of liquid thus withdrawn. Secondarily, injury is caused
by an interruption of the circulation in the plant, due
to a hardening of the exhausted tissue, or the drying

42 INSECTS

out of the cells from which the liquid matter has been
abstracted. More rarely a positive poisoning of the
tissue occurs, due apparently to the injection into it
of the salivary secretion of the insect, and this may
result in the death of all that portion of the plant be-
yond the puncture. That sort of injury is often pro-

PIG. 12. — Mouth parts of a plant louse — a, the jointed beak; b, the
lancets; c, the feeler; d, the foot.

duced on succulent plants like the Cucurbs, including
cucumbers, melons and the like, or Solanacea, includ-
ing potatoes, tomatoes, egg-plants, etc., the offenders
being mostly plant bugs of the families Capsidce, Lyg-
(zidaz or Coreidcs.

Plant lice are universally distributed and there is
scarcely a plant not in some way subject to their attacks.

THEIR RELATION TO PLANTS 43

They are insignificant as individuals; but dangerous
in hosts: and hosts grow out of individuals in an in-
credibly short time, owing to their fecundity. Given
a few eggs on the tip of an apple twig in winter, they
hatch into young lice as soon as the leaf-buds open
and, in a week or ten days, depending upon weather
conditions, these begin to bear living young. All the
specimens hatching from the winter eggs are parthen-
ogenetic females; i.e., females which do not require
to be mated with a male before reproducing their kind;
and, when once reproduction begins, it is in the nature
of a continuous performance; four, six, eight or more
young being produced in a day and for several days in
succession. Long before this stem-mother has reached
her limit of increase, the first-born daughters, partheno-
genetic like herself, have in turn begun the task of
multiplication so that, by the time the leaves are fully
formed, the surfaces are covered by plant lice, and in-
stead of unfolding and reaching full size, they are
curled, twisted and crippled, forming an unsightly
mass instead of a beautifully unfolded cluster or tuft.
And now we are apt to get a secondary effect due to
a peculiarity in feeding. Not content with absorbing
only enough to sustain life and to reproduce, the insects
gorge continuously and, when incapable of containing
more, they eject through the anus a stream of a clear
sweetish liquid, known as honey -dew. It was cur-
rently believed that the two tube-like structures near
the end of the abdomen were the chief organs through
which this honey-dew is excreted and they are there-
fore popularly known as "honey-tubes": more technic-
ally they are termed cornicles, which conveys no opinion
as to their function. This honey-dew drops upon the
leaves below, often in such abundance as to form a
complete coating and that, in turn, is an excellent

44 INSECTS

culture medium for a soot fungus which forms a black
covering -that disfigures if it does not kill the foliage or
fruit. It goes without saying that what is true of the
apple, which I have chosen for an illustration, is equally
true of the cherry, the maple, the orange, lemon or any
other tree or plant subject to the attacks of plant lice or
others of their allies also producing honey-dew — mealy
bugs, white-fly, Psyllids and even some scales.

FIG. 13. — The apple louse: b, stem-mother; a, winged parthenogenetic form;
c, adult male; d, winter eggs on twig.

To return, however, to our stem-mother on the
apple, whom we left engaged in the task of increasing
her kind. She was born without wings and never
acquires them, and her daughters are like her in this
respect. But after the second generation matters
become crowded, and unless relief is somehow obtained
there will be more than can be maintained on the orig-
inal tree. And so in the third and later generations a

THEIR RELATION TO PLANTS 45

variable number of individuals develops further and
becomes winged. There is not in this case any genera-
tion in which all the individuals are winged, although
there are species in which such a condition exists. It
is simply that out of a dozen individuals born of the
same mother on the same day, a number develop
wings and fly away to other trees or plants. They are
no further advanced, sexually, than the stem-mother
and when they reach their new homes they also pro-
duce living young, which may become winged or re-
main wingless; and this sort of reproduction continues
until the end of the season and the gradual decrease
of . sap in the trees and plants forces a provision for
winter rest. Late in the fall, therefore, a generation is
produced in which both sexes are represented and
from a union of these the winter egg is produced.

Now while this in a way epitomizes the usual his-
tory of plant lice, there is an infinite amount of varia-
tion. A species that is confined to one tree or similar
food plant may do very well without much modifica-
tion; but a species which feeds during the summer on
a plant that dies down completely before winter, needs
some provision that enables it to continue its kind
elsewhere; hence we have migrations in early summer
from and in late fall to the winter host. In a melon
field, for instance, there may not be a plant louse until
the vines are well developed: then on some warm,
almost windless day in June, the air will be found full
of drifting, winged aphids and next day a sprinkling
of them may be noted all over the melons, giving rise
to the summer generations which, in late fall, again
produce return migrants that find their way to plants
upon which they can pass the winter. Sometimes
there seems to be a direct relationship between two
plants, as apple and wheat for one form of Aphid that

46 INSECTS

attacks both, or between the plum and the hop, where
the insect cannot exist unless both its alternate hosts
are present. At other times, as in the case of the melon-
louse, the insect has a variety of food plants and the
migration is not essential to the continuance of the
species. In fact it is not even necessary for all plant
lice to go into the egg stage, for some species winter as
parthenogenetic females on plant remnants or on stools
like the rosettes of cruciferous plants. In tropical coun-
tries the resting stage is often during the dry season,
when vegetation has little spare moisture.

Some species attack only the roots of plants, and
these are usually wingless, and often without honey-
tubes or cornicles. Some inhabit the roots at one
season and the leaves at another, the winter being
usually spent underground, while a large part of the
growing period may be passed on the foliage, the spread
of the species being provided for there. Such species
may be very little modified, like the black species that
occurs on peach, or very greatly specialized like the
Phylloxera that occurs on grape, and is so great a
factor in all countries where the vine forms an impor-
tant part of the agricultural product. This Phylloxera
vastatrix winters on the roots as a partly grown, wing-
less form. It grows rapidly in spring and lays eggs,
the young from which are, like their mothers, wingless
and parthenogenetic, laying eggs and producing others
like them in turn throughout the season, always from
unfertilized eggs. In most localities, about midsummer,
some specimens acquire wings, work their way to the
surface and fly to other vines, thus providing for the
rapid spread of the species. These winged forms lay
from three to eight eggs on the leaves, some of them
large, producing females, the others small, producing
males. These sexed forms seem to be produced only

THEIR RELATION TO PLANTS

47

for the purpose of renewing the vitality of the species
for they are without wings, incapable of flight and with-
out mouth parts, incapable of feeding. They are

FIG. 14. — Phylloxera vastatrix — a, sound grape rootlets; b, rootlets with newly
formed galls; c, same with old, dried up tissue; dd, groups of lice on roots and
rootlets; e, f, female pupa, above and beneath; g, h, winged females; «, antenna;
j, oviparous wingless female and her eggs; k~, root showing location of the eggs.

sexually mature when born, copulate soon afterward,
and each female produces one egg which hatches into
a form similar to that which started the cycle in spring.
But the winged form is not essential for this renewal,

48 INvSECTS

for at any time during the summer the underground
forms may lay eggs of two sizes producing similar sexed
forms that act precisely as did those above ground.
So, some of the parthenogenetic forms may leave the
roots and crawl up the stem to the foliage, where their
progeny form those characteristic galls which strike ter-
ror into the heart of the European viticulturist, while
they are frequently not even recognized by the vine-
grower of the eastern United States. Nor is this leaf-
form a necessary feature in the cycle and it does not
occur in all localities, so that outward indications of
Phylloxera infestation may be completely lacking ex-
cept in the condition of the vine. The Phylloxera are
gall-makers as a rule, and on the roots of grape pro-
duce swellings and distortions which, on vines not
accustomed to them, result in the death of the roots
or serious disturbance in function, so that the vines
sicken and may die. In the original home of the species
in eastern North America no especial injury is caused;
on the Pacific Coast injury may be severe, but the
insect does not spread readily, and so its march may
be checked; while in European countries the native
vines succumb very easily to the attack of the insect
and its spread is rapid where energetic measures for
its destruction are not resorted to.

There are other species of plant lice producing galls:
some on hickory make bladder-like structures of con-
siderable size, and others produce ridges aptly com-
pared to a cock's comb, on elm. In fact, from the
simple distortion produced by a feeding along the veins
on the under side, to characteristic bladder-like struct-
ures, every sort of intermediate form exists, and as
a rule these produce no very serious results on the
plant. It is astonishing how great a number of such
insects a plant may support without interfering with

THEIR RELATION TO PLANTS 49

its power to maintain life and reproduce its kind ; which
be it noted, is quite a different matter from an injury
which will make the plant unprofitable to the farmer
or fruit-grower.

Scale insects are close allies of plant lice in many
ways and yet totally different in many others. The
popular name is derived from the fact that most of the
species have the appearance of a fragment or scale of
tissue plastered upon or against the bark or foliage
of the plant attacked. And so we have soft scales and
armored scales, which differ radically from each other.
In the soft scales, so named because the outer covering
is usually waxy in texture, the outer covering or scale
is part of the insect itself, not separable from it in any
way, and the term, scale insect, is strictly correct. In
the armored scales, on the other hand, the scale or
covering mass is tougher, more parchment-like, and
forms no part of the insect, although produced or ex-
creted by it. It is possible, therefore, to lift the scale
without in any way interfering with the creature be-
neath it; the covering being formed in part by the
cast skin of the insect and in part by a fibrous excre-
tion from special glands.

Scale insects, like plant lice, are capable of enormous
feats in the reproductive line, one thousand million de-
scendants for a single pair, during a single season,
having been figured out for one of the species! Thus,
given a scale introduced without natural checks into
a region where conditions favor it, and the effect upon
its host-plant can be readily imagined. The practical
experience of the Pacific Coast with the cottony cushion
scale on citrus fruits, and of the Atlantic Coast with
the San Jose scale, are recent instances that illustrate
the destructive powers of scales; the first a soft, the
latter an armored form.

4

So INSECTS

Scale insects feed on the juices of their host as do
the plant lice, differing in the fact that they are more
or less fixed to a single spot on the plant: absolutely
fixed in the armored scales, with a very limited range
of motion during a part of their life in the soft scales;
the latter being in some cases not far removed from the
mealy bugs which are active throughout their life and
produce a powdery material that does not form a com-
plete covering. Some produce living young and breed
throughout the season, like the San Jose scale; others
are oviparous and have only one distinct brood, like the
cottony maple scale. In some there are only a few
eggs, in others they are almost uncountable, and thus
there is a great range in the life cycle, although the
nature of the injury done is always the same.

One characteristic feature is the difference between
the sexes. The males, throughout the Coccidce, are
very minute, frail, two- winged creatures without func-
tional mouth parts and two pairs of eyes; one pair
replacing the lost feeding organs. These males are
often furnished with long anal styles or filaments, and
their only function is to fecundate the female. The
latter feeds throughout life, never becomes winged, and
her dead body often serves as a cover or shelter for the
egg mass that she produces.

The injury caused is primarily due to the abstrac-
tion of sap; but quite a number of species produce a
distinct poisoning of the bast or bark tissue, often
evidenced by a red or purplish discoloration. Where
this occurs the twig or branch dies sooner or later.
Sometimes pits or depressions are formed where a
little group of scales is lodged and, in fact, there are
infinite variations in the character of the injury, due
to the peculiarities of the plant attacked and to the
method of feeding by the insects. Some of the soft

THEIR RELATION TO PLANTS

FIG. 15. — Development of the San Jose" scale: a, larva; 6, its antenna; c,
female with young showing through body wall; d, outline of anal plate; e, male
adult.

52 INSECTS

scales produce honey-dew in great quantity, and the
resulting soot fungus does almost as much injury as
the insect. In the olive and citrus groves of the Pacific
Coast, trees infested by the black scale are often recog-
nizable as far as they can be clearly seen, and discolora-
tion of fruit is a distinct element of the injury caused.

Quite a number of others among the allies of scales
and plant lice produce honey-dew and its consequences,
and there is a long series of species, including the leaf-
hoppers, tree-hoppers and others of the Homopterous
section, that cause more or less in jury 'to their food
plants by the direct robbery of the vital juice or sap;
but there are none differing so greatly from the methods
of plant lice and scale insects as to require special
attention here.

A somewhat different type of injury is caused by
some tree-hoppers and Cicadas or harvest flies. These
do little or no harm by direct feeding; but utilize the
twigs and branches of the plants on which they live
as places of deposit for their eggs in such a way as to
kill or severely cripple them. Some of the tree-hoppers
cut little slits in the twigs to receive their eggs, and
these slits never heal. The tendency is rather to an
enlargement of the scar which permanently weakens the
shoot and sooner or later causes a break. The chief
sinner in this direction is the periodical Cicada, better
known as the "ly-year locust," and wherever and
whenever that makes its appearance in numbers, the
tips of the forest trees in early fall show brown ends
as if a fire had passed over them. In such forests it
means only a moderate pruning and no real injury to
the trees; but in orchards, especially of young trees,
injury is often severe, weakening the shoots and branches
so that they break under a load of fruit. And these
punctures also refuse to heal, and remain permanent

THEIR RELATION TO PLANTS

S3

sources of weakness, apt to result in a break at any
time. I would never advise planting a nursery tree
whose trunk had been used by Cicadas for ovipositing.
In the Heteropterous series the species are usually
larger; but the life histories are simpler and the injury
is not materially different. Here, among the plant

FIG. 16. — a, Ceresa bubalus, a tree-hopper, ovipositing in slits b; the eggs, d,
arranged as at c; old scarred punctures at e.

bugs, the poisoning effect already referred to is often
noticeable, and is frequently of more importance than
the exhaustion caused by the direct feeding. The
chinch-bug may serve as the best known example of
the destruction causable by these species and of the
results that come only from the enormous numbers
in which they feed. There is nothing here but a direct
loss of vitality due to the abstraction of the plant juices.

54 INSECTS

The order Orthoptera, as a whole, consists of plant
feeders: from the earwigs to the crickets there are
only a few groups where vegetation is not the chief
or only food. The earwigs are curious because of
their resemblance to beetles and their large anal for-
ceps, and they feed largely in, though not always on
flowers. Not many occur in North America and their
chief interest lies in the fact that the female broods
over her eggs after they are laid: an altogether unusual
character in this series of species. The roaches are
not normally troublesome to growing vegetation and
are of most interest as household pests, where more
is said of them. The Mantidcz or graspers is the
only group of distinctively predatory species in the
order and they are very few in number. The Phasmidce
or "walking sticks" are devourers of plant tissue,
interesting because of their resemblance to the twigs
and leaves among which they live, and because of
their habit of dropping their eggs to the ground with-
out care as to their location and future ; as far removed
as possible from the habit of the earwigs. Their injury
to the plants is of the simplest possible description
and confined to a partial destruction of foliage, which
means little or nothing to the plant.

The grasshoppers, on the other hand, are among
the best known of plant destroyers. Under the name
"locusts" their ravages have been written of in the
Bible and by later writers on conditions in Africa and
the Mediterranean countries. The migratory locust
has thus come to represent the very type of destruc-
tive invasion, and the Rocky Mountain locust or grass-
hopper in our own country is not less well and unfavor-
ably known for its injuries. '

The short-horned grasshoppers, which are the
species now under consideration, quite usually lay

THEIR RELATION TO PLANTS

their eggs in little masses in holes in the ground, which
they bore with the horny valves at the end of the
body, and they select moderately firm, dry ground for
that purpose. Much moisture is dangerous or even
fatal to the eggs, hence it is in desert or semi-arid
countries that they are most abundant. Such condi-
tions in our country exist among the foot-hills of the
Rocky Mountains and no place that I have ever seen
exceeds that region in the variety and abundance of
its grasshoppers in a normal season. Sometimes,
when conditions become unusually favorable, grass-

FIG. 17. — The American grasshopper or locust, Schistocerca americana.

hoppers may become so very abundant that the vege-
tation in their native locality is insufficient to support
them, and then some species better fitted for flight
than others, take wing and seek new feeding grounds.
Some are unable to get very far, and rest as close to
home as they can, starving if they get beyond the limits
of their strength without discovering new pastures;
but other, longer winged species, accomplish hundreds
of miles from the Rocky Mountains to the Mississippi
Valley, alighting first where cultivated lands begin.
Thus Kansas, Nebraska and the Dakotas were pre-
eminently sufferers from grasshopper invasions, and
not infrequently conditions were sufficiently good
there to permit the insects to lay their eggs, providing
for a brood which the year following destroyed the

56 INSECTS

vegetation while still unfledged, and then migrated
yet further east to do destructive work as adults and
to perish gradually, in the egg stage, in the moist un-
suitable soil. No one who has not seen grasshoppers
in this western country can form any real idea of their
actual abundance, and their destructiveness has been
the theme of many a writer. They eat any green thing
if they must; but favor the low plants of field and
meadow so long as they last.

Conditions now are much better than they were
and can never again be quite as bad. A large area of
what was at one time ideal breeding ground, is now
irrigated and under cultivation, and the enormous
belt of alfalfa and other crops now basing the foot-
hills, checks and takes up the migrating hordes that
occasionally start from the uncultivated areas. The
march of advancing cultivation spells the doom of
some of these grasshopper species, as it has that of
many another animal; but meanwhile the grass-
hopper is putting up a good fight and is still causing
trouble.

While there is considerable variation in grasshopper
habits and life history, some of them laying their eggs
in soft or decaying wood tissue, there is little in the
character of the injury caused; it is always a direct
eating of the plant, rarely threatening its life, however
much it may be injured for agricultural purposes.

The long-horned or meadow grasshoppers are most
abundant in the places shunned by the short-horned
species. They delight in moist meadows, in reedy
open swamps, and are abundant in the marshes along
the sea and lake coasts. They are usually of some shade
of green in color, and have a more or less well marked
blade-like ovipositor, by means of which they lay their
eggs in the stems or leaves of the grasses and other

THEIR RELATION TO PLANTS 57

vegetation among which they live. They are largely
seed feeders when seeds are to be obtained, but eat
grassy tissue as well. A character of interest is found
at the base of the wings in the males, where the over-
lapping parts are ridged and toughened to form a
stridulating or musical apparatus of a very effective
order. The best known among this type are the Katy-
dids, which are often tree and shrub dwellers but do
not differ markedly in other respects from the more
lowlv meadow inhabitants.

FIG. 1 8. — A long- horned grasshopper, Microcentrum sp.

The crickets are very diverse in their habits, both
as to dwelling places and as to food; some confined to
vegetable matter only, a few omnivorous and the tree
crickets carnivorous. The latter are really the only
injurious forms for, while they eat plant lice and similar
creatures, they lay their eggs in the shoots of plants
and sometimes cause their death; but this is an in-
significant item as against their usefulness from the
farmer's point of view.

On the whole, while the order Orthoptera contains
many plant destroyers, the destruction is rarely total:
that is, it is confined to defoliation which does not
threaten the actual life of the plant, however completely
it may destroy its value agriculturally.

5$ INSECTS

In the order Coleoptera or beetles we have a very
large number of species and a very great diversity of
habits. They live under almost every conceivable
condition where insect life is possible at all, and there
is no organic matter, living or dead, which is not eaten
by some Coleopteron in either the adult or larval stage.
We may therefore expect to and do find enemies to all
sorts of plant life and there is no part, from the tip of
the finest rootlet to the topmost leaf, that is exempt.

Just how it happened that certain types of struct-
ure became associated with certain feeding habits
makes a very interesting question on which there are
widely divergent opinions; but for our purpose we can
simply accept the fact that the general life habits of
any beetle can be approximately stated from an ex-
amination of the feet, the antennae or feelers and the
general type of mouth. There are exceptions in every
large group as the result of special adaptation, but for
general purposes the test answers well.

We have a large series of species, most of them
terrestrial but a few aquatic, in which the antennae
are slender, made up of usually eleven joints of similar
form, and the feet are 5-jointed on all legs. All these
are predatory in general habits, both as larvae and
adults, and none are characteristically enemies of plant
life. There are some that eat plants, and a few have
caused injury at times; but these are exceptional
instances.

Coming next in the order of series are the Clavicorns
in which the antennae are thickened toward the tip so
as to form a distinct enlargement or club: the feet, all
of them with the same number of joints, though the
number may be from three to five, none of them with
the third joint lobed. By far the largest part of this
series are scavengers, living in fermenting, dry or de-

THEIR RELATION TO PLANTS

59

caying animal and vegetable material of all kinds.
A very few, comparatively, are predatory and yet a
smaller number are feeders upon living vegetation;
none of them in any very characteristic way nor so as
to threaten the existence of the plant attacked; but
still giving variety to the series.

These are followed by the Serricornia, in which the
antennae have the joints more or less trigonate, or

FIG. 19. — Antennal structure of Coleoptera. a, filiform; b, clavate; c, serrate;
d, lamellate; e, moniliform.

saw-toothed, and the feet 5-jointed as a rule; always
with the same number on all feet. Among these the
vast majority are vegetable feeders, but this vegeta-
tion may be dead or alive, and most of the feeding is
on woody tissue rather than foliage. The " click beetles, ' '
"snapping beetles" or Elateridce are characteristic
members of this series, and as wire- worms their larvae
are very often feeders on root tissue. The beetles gain
their common names by the loose-jointed structure

6o

INSECTS

between the prothorax and the rest of the body, and
their habit of snapping or springing up with a jerk
when turned on their backs. The wire-worms gain
their name from the tough leathery texture combined
with a slender wormlike form and most of them feed
underground, devouring the roots of many sorts of
plants, severely injuring or actually destroying such
as they attack. But there is also a large contingent
that lives in woody tissue — nearly always dead tissue
and quite generally such as is well advanced in decay.
Thu insects can scarcely be
called borers, because they are
hardly fitted to make their way
in sound wood ; but in logs and
stumps or even dead standing
trunks they are often found in
goodly numbers.

Typical wood-borers are
found among the Buprestidce,
which are usually metallic, hard-
shelled beetles, generally of good

size, often with handsomely sculptured wing-covers. In
the larval stage these are known as flat-headed borers
or "hammer-heads" because, immediately behind the
mouth structures the first thoracic segment is much en-
larged and often chitinized, giving the appearance of a
very broad, flattened head, followed by a long slender
body in which all the joints are well marked. These bor-
ers work in the bast and sap-wood of the trunks and
branches of trees and shrubs, making shallow galleries of
more or less characteristic shape and sometimes enor-
mous length. A single borer not over an inch and a
quarter long, may make a gallery an eighth of an inch
wide and over ten feet in length, leaving a trail of dead
tissue that the tree in many cases cannot replace or mend.

FIG. 20.— Click-beetle and wire-
worm from side and top.

THEIR RELATION TO PLANTS

61

If this trail is along or with the grain, not much harm is
done; but in many cases it tends to a girdling or to a
cutting across the grain that involves a large part of the
circumference. And when there are several such borers
at work in one tree, fatal results follow. I have seen
entire orchards of pear trees and fields of blackberry
killed by borers of this character.

Sometimes, the larva, instead of making a long
narrow gallery, eats out an irregular chamber beneath

FIG. 21. — Flat-head apple borer: a,
larva; b, pupa; d, adult.

FIG. 22. — An irregular gallery made
by a flat-head borer.

the bark, and that sort of injury is not nearly so serious,
since it does not so much interrupt the circulation of
sap. So there is quite a little difference of habit in the
selection of the tree to be attacked. Some species
never enter living trees and these are, perhaps, in the
majority; but some never attack other than healthy
tissue. As a rule, if trees are found infested by flat-
headed borers, it can be assumed that they were al-
ready in rather poor condition before the entry; this
new attack marking the first step in nature's attempt
to get rid of an organism no longer aggressively healthy.

62

INSECTS

In those species that attack dead tissue only, some
of which, like the cigarette beetle and death watch,
are treated in Chapter X, we get an approach to the
scavenger type; and yet the term scavenger seems
scarcely a fitting one since the material attacked is
not in a condition of either ferment or active decay.

In the "soldier beetles" and "fireflies," which by
the form of their antennae are members of this series,

FIG. 23. — May beetle: i, pupa in earthen cell; 2, larva or white grub;
3, 4, beetle from side and above.

we have a wide departure from the general feeding
habit, most of them being predatory in the larval
stage, and feeders among flowers, where they feed at
all, as adults.

The series Lamellicornia, containing species with
the feet 5 -jointed and the antennae terminated by a
leaf -like club, includes vegetable feeders almost ex-
clusively, in both larval and adult stages, and, in gen-
eral, the feeding is upon live vegetation. There are

THEIR RELATION TO PLANTS

the usual exceptions of course, but really very few in
number. The common "May-beetle" or "June-bug"
may be selected as a good type and this, as an adult,
exemplifies the habits of the series in its voracious
feeding. Most of the beetles of this series feed in the
adult stage, and in almost all instances it is a direct
straightforward devouring of growing tissue which
does not endanger the life of the plant. In the larval
stage the species are known
as white-grubs and in this they
are much more dangerous since
they feed upon the roots, often
destroying the smaller plants
such as grasses, berries and the
like. The step from living to
dead vegetable matter is a very
short one and so we find here
also quite a number of feeders
on dead or even decaying
plants, which of course are not
among the direct plant enemies.
In that great series of Phy-
tophaga, which contains the
families Chrysomelidce or plant

beetles, and Ceramby tides or long-horned beetles, we find
all the tarsi or feet apparently 4-jointed, the third joint
lobed or divided into distinct parts. This is a very char-
acteristic structure and almost always indicates a leaf-
feeder. Most of the adult beetles in the Chrysomelidae
feed very simply and openly on leaf tissue, devouring
without plan or aim except to get enough. Occasionally
we do get some characteristic bit of feeding like that
of some flea beetles which eat little round holes, or
make channels that render their work readily identi-
fiable. The larvae vary more in their habits and, while

FIG. 24. — Tarsi of Coleoptera:
a, normally 5 - jointed ; b, 4-
jointed ; c, 4-jointed with srd joint
lobed; d, same from side: c & d
always indicate a plant-feeder.

64 INSECTS

the vast majority are soft, naked, slug-like creatures,
similar to those of the potato beetle, or only scantily
clothed like those of the elm leaf beetle, there are some
that are more slender, white, and worm-like, mining
in stems, leaves or even roots, and making more or
less characteristic galleries, channels or chambers.
They may be only surface channels like those made
on cucurbs by certain species of Diabrotica; they may
be real borings like those made in root tissue by some
flea beetles; or they may be mines in leaf tissue, like
those made by some of the species of Hispids. It is
rare that the attack of a Chrysomelid really threatens
the life of a plant, though there are exceptions to this;
the grape-vine root- worm for instance, and other
root-feeders.

In the long-horned beetles, or CerambycidcB, the
adults do very little feeding; but the larvae are borers
in woody tissue or in stems of plants, differing from
those of the Buprestids by being more cylindrical
and with a less prominently dilated anterior portion.
They are known as round-headed borers as distin-
guished from the flat-headed kind already described,
and their galleries in section are nearly round instead
of transversely oval. As a rule, also, they are more gen-
erally borers in heart-wood and do not make the irreg-
ular shallow galleries under bark that are so char-
acteristic of the flat-headed types. There is no part
of a tree that is exempt from their attacks: from the
roots to the very tips of the twigs it may be in-
fested, and they do not confine themselves to sick or
dying trees either: a perfectly sound tree is just as
likely to be attacked as any other and, indeed, some
species are found in sound trees only. There are many
interesting points connected with the development
of these borers, the life period of some of them being

THEIR RELATION TO PLANTS 65

drawn out enormously under unfavorable conditions.
Thus, if a piece of infested timber is worked up into
furniture, a larva which normally matures in two or
three years may live for eight or ten years or even
longer; and in some cases wainscoting has been found
infested, several years after it has been in place, var-
nished and polished so as to forbid the idea that some
misguided adult oviposited there after the boards

FIG. 25. — Round- head apple borer: a, puncture where egg is laid; 6, same
in section; e, hole from which beetle has issued; /, same in section; g, pupa.

were in position. Some species require the wood in
a particular condition to secure their best development,
and so a beetle, before laying its egg, may girdle the
twig so as to interrupt the flow of sap and then oviposit
above the girdled point. Other larvae bore into live
twigs and, when ready to transform to the pupal stage,
cut through from the inside until only the bark and a
mere shred of woody tissue remain. Then the burrow
is securely plugged with sawdust and the larva retreats
5

66 INSECTS

into its gallery, above the point of cincture, certain
that the next high wind will bring it safely to the ground.
Considering the enormous variety of species and the
number of points attacked, it is surprising that the
amount of injury caused is not much greater than it
is. But, aside from the natural checks, the insects
grow slowly in the larval stage and are rarely great
eaters; the borings of some of them being surprisingly
short, considering the size of the larva and the length
of time it feeds; furthermore, the twig and branch
borers in most cases produce only a more or less in-
judicious pruning, while the
• borings in the heart wood
on a large tree do not neces-
sarily threaten, its existence.
Still, these round-headed
borers may be accounted
among the more serious
enemies of woody plants.

FIG. 26.— Bean- weevil, natural A little offshoot from the

size and enlarged, and a much in- , , r . . , ,

fested bean. plant-feeding beetles are the

BruchidcB, commonly known

as bean- and pea-weevils because the majority of them
attack the seeds of plants belonging to the Leguminoscz
or pod-bearing family. This includes not only the bean
and pea of the garden, but such tree forms as the locusts,
and almost every series has its own species of Bruchid
that lives and comes to maturity in the seeds. The term
weevil is not strictly applicable to these insects for, al-
though the head is very small and pointed, it is not pro-
duced into a snout, and the body is unusually obese, the
wing-covers squarely cut off behind and leaving a large
area of abdomen exposed posteriorly.

Next comes a series known as the Heteromera, in
which the anterior and middle feet have five joints

THEIR RELATION TO PLANTS 67

but the posterior four joints only. It includes a great
variety of species, many of them of sombre, uniform
color, shunning the light, living in concealment and
often or even generally feeding on dead or dry vege-
table matter. Yet there are exceptions to this, as for
instance the blister beetles which, in the larval stage,
are semiparasitic, and as adults feed ravenously on
vegetation. When they are feeders on living plants,
however, it is as straight-forward devourers of leaf
tissue that they appear, and they do not threaten the
existence of the plant attacked, however much they
may injure it for the farmer's purpose.

And now we get the Rhynchophora or snout beetles
which, broadly speaking, include the bark beetles or
Scolytids and with them some of the most dangerous
enemies to plant life. Popularly most of these species
are known as weevils and, so far as I am aware, all of
them are plant feeders. And there is no part of the
plant from root to tip that is not attacked; no
stage from seed to pollen that is not eaten by them.
They are among the oldest of the Coleoptera in the
geologic record and have adapted themselves to life
on vegetation under all sorts of conditions. The term
snout beetles calls attention to one of the most prom-
inent external structures — the elongated head drawn
out into a beak of varying length, at the end of which
the small mouth parts are situated. For feeding pur-
poses these do not seem to be especially well designed,
indeed in many species the mandibles are deciduous
and are shed soon after the adult is developed; but
for hiding and placing the eggs no better nor more
practical tool can be imagined. For instance, almost
every one that has gathered nuts has had the experi-
ence of finding some of them wormy, with absolutely
no trace of an opening on the outside to show how

68

INSECTS

that worm or grub ever got into it. If the grub is bred
to maturity it will develop into a snout beetle with a
very slender brown beak, from one half to three quarters
of an inch in length or even longer. With this long
snout the parent punctures the forming burr of the
chestnut or husk of the other nuts, and into the very
centre it runs its minute channel. It then turns, places
an egg into the mouth of the opening so made and
again turning, slowly and gradually forces the egg into
place with the beak. The rapidly growing plant tissue
effaces all trace of this puncture, and there we have

FIG. 27. — A nut- weevil: Balaninus sp.: a, from above; b, from side; c, larva.

our embyro grub already in place, almost before there
is any differentiation between shell and kernel. It is
interesting to note in this connection how carefully
nature guards against the extinction of any of her
creatures by a season of adverse conditions. A species
dependent upon the hickory-nut for instance might,
in case of a total failure of that crop for some one year,
become locally exterminated if all specimens followed
the same routine. But were we to put 100 grubs into
confinement in fall, when nuts are ripe, and permit
them to go underground to pupate, we would probably
get not over sixty adults the spring following; and if

THEIR RELATION TO PLANTS 69

we left our specimens undisturbed we would probably
get thirty more the next year thereafter and the re-
mainder the third year following. This seems to be
rather a wide-spread provision for tiding insects over
a bad season and, not only in the snout beetles but in
many other groups, single-brooded species that pass
the winter in the pupal stage, may lie over for one
or even two years after the bulk of the brood has
become adult.

By virtue of this provision for placing eggs, many
of the snout-beetle larvae are feeders in blossoms, fruits
and seeds, and enormous damage is caused to trees
and plants by limiting their seed bearing powers. When
these fruits are of commercial importance like the plum,
the horticulturist classes the "plum curculio" as a
first class pest and a subject for investigation by the
economic entomologist. If I mention once again the
cotton -boll weevil, and cite as a further example of seed
destruction the strawberry weevil, the danger of this
sort of insect to plant life may be appreciated. It is
of course the larva that does the injury, and curculio
larvae are all more or less grub-like in character; mostly
white like the generality of internal feeders, and usually
with a brown chitinous head furnished with well-de-
veloped jaws or manidbles.

Blossoms, fruits and seeds furnish only one article
of diet for weevils and their larvae: many bore into
the stems of herbaceous plants, as the rhubarb weevil;
others bore into wood tissue like the white pine weevil,
and the latter, by killing off the leading shoots, fre-
quently distorts a tree to such an extent as to make
it commercially useless. A comparatively small number
are external feeders on plant tissue like the clover-
leaf beetle; a few make tubes or other cases out of the
leaves on which they feed, and some cause galls or

70 INSECTS

other enlargements. There is, therefore, scarcely a
method of attack that is not represented among the
snout beetles.

FIG. 28. — A piece of hickory bark, illustrating the work of Scolytus
4-spinosus and its larva.

The Scolytids or bark beetles deserve separate
mention, as they are among the most dangerous of all
tree enemies and the greatest destroyers of wood tissue,

THEIR RELATION TO PLANTS 71

living or dead. The name bark beetle is a misnomer
for many of the species, which never bore into or
under bark at all; but it applies well to a very large
number that make characteristic borings or galleries
beneath the bark or in the sap-wood. In forms of
which the common fruit bark beetle may be considered
typical, the adult bores a longitudinal channel in the
sap-wood and lays eggs on each side in little notches
cut for that purpose. These beetles are all more or
less cylindrical, slender and elongate, with a very short
or scarcely perceptible snout and well-developed jaws
or mandibles. The larvae that hatch from the large
white eggs are of the usual grub-shape, white with
brownish head, and each larva makes its burrow at
right angles to the main gallery, diverging a little up-
ward or downward as it increases in size so as to avoid
its neighbors, and making a pattern so distinctive
that the species may be recognized by its borings alone.
Quite usually beetles of this character attack trees that
are a little weakened or unhealthy, but some take to
perfectly sound trees and cause serious trouble. Other
species bore into the heart wood, their galleries being
cylindrical, often blackened or discolored, and these
are sometimes called shot-hole borers.

No kind of tree is exempt from the attacks of
such beetles, and thousands of acres of forest lands
in all sections of the United States are annually de-
stroyed by them. And much timber is rendered useless
or lessened in value by the borings which disfigure or
weaken it, where the life of the tree itself is not threat-
ened. In trunk, in twig and even in the roots these
Scolytid borers are found, and our knowledge of them
still leaves much to be desired. Only a small propor-
tion of our species are actually known, and their classi-
fication at present is merely tentative. They are re-

72 INSECTS

ceiving more attention now than ever before, and they
merit more attention than they are receiving.

Altogether, the Coleoptera, among the dominant
orders, furnish a very large number of destroyers of
plant tissue living and dead, and many that may be
ranked as destroyers of plant life.

The order Lepidoptera includes the butterflies and
moths and their larvae are known as caterpillars. Cater-
pillars with few exceptions feed on plant tissue, hence,
as a whole, the members of the order may be consid-
ered as enemies of plant life. Mainly they are open
and above-board enemies: direct feeders upon the leaf
tissue, without modification or concealment. Such
feeding in itself does not endanger plant life except in
cases where there is an unusual number of caterpillars
or the plant is one that will not survive defoliation;
therefore the number of species dangerous to plant
life in this way, is not really very great. There are
such species, of course, for in the State of Massachu-
setts there are hundreds of conifers dead as the result
of defoliation from gypsy moth, and in general, any
species that can completely strip a tree may cause its
death.

A comparatively small number of Lepidopterous
larvae are borers in woody tissue, and these are mainly
members of the families Sesiida, Cossidce and Hepi-
alidcB'. all Tineites under the modern classification.
The Sesiids are small clear-winged moths resembling
wasps in appearance, and their larvae bore into trees
and in the stems of herbaceous plants. The peach
tree borers are types of the former, working under the
bark at the surface of the ground and often causing
the death of young trees; the squash borer is a type
of the latter, boring into the stem of the plant at almost
any point; but most often at the base. Both types

THEIR RELATION TO PLANTS 73

frequently cause the death of the plants attacked;
but there are others, like those attacking the trunks
and branches of oak and maple, that may infest their
host for years without causing obvious harm. Not
only the tissue above ground is attacked, for one species

FIG. 29. — The peach borer, Sanninoida exitiosa; male above, female below.

at least occurs on the roots of grape, and others are
underground on oak.

The Cossids are much larger forms and correspond-
ingly more dangerous. The European Zeuzera pyrina
or wood-leopard moth, which has been introduced
into the eastern United States, frequently girdles
young trees and often weakens the branches of older
ones to such an extent as to make them easy victims

74

INSECTS

to wind storms. Some of our own carpenter worms
make simpler borings; but owing to their methods
of work, leave sore spots that often form points of en-
trance for germs of decay. Thousands of oak trees in
the eastern United States are "doated" as the result

FIG. 30. — Wood-leopard moth, Zeuzera pyrina: a, b, larva; c, male; d, female
moth; e, larva burrow.

of the work of these borers; stunted in growth and
useless as timber. Fortunately the number of species
is small and very few of them are at all numerous in
specimens.

The Hepialids are very ancient in type and they
are few in number of species and specimens. The
larvae are large and make large channels in roots and

THEIR RELATION TO PLANTS 75

trunks; but I have never known of any serious injury
done by them.

There are many others among the Tineid families
that are borers in herbaceous and shrubby plants and
some cause galls or other abnormal swellings in the
infested stems; and there are many others that mine
or bore in leaves, causing a great variety of disfiguring
injury, but rarely anything that threatens the life of
the plant itself. Many of these little caterpillars and
a few larger species make cases or covers of the most
diverse character, and others live in shelters spun by
the members of one brood from a single laying of eggs.
Some live altogether in silken tubes spun by the cater-
pillars, and of these some feed underground on the
roots of corn and other plants. Quite a number feed
inside of fruits, like the Codling moth of the apple or
the berry moth of the grape, and a few get into seeds
like the Angoumois grain moth.

We have, then, among the Lepidoptera, a very large
number of feeders on vegetable tissue, that destroy
portions of the plant without endangering its life,
and a comparatively few that are really dangerous to
the existence of the organism attacked, however much
it may be injured from an economic standpoint.

The order Hymenoptera contains a large number
of species of very great interest: some of them vitally
important to the continuation of plant life, and on the
contrary a few that are destructive to it: but it is
interesting to note that among the bees which have been
shown in the preceding chapter to be among the great-
est benefactors of plants, we should also find an element
of danger. Plants suffer from "blights," "rusts,"
"scabs" and a variety of other diseases and, recently,
plant pathologists have charged that bees in their
visits to flowers engaged in the beneficial work of

7 6 INSECTS

pollination, at the same time carried also the germs
of fire-blight and similar diseases, introducing them
into the sensitive tissues of the blossom. It is an old
story, of course, that disease organisms frequently find
entrance through wounds made by insects; but that
is merely putting the insects on a par with other causes
that produce abrasions, cuts or bruises: this is a dif-
ferent matter, the insect being charged as the active
transmitter, much as a fly carries typhoid germs to the
human organism.

Direct plant feeders are found among the Hymen-
optera in the Sessiliventres, — "saw-flies" and "horn-
tails," — which derive their technical name from the
fact that the abdomen is joined to the thorax for its
full width and is thus sessile, while in the majority of
the species in this order it is stalked or pedunculate,
attached at a narrow point only. The saw-flies are
somewhat clumsy in appearance and more sluggish
than the other Hymenoptera, the body rather uniform
in size from end to end, the wings large, with many
complete cells, and folded over the back when at rest.
They derive their common name from the fact that the
ovipositor is made up of parallel blades variously
toothed at the edge, by means of which the female
cuts a slit or pocket into a leaf, stem or twig, for the
reception of an egg. The larvae that hatch from these
eggs are caterpillar-like in appearance but have five
pairs of abdominal prolegs instead of four or less, as
is the case in the true caterpillars. They are mostly
feeders on foliage, like the currant worm, and they
sometimes appear in enormous numbers ; but they do not
often threaten the life of the plant. Some of them only
scrape the surface of the leaves like the pear slug,
while others eat characteristic holes in them like the
blackberry saw-fly. A considerable number are gall-

THEIR RELATION TO PLANTS 77

makers, largely on willow, the excrescences being
quite characteristic.

The "horn-tails" have the ovipositor modified into
an augur-like process for making holes in plant tissue,
and the larvae are mostly borers: some in wood, most

FIG. 31. — The currant worm: a, adults; b, larvae in various stages of devel-
opment; c, pupa; e, eggs along veins on leaf.

of them in shrubs or grasses. These very often threaten
the life of the plant attacked, especially when wheat or
other grasses are infested. But on the whole the number
of these boring species is small, nor are they often
numerous in examples.

A very characteristic set of species is found in the
"gall- wasps" or Cynipids now ranked as a superfamily

78 INSECTS

under the term Cynipoidea. These gall-wasps produce
in the plants attacked abnormal swellings or growths
known as galls, which are constant for every species
and differ as the species differ. Thus for those forms
whose life history is known, the gall is as good an index
to its kind as a specimen of the wasp. And the re-
markable point is, that the gall is purely a production
of the plant and the insect has, apparently, nothing
at all to do with it. The female lays the egg arid in
due time a minute larva hatches. Immediately there
begins to develop around this larva an abnormal growth
centered by a smooth cell in which the larva lies, a
white helpless grub, feeding upon the exudations that
come from the inner side of the cell. The relation be-
tween the irritation set up by the minute larva just
out of the egg and the remarkably complicated struct-
ure of plant cells built up around it has never been
clearly elucidated and offers an excellent opportunity
for research. Some galls are spongy in texture, some
are solid; some are filled with radiating fibres extend-
ing from the central cell to the covering sphere; some
are no larger than necessary to accommodate the insect
and yet others are huge bladder-like affairs, out of all
proportion to the size of the larva. Some galls are on
leaves, some on twigs and branches and a few are on
roots. On the roots and stems the growths are often
corky or woody, and sometimes mere enlargements
of the normal growth. More generally the galls are
unicellular, i.e., they have only a single central cell
containing one larva; but very often also they are
multicellular, a large growth containing many larval
cells which, in turn, may be very regularly or very
irregularly disposed in the larger mass.

These gall-wasps have a number of very interesting
features. Some of them appear, year after year, males

THEIR RELATION TO PLANTS 79

and females, without variation; always making the
same kind of gall. Others appear in spring from over-
wintered galls, normal males and females: the latter
lay eggs, galls appear, but from them only females
make their appearance; these in turn lay eggs and from
their galls males and females appear again the year
following. This is termed an "alternation of genera-
tions" and so long as the galls are similar and the fe-

FIG. 32. — An oak gall, made by Cynips q-spongifica; a, showing the
larva in its cell; b, exit hole of adult.

males are similar, no confusion is caused. But it some-
times happens that the summer generation is very
different in appearance from the hibernating form,
while the gall itself is different and on a different kind
of tree, so that there appears to be no sort of connec-
tion between them until the life history has been com-
pletely followed out — no light task in species of this
character. For some species no males have ever been
found and, so far as we know, these are maintained
by parthenogenetic females alone.

8o INSECTS

It also happens sometimes that a normal constituent
of plant tissue, like tannin, is greatly intensified in the
gall structure which may contain many times more
tannic acid than any other part of the tree. The galls,
therefore, become of commercial value and in some
localities the oak forests yield a considerable revenue
from this source.

Few Cynipid galls are really injurious to the plants
on which they appear. Those on the leaves are never
so; those on twigs are rarely so; those on the larger
branches sometimes cause a choking and sometimes
a weakening that results in a fracture under strain;
but frequently a badly galled branch will in its de-
velopment split off and shed the old galls. Root galls
sometimes threaten the life of a plant; but most of
the fatal galls found on trees, shrubs, and vines are due
to other causes.

In the Diptera we have plant feeders in great variety ,
and many of them endanger the life of the plants at-
tacked; but they have a decided preference for soft
tissues and there are no borers in solid, living wood.

Among the long-legged, mosquito-like species with
long antennae, the crane-flies have larvae that live
underground and feed on the plant roots. They are
sometimes called "wire-worms" because of their long
slender form, and "leather-jackets" because of their
texture. They differ from the beetle larvae that are
also called wire- worms, by the more cylindric shape,
the more pointed head, and absence of legs. Their
feeding on roots is sometimes extensive enough to
cause the death of the plant attacked. The crane-
flies are the largest of the long-legged forms, some of
them measuring with legs extended nearly three inches.

The gall-midges are at the other extreme and in-
clude very small species with very long, often prettily

THEIR RELATION TO PLANTS

81

beaded antennae. Their larvae are little footless grubs,
peculiar by having a single chitinous rod or anchor-
like structure known as a breast-bone, which serves
to scrape the plant tissue on which the creature feeds.
These gall-midges or Cecidomyiids attack a great va-
riety of plants at all sorts of points, and cause a great

FIG. 33. — The pear midge, Diplosis pyrivora: a, female adult; c, pupa; other
references to structural details.

variety of deformations that are commonly known
as galls, although they differ totally in character from
the galls caused by the Cynipids. For instance, the
pear midge lays its eggs in the pear blossom; the
larvae enter the seed capsule of the fruit and the latter
becomes somewhat abnormal in shape so that to the
practised eye the galling is perceptible. The Hessian
fly lays its egg in the sheath of the wheat leaf near
6

82 INSECTS

the ground; the larva starts its feeding there and
causes an injury which the plant, in its efforts to repair,
marks by an enlargement. A midge lays its eggs in
the tip of a willow shoot, the larvae feed at the base
of the forming leaves and the plant becomes crippled,
producing a cabbage-like head instead of a shoot with
developed foliage. And so we have every gradation
from a feeding without any perceptible enlargement
or swelling at all, to a well-formed abnormity formed
by a crippling of the natural growth, and not a distinct-
ly separate structure, unrelated to normal growth.
There are other types of midge-galls, like those on the
grape, which are mere fleshy swellings of the normal
tissue, and sometimes more characteristic enlargements
of infested twigs; but generally no separable galls.

As to the actual injury caused, that varies enor-
mously. Many of the midge-galls cause no real or per-
manent injury whatever to the plant attacked. Others
destroy either the plant or the seed beyond all chance
of recovery. These midges are to be accounted among
the most serious plant enemies, although soft her-
baceous plants and grasses are more apt to suffer;
very few of them occurring in genuinely woody tissue.

Among the Muscid flies resembling in general type
and appearance the house-flies, the An thorny iids are
the most troublesome and dangerous. They attack
a very great variety of plants and may be miners in
the thick leafed forms like beets, or feeders in roots
like those of the radish, cabbage or onion. And these
root maggots are very generally fatal to the plant
attacked, so that their rank as .destroyers is high.
The maggots themselves differ very little from the
other Muscid larvae; in fact not at all to ordinary view,
and they gain their food in the same way by scraping
and disintegrating the tissue and then absorbing the

THEIR RELATION TO PLANTS 83

liquid mess. There is, in consequence, nearly always
an appearance of decay associated with the work of
such maggots, and that appearance is very real in
cases where the wounded surface gives entrance to
soft rots of various sorts. As for the leaf miners, their
work is not so destructive in character, although natur-
ally every injury that impairs the usefulness of the foli-
age to the plant, reacts upon the entire organism to
some extent.

There are other maggot-like larvae that work in
plant or fruit tissue such as the apple maggot, the
orange fruit fly and a considerable number of other
fruit flies which, while they seriously affect the com-
mercial value of the product, do absolutely no injury
to the plant, since neither the seed nor the tree itself
is affected. Only the pulpy covering to the seed is
harmed and that is of no importance at all to the plant
however much it may be to man.

We have thus reviewed very briefly the various
orders of insects, and have called attention very cur-
sorily to the kind of injury which is caused by them.
From the time it appears above ground to the period
of maturity, almost every species of plant serves as
food for insects; and if it survives their various as-
saults and reproduces its kind, its decay and return
to the inorganic constituents from which it made its
growth is hastened by yet other species. And that
applies as much to the forest giant, aged hundreds of
years, as to the humble cabbage plant that runs its
course in a single season.

CHAPTER IV

THEIR RELATION TO EACH OTHER

IT has been brought out, directly and incidentally,
that insects are among the most prolific animals. If all
the feeders on vegetable life were allowed to develop
absolutely without check during two successive years,
the first of them would see every green thing swept
from the face of the earth, and the second would destroy
all possibility of the future recurrence of fully 90 per
cent, of all the existing plants. And if during the same
period all forms feeding upon vertebrate life were
allowed to develop in the same way, our globe would
be a practically uninhabited and uninhabitable desert.

But the very fact that they are so remarkably
fecund is an indication that they have many dangers
to contend with and many difficulties to surmount
before reaching the adult or reproductive stage. Under
normal conditions and in the long run, one pair of
moths, producing say 500 eggs, are represented next
year by another pair of the same species, and no more:
that is, out of 500 eggs, producing 500 caterpillars,
498 are destroyed in some way. Naturally this varies
from year to year to some extent, favorable conditions
permitting an increase one year and causing a decrease
at some other period. And, equally of course, while
some broods may be completely destroyed, others
may all come to maturity.

Now the very fact that an insect exists at all, is
proof that it is adjusted to its surroundings, including
its parasitic and predatory enemies and all the other
natural checks. And when it occurs as an abundant

84

THEIR RELATION TO EACH OTHER 85

Ovarian
\Jubesmth

eggs

species it means that this abundance is normal, and
that the natural adjustments are such as to maintain
that abundance in relation to its food unless man in-
terferes, and the results of such interference will be the
subject of further discussion, later. The important
point is that a species abundant in number of specimens
has become so in spite of the combination of all its
natural checks and, condi-
tions remaining equal, will
maintain itself in the same
ratio, just as a rare species
barely maintains itself
against the combination op-
posing it. It happens again
and again that a common
species becomes more than
usually abundant, and it oc-
curs occasionally that a
species normally rare escapes
from its control and makes
its mark as an injurious
form. But even without
human interference this
rights itself in a season or
two: the common species

may even be reduced for a time to less than its usual
numbers, while the rare species drops back out of sight
of all but the collector. The checks or natural enemies
of neither form ever increase sufficiently under normal
conditions to do more than restore the original ratio.
What then are these checks that prevent with such
absolute effect any undue increase of a species despite
enormous reproductive powers? They are really very
numerous and of decidedly unequal effect on the dif-
ferent forms. We have weather, disease, insectivorous

FIG. 34. — Ovaries of a bee show-
ing the different parts.

86 INSECTS

animals of many species, birds and, last but by no means
least, in the war of insect upon insect, the predatory
and parasitic forms. It was almost inevitable that
in the course of development some originally plant-
feeding insect would find itself in position to get its
plant juices at second hand, so that, instead of feeding
upon plant tissue directly, it fed upon its next neighbor
and got the same material indirectly. We have, even
now, examples in Hemiptera and Coleoptera of species
that feed upon vegetable tissue and also upon other
insects when they get in the way; or of species which,
while normally predatory, occasionally feed upon
vegetation. In the Hemiptera I know of examples of
this kind in the Pentatomida and in Coleoptera they
occur in the Carabidce and Coccinellidce. And the
step from predatory to parasitic habits is an easy one,
albeit a much greater specialization. Insect feeders
upon vegetable life were first developed; predatory
forms came very soon afterward and occur in almost
if not quite all orders; parasitism on other insects
came much later, and is best developed in the highest
and most specialized orders, being practically non-
existent in the lower or primitive types. Parasites
on higher animals, such as the biting and sucking lice
which occur in the Neuroptera and Hemiptera, are not
in any way comparable with the insect parasites that
occur in the Hymenoptera and Diptera, to which highly
specialized and most recently developed orders the
great majority of all the parasites on insect life belong.
There are few true parasites in any other of the orders.
Among the Thysanura we have no parasites and no
predatory forms. In the Neuroptera we have many
decidedly predatory forms and the beginnings of par-
asitism. The Neuroptera as limited in Chapter I, con-
sists of a number of remnants of earlier types, agreeing

THEIR RELATION TO EACH OTHER 87

only in the fact that the wings have numerous longi-
tudinal and transverse veins, breaking them up into
many small areas so as to appear more or less netted.
But in the detailing of habits and suggesting lines of
descent, further subdivision is convenient.

Thus the Ephemerida or May-flies contain neither
parasitic nor predatory forms. In the larval or early
stages they live in the muddy bottom of streams, feed
on the organic life contained in this material and, in
the adult stage, do not feed at all. Yet it is here that
the highest orders get their start and in them predatory
and parasitic types are numerous.

In the Plecoptera or stone-flies we have a similar
record except that the mouth structures in all stages
are much better developed. Here the larval stages
are passed under submerged stones, usually in running
streams, and the food consists of such floating organic
material as is carried in. The adults in s/pite of their
rather well-developed mouth organs have not been
observed feeding.

The Mallophaga or biting lice are animal parasites
and are dealt with in Chapter VII, and the Corrodentia
or book- and bark-lice are feeders on dry or dead or-
ganic matter; not really scavengers, but nevertheless
removers of dead material.

The order Isoptera, containing the Termites or
white ants, is interesting from its communal life and
will be referred to again; but it depends entirely upon
vegetable matter for its subsistence and mainly upon
dead tissue.

The order Platyptera is the first of the Neuropterous
types to contain predatory forms and, while it is aquatic
like the Plecoptera, has the metamorphosis complete and
is altogether much better developed, albeit the adults
are loose- join ted and flabby enough, when handled.

88

INSECTS

The larvae have the jaws and other mouth parts well
developed and feed upon other soft-bodied aquatic
forms. They assist in checking the increase of the
May-flies and stone-flies, and are themselves hunted
by fish, which keep them down to normal numbers.

CL

FIG. 35. — The " hellgrammite " or "Dobson": a, larva; b, pupa; c, male adult;
d, head of female.

The order Neuroptera, strictly speaking, contains
only predatory forms and the beginning of parasitic
habits. With few exceptions the species are terrestrial.
The families Coniopterygidce, Chrysopidce , Hemerobiidcz
and Myrmeleonida , are rather similar in the larval

THEIR RELATION TO EACH OTHER 89

stage; the body being more or less ovate, set with
lateral tubercles giving rise to groups of bristles, while
the mandibles are long, slender and pointed, peculiar
in being grooved on the inner side so that the body
juices of the prey may run down through them into the
mouth cavity. The Chrysopidce are known as Aphis-
lions, and when they capture a plant louse it is held
up, impaled on the mandibles, until the juices are all

FIG. 36. — A lace-wing fly, Chrysopa oculata: a, eggs on stalks; b, larva; d, same
feeding on pear psylla; e, the cocoon from which /, the adult, has escaped.

absorbed; then the dry carcass is thrown away. The
Myrmeleonidce or ant-lions build a pit in the sand to
entrap any unwary insect that may come along, and
anything that does come is seized in the same way and
exhausted, the empty shell being thrown out later.
Not all ant-lions build pits and not all the members of
the families named agree in all respects with the general
statements as to larval form and characters; but for
the majority of the species that come under observa-
tion they are correct.

90 INSECTS

The Raphidiidcc are very curious creatures peculiar
to the Pacific Coast, in which the head and prothorax
of the adult are greatly elongated and it, as well as
the slender elongated larva, is predatory. In the pre-
ceding families, while the larvae are voracious feeders,
the adults feed little or not at all.

The Mantispida are similar to the Raphidiidce in
the elongation of the prothorax; but the head is much
shorter and the fore legs are enormously developed
for grasping, this series being also predatory in the

adult stage. But the interest-
ing feature is that we find in
the larva the first tendency
toward parasitism and the
specializations accompanying
it. The eggs are laid on stalks
like those of the Aphis-lions,
but the resulting young live
for months without food, until
FIG 37. — Mantispa species the egg sacs of certain Lycosid

from above and in outline from

side. spiders have been formed.

The lucky larva that finds

such a sac bites its way through the covering and feeds
upon the contents. As it feeds and grows it loses its
large head and long legs, and becomes helpless except
to feed upon the surrounding material which serves
to bring it to maturity. While in a general way these
insects are said to be parasitic in the egg sacs of spiders
yet this is not really a true parasitism at all; it is
simply a feeding upon the eggs and young spiders as
any predatory species might feed upon them, the only
difference being that here the larva makes itself at
home and does its feeding gradually, so as to secure
enough to reach maturity.

The order Mecoptera is a curious one, only a few

THEIR RELATION TO EACH OTHER 91

genera and species remaining as representatives in
our fauna. All of them are feeders on animal matter
and most of them are predatory in all stages. The
best known forms are the scorpion flies, so called from
the curious anal appendages of the male, which bear a
remote resemblance to a scorpion tail without its ter-
minal sting. The larvae, which are somewhat caterpillar-
like, live under ground and prefer rather damp places.
There are not enough of the insects to make them of
any importance as checks to anything in particular,

FIG. 38. — A Panorpa or scorpion fly and its larva.

and as they feed rather indiscriminately on soft-bodied
insects, chiefly flies, they are of no economic value.
It is probable that this order represents the type from
which the Diptera and Hymenoptera were derived.

The caddice flies or Trichoptera are aquatic in the
larval stages and as aerial adults do not feed at all.
As larvae they derive their name from their habit of
making cases or "caddices" of various shapes from
little sticks or stones closely fitted and held together
with silk. Some of the species are feeders upon vege-
table matter, others appear to be predatory, or feeders
upon animal matter at least. They are very numerous
in specimens and species, but naturally do not influence

92 INSECTS

any terrestrial forms. The adults have the wings
covered with fine hair and some of the small forms
resemble Tineid moths so closely that they are con-
fused with them. It is believed, indeed, that this is
the direct ancestral form of the Lepidoptera.

And now comes the order Odonata, containing the
dragon flies, large and small and all of them predatory
in habit in all stages. As larvae they are aquatic, living
in ponds, streams or even the more permanent pools

FIG. 39. — Dragon fly and its development: larva and pupa feeding at i and
3; 2, nymph ready to change; 4, pupa skin from which 5, the adult, has emerged.

and puddles; some of them active, moving about
freely among the vegetation, others sluggish, lying in
the soft bottom mud or under stones or other shelter,
waiting for things to come their way. They are pecu-
liarly adapted by their elongated hinged under lip,
or labium, to reach such small creatures as fate may
send within half an inch of them and, with a little for-
ward jerk of . the body and a rapid extension of the
armed labium, the prey is seized. This prey varies in
character according to the habits of the larvae. Some
of the more active forms destroy a large number of

THEIR RELATION TO EACH OTHER 93

mosquito wrigglers and display surprising skill in cap-
turing them. Others take in anything that comes along,
be it insect, crustacean, or even small pollywog or fish.
They have no aversion to their own kind and will eat
each other if food is scarce or not easily obtainable.
As for the adults, anything that comes within their
range will answer as prey ; but in general small flies are
the most abundant victims. The common name "mos-
quito hawk" indicates one common article of food,
and there is no doubt that a very large number of
specimens is eaten. In some cases the mosquito pest
may even be materially lessened by them during the
period of adult flight; but they scarcely rank among
the really controlling " checks because they are active
only during the day while the mosquitoes prefer the
night for their flight; and the dragons prefer the open
sunlit area around ponds or along streams, while those
mosquitoes that fly at all during the day prefer shel-
tered, shaded and darkened places. Most of the dragon
flies are simply general predatory feeders on any soft-
bodied insects which they can overtake, rather than
specific enemies of any one form.

In the order Hemiptera there are no parasites on
insect life. The lice, parasitic on vertebrate animals,
are elsewhere considered, and nowhere else do we find,
in this order, any approach to true parasitism. Of
predatory forms there are a large number; indeed
among the aquatic species the majority are predatory,
feeding on other water insects and even fish. Among
these the little Corisidce and N otonectidce , water-boatmen
and back-swimmers, are especially vicious and active,
easily forming a very notable factor in the control of
aquatic insect life.

Among the terrestrial forms the entire series Hom-
optera lacks predatory types; in the Heteroptera we

94

INSECTS

find that modification of habit which is elsewhere re-
ferred to — a tendency to get plant juices at second
hand, by sucking the juices of such soft-bodied larvae
as have just fed upon plant tissue. This is found in
quite a large number of the families, making a con-

FIG. 40. — The wheel-bug, Prionidus cristatus, in all its stages.

siderable series of species that feed indifferently on
plant or soft insect tissue. But there is also a large
number of species with short stiff beaks and small
narrow heads that are distinctly and exclusively pred-
atory. These are the Reduviida commonly known as
" pirate " or " assassin bugs " from their habit of stabbing
or piercing the specimens upon which they feed.

THEIR RELATION TO EACH OTHER 95

These bugs are of considerable importance as checks
to certain plant feeders and as they feed in the same
way throughout their life, each individual accounts
for a notable number of victims. Their weak point
is the limited power of reproduction. Most of them
lay only a small number of eggs and have only a single
or at most two broods during the season. As a control
factor, therefore, they lack flexibility and do not rise
to any sudden increase in the plant feeders. There is
a common species that in New Jersey feeds on the
larvae of the elm-leaf beetle, and each season is busily
engaged on the infested trees in fair numbers. In
years when the beetle is not abundant the marks of
its feeding are quite conspicuous; but in a season when
the beetle is unusually plentiful and destructive, the
bugs are present in almost exactly the same numbers
and their work is absolutely unnoticeable when effec-
tiveness is most urgently needed, nor does there seem
to be any considerable increase during the season fol-
lowing such an abundance. This same feature exists
with most of the species known to me and limits their
usefulness to very narrow bounds; they constitute
one check which is almost a fixed quantity and to which
the host insects are adapted.

The order Orthoptera, including roaches, grass-
hoppers, locusts, crickets and the like, contains no true
parasites and but few predatory forms. Some of the
roaches are omnivorous and pick up occasional speci-
mens of insects and animal matter; but they can
scarcely be ranked as important checks to any other
species. And so the Mantids or soothsayers are vora-
cious feeders, preying upon almost any sort of insects
which they can secure; but they are few in number
both as to species and specimens, while their food is
so various that they are not of importance in the life

96

INSECTS

cycle of any one kind. Crickets there are of many
sorts, and some of these are general feeders, eating
each other as freely as they do vegetation and other
things. The tree-crickets are more definitely predatory
in habits and feed largely upon plant lice; but they
also are too few and too slow in reproducing to be able
to exert a very important influence on the increase of
their prey. Furthermore, they are limited as to the
places which they inhabit, and no field crops of any
sort harbor them.

FIG. 41. — Stylops and its development: a, female in body of bee; b, same in
outline; c, d, male from above and side.

In the order Coleoptera or beetles we have few
truly parasitic forms. We may for the present consider
the family Stylopidcz as true Coleoptera and these are
found in the abdomen of various insects, chiefly bees
and wasps although some Hemiptera and perhaps
other orders are also infested. But they are so very
rare that they exert little influence on the numbers
of the species which they infest. Their life history
and complicated metamorphoses are extremely inter-
esting, the female being wingless and living in the
abdominal cavity of its host, with the head projecting

THEIR RELATION TO EACH OTHER 97

between the segments. The young are minute, active
creatures like those of the blister beetles, and run
about freely until they find some suitable host in which
their future development may be continued. Then
they lose their feet and prominent jaws, becoming
grub-like and inactive as the necessity for seeking
food is removed.

The blister beetles or Meloida are semiparasitic
in habit and are quite numerous in specimens and
species. Some of them live in the egg-pods of grass-
hoppers and others in the nests of digger bees, chiefly
Andrenidce, feeding on the food stored by their hosts
and, incidentally, devouring the egg or young larva
of the bee. These blister beetles will be referred to
again in their relation to man, but in their relation to
the insects upon which the larvae feed they rank as most
effective checks. The female beetle lays her eggs on
flowers or on the ground as the case may be, and the
resulting larvae are active creatures with long legs
and large jaws known as " triungulins. " These are
able to go for long periods without food and they seek
either a grasshopper egg-pod or some plant or flower
frequented by bees, as the need may be. The forms
that hunt egg-pods, when they succeed in finding one,
immediately begin to feed. The forms that wait for
bees attach themselves to almost any hairy insect
that comes along and the lucky specimen that gets
upon a bee of the right kind is carried by it into its
burrow. When the bee with its burden of pollen plus
the parasite gets into the cell which it is filling with
food for its larva, the triungulin slips off, devours the
egg of its host as soon as laid, and that suffices to
bring it to the end of the first stage. From this point
the changes in both kinds of larvae are similar. They
are in direct contact with abundant food, the legs
7

98

INSECTS

and large jaws are useless and they enter what is known
as the "Carabidoid" stage in which they resemble the
larvae of ground beetles. Continued good feeding re-
sults in a further reduction of parts and the third instar
is even more grub-like and therefore termed the "Scar-
abidoid" stage, during which it exhausts its food sup-
ply,—either the egg-pod or the stored material in the

FiG.,42. — Development of a blister beetle: a, grasshopper egg pod with tri-
ungulin at // b, a few grasshopper eggs; c, triungulin; d, carabidoid larva; e,
scarabidoid larva.

bee cell. Then the outer skin hardens, the larva loses
shape and enters the coarctate stage in which it lies
dormant until the period when the adult is due to
appear. When this comes, the hardened larval skin
is shed and the true pupa, of the ordinary beetle type,
appears. When the proper hour arrives, as if at the
striking of a clock, the transformation to the adult
is completed and the blister beetles emerge, ready to
feed and propagate. And now the story changes, for
while we can have only words of praise for those larvae

THEIR RELATION TO EACH OTHER

99

that feed on grasshopper eggs, the adult beetles almost
without exception are devourers of plant tissue. Their
habit of coming to maturity at about the same time
brings clouds of them upon their food plants at once,
and gardens and certain truck crops suffer. It becomes
a question then, whether the insects are economically
more useful as destroyers of grasshoppers or more
destructive as feeders on crops. As to the species
feeding in the nests of bees, they are without question
economically injurious in all stages.

FIG. 43. — Two common blister beetles: a, Macrobasis unicolor; b, Epicauta
Pennsylvania .

But there can be no doubt either that in regions
where grasshoppers are very abundant, as they are
in the Rocky Mountain and some of the southwestern
areas of the United States, these blister beetles are a
most important check and one that has a large amount
of flexibility in effectiveness despite the fact that there
is only one annual brood. This is obtained by the
large number of eggs laid by the female, which in some
species runs into the thousands. The adults make no
attempt to place these near egg-pods, but only on
ground where such pods are likely to occur. It is up
to the young larva to find its own hotel accommoda-
tions or starve to death. When grasshoppers have been
scarce and pods are widely scattered, a very large per-

ioo INSECTS

centage of the triungulins never get beyond that stage;
but when there has been an abundance of hoppers and
egg-pods are numerous, matters are easier for the
enemy and a larger percentage secures food. In this
way it happens that after a season of grasshopper
abundance a season of blister beetle abundance is al-
most certain to follow, and any abnormal increase of
the former is almost sure to be checked by the cor-
responding increase of the latter.

A very material change is introduced by the migrat-
ing habit of some of the host species. Blister beetles
are not great travellers, while a grasshopper swarm
may fly for hundreds of miles, clear out of the faunal
range of their check. But in such instances, while
they may have a year or two of unusual freedom for
development, they become in time victims of the un-
favorable climatic conditions in their new surroundings
and are crowded back into their natural domains, under
the control of their normal enemies.

While, in a way, it is correct to refer to these beetles
as parasitic, they are not really more so than the Man-
tispids that feed in spider egg-sacs, and in the case of
those feeding in the cells of bees they are even less so.
For here the egg or young larva of the bee is only eaten
to remove the owner of the stored food and the real
object of the "parasite" is the stored provender. It
is therefore a robber rather than a parasite, unless we
use the latter term in a very broad sense.

As to predatory forms, the order Coleoptera con-
tains a great number. All those species that have
filiform or thread-like antennae, comprising the fami-
lies Cicindelidce (tiger-beetles), and Car abides (ground
beetles), Haliplidce (diving beetles), and Dytiscidce
(water tigers), are predominatingly feeders upon other
insects. A few feed on vegetable tissues as well or as

THEIR RELATION TO EACH OTHER 101

an alternate, and a very few seem confined to a plant
diet; but, as a whole, this immense series of species
feeds on other insects in both larval and adult stage.
Most of them are rather general feeders, taking all
things that come in their way, and they are not at all
particular whether this prey is another predatory form
or a plant feeder. And we have species that frequent
trees, shrubs and flowers as well as those confined to
the ground: the smaller forms capable of feeding only
upon eggs, the larger climbing trees for the caterpillars

FIG. 44. — A caterpillar- hunting ground
beetle and its larva.

FIG. 45. — A common type
of ground beetle.

to be tound on them. Some of the species have the
advantage of being able to adapt themselves to the
conditions found in cultivated fields and orchards and
the number of larvae and pupae of plant-feeding forms
that go under ground for pupation or hibernation that
are destroyed by them is beyond all computation.
While I do not recollect at this time any species that
devotes itself to any one particular kind of prey, there
is no sort of doubt of the reality of the check which the
ground beetles exercise over the increase of plant-
feeding forms— ^especially those which pupate on or
under the surface. But we must limit this praise just

IO2

INSECTS

a little: none of them bother with such small fry as
plant lice and scale insects and their cannibalistic
habits do much to limit their usefulness.

In the series of rove-beetles or StaphylinidG, which
are scavengers as a rule, there are many small species
that are predaceous, and what a battle goes on between
these and other breeders in or among damp, decaying
vegetation we can only guess when, with a sieve, we
collect out of a handful of forest leaves sometimes a
dozen species of adult beetles and hundreds of minute
larvae and wriggling creatures of
all sorts. The collector who cov-
ers a dozen miles in a day and at
night has a box of butterflies,
beetles and other insects to show
for it, has seen much; but he has
seen nothing of the intimate life
of insects as compared with the
man who has spent the same
period in an open glade in a
deciduous wood. It is not in the
open air and on the surface that

the most interesting matters are to be observed; it is
under the shelter of fallen leaves, in the very centre
of a decaying stump or log, or beneath a stone and
sometimes deep in the very soil that insect life man-
ifests itself in its most wonderful ways. It means
patient watching and persistent study to unravel all
these mysterious happenings that come to our atten-
tion, and it is because we have not yet done enough
of this, that we know so very little about these rove-
beetles and their minute allies; but we do know that
they are not all scavengers at any rate.

Among the Coccinellidcz popularly known as "lady-
birds," "ladybird beetles" or simply "ladybugs,"

PIG. 46. — A rove-beetle
and its larva.

THEIR RELATION TO EACH OTHER 103

we find a very decided specialization as to the char-
acter of the prey. Almost all the members of the family
are predatory during the larval stage, but they are not
general feeders; some of them are even very closely
limited as to food, and form specific checks of the very
highest importance. Remove one of these checks and
the host may become immeasurably destructive: re-
store it and, no matter how much the host has gained,
the check will regain control. Plant lice and scale
insects are the especial prey Df these beetles and the
facts just recited are within the observation of almost
every student of entomology. We are in the habit of
thinking of "ladybird beetles" as being red or yellow
in color with black spots, and as nearly hemispherical
or at least convexly oval in form. The form is quite
constant indeed, but the colors are by no means all
gay. Besides the red, yellow and black species there
are those that reach to metallic blue and yet others
that are dull or shining black with very little if any
maculation. The variation in size is also considerable,
for while we have giants half an inch in length, we
have Mso midgets not much more than one one-hun-
dredth of an inch over all.

Is there any unusual increase of a plant louse or
scale species: in a few weeks their ladybird enemies
will be found to be on the increase as well, and very
often, even before the end of the season, the control
will be re-established; for many of these species have
several broods during the year and plenty of food is
conducive to quick development. Even a normally
rare species may under such a spur become abundant.
An example of such control I have seen on several
occasions in the case of a plant louse that infests Nor-
way maples, by the i5~spotted ladybird, which is not
usually common. When weather conditions during

IO4

INSECTS

early spring favor the plant lice they increase until
June, when the first hot, dry spell puts a period to their
work. An unusually cold, wet spring will be accom-
panied by an unusual abundance of lice, and on three
occasions within twenty years when the cold, wet
weather extended into late June, infestation became
so serious that the leaves were covered with honey-
dew and soot-fungus, so that they choked and began

to drop. But about this
time the ladybirds were
also in the running and
had become so numerous
that they were fast reduc-
ing the plant lice and put-
ting a period to the infes-
tation. And then came the
long deferred hot spell in
early July, wiping out the
plant lice as with a sponge
and leaving thousands of
beetle larvae without food.
What did they do? First
the larvae ate all the eggs

of their own kind yet on the leaves; then they ate the
helpless pupae getting ready to change to the adult stage ;
then the large larvae ate the smaller ones and as they
became full fed and pupated, they in turn became vic-
tims to those that had escaped the slaughter. And before
the end of July the 15 -spotted ladybird beetle was again
a rare insect and no outward sign remained to tell what
crowds of them had been on the scene a month before.
But not all Coccinellids are able to increase so
rapidly; some species being strictly limited to one
brood. The cottony maple scale in the east is con-
trolled by the signate ladybird, Hyperaspis signata,

FIG. 47. — is-spotted lady-beetle: a,
larva; b, pupa; d-g, adult varieties.

THEIR RELATION TO EACH OTHER 105

a little black species with one red spot on each wing-
cover. About once every decade the scale escapes con-
trol, and for a series of three or four years becomes in-
creasingly abundant so that tree owners are thoroughly
scared and demand remedial measures. Experience
has enabled me to assure these owners that when mat-
ters are apparently getting serious, the worst is over;
because by the end of the third year the Hyperaspis
has caught up with its host and almost every scale

FIG. 48.— The signate lady-beetle.

egg mass contains one or more beetle larvae feeding in
and upon it. The year following, scales may be difficult
to find and the Hyperaspids are forced to other species
upon which they fail to maintain themselves and
perish — all save a few that find enough congenial food
to maintain the species.

What happens when an insect of this character is
entirely freed from its normal check, was demonstrated
in California when the cottony cushion scale, I eery a
purchasi, was introduced from Australia without the
Vedalia cardinalis. In a few years the Icerya had as-

io6 INSECTS

sumed the dimensions of a calamity and, as one excited
grower informed me, even the hitching posts became
infested. The introduction of the ladybird enemy
which had been discovered in the native home of the
scale turned the tables at once. In less time than it
had taken the scale to overrun the country, the Vedalia
aided by artificial breedings and distribution, cleaned
it out, until now both scale and beetle barely maintain
themselves. There are undoubtedly many other similar
relations, but on this point we have yet much to learn.
It rarely happens that a Coccinellid beetle ranges
far from its normal food or a very closely allied species,
and- however flexible and adaptable it may be in rela-
tion to its normal prey, it generally fails when pitted
against an unknown or new form. The San Jose or
pernicious scale is a rather close ally of several of our
native armored scales, and the Coccinellids that feed
upon these also attack this introduced form; but east
of the Rocky Mountains none of them exercise the
least real control over it. On the Pacific Coast the
Chilocorus bivulnerus or twice-stabbed ladybird does
act as an effective check because, having several broods
during the season, it becomes plentiful enough to de-
vour a large percentage of the hibernating forms. In
the east this same species has only a single brood and
is absolutely impotent. And when we brought in the
closely allied Asiatic Chilocorus similis to help us out,
that flourished for a year or two in one of our southern
states and then died off. In the more northern states
it never gained a foothold at all. The little Smilia
misella, native to the Atlantic states, becomes plenti-
ful enough at times, and may be found feeding even in
midwinter; but while it undoubtedly helps to keep
down numbers somewhat, it cannot be considered an
effective enemy.

THEIR RELATION TO EACH OTHER 107

And so we have in these Coccinellid beetles a series
of the most highly important checks to some of the
most destructive insect types, the removal of which
would cause a serious derangement of conditions as

FIG. 49. — Chilocorus similis: a, beetle laying egg under scale; b, c. scales
showing egg in place; d, egg in scale; e, egg; /, eggs under bark flap; g, same,
natural size; h, i, young larvae; /, same feeding.

they at present exist. These checks are flexible within
limits, and automatically, by simply devouring each
other, restore themselves to inconspicuous numbers
when their services are no longer needed. But we are
not yet in position to train them to our service nor to
induce them to feed on unfamiliar species.

io8

INSECTS

In the family Lampyrida, containing the fire-flies
and soldier beetles, and among the flower beetles of
the families Malachidcs and Cleridce, we have a series
of species of which a large number are predatory in
the larval stages, while the adults are feeders on pollen
or vegetable tissue. Among the fire-flies some of the
larvae are feeders on snails, while others, with those
of the soldier beetles, are limited to an insect diet.
They are largely found on the surface of the ground
or just beneath it, and they get a great many of the
plant-feeding forms that go underground to pupate.

Withal they are rather gen-
eral feeders and not specific
checks. Among the Clerida
the majority of the species
are predatory on wood-boring
forms, and some of them are
specific checks on the bark-
boring Scolytids. The larvae
are elongate, rather slender
and flattened creatures with

a large head and prominent jaws, and they enter
into and follow the galleries of their prey, which is un-
able to escape and absolutely incapable of resistance.
Under normal conditions these species are capable
of dealing with a large percentage of the wood-borers;
but it seems rather easy to turn the scale against them,
and the Scolytids often do a great deal of injury when
favored by careless forest practice, fire injury or other
checks to tree development. Taken as a whole the pred-
atory and semiparasitic forms among the beetles are
a very important factor in keeping down plant-feeding
forms and in preventing the undue increase of other
species which are not directly harmful and may even
be beneficial.

FIG. 50. — A soldier beetle and
its larva.

THEIR RELATION TO EACH OTHER 109

The order Lepidoptera contains no parasites and
very few species which, in the larval stage, are preda-
tory. In the adult stage the mouth structure of butter-
flies and moths precludes their feeding on other than
liquid food where they feed at all. A very few of the
larvae or caterpillars are predatory, feeding on scale
insects or plant lice. Generally speaking these insect-
feeding caterpillars are rare; but that of the little
Phycitid Lcetilia coccidivora is really a very effective
control for certain of the soft scales. It is a species
that belongs to the same series as the flour moths and*
meal moths, making the same sort of silken tube as a
home; only, instead of webbing together kernels of
wheat, etc., it spins up a mass of scales and feeds upon
the eggs or young even before they have issued from
beneath the mother body.

In the order Diptera we have a very interesting
mixture of forms, including many that are of the high-
est importance as parasitic or predatory checks to
other species; but we are less able to limit these species
to certain families. Here we may have, in apparent
close relation, species that as larvae are plant feeders,
scavengers and true parasites; and there is nothing
in the adult which indicates the habit of the larva,
so far as our studies have yet carried us. Even in the
midges, which are certainly to be ranked as plant
feeders, there are a few that have been credited with
feeding on certain of the smaller plant lice. Among
the Culicidaz or mosquitoes there are a number of larvae
that are truly predaceous, and a few of them, like those
of Psorophora, are veritable wolves among the other
wrigglers. They have the same fault that I have
already deplored for other species : — they limit their own
increase by feeding upon their brethren when other
wrigglers have given out.

no

INSECTS

The blood-sucking flies are considered in another
chapter and have no important relation to other in-
sects, although some of the larvae, notably those of
the Tabanidce, or horse-flies, live to some extent on
other insect larvae inhabiting swampy and marshy
soil. The robber flies of the family Asilidce are veritable
falcons of the insect world and capture their prey by
pouncing upon it in flight, sucking its juices by means
of their powerful battery of lancets, and then discard-
ing the dry husk. They are not at all particular as to

what sort of species comes
into their way, — a fly, a bee,
a beetle or a butterfly, — any-
thing answers. And so while
they devour an enormous
number of specimens, they are
not specific checks to any line
of plant feeders. Indeed, as a
matter of fact the robber flies
do not discriminate in the
least: they will as cheerfully
devour a dragon fly or a
ground beetle as a butterfly or
June-bug; it is all a matter of which comes along first.
Among the bee-flies or Bombyliidce, we find in the
larvae both parasitic and predatory types, and forms
which, like the blister beetles, devour the stored ma-
terial of bees and other species. The adult flies them-
selves are often bright colored and hairy, some of them
resembling bumble-bees in appearance and some with
long, bee-like mouth parts. In the larval stage some
are true parasites on caterpillars, notably cut- worms,
while others feed in the egg-pods of grasshoppers,
devouring all the eggs in a single pod in attaining full
growth. Those that feed on the stored food in bee

FIG. 51. — A robber fly, with larva
and pupa.

THEIR RELATION TO EACH OTHER in

cells are cuckoos in habit and are effective in limiting
bee increase. As parasites they are not of so much
importance, for while they do their share in limiting
numbers under normal conditions, they do not readily
increase in abundance when the host becomes un-
usually plentiful. Of much greater importance are
those species that depend upon grasshoppers; for
these do really aid in effective control, the larvae in-
creasing in relative numbers as the egg-pods themselves

FIG. 52. — A bee-fly and its pupa.

become plentiful. There are other predatory larvae
among the Empidce or dance flies and similar small
families; but none of any great importance, until we
reach the Syrphidce or flower flies. Among these we
find a large number that are specific feeders on plant
lice and among their important checks.

In this connection it is interesting to note that in
every order in which there are predatory insects at
all, there are some that feed largely or exclusively on
plant lice. We will also find, in another connection,
that these same plant lice are also seriously influenced

ii2 INSECTS

by diseases and weather conditions, and yet, in spite
of all these factors, some species escape from their
checks almost annually to the greater or less detriment
of the plant hosts. And they always maintain them-
selves as against all these combined checks even when
each exercises its maximum influence. It is easily
appreciable, therefore, that when one or two of these
factors fail, e.g., weather and diseases, as not infre-
quently happens, it demands a great increase on the
part of the other checks to prevent the Aphids from

FIG. 53. — A Syrphid fly, Mesograpta polita.

getting out of hand altogether. The Coccinellid beetles
have been already referred to in this connection and
the larvae of the Syrphid flies make a very good second.
The flies lay their eggs in the very midst of the lice and
the resulting larva, which is a slug-like creature with-
out legs and with a very extensile anterior portion
of the body, begins feeding at once on the specimen
nearest at hand. This feeding is interesting, for the
larva fixes the little hooks that serve it as jaws into
the body of the louse, lifts it high in the air, and holds
it thus helpless, until the juices have been completely
extracted. As each of these slugs feeds almost con-
tinuously from ten days to three weeks, it gains grad-

THEIR RELATION TO EACH OTHER 113

ually even on the plant lice surrounding it, and not only
checks increase but lessens infestation. Not all the
Syrphid flies are carnivorous, however; quite a num-
ber are scavengers, some are pollen feeders and others
live in the tissues of succulent leaves or stems.

The really important parasitic group is found among
the Tachinid flies and their close allies resembling
house-flies, blow-flies, flesh-flies and others of that
character. Some of them — the majority indeed — are
inconspicuous grayish flies of moderate size; others are
metallic blue or
green, with or with-
out stripes, more or

FIG. 54. — Syrphus

larva eating plant FIG. 55. — A Tachinid fly: its eggs on body of
louse. caterpillar, larva and pupa.

less spiny, while a few are large, set with long bristles
and marked with contrasting colors, appearing formi-
dable and dangerous, even if they are not actually so.

These flies lay their eggs on a variety of insects,
but more frequently on caterpillars, and may be said
to be specific checks to a great variety of cut- worms,
including the army-worm. The eggs are often laid on
the outside of the caterpillars just back of the head
where the insect cannot reach them, and as they are
white and of good size, they are easily seen. These
Tachinids come nearer to being able to keep up with
the increase of their hosts than almost any other forms
that I know, and I have on several occasions seen army-
8

ii4 INSECTS

worms on the march, almost every one of them with
the seeds of death conspicuously placed upon them.
Out of hundreds of pupae gathered where armies had
been feeding, only single examples of moths were ob-
tained.

And in this connection we might note that a check
to the further increase of any plant-feeding species
does not necessarily mean an immediate cessation of
injury. Indeed in the armies of parasitized caterpillars,
every one fed until it was fully grown, and so far as
injury to the crop was concerned, it made not an ounce
of difference to the owner of the grain. And so we
must realize clearly that all these natural checks are
not imposed to prevent the plant-feeding insects from
injuring the farmer's crop, but simply to prevent undue
increase in relation to the surroundings and to preserve
the balance of nature.

Yet these Tachinid flies are among the most effec-
tive engines of destruction to the species which they
infest. They develop quickly, the females lay a large
number of eggs and they are themselves not seriously
affected by secondary parasites. They are therefore
able to maintain their relative proportion to their host
no matter how rapidly that multiplies because of the
removal of other checks.

Not all Tachinids lay their eggs directly on the
body of the host. It has recently been demonstrated
by a series of most interesting observations made in
the course of the gypsy moth work in Massachusetts,
that some species lay very small eggs on the leaves of
infested trees and that these eggs, eaten by the cater-
pillar with the leaf tissue, hatch when they get into
the stomach and bore through the walls into the body
cavity. Yet other forms lay their eggs on leaves, on
which caterpillars are feeding, fastening each to the

THEIR RELATION TO EACH OTHER 115

surface by a little capsule which serves to hold the
active young larva that hatches almost as soon as the
egg is laid. Sooner or later the feeding caterpillar
comes within range of this waiting maggot and then
with a dart the parasite hooks into the skin of its host,
is torn from the capsule attached to the leaf and bores
its way in. It will be readily appreciated that this
plan of scattering the numerous minute eggs over the
foliage on which caterpillars are feeding is likely to
reach the hosts in proportion to their abundance.
If, for instance, a brood of gypsies completely strips
a tree, every Tachinid egg on it will also get into the
caterpillar stomachs to the undoing of a vast percentage
of them. It seems like a hap-hazard way of doing
things and, no doubt, when caterpillars are scarce,
very few of the thousands of Tachinid eggs ever find
their way into any appropriate host.

It is in the order Hymenoptera, including the bees,
wasps, ants and the like, that we find the most inter-
esting specializations in the way of predaceous and
parasitic habits; specializations so numerous and
interesting that they demand volumes for their proper
presentation and can be only referred to here.

First of all, there is that enormous series of solitary
wasps, including the mud- wasps, digger-wasps, wood-
wasps and whatever other modifications of the term
may be employed; all of which make cells of some
kind either in the ground, in pithy stalks, against an
angle, in a crevice or even attached to a twig, and these
cells are stored with food enough to bring the larva to
maturity. Most of the wasp larvae are helpless, foot-
less creatures, absolutely incapable of seeking their
own food, and they depend altogether upon the store
that has been gathered by the parent, and that store
consists largely of insects or spiders, which are par-

n6

INSECTS

alyzed by stinging the nerve-centres and then retain
life enough to remain without decaying until the wasp
larva has reached maturity. One of the commonest
examples of this sort is seen in the shapeless cell made
by our blue mud- wasps under porches, between the
slats of shutters, under the eaves or even in garrets.
If we open one of these cells in summer we find it stored
with small motionless caterpillars or spiders, and either
an egg or an actively feeding wasp larva among them.

FIG. 56. — A potter- wasp, Eumenes fraterna, at a, its cell b broken open at c, to
show stored caterpillars.

On the same order, but much more neatly built, are
the mud cells of the potter-wasps, which we find fre-
quently attached to low bushes. These are usually
filled with small caterpillars, all very much of a size,
and so closely packed as to fill the cell completely.
As every one of these cells requires from ten to twenty
larvae to fill it and a single wasp makes a dozen or more
cells, the number of specimens thus used up becomes
quite a factor. Not all wasps feed on caterpillars; in-
deed, there is scarcely an order that is not fed upon.
Some digger-wasps fill their cells with grasshoppers;
others, that make their cells in the hollow shoots of

THEIR RELATION TO EACH OTHER 117

pithy plants, collect plant lice, the larvae of small beetles,
flies, or even other Hymenoptera. There is hardly a
species so small as not to be attractive to some of the
smaller wasps, and on the other hand, the largest Cicada
or tarantula is not safe from these formidable enemies.
When large species are fed upon, a single specimen
often serves to bring a larva to maturity. The "taran-

FIG. 57. — Sphecius speciosus carrying a cicada to its home.

tula hawk," when it has succeeded in finding a suitable
spider, and has succeeded in quieting it with the formi-
dable sting, buries its prey and lays a single egg on it.
We have quite a number of wasps that do little more
than bury their host and lay an egg on it. The hand-
some large Sphecius that preys on the Cicadas or dog-
day harvest-flies, makes a burrow with several laterals,
in each of which it stores a specimen or two which
serve to bring to maturity one of the wasp larvae.
There is an exotic species living on one of the large
roaches, which, after stinging its prey so as to deprive

n8 INSECTS

it of voluntary motion, is said to seize it by an antenna
and lead it into a sheltered spot before it deposits the
egg. The roach simply stays where it was led until
the wasp larva kills it by feeding.

This method of stupefying prey is a very high
specialization and the stinging is by no means a hap-
hazard one. The wasp seeks the thoracic ganglion of
the nervous system of adult insects, and may sting
several ganglia in caterpillars, to make them entirely
quiet. The poison introduced is said to resemble formic
acid in composition and to act as a preservative as well
as a paralyzing agent. But this preservative effect
has been disputed and there are yet many interesting
points to be elucidated in the biology of these predatory
wasps. The number of specimens collected and stored
by them is very little appreciated, but it is enormous,
and the reduction in the number of specimens thus
preyed upon forms a very important factor in the
check to undue increase.

The social or paper-making wasps are also feeders
upon insects; but not so exclusively, and they make
no store of food for their larvae. They feed the young
from day to day with prepared food, chewed into proper
condition by the nurses, and consisting partly of insect
fragments and partly of plant juices.

Ants destroy many insects, but do not usually
make specific war upon any one species. They are
very apt to attack, kill and eat almost any sort of
helpless creature that they find, but few of the species
of the temperate zone feed largely enough upon insect
food to form a notable check to any species.

Several families are exclusively or almost exclu-
sively parasitic, and these range in size from forms
so small as to be scarcely visible to the untrained eye,
to specimens expanding two inches or more, with ovi-

THEIR RELATION TO EACH OTHER 119

positors four or five inches long. Very often, especially
among the smaller species, the colors are brilliantly
metallic, and they range all the way from smoothly
shining to deeply pitted as to surface.

There is no species so small and none so well con-
cealed in feeding as to save it from parasites, and
these latter may infest any stage from the egg to the
adult. It is not unusual to find a batch of "bug"
(Hemipterous) eggs and to hatch from them a brood of
minute wasps instead of the little bugs that were ex-
pected. And when a lot of pupae or chrysalids have

FIG. 58. — Aphelinus, parasite on armored scales.

been collected, the result may be butterflies or moths,
but is just as likely to be several hundred or only a
few parasites instead. The size of the chrysalis is
no indication of the number of parasites to be expected.
Out of a large Papilio or swallow-tail we may get a
single large Trogus and out of a small Pieris or cabbage
butterfly we may get one hundred or more little bronze
Chalcids. On a twig infested by scales one may often
see a large percentage with little round holes through
the shell — proof positive that from each a minute
little wasp has issued; and on a. leaf infested by plant
lice, we often see some that are abnormally swollen or
rounded and tending to turn gray. These also are
parasitized and will shortly show a nice little round

120 INSECTS

hole through an empty skin as a reminder of the tragedy.
Such parasites not only kill the individual, but at once
stop all reproduction, so that every infested louse is
at once eliminated as a factor in the increase of the
species.

There are several families of these parasitic wasp-
lets; there is an enormous number of species, often of
the most bizarre type of structure and with extreme
diversity in habits. Some species remain within the
body of their host until they emerge as adults, often
giving no indication of infestation; others, when fully
grown, bore out through the skin and form little white

cocoons on the surface. Some
of the large Sphinx caterpillars
or horn-worms are often cov-
ered with so many of these
FIG. 59- — Sphinx caterpillar little cocoons as to make them

covered with cocoons of para- . , .

sites. conspicuous objects. And

not infrequently the farmer or

gardener carefully destroys these particular specimens,
because, in his opinion, they are covered with eggs —
forgetting the fact that a caterpillar is incapable of re-
production until it has first become a butterfly or moth.

A few species, usually those feeding on borers, are
external feeders, the parasitic larva clinging to the
outside of its host and sucking its juices through a
small opening in the skin.

Some parasites proclaim their character by an ex-
ternal protruding ovipositor or egg-laying tube, while
others have it modified into a sting-like organ. The
sting throughout the Hymenoptera is nothing more
than a modified ovipositor, and that explains why
only females of bees, wasps, ants, etc., have it. When
the ovipositor is external and extended, it varies greatly
in length. Sometimes it is short and rigid, almost

THEIR RELATION TO EACH OTHER 121

like a little borer, at others it is long, slender and flex-
ible, like a hair or bristle. Many of these elongated
types are found among species that attack boring
insects and some are quite capable of piercing deeply
into woody tissues. Excellent examples of this type
are found in the species of Thalessa, which expand
nearly two inches and have ovipositors almost or quite
four inches in length. These are parasitic on boring

« S -

FIG. 60. — Pimpla conquisitor; a common parasite, with its larva and pupa.

larvae of the genus Tremex which live in burrows in
the trunks of maple and other trees. In some way
these huge parasites seem able to recognize infested
trees and to locate, at least approximately, the bur-
rows in which the borers are working. Then the long
ovipositor comes into play, and by a unique mechanical
contrivance the slender, bristle-like structure is forced
into the solid wood for sometimes its full length before
the desired burrow is reached and an egg can be de-
posited. It would be asking too much that the ovi-
positor should hit the exact point where the borer

122 INSECTS

happens to be at the time, and when the parasitic egg
is once in the gallery, the mother insect has done her
work. The young 'larva that hatches in the burrow
makes its way along until it finds its prey, attaches
itself, and calmly enjoys life at the expense of its host.
But the mother insect is by no means infallible, and
sometimes her ovipositor fails to hit a boring, either
because it is too deeply located or because it has been
missed by bad judgment; then nothing remains but
to try over again. Sometimes, in a vigorously growing
tree, the sappy wood grips the ovipositor and holds so
tightly that it cannot be moved one way or the other.
Every one who has ever tried sawing through a green
log' knows what sort of grip such wood may have, and
the unfortunate Thalessa that is caught in that way
is doomed — usually to be picked off by some inquisitive
bird, sometimes to die of over-exertion. I have several
times tried to draw out ovipositors caught in that way
and have never succeeded: the ovipositor always
broke under the strain put upon it.

Maturing as quickly as many of them do, they are
able, as a rule, to keep up with any unusual increase
of their host, and to enable them to do this even more
effectively, some species have developed the remark-
able ability of producing a large number of specimens
from one egg — polyembryony, as it is called. One of
these minute species finds, for instance, a butterfly egg,
and in that lays its own egg, so minute in size as not
to interfere with the normal development of the cater-
pillar which hatches in due time, but with that parasite
egg within its body. The caterpillar grows and so does
the parasite; but instead of forming a larva and grow-
ing normally, this parasitic egg forms a structure which
divides and subdivides and gives off segments almost
like those of a tape-worm. Each of these segments

THEIR RELATION TO EACH OTHER 123

forms a larva which develops as the host develops
and finally, when the latter is full grown, it is filled
with minute, maggot-like grubs ready to form pupa
cases which will fill the caterpillar skin so completely
that it seems ready to burst. From a single parasite
egg, we may thus get fifty
or more adults; but they
will all be of one sex as
determined by the egg
originally laid. It will be
readily seen what enor-
mous reproductive powers
some of these minute spec-
imens really have, for even
if each laid only ten eggs
and each egg produced
fifty adults, the progeny
would still number 500:
not at all bad for such
small creatures!

With such enormous
powers of reproduction, it
seems surprising that the
hosts are not completely
exterminated; and yet as
we know, they are not.
If we collect chrysalids of

cabbage butterflies in spring, the chances are that out
of one hundred we may get ten butterflies and several
thousand parasites; more than enough it would seem to
overpower the next brood of caterpillars completely.
But now, if we collect full-grown caterpillars from the
scant lot produced by the few spring butterflies, we are
likely to get a butterfly from every caterpillar. From
the second brood we are likely to get almost as clean a

FIG. 61. — a, Listomastix parasite
laying a single egg in the egg of a moth ;
b, the full-grown caterpillar with par-
asitic cocoons from the single egg.
After Marchal.

124 INSECTS

record, and then butterflies become so plentiful that the
last brood of caterpillars plays havoc in our cabbage
fields. By this time the parasites are in evidence again,
and the hibernating chrysalids are as badly infested as
they were the year before. The parasite has accom-
plished its full purpose, the butterflies are not conspicu-
ously more abundant than they were the spring before;
but throughout the summer the farmer's cabbage has
paid the bill imposed by nature's methods.

There is yet another factor in this connection,
and that is the matter of what is known as hyper-
parasitism, i.e., a parasite on a parasite. Not only do
these parasites infest predatory forms in other orders,
as for instance the larvae and even adult ladybird
beetles, but they infest primary parasites among the
Diptera and in the Hymenoptera, very materially re-
ducing their effectiveness as checks from the human
standpoint, but serving an important part in preserving
nature's balance and preventing the extermination of
the primary host. The terrific extent of this secondary
parasitism can best be illustrated by recording a
personal experience. I sorted out of a collection of
cocoons of the Cecropia moth 295 specimens that
were obviously parasitized. Of these seventy -six
specimens were infested by Ophion containing only a
single example to each cocoon ; the others con-
tained species of Spilochalcis and Spilocryptus, each
cocoon with a mass of at least twenty examples. Out
of these I bred nineteen specimens of Ophion, the
others dying of disease, fifty-one specimens of Spilo-
chalcis and 126 specimens of Spilocryptus: but in ad-
dition I also bred nearly 50,000 specimens of Dibrachis,
a secondary parasite upon the two primaries! And the
matter goes even further: for besides secondary par-
asites we may have others infesting these, or tertiary

THEIR RELATION TO EACH OTHER 125

parasites, checking in turn too great a reduction among
the primaries.

It is a merry war in which all these organisms are
engaged, each one aiming only at food for itself and
its progeny, and yet each playing its part in that game
of life in which man seems to be the only one capable
of appreciating the conditions, though he is himself
involved and a sufferer as well as a factor in the game.

It is a pleasure to be able to say that the relation
of active hostility is not the only one existing between
insects. Between some there is at least toleration;
as between others an active friendship based on mutual
advantage; in a few cases there is almost absolute
dependence.

The first case of this kind that comes to mind is the
relation of certain ants to certain plant lice, and assuredly
we have nothing in the range of insect behavior that
exceeds in interest this cultivation or fostering of a
creature so far different, until we get it in the relation
of the human being to his domestic animals. The
relation is even closer, because so much has the lapse
of time acted upon this interdependence that, while
the elimination of the plant louse might make little
difference to the ant, the elimination of the ant would,
in many cases, mean the destruction of the plant louse.

It is not possible in this connection to do more than
mention the fact that among the social insects there
are a number of different castes and forms, each of which
has its own function in the community. That is a mat-
ter of internal administration and is regulated by each
species in accordance with the conditions which have
been developed by the stress of the surroundings. It
is a little different when the matter of slavery comes
to be considered; when we find that certain species
of ants actually make war upon weaker forms to obtain

126 INSECTS

servants to do their work; and yet even this is a matter
of domestic economy to be covered rather by a
student who, like Dr. William Morton Wheeler, has
•studied the ants in their relation to each other, than
by a general work, dealing rather with the relations
of different kinds of insects.

In the domestic economy of ants, we have to con-
sider those species which are of use to the ants them-
selves and are fostered and cultivated for that reason,
and those that maintain themselves in the nests in
spite of opposition or by toleration only. The first
series are those from which the ants derive a direct
benefit; the others are those which do them no direct
harm and rather indirectly benefit them.

Perhaps plant lice are the best known of those
that are directly fostered, and they are favored because
of the saccharine secretion or "honey" which they
produce. The simplest form of this relation is where ants
visit colonies of plant lice on vegetation and, by stim-
ulating or irritating the specimens with their antennae,
induce them to eject a drop of the sweet secretion which
is then gathered up. In return the ants attack and
drive off a great many enemies that would otherwise
destroy their herds. The next stage is when ants
build galleries around roots infested by plant lice and
directly favor them by freeing from soil and other in-
cumbrances an abundance of feeding surface. This
would seem to give the plant lice a free field for increase ;
but not only do parasites find their way into the nests
but even larvae of ladybird beetles occur in consider-
able numbers. These latter, however, in almost every
case, produce from specialized glandular structures,
waxy fibres which seem almost or quite as attractive
to the ants as the secretions of the plant lice. They
therefore feed upon these processes or rather excre-

THEIR RELATION TO EACH OTHER 127

tions, and appear to forgive the intruders their tres-
passes against the Aphids. A still further special-
ization, decidedly more important from the economic
standpoint, is found among those ants that gather and
preserve the eggs of plant lice during the fall and winter,
and colonize them on suitable food plants in the spring.
The strawberry louse and corn-root louse are examples
of this kind, and both of these Aphids would find it
difficult if not impossible to maintain themselves were
it not for the assistance given by the ants. The economic
importance of the matter comes in when we consider
that, except for the ants, it would be easy to starve
out the Aphids by a mere rotation of crops. In some
instances, where the plant lice will not live under-
ground, the ants build protecting shelters around the
colonies on their food plants, and thus gain all the
advantages that other species get from their under-
ground forms.

Indirectly, therefore, ants may become decidedly
injurious to a growing crop, even though they do
not themselves feed upon it, and the best way of
dealing with an injurious form may be through its
protecting ant.

Besides plant lice, scales are often visited and here
again the protection accorded by ants in the destruc-
tion of forms inimical to the scales is the return ren-
dered for the food supply. It has been charged, indeed,
that the Scutellista introduced into California to con-
trol the black scale, has been practically destroyed by
ants that obtain honey-dew from the scales. Scales,
however, are never really domesticated like plant lice,
and while they are of very great importance to some
ants they are never entirely dependent upon them for
existence. Some few species among the tree-hoppers
and frog- hoppers, also excreting honey-dew or waxy

128

INSECTS

matter, are found in the nests or galleries of ants, and
are at least tolerated if not directly favored.

Then, as in all great cities, so the large formicaries
are inhabited by a rabble of scavengers, thieves, mess-
mates of all kinds, living in friendly or hostile relations
as the case may be. These are of the most diverse
characters, from the lowly Thysanuran to the fellow
ant of smaller size or dominating type. Over 1000
species of Myrmecophiles, as such species are called,

have been already listed
and their habits more or
less fully studied and there
is no doubt that there are
at least as many more.
Some of these, like a va-
riety of rove-beetles and
some other of the Clavi-
corn series, are scavengers,
living on the decaying par-
ticles of organic matter
found in the galleries, and
may repay the ants by ex-
cretory substances coming

from specialized tufts of hair or glandular surfaces.
These are favored and protected, while others that pay
nothing for their living usually keep out of the way as
much as possible. Some few species, belonging to the
Histeridcz or pill beetles, are positively harmful to the
colonies, but are so well protected by their shining armor
of chitin, that the ants can do nothing with them. It is
a case of simply enduring what cannot be cured, and
such intruders must be constantly on their guard not
to expose leg or antenna w^hen the owners of the nest
are about. A few caterpillars have been found in for-
micaries and these feed on the dead leaves in, over, or

FIG. 62. — Hister species found in
ants' nests.

THEIR RELATION TO EACH OTHER I2Q

about the nests. The ants seem to pay little attention
to any save a few Lycaenid larvae that have glandular
structures producing attractive secretions. A few
species of small crickets and other Orthoptera help to
swell the list of guests, and several fly larvae occur.
Some of these inhabitants steal the supplies gathered
by the owners of the nest, and against these relentless
war is waged whenever the ants recognize them; but
there are curiosities in ant intelligence which, in
some cases, seems to amount to downright stupidity,
and which prevents them from recognizing the thieves
in the most vulnerable stage. Perhaps the worst
thieves in the formicaries of large species are other,
much smaller ants that run their narrow galleries so
as to tap the larger tunnels, and when they are de-
tected stealing disappear into their own streets into
which the larger form cannot follow. There are also
direct parasites adapted to live in such communities
without recognition, but only mere mention can be
made of these. There is a good deal of human nature
in an ant city and the history of what takes place in
such a city has been written most accurately and en-
tertainingly by Dr. Wheeler, who is on terms of most
intimate acquaintance with these species.

CHAPTER V.

THEIR RELATION TO THE ANIMALS THAT
FEED ON THEM

THIS subject might be dismissed with a very few
words in the statement that a large number of birds sub-
sists entirely on insect food, another large number feeds
on insects during certain seasons or takes them indiffer-
ently as part of the general diet, and that the same is
true of certain mammals, reptiles, batrachians and the
like. Active defence very few insects are able to make
against any of these enemies, and we may say broadly
that the number of insects that may be destroyed by ver-
tebrate enemies is limited only by their appetite and
their ability to find prey. The only practical defences
that an insect has, are its ability to escape the notice of
its pursuer and its enormous fecundity ; points that have
been elucidated to some extent in a previous chapter.

So we can say, roughly, that all kinds of insects
serve as food for some kind of animal. That is not
strictly true, of course, for there are some that are so
minute that they are taken only by accident and a few
others that seem to be so offensive that no animal will
touch them; but as a general statement it is accurate
enough. Some birds and animals eat indifferently
any thing that comes along; others have a very limited
diet and go outside of their normal range only under
the pressure of necessity, which is usually spelled
hunger. Some animals eat what others avoid, e.g.,
hairy caterpillars, and some insects feed so as to be out
of reach of all save animals especially adapted to find
them, e.g., borers sought by woodpeckers.

130

THEIR RELATION TO ANIMALS 131

Among animal feeders on insects we may enu-
merate toads, frogs, snakes, lizards and all their rela-
tives; the tortoises generally; rats and mice and their
allies; the shrews and their allies ; bats, coons, opossums,
moles and, to a less extent, the larger carnivora. The
smaller species of the cat and dog tribe eat a large
number of insects and even bears count them among
their list of eatables. Fish eat the aquatic species when-
ever they can get at them, and birds have been already
referred to. Now, when we realize that the insecti-
vores among the mammals form a very numerous
and important series, and that the carnivores assist,
we get at once a formidable list of destroyers against
which, as already stated, the insects have little defence.
The matter of protective resemblance of course comes
in; but that plays really a very subordinate part.
There is no doubt that many insects resemble their
surroundings so closely that they are with difficulty
to be seen; but they can be seen by the trained eye.
Some species of moths sit openly on the tree trunks
in city streets and hundreds of passers-by absolutely
fail to see them; but to the first entomologist that
comes along they are as obvious as if they had been
placed there to attract his attention. It would be
ranking bird and animal senses very low indeed if we
seriously believed that such resemblances made them
actually invisible to those who have in hunger the
best sharpener for the senses that can be imagined.
That such resemblances do protect from casual ma-
rauders there is little doubt, and that there is a better
chance of escape from a casual search than there would
be were the insects more conspicuous we may assume;
but that the resemblance is protective to the extent that
is sometimes claimed is at least open to serious doubt.

"Playing possum" is a much better protection,

132 INSECTS

and is resorted to by many insects. This means that
when they are disturbed and apprehend danger, the
specimens draw in legs and feelers, permit themselves
to drop to the ground and remain absolutely quiescent
until they believe the danger past. This very habit,
however, delivers some of the economically important
species into the hands of their arch-enemy man, who
spreads a sheet or other catcher beneath a tree or vine,
jars the infested plant and gathers in the specimens
which on the white background are conspicuous enough,
though in sod or on the bare earth they would be
well-nigh invisible.

Warning colors and protective mimicry are other
passive defenses. Warning colors are simply bright
or contrasting tints that indicate a species unpalatable
to ordinary animal feeders on insects of that descrip-
tion. That there are such species there is no doubt,
for they seem almost entirely safe from predatory foes.
Their dress expresses the legend "not good to eat"
and so they are left unharmed. Now one type of pro-
tective mimicry is found where a species of another
group or series normally good to eat so closely re-
sembles this unpalatable form as to be readily mis-
taken for it, and some of these resemblances are ex-
tremely close. Another type is when an inoffensive
insect so closely resembles one that is capable of de-
fence, that its enemies hesitate to attack. The re-
semblance of some Sesiid moths and Conopid flies to
wasps is a case in point. In such instances it is quite
usual to find that the mimic has some of the same
tricks of habit as the protected form and this is at
least as powerful a safeguard as the color alone.

Now what place do these vertebrate enemies hold
in the series of checks to insect increase, and how much
do they benefit man — the farmer and fruit grower?

THEIR RELATION TO ANIMALS 133

We have here two questions of very great interest and
importance and the answer to the one does not by any
means determine the answer to the other. That all
these birds and other animals eat untold thousands
of insects each year is undoubtedly true, and that this
is an important factor in limiting the number of speci-
mens, is unquestionable; but compared with the num-
bers destroyed by disease, by climatic conditions and
by other insects, the figures are really insignificant.
It goes without saying that these remarks are based
on normal, natural conditions, for it is quite possible
to change the conclusion under control. For instance,
if I turn a flock of guinea-hens into a field infested
with grasshoppers, the fate of those hoppers is sealed,
provided there are guineas enough to eat them. I
have seen some fields of alfalfa, however, in the foot-
hills of the Rocky Mountains, where the grasshoppers
were so numerous that all the guineas within the county
would make no serious impression on them.

As to the food of birds we are left in little doubt.
Many species have been shot in large numbers at all
seasons and have had the stomach contents carefully
determined and classified. One striking fact that
appears from all the lists that have been published, is
that the large majority of insect feeders among the
birds pick up anything they can get hold of most easily,
and that the commonest reasonably palatable forms
are those most frequently taken. Naturally, though,
this does not apply to birds fitted for a special diet like
the woodpeckers. Among the other animals almost
the same conclusion applies, again making exceptions
of such creatures as moles and others which are natur-
ally limited to underground forms or to species occur-
ring in limited or specialized areas.

One consequence of this is that a great many eco-

134 INSECTS

nomically harmless insects furnish a large percentage
of the food: ants, flies, fly larvae in excrement and
similar species. Another is, that a great many posi-
tively useful insects are taken ; less so those of absolute
importance to man by reason of their direct contri-
butions than those indirect friends, the predatory and
parasitic forms; and spiders may for this purpose be
counted as useful insects. Furthermore birds do not
discriminate between insects that are parasitized and
those that are not. Hence in eating cut- worms there
is at least an even chance that parasitized forms are
taken as freely as those not so infested. In eating a
parasitized specimen the only benefit derived by cut-
ting short its life is the saving of its food for a few days,
because it could not have come to the reproductive
stage anyway; while a positive harm has been done
in cutting short the parasites which might have de-
stroyed a hundred cut-worms the season following.
It is always possible to draw a variety of conclusions
from a list of insects found in bird stomachs, and that
generally drawn, to wit, that birds are always of very
great importance to the farmer and fruit-grower, is
usually no more warranted than the contrary one that
birds are of no use whatever.

There never yet was an apple orchard kept free
from codling moth by birds no matter how much chance
the birds had: in fact in neglected old orchards where
birds and other animals are never disturbed it is rather
the exception to find a fruit free from insect attack.
The same is true of the plum curculio. There never
yet was a field of grain freed of green-fly by birds, nor a
tree of any kind saved by them from destruction by San
Jose" scale. In many cases woodpeckers do more real in-
jury to a tree than the larva they get out would have
done, and the elm in a grove where birds hold undisturbed

THEIR RELATION TO ANIMALS 13$

sway is just as likely to be defoliated by the elm-leaf
beetle as its fellow in the city streets where the English
sparrow holds the fort. It is correct to say that as
against the common pests of the farm, the field, the or-
chard and the garden, neither birds nor other vertebrate
animals are of the least practical benefit and that the
farmer and fruit-grower would as to them be no worse off
if every insectivorous bird and other animal were killed.

And yet withal it is not a fair conclusion, to con-
tend that insectivorous birds and animals do no good.
They do, no doubt, constitute a very useful and im-
portant check to many species that would otherwise
be much more abundant than they are, and a careful
preservation of every insectivorous bird and animal is
good policy — even such forms as quail, partridges and
their allies, which are now guarded at one season simply
that they may be shot at another.

It must again be emphasized that birds and other
animals constitute only one of the checks to insect in-
crease and, as against climate, disease, parasitic and
predatory insects, a very minor and insignificant one.
We must also remember again that for a naturally
abundant species the abundance was fixed in spite
of all the natural checks, including birds and animals.
Now when such an abundant insect becomes destruc-
tive by reason of undue increase from any cause, the
very last factor to become important in bringing it
back to normal conditions is the vertebrate enemy
list, including birds, because their number and ability
to consume remains practically a fixed quantity due
to their slow rate of multiplication. It sounds large
when we find 100 larvae of an elm-leaf beetle in a bird
stomach and find 100 birds to an acre; but when we
find 100 larvae on a dozen leaves and many thousands
of leaves on a tree, the figures lose in impressiveness.

i36 INSECTS

It must be realized that under natural conditions in-
sectivorous animals depend on insects for their con-
tinued existence, and that when fed to the full, there
must yet remain enough to supply food for the season
to come in spite of all other natural checks, as other-
wise the animals, birds and others, would themselves
starve to death. I have already pointed out how pecu-
liarly well some of the parasitic and predatory forms
are adapted to gain control of a runaway species, and
it remains to be added that among the effective forms
that check the undue increase of parasites, are the
birds and other animals that eat parasites and par-
asitized insects.

Now, in spite of the fact that I am convinced that
all vertebrate animal life, so far as it affects the insects
that are injurious to our farm crops, is of little real
benefit to the farmer and fruit-grower, I would not
for a moment argue in favor of the destruction of any
form of bird or animal life not absolutely harmful to
cultivated crops. Birds have their place in preserving
the balance of nature and any interference with them
is sure to react unfavorably to the agriculturist by
increasing his troubles in some direction; and while
under normal conditions birds may be of little value,
yet under abnormal conditions which tend to remove
checks of other kinds, any increase in bird and similar
enemies would assist in replacing the other checks.

I would, therefore, rigidly protect every insectivorous
bird and other animal, including non- venomous snakes
and toads, and I would also protect every animal that
feeds upon insects at any time, providing the direct in-
jury done to crops or other farm products is not at any
time sufficient to cause appreciable loss to agriculturists.

I would not hesitate advising the destruction of
robins, crows, blackbirds or others when actually en-

THEIR RELATION TO ANIMALS 137

gaged in feeding on fruit or grain ; but I would absolute-
ly prohibit their killing at any time as a mere matter of
sport. I would be in favor of protecting every bird not
absolutely harmful ; but of no protection whatever to any
animal merely for the purpose of keeping it to be shot
at during some specified period by so-called sportsmen.

I have no point of difference with those who are
seeking the protection of bird and other animal life.
I simply wish to record my disagreement with some of
the reasons and arguments advanced by them, and to
guard against an exaggerated belief in the value and
usefulness of our furred and feathered friends.

Interference with natural conditions by introducing
new factors does not always turn out well and should
not be resorted to without a careful preliminary study
of possible consequences from all points of view. When
the English sparrow was introduced into North America
only one point was kept in mind: get something that
will eat the span-worm, the larva of the geometrid
moth, Ennomos subsignaria. The sparrow really did
accomplish that feat; but is now a greater nuisance
than the span-worms ever were and is a direct pro-
tector of certain species which never occur in trouble-
some numbers outside the region dominated by it.
The common Tussock or vaporer moth of the east is an
excellent example of this, and hardly less striking is the
case of the wood-leopard moth which has not become
injurious in this country anywhere except in cities and
towns where the sparrows keep all other birds out.

Chickens, ducks, geese, and especially turkeys and
guinea-fowl are great feeders on insect life and may
sometimes be used practically, and the useful hog
esteems wire- worms, white grubs and similar creatures
as tid-bits to be eagerly sought and worthy of con-
siderable rooting for.

CHAPTER VI

THEIR RELATION TO WEATHER AND DISEASES
THAT AFFECT THEM

VERY few insects occur throughout the world, and
those that do are usually such as have been distributed
by or have followed in the track of man or his commerce ;
but there is no portion of our globe where life occurs
at all, in which insects are not found. In the polar
regions they are often unpleasantly conspicuous, and
in the tropics they frequently render life burdensome.
When the arctic snows begin to melt during the short
summer and form puddles on the mossy surface, mos-
quito larvae appear, and even when there is an ice coat-
ing over the pools at times they maintain themselves
and come to maturity. Indeed some wrigglers and other
insects will stand freezing or imbedding in ice, and come
out none the worse when a warmer temperature thaws
them into a liquid medium. There are insects, then,
that survive in one condition or another the extremes
of arctic cold: there are others that flourish under the
opposite conditions of tropical heat. Indeed the lux-
uriant vegetation of the equatorial regions is accom-
panied by an infinite variety of insect life, a variety so
great that we have just begun to appreciate it, and
which will give a field for study to entomologists for
generations to come. Furthermore, as we have found
aquatic forms in water at temperatures low enough to
form ice, so we find others in waters whose temperature
ranges close to the boiling point. There are some
regions so arid that neither vegetable nor animal life
exists in them; but if at any time under the influence

138

THEIR RELATION TO WEATHER 139

of rain, vegetation appears at all, insects will be found
on it. And again, some insects occur in midocean
among masses of seaweed, undergo their transforma-
tions and develop generation after generation without
ever coming within reach of land.

So we find that there is no climate and almost no
earthly condition in or under which insects do not
exist; yet, on the other hand, insects are, as a rule,
extremely sensitive to changes in climatic conditions,
and some of them succumb easily to any extreme range
of temperature, even within their native home. Zo-
ologists have divided the world into faunal regions
based on climate, and have subdivided these into
smaller regions based on the geographical conforma-
tion of the country whose fauna is under considera-
tion; and we have found in our studies that a large
number of insect species have an extremely restricted
faunal range. Beyond that range they do not thrive at
all, and not infrequently, where no natural barrier
seems to exist, spread nevertheless does not take place.
The check in such cases is weather in the broad sense
of that term, or, more accurately, the meteorological
conditions. The mere fact that any species of insect
is regionally distributed usually indicates that any
climatic condition not normal to such region would
be fatal to it. An apparent exception occurs when
insects are confined to one food plant — the occurrence
of such plant being then a condition precedent 10 its
existence at all. But this is merely shifting factors
about a little, for usually the climatic conditions deter-
mine the distribution of the plant and, in consequence,
really of the insect as well.

We know that occasionally we have abnormal
seasons, and sometimes several seasons of the same
kind may occur in succession. When that happens

i4o INSECTS

insects may begin a migration beyond tlieir original
limits and may extend a long distance into adjacent
territory, only to be destroyed when a recurrence of
normal weather conditions renders the invaded area
unfit as a place of habitation. An example of that
character occurred in 1896 when the Harlequin cabbage
bug invaded New Jersey and Pennsylvania, its normal
range not extending north of Maryland along the At-
lantic coast. But although it was present in that year
in destructive numbers, it was completely killed off
during the winter following and has not been found
in New Jersey since. It is an example of an insect
rigorously restricted in distribution by climatic con-
ditions, although its food plants are widely distributed
outside of its own faunal limitations.

But occasionally matters do not terminate as sim-
ply. It may happen that an insect long confined to
a definite faunal area may be started on a migration
along the line of its food plant, and may be found to
possess sufficient powers of adaptation to continue its
life under conditions varying materially from those in
which it started. A striking example of this is found
in the case of the Sphinx catalpa which in its caterpillar
stage feeds only on Catalpa and which, up to a few
years ago, did not range north of Virginia and Ken-
tucky, although its food plant extends into New York
and Pennsylvania. Somewhere about 1897 it began
to extend northward through Maryland and Delaware
into Pennsylvania, and year by year it has extended
that range until it has reached the headwaters of the
Delaware River, and has extended throughout New
Jersey into New York State. And this extension is
not of a few individuals only; but of a horde, capable
of causing defoliation and serious injury to the trees
attacked. At present it seems as if the species had

THEIR RELATION TO WEATHER 141

•succeeded in establishing itself in a faunal region defi-
nitely varying from that in which it started; but there
are indications also that it has reached its limit.

A yet more striking case is found in the migration
of the cotton -boll weevil, a species indigenous south of
the line between Mexico and the United States, which
began its invasion into our territory somewhere about
1893 and has been annually extending its range through
the cotton-growing states since that time. So great a
variety of climatic conditions is now represented in
its distribution, that there seems to be no reason to
believe that its spread will be checked until it has
reached the faunal limits of its food plant; although
that period may be materially retarded by the quaran-
tine and other regulations now adopted by the cotton-
growing states.

These are instances of natural spread from one
faunal region to one adjacent thereto, along the line
of the food plant. There are other cases where insects
have been accidentally introduced on trees, shrubs or
plants from one country to another, into which it could
not have spread naturally and where the climatic con-
ditions in the new home suited the species so much better
that injury became much more severe as specimens
became more numerous. An example of this character
is found in the recent introduction of the "white-fly"
of the Citrus from Florida to California, where the dry
climate exempts the insect from certain disease and
other checks favored by the more humid climate of the
eastern country.

Leaving aside for the moment cases where migra-
tions have been from south to north when, under favor-
ing conditions insects from mild temperature regions
extended into normally more rigorous climates, it
sometimes happens that conditions reverse, and in-

142 INSECTS

stead of a higher temperature extending northward,'
a low temperature extends southward. This is rarely
followed or accompanied by a southward migration,
but is very frequently attended by a great mortality
among the southern insects which are unable to with-
stand the drop in temperature. Some species, indeed,
are so sensitive to cold that a drop of 10° or even 5°
below the normal winter temperature causes a serious
mortality.

Besides temperature, the amount of moisture has
a very decided effect on insect life. Some species do
best in dry weather, others flourish only when there
is an abundance of moisture, and sometimes a sudden
change from one condition to another will produce a
complete change in insect conditions within twenty-
four hours. Thripids as a rule require dry weather,
and after a period of drought and heat, the air may
be full of the little creatures not over an eighth of an
inch in length and so slender as to be almost invisible.
A cold rain lasting a few hours may reduce them to
so small a number as to make them practically undis-
coverable. Agriculturists sometimes take advantage
of this peculiarity by spraying infested plants with cold
water, and that is really about as satisfactory a method
of control as we have.

Every one who observes nature at all, has probably
noticed that in some seasons insects are much more
abundant than they are in others, and, more specifi-
cally, certain kinds may be almost completely absent
or on the other hand frightfully abundant. Now in
most cases these differences are largely and in some
even exclusively due to climatic conditions. There
is no greater check to insect life than adverse weather,
and many of the differences in abundance attributed
to other causes are really due to climate.

THEIR RELATION TO WEATHER 143

During a wet spring certain species of plant lice
may become so abundant as to threaten a given crop,
with their natural enemies so far in the rear as to seem
hopelessly out of the running. A sudden change to
hot dry weather will change conditions so radically,
that within a week the lice are gone, while ladybird
larvae and other plant louse destroyers are feeding
upon each other.

No kind of insect is more sensitive to weather
changes than are the Aphids, and few of them are able
to resist a sudden change of temperature exceeding
30° in range; but an increasev is not nearly so fatal to
most of them as a sudden drop. By the term sudden
I mean within an hour or two, because ranges of 30° or
over within twenty-four hours, are* not uncommon in
most portions of the United States.

The character of the winter has much to do with
the abundance of insects during the summer following.
It is not so much the hard or the mild winter as the
variable winter that is fatal to insect life. When an
insect goes into hibernation in either larval or adult
stage it becomes torpid and capable of resisting all
usual degrees of cold. Even if the cold is long continued
at its most intense point it makes little difference and,
in general, we may say that a continuously severe
winter is favorable to insect life. The insect simply
remains torpid and no change in condition occurs. On
the other hand if there are alternations of freezing and
thawing, the insect may become partially or altogether
active and again torpid, losing in vitality at every
change until it dies or reaches spring in such condition
as to be unable to complete its tranformations or to
reproduce its kind. Such alternations are particularly
hard on pupae and on larvae that winter underground
in cells. A thaw results in softening the ground and

144 INSECTS

partially disintegrating the walls of the cell: a heavy
frost following heaves the surface, and the water in
the soil in freezing breaks up the cells completely,
bringing the soil into direct contact with the soft in-
sects, crushing or otherwise destroying them.

A variable winter, therefore, is a hard one on insect
life, and during the summer following certain species
are likely to be conspicuous by their absence. It is
such factors as these that tend to limit a fauna; only
species capable of withstanding their variations being
capable of continued existence under them. The com-
mon and widely distributed species are those that
have become adapted to a wide range of tempera-
ture and relative humidity; the others are more lim-
ited as to the conditions under which they can exist
and die off in proportionately large numbers when
conditions are adverse.

While climatic conditions are important factors in
limiting both numbers and distribution, they are per-
haps more effective in limiting distribution, since the
occurrence of a species within a faunal region presup-
poses an adaptation to its normal ranges of temperature
and moisture. A more effective agent in limiting num-
bers is found in the diseases to which insects are subject,
and yet the effectiveness of diseases as a check is in
large part due to climatic conditions, most of them
developing best or only in moist hot weather.

Insects suffer severely from epidemic diseases due
to micro-organisms — fungus and bacterial — and of
these diseases we know, as yet, comparatively little. Al-
most every observant individual has seen late in the
season, attached to a window pane, specimens of the
common house-fly with abdomen distended and a
little whitish powder surrounding the points of attach-
ment. Such flies have been killed by a disease that is

THEIR RELATION TO WEATHER 145

contagious and frequently kills large numbers of speci-
mens. Grasshoppers are often seen dead and dry, on
top of some stalk of grass or at the tip of some weed,
and this death also is due to disease. When we break
up such a grasshopper we find it filled with a powdery
mass — the spores of the disease that caused death.
Caterpillars are sometimes found presenting a peculiarly
limp appearance, and these when touched prove but a
pasty mass of bacterial organisms. On a cabbage leaf
infested by plant lice we may almost always find a
portion that are dull yellowish-brown in color and
opaque: victims of disease, easily distinguishable from
the parasitized examples which are more distended
and somewhat shining or glazed. And so in every
order, attacking either larvae or adults, there are dis-
eases that lie in wait for them and carry off large per-
centages. Some of these diseases have been long known
and their effectiveness is so great that efforts have been
made to propagate with the view of using them prac-
tically. But it was found that, while some effect was
always produced, and while some diseases seemed
equally effective year after year, others acted only when
weather conditions were just right and were therefore
unreliable, because these conditions could not be con-
trolled even though the germs of the disease might be
supplied.

The most extensive and most interesting experi-
ments of this nature were carried on a few years ago in
some of the states of the central west against the chinch-
bug, which is one of the most serious enemies to grain
and corn culture in those sections. The chinch-bug
is a sucking insect belonging to the order Hemiptera,
and therefore cannot be reached by any stomach poison.
It is killable by certain contact insecticides, but the
task of spraying the enormous grain and corn fields

146 INSECTS

of Kansas and other states of that section loomed up
so large and expensive, that it seemed discouraging.
In the exhaustive study carried on by a number of
entomologists, it was noticed that the species was
subject to certain diseases and that at least one of
these was often epidemic in character and capable of
being propagated. The suggestion was therefore made
that this disease furnished the natural method for
dealing with the insect, and field experiments seemed
to bear out the suggestion. The result was the estab-
lishment of laboratories for the propagation and dis-
tribution of chinch-bug disease, in almost every state
subject to chinch-bug attack, and the introduction of the
disease into every section where the insect occurred in
sufficient numbers to attract attention. There were
some wonderfully successful results reported, and fully
as many absolute failures, and this eventuated in the
discovery, after much patient observation, that the
chinch-bug flourished and delighted in dry weather,
being most active and vigorous in droughty times,
when the food plants themselves were in the poorest
condition to withstand attack. In times of moisture
the bugs were sluggish, inert, and low in vitality, while
the plants, on the other hand, were vigorous and capable
of out-growing and resisting injury. The disease, on
its part, would not develop nor spread in dry weather
when the bugs were most troublesome; but it did
spread like wild-fire in a wet season when it was least
needed. As a dependence to check the spread of the
insects when danger was imminent, the experiment was
a failure; but the practice was nevertheless a success,
because the disease has now been introduced every-
where and is a constant danger to the bugs, reducing
them to such small numbers during moist seasons that
in dry seasons there are not enough of them living over

THEIR RELATION TO WEATHER 147

to become dangerous. It would now require a series
of two or three dry seasons in succession to provide
for a dangerous outbreak. And this seems, in a way,
to measure our present ability to use diseases as a check
to insect increase, i.e., we can plant them where they
will lie dormant and ready to fall upon the insects
whenever conditions become favorable. Our knowl-
edge is as yet altogether too rudimentary to enable us
to predict future possibilities.

A disease of the grasshopper has been referred to,
and this has formed a subject for extensive research
work in South Africa where the migratory forms are
among the most destructive pests. It was found that
there is a disease that sometimes appears among the
flying hordes and destroys enormous numbers of them.
This disease has been studied, has been propagated on
culture media, and has been distributed in pure cultures
with directions as to how swarms may be infected
through a prepared food. They depend in this instance
upon infecting bran, meal or a similar material with
the disease culture, to be exposed where the wingless
grasshoppers will find and eat it. They thus become
inoculated with the germs and establish the disease in
the swarms in which it afterwards spreads naturally.
The results on these South African forms are said to
be very satisfactory. The attempts to establish the
same disease in our American species have not produced
any marked results as yet.

Scale insects are quite subject to disease attack,
especially in climates like that of Florida, where certain
of the armored scales are kept at harmless numbers by
fungi. One of these attacked the San Jose" or pernicious
scale when it was introduced into that region, keeping
it down without much assistance on the part of the
fruit-growers. Efforts to introduce this disease into

148 INSECTS

Illinois and New Jersey succeeded in so far that it was
actually established, but proved utterly incapable of
catching up with the insects during the hot dry spells
of midsummer when it rested dormant, while the scale
flourished and multiplied. When rains came, the tem-
perature fell below that needed by the disease, and we
found an evident case of climatic limitation. Evi-
dences of the existence of the disease may even now
be found in New Jersey in some localities, ten years
after it was first introduced; but it never yet cleared
even a single tree of scales!

This brings up a point of some interest and much
importance: the length of time during which a dis-
ease may lie dormant and retain its virulence. On this
point our information is very scant; but an example
in illustration may be given. The periodical Cicada,
or " 1 7 -year locust" as it is more popularly known,
is attacked in the adult condition by a fungus disease
that attacks the body of the male, destroys the sexual
organs and causes the abdomen to drop, so that during
the latter days of a Cicada invasion a large percentage
of male examples will be found mutilated in this way.
So far as is known this disease attacks no other insects,
and for seventeen years it lies dormant, somewhere,
ready to become active again when a new brood makes
its appearance.

Certain kinds of plant lice are always more or less
attacked by disease, and some show more diseased
than parasitized specimens at all times. Indeed I am
inclined to believe that, aside from temperature con-
ditions, diseases are the most effective of all checks to
plant lice increase; but so far as I am aware, no at-
tempts have yet been made to use any of them prac-
tically. Perhaps I should guard myself here against
being misunderstood. I am quite aware that some

THEIR RELATION TO WEATHER 149

species of plant lice are so heavily parasitized that
even when they get a good start early in the year,
their enemies usually overhaul them before they have
destroyed or even severely injured their host plant;
nevertheless I am ready to allow my statement to stand
as an expression of general conditions, applicable to
the ordinary run of species.

I have already referred to the fact that caterpillars
are subject to disease and the check to certain species
is, I believe, much greater than is generally recognized.
On that point I made a very interesting study on a
large series of light cocoons of the Cecropia moth,
finding that more than two thirds of all the caterpillars
died of some trouble other than parasites after the
cocoons had been completed, but before the change
to pupa had taken place. Others as well as I have
observed entire broods of caterpillars dying, and one
of the characteristic attitudes of such diseased cater-
pillars is that the twig or leaf is clasped by the pro-
legs along the sides of the body, while the portions
anterior and posterior to this hang limp and lifeless.
Eventually the whole thing dries and shrivels up almost
to a skin. This sort of condition I observed in Massa-
chusetts in 1907, in territory infested by gypsy and
brown-tail moths; fully 50 per cent, of all the larvae
seen showing evidences of disease: and that condition
existed to a still greater extent in 1906, when a large
proportion of the caterpillars of the brown-tail moth
were wiped out of existence.

This is eminently one of those cases where an ear-
nest effort should be made to use the disease-producing
organisms to check increase and spread, and the study
of the subject has been actually taken up. It is quite
probable that it will be found that the disease has its
limitations, and that it requires certain climatic con-

iSo INSECTS

ditions for its greatest efficiency. But we can, at least,
follow up the spread of the insects with the disease,
and by getting the germs into every colony as fast as
it is established, introduce a check which is ready to
act when conditions become favorable, and which may,
in some localities, control it absolutely.

Only a small number of insects have been specifi-
cally mentioned as suffering from disease attack;
but this does not begin to indicate the actual extent
to which they suffer, nor the varying character of the
infestations. And it is not only those species that live
above ground on trees or foliage that are affected.
Some of the underground forms like white grubs, wire-
worms and others are subject to the attacks of growths
which change the entire insect into a corky mass, giving
rise in some cases to processes that reach above ground
as though the grub itself had begun to sprout. The
extent to which such conditions occur we cannot esti-
mate because they are mostly out of our view; but we
do not find them often enough to indicate that they ex-
ercise any great influence upon the number of examples
that come to maturity.

Among aquatic insects diseases also occur, and I
have frequently lost entire broods of mosquito larvae
that have been the subject of some trouble which caused
a cheesy degeneration.

Every breeder of insects has had some of his cages
infected with disease germs so that every brood sub-
sequently introduced died off altogether or in large
part, and the experienced man to whom this happened
destroyed those cages altogether if he could, or cleaned,
disinfected and exposed them to the action of the sun
and air if for any reason keeping them was necessary.
He realized that, once established, a germ disease was
extremely difficult to get rid of by any but the most

THEIR RELATION TO WEATHER 151

drastic measures. Many years ago the breeders of silk-
worms in France found their caterpillars dying at such
a rate as to threaten the very existence of the industry.
It was a germ disease of course, but nothing was known
of such things at that time and it afforded an oppor-
tunity for Pasteur to win renown and to benefit his
fellows to a degree that few in that or any other country
have really appreciated. It gave a striking illustration
of what epidemic disease could do under favorable
conditions, and it is still suggestive as to possibilities
when we attempt to reverse the Pasteur objective.

At the present time many bee-colonies are suffering
from what is known as "foul-brood," a disease or dis-
eases of micro-organic origin which carries off enormous
numbers of specimens annually. The character of the
organisms causing these diseases is now known and,
in a general way, the treatment to be adopted, so there
is nothing at all mysterious except the negligence of
the bee-keeper who permits the disease to develop un-
checked in so many instances. It is probably rare that
an insect once attacked by disease, recovers. In my
breeding experiences and in field observations I have
never known of such a case. I have often seen among
a brood that sickened, one or a very few individuals
that showed no trace of disease, that fed normally
and developed naturally; but I have never seen such
a larva show signs of the sickness and then resume
growth; so in a general way these diseases may be con-
sidered as fatal when they once gain a foothold.

We have now seen that, while in general there are
no conditions of climate where insects do not occur,
yet climatic conditions may and do in many cases
check not only the distribution but the numbers of
insects: that while many species are fitted to live under
widely varying conditions, others are adaptable within

152 INSECTS

very narrow limits only, and succumb readily to vari-
ations beyond the normal range.

We have seen also that, not only dp insects suffer
from germ diseases, but that these ofteft assume the
dimensions of epidemics and form a very important
factor in nature's scheme of insect control; a factor of
which we have not yet made the utmost possible use
in our dealing with the economically important species.

CHAPTER VII

THEIR RELATION TO OTHER ANIMALS

IN the course of their development insects have
established the closest kind of relations to the rest of
the animal kingdom, and there is scarcely a vertebrate
terrestrial animal that is not more or less affected by
parasites — man not excluded. Some of this parasitism
is of the most highly specialized character. We have
somehow come to think of parasites as being simple,
lowly organized creatures, of very inferior rank, and
yet a moment's thought will show that there could be
no parasites of vertebrates un.til the vertebrates them-
selves existed, and as the insects long antedated verte-
brates, parasitism must have come as a specialization
from an already well-developed organism.

Nor is such parasitism confined to what we call the
lower orders, for we find none of it in the Thysanura
or primitive forms; but its most elaborate development
occurs in the Diptera, or flies, which are the highest in
the scale so far as physiological specialization goes.

As might be supposed, the Hemiptera, gaining their
food by piercing and sucking, rank well among the
orders containing animal parasites; indeed, broadly
speaking, a large percentage of the order is strictly
parasitic on either plants or animals. The scale insects,
for instance, are absolutely dependent upon the host
plants to which they attach themselves, and many of
them if once removed from their attachment, are help-
less and die. The plant lice are less strictly parasitic
and yet the term "lice" is a good one when we compare
it with the same term used for those suckers that feed

154

INSECTS

on vertebrate blood. But the parasitism here is of an
exceedingly simple character, and means only the
adaptation of the external form
to a life among fur, hair or
feathers, and the development
of some sort of structures to
hold on with.

Most hairy animals, from the
little field mouse through all the
ruminants to man himself, are
subject to the attacks of sucking
lice. Now, while man cannot be
strictly ranged as a hairy animal
nowadays, some of his anthro-
poid allies come conveniently
under such a definition, and the
few species that infest humanity
are some of the remaining dis-
advantages of a former closer
relationship with ape-like forms.
That man has been in this com-
paratively hairless condition for
a long time is shown by the fact
that one of his parasites has be-
come especially adapted to life
under such conditions, and that
another has undergone an even
more profound modification in
habit since he was a clothed
animal.

These sucking lice are, in
general, small flattened creat-
ures, gray, whitish or yellowish
in color, with an elongate oval body or abdomen cov-
ered with short hair or spines, and a more or less

FlG' ^

°f a

RELATION TO OTHER ANIMALS 155

pointed head from which a pair of slender styles or
lancets may be protruded. In many cases there is at
the base of these sucking structures a series of recurved
hooks or small horny processes, by means of which the
creature anchors itself in the tissue of its host and sucks
at its convenience. Such structures are apt to be devel-
oped in forms infesting animals with rather scant short
hair, where some method of holding fast is desirable.
Another development is on the feet, where the tarsal

FIG. 64. — a, body louse of man; b, hog louse; c, head louse of man.

joints are arranged so as to be opposable to the end
of the tibia, like a thumb. In this structure an in-
dividual hair is seized and held so tightly that it may be
pulled from its socket sooner than the insect from it.
This type has been called "scansorial" or climbing,
because the insect moves about by grasping the hair
nearest to its position and pulling itself along from one
foothold to another. An extremely pretty illustration
of this sort is found in the hog louse, and another in
the crab louse of man.

By far the greater number of these parasites attach
their eggs directly to the hair or bristles of their host,

156 INSECTS

and pass their entire life upon it. They are incapable
of existence away from this host and have no power
of gaining food from any other source. The young
are not very different except in size, from the adults,
and there is no obvious metamorphosis.

Three species live on man and their distribution
is coincident with that of humanity. The head louse,
Pediculus capitis, lives among the longer hair of the
body, usually confined to the head. Its legs are not
scansorial, it has the anchoring process at the base of
the head well-developed, and the
eggs or "nits" are attached to the
hair. The crab louse, Phihirius in-
gumaiis, lives among the coarser, less
abundant hair of the pubic and ax-
illary regions and in hairy individ-
uals also on other parts of the body.
The legs here are scansorial, as of
FIG. 65.— An egg or necessity they must be to enable the
nit, attached to a hair. insect to maintain itself , and it also
glues its eggs to the hair among
which it lives. The body louse, Pediculus vestimenti,
lives among the thinner body hair and almost alto-
gether on parts normally covered by clothing. Its legs
are not well fitted for grasping, but the anchor proc-
esses of the mouth are well developed. The peculiarity
of this species is that it remains on the body of the host
only while it is feeding and at other times hides in his
clothing, where also it deposits its eggs. Man, there-
fore, has worn clothing for a period long enough to
enable this parasite to adapt its mode of life to this
habit, and to depend upon his garments for protection
and as a nidus for its ova.

These parasites sometimes become exceedingly
abundant when men are herded together in camps,

RELATION TO OTHER ANIMALS 157

ships, or prisons, and specific irritations known as
Pediculosis and Phthiriasis are produced by them.
It has been calculated that a single adult female of
the body louse might have, in eight weeks, a progeny
of 5000, and while this is not equal to the performances
of some other insects it does, nevertheless, serve to
make possible a very rapid and complete infestation
where they are allowed to develop unchecked.

Of course personal cleanliness is the best of all
methods to be and become free from such parasitism;
but infestation in modern conveyances is always pos-
sible, and with even the greatest care a parasite may
obtain a foothold. Children, who are not always choice
in their companions, not infrequently become infested
by head lice. A fine-tooth comb and a thorough greas-
ing of the hair with pomade or any fatty material,
repeated twice at intervals of a week each, will clear
out the parasites. The grease enters into and clogs
the breathing pores of the lice and chokes them; but
it does not affect the eggs or -'nits." The later
applications are intended to reach the young that
have hatched from the eggs since the previous ones.
As the eggs may remain unhatched for ten days or
two weeks, this period of time will be necessary to
insure freedom.

As for the body louse, the infested clothing should
be discarded for a time. Underclothing may be sub-
jected to lengthy boiling to kill both adults and eggs.
Outer garments should be steamed or baked if possible,
or should be dipped into gasoline; this latter applica-
tion to be repeated in ten 'days, to reach later hatchings.
The gasoline process is simplest as it kills all the adults
at once, and if it can be repeated at short intervals,
the clothing can be worn in the periods between
treatments.

158 INSECTS

The crab louse is treated by local applications of
mercurial ointment or by tincture of larkspur (Del-
phinium), the latter of which is also used against the
head louse.

The habit that some savages have of covering them-
selves with grease, oil or paint, is not entirely without
practical advantage, for thereby they do undoubtedly
keep themselves measurably free from these parasitic
forms. The use of ants to rid infested clothing of para-
sites is referred to by Mark Twain in his inimitable

way, and it was a recognized
practice in the far west in
olden days, when changes of
clothing were not readily ob-
tainable, and when lodgings
and lodgers could not be
chosen but had to be ac-
cepted as found. It meant
•simply stripping naked, and
FIG. 66.— Crab louse of man. placing all the clothing on

an ant hill, where it would

be immediately invaded by the ants anxious to attack
and destroy every living thing on or in this foreign
material. In a short time the clothing could be again
put on with the comforting assurance that it was at
least temporarily free.

Most of our hairy domestic animals are subject to
the attacks of similar parasites, each of which lives
and propagates on the body of its respective host.
Spread from one animal to another occurs when they
are in contact in stables, or herded closely together for
shade in the pasture. Sometimes a parasite leaves
its host voluntarily or is rubbed off by it in the stable,
kennel or field. It may then crawl about on woodwork,
plant or tree, hiding in crevices until another host

RELATION TO OTHER ANIMALS 159

animal comes into such a position as to enable it to
crawl among the hair or wool.

As uncivilized man greases or paints himself, so
animals have developed a method for securing freedom
from parasites: they dust themselves or coat them-
selves with mud. The spiracles of most lice are not well
protected, so when animals get into a dusty road and
roll about, this serves a very practical purpose and
those that get into a mud hole and wallow are often
seeking similar relief. Other species of Hemiptera
preying upon man will be considered under the heading
of household pests.

Besides the sucking lice belonging to the order
Hemiptera, many animals and most birds are also sub-
ject to the attacks of biting lice, belonging to the order
Mallophaga, which means, literally, wool-eaters, and
is somewhat misleading. Commonly they are also
known as "bird-lice" because they very usually infest
the feathered tribe. In color and appearance they do
not much differ from the sucking lice; but the head
is usually more blunt, and instead of puncturing the
skin and living on blood, they have mouth parts formed
for chewing and biting, and live rather on the surface
scales and scurf at the roots of the hair and feathers.
They do not puncture the skin to reach blood, but will
feed on clotted blood at the edge of any wound and may
prevent healing, or even cause the extension of a sore
spot. And so, while a few individuals on the skin
cause little inconvenience or unpleasant effect, yet
when a great number are at work, the feeding at the
base of the hair and of the smaller feathers results in
the death of these out-growths and the infested animal
becomes "mangy" in appearance. The true mange
is, of course, due to a mite parasite of quite a different
kind; but that "mange" which consists of bare spots

i6o

INSECTS

on a hairy animal or thin plumage on a chicken or
other bird, is very apt to be due to biting lice. In breed-
ing habits they resemble the Pediculids very nearly;
the eggs are fastened to the hair or feathers and there
is little apparent change in outward appearance from
the nymph just out of the egg, to the adult ready to
reproduce. None of these species are found on man;
but nearly all farm animals and all the domesticated
birds are likely to become infested, each with its own

A ''fl ~ B

FIG. 67. — a, chicken louse; b, turkey louse.

peculiar species. It is rare that one species of parasite
is found on two species of animals not very closely
allied; but it is not uncommon for a single species of
animal to harbor two or more kinds of parasites.

Birds are as fond of a powder bath as are the four-
footed animals, and poultry keepers have long recog-
nized the importance of the dust box in keeping their
charges in good condition. It should always be the
finest of dust available and there should always be
plenty of it in a box of generous size so that even the
largest bird can cover itself thoroughly without scat-
tering the material beyond the edge of the container.

RELATION TO OTHER ANIMALS

161

Horses and cattle can be very readily freed from
lice parasites by a free use of curry-comb and brush,
and if occasionally the brush 'be dipped into a pan of
crude petroleum so that the tips of the bristles become
wet, the coat of the animal will be materially improved,
and any louse that is hit will be killed. Kerosene must not
be used because that is likely to kill the hair ; but crude
petroleum acts as a stimulant and improves its growth.

There are no animal parasites in the other Neurop-
terous orders, and in the great
order Coleoptera or beetles there
are very few. We have scaven-
gers and feeders on dead and de-
caying material in great abund-
ance, and many beetles live with
specific animals in very close re-
lationship ; but very few actually
occur on the animals themselves.
In the United States the mem-
bers of the family Platypsyllidce
and LeptinidcB are known to live
on the beaver and a few other ro-
dents that have a dense fur.

Just what the relation of these parasites is to the host
is not entirely clear, but the larvse do not live on it,
and feed rather on the waste material in the nests.

Animal parasites would scarcely be expected among
the order Lepidoptera, or butterflies and moths, and
strictly speaking there are none. Yet it is certain that
some of the small moths belonging to the Tineids,
which include our "clothes moths," do actually breed
and develop in the fur or wool of animals like the sloth,
certain sheep, etc. There is such a thing, then, as a
fur or pelt becoming moth-eaten, even while it still
covers the body of its owner,
ii

FIG. 68. — Platypsylla cas-
toris: parasite on beaver. After
Westwood.

i62 INSECTS

The great order Hymenoptera, in which insect para-
sitism is developed to a remarkable extent, contains
no species that live on vertebrate animals.

The Diptera, or flies, on the other hand, in which
specialization has been almost as extreme as in the
Hymenoptera, have developed a considerable number
of forms that depend for their living entirely upon the
higher animals.

FIG. 69. — A rabbit flea.

The little family of fleas, which are very highly
specialized flies, although now usually classed in an
order by themselves, are all parasites on warm-blooded
animals covered with hair or feathers. They are small,
brown, transversely flattened, set with spines or stiff
hair directed backward, and the legs are powerful,
fitted for jumping. This characteristic form makes it
very easy for them to move about among the hair and
feathers, and this they do in a sort of jerky way as if
they were making short jumps, each of which carries
them a shorter or longer distance and enables them

RELATION TO OTHER ANIMALS

163

to easily avoid the paw or foot of the animal when it
scratches the place where it feels a bite. Although
parasitic in so far as it lives during its adult stage upon
the host animal, yet the insect moves about freely,
and the early stages are passed in most if not all cases
among the litter in the nest or den of the host, and not
on its body. In its early stages, then, the flea is not a

FIG. 70. — The jigger flea: a, normal female; b, distended with eggs; c, larva.

parasite, but rather a scavenger; in its adult stage it
feeds on blood and differs from mosquitoes and other
flies that have the same habit, chiefly in remaining on
the host animal during the period when it is not feed-
ing. As soon as an animal is dead and cold the fleas
leave it. Of fleas in their relation to man there will be
more to say in a later chapter.

There is one little group of fleas roughly known as
"jiggers" that depart somewhat from the normal life
history. In these species the female after copulation
seeks some host into which it may burrow or imbed

1 64 INSECTS

itself. Any animal, including man, will serve, and
entrance is usually made between the toes or under
toe-nails or claws, because penetration is easiest there.
When once in position under the skin, the body of the
female enlarges as the eggs develop until it is as big
as a pea in an extremely painful and usually festering
tumor. The eggs, when ready to be laid, are discharged
into the sore, and the wriggling larvae make their way
out as best they can, to develop as do others of their
kind. Animals often suffer severely from the attacks
of these pests which inhabit the southern parts of our
country and the tropics, and man is not infrequently
attacked where he goes bare-footed. Where "jiggers"
are well known the nature of the attack is usually recog-
nized at once, and the insect removed with a needle or
a knife-point; sometimes a wet quid of tobacco is tied
over the infested spot for a few hours, and this softens
the skin and usually kills the pest so that removal is
easy. If the matter is neglected and removal is not
attempted until the eggs are developed, the work must
be carefully done so as to avoid breaking the body of
the female and discharging the eggs into the wound.
Usually, on domestic animals, cleanliness and the
free use of lime where the larvae breed is sufficient to
avoid trouble. But in some sandy regions fowls suffer
severely from the species that attacks them. The hen
flea is an ally of the "jigger" and while it does not bore
into the tissue of the bird, the female does fasten itself
firmly into the skin and remains attached until dis-
turbed by some outside force. On young chicks they
often fasten to the head and neck in such numbers as
to kill their host. A free use of carbolated vaseline is
indicated in cases of that kind. This material not only
kills the fleas but acts as a disinfectant and promotes
the healing of the sores.

RELATION TO OTHER ANIMALS 165

There are many other kinds of fleas and they infest
almost every sort of animal capable of affording them
shelter; but there is a very general ..agreement in life
history and in the character of the methods to be used
in their control when control becomes a matter of im-
portance. Some further word concerning these in-sects
as carriers of disease will be found in a subsequent
chapter, where also the closer relation of those fleas
that occasionally occur in our houses is more fully
elucidated.

FIG. 71. — Chicken flea.

Among the true flies there are a great number of
species that prey upon vertebrate animals, and they
do this in two ways: either by feeding upon them in
the adult stage alone, or by actually living upon them
in early stages, and thus becoming true parasites. As
the flies are among the most recent of insects, so their
relations to the vertebrates, the most recent develop-
ments in the higher animals, are also most close.

The simplest form of relationship is that afforded
by the various blood-sucking flies — the mosquitoes,
gnats, midges, horse-flies, stable flies and others allied
to them. In all these species the mouth structures
are developed into a series of long slender lancets

1 66 INSECTS

formed so as to be able to Duncture the skin of the host
and to suck the blood beneath it. In almost every
instance the early stages are passed elsewhere than on
the host that serves as food in the adult stage, and some-
times not even in the same medium. The mosquitoes,
for instance, attack all sorts of vertebrates, cold-blooded
as well as warm-blooded; but so far as known, all the
larvae are strictly aquatic, dwellers in water and adapted
to secure their food only in that medium. Yet while
the direct relations between animals and mosquitoes
are simple enough, the indirect influence that they
exert as intermediate hosts for certain disease-produc-
ing organisms are of so great importance as to require
more specific treatment in another connection.

The Simuliidce, containing those species known as
"black flies," "midges," "Buffalo gnats" and others
of similar character, are in somewhat the same case.
The adults feed on warm-blooded animals, the larvae
are found only in water usually adhering to stones,
logs, roots or other points of attachment and gaining
their food supply entirely from beneath the surface.
As both mosquitoes and gnats develop in water, their
presence as adults in some localities is coincident, and
a better combination for making life miserable can
scarcely be imagined. The gnats are preferably day
fliers, the mosquitoes preferably night fliers, so the
entire diurnal cycle is thus provided for. The "black
flies" do not worry their victims by buzzing or "sing-
ing." They are extremely business-like in their method
and as soon as they alight they set to work. Their
puncture is recognizable at once and resembles the
prick of a hot, very fine needle, much more than any
other bite known to me. The mouth parts are short,
not nearly so compact as those of the mosquitoes, and
the flies appear to veritably dig into the skin leaving,

RELATION TO OTHER ANIMALS 167

when driven off, a wound large enough to bleed — a
butchery of which no mosquito is ever guilty. The
small black flies, usually called "midges," are not con-
tent to attack only the exposed parts of the body:
they crawl into the ears, the nose, under the clothing
at the ankles, wrists or neck, and where a novice goes

FIG. 72. — "Buffalo gnat" or "black fly."

unprepared into an infested territory, he usually stays
there only as long as is absolutely necessary. Even
the veteran is sometimes forced to run when he has not
provided himself with some repellant substance. Of
these "dopes" there are various sorts known to the
woodmen, and their basis is usually a cotton-seed or
olive oil, with an admixture of oil of tar, oil of penny-
royal, menthol or some similar volatile oil. Oil of
citionella is in great favor with many and, in my own

1 68

INSECTS

experience is a little the most satisfactory and agree-
able. The odor is offensive to others, however, and
these may find the menthol preparations more satis-
factory. Cattle and animals not being able to resort to
repellants often suffer cruelly, and in countries where
buffalo and similar larger gnats are plentiful, they
are sometimes driven literally insane by the pain and

irritation of the attack.

The early stages being
passed continually under
the water surface, offer no
points for an attack with
oils. No matter how the

1 PHI ^^K^^ uPPer la^er ma^ be coat~

J (M ed, the insects on the bot-

torn will be little or not at
all disturbed, and as they
usually inhabit running
streams, it is practically
impossible to maintain a
surface covering anyhow.
Those species that attach
themselves to logs and
sunken or surface-lodged

tree trunks or the like, may be mitigated by cleaning
but such obstructions and points of attachment; but
for such species as attach themselves to stones on the
bottom we have no remedy that is not also likely to be
fatal to fish and other forms of aquatic life. Thus far
no charge has ever been made against any of the
Simuliidce that they are carriers of disease in man or
animals ; but our actual acquaintance with the flies and
with the diseases of the animals that inhabit their ter-
ritory is slight, so that it would hardly be safe to say
that they are not dangerous in such direction.

FIG. 73. — Larva and pupa of buffalo
gnat.

RELATION TO OTHER ANIMALS

169

The Tabanidce, including those forms known as
"horse-flies," "deer-flies," "green-heads," "breeze-flies,"
" golden -eyed flies, " and perhaps a number of other pop-
ular terms, are all much larger species, some of them
among the largest in the order. They are all blood
suckers in the female and feeders on nectar or other
plant secretions in the male. In fact the males are
as shy and retiring as the females are bold and obtru-

Fio. 74. — Black horse-fly, Tabanus atratus: a, larva; b, pupa; c, adult.

sive, and very little is actually known of them and their
habits. The popular names are all applied to the fe-
males and are chiefly based on their habits or appear-
ance. The "horse-flies" are among the largest of the
species — some of them great massive fellows an inch
or more in length; black, blue, brown or striped with
yellow; sometimes covered with a bluish, whitish or
golden bloom. They attack horses or cattle in their
districts and so stout and short are their horny lancets
that blood comes almost as they settle. High-strung,
thin-skinned horses are sometimes driven frantic by

i;o INSECTS

the bites and by the circling of the flies seeking a place
to alight, and high-bred cattle fall off seriously in fly-
infested pastures.

I have referred to districts in connection with these
flies and not unintentionally, because they are by no
means generally distributed. Each species has its
favorite haunt and cannot be found outside of it; so,
in driving, one may enter a fly district and get out of it
again in a few minutes. Or, after being bothered for
a few minutes by a large black fly, it may be noticed
that a large brown or striped one has taken its place.

The "green-heads" are usually found along the
sea-shore and their name is due to the bright green eyes
which cover so much of the head that nothing else is
ordinarily noticed. The rest of the body is generally
of some light or yellowish shade that is inconspicuous in
the surroundings in which they occur.

The "golden-eyes," "deer-" or "breeze-" flies are
usually inhabitants of damp woods and their names
are derived partly from the golden brown mottled eyes,
partly from their supposed habit and partly from their
manner of attack. These are, as a rule, smaller flies
and many of them have the wings barred or mottled
with brown or black. The golden markings of the eyes
are quite conspicuous, and it has been interestingly
demonstrated that this is due to a distinct pattern for
each species and that in life many forms are identifiable
by this character alone.

The Tabanid larvae so far as we know them, live in
mud or at least in moist earth along the banks of streams
or almost in water itself; and they feed on the minute
forms of life inhabiting such places. Some occur on
salt marshes, some in low meadows and some in the
damp leaf mould in low woods, and this, in a measure,
accounts for the local distribution of the adults: they

RELATION TO OTHER ANIMALS 171

do not get very far away from the place where they
normally breed.

As a protection against these insects nettings are
used on driving horses, and cattle are sometimes pro-
tected by smears of carbolated grease or fish oil. The
larger horse-flies do not usually attack man, as the
green-heads and deer-flies generally do. Where they
are abundant enough to cause trouble, the same
repellants that serve for black flies will serve against
the Tabanids as well, As the ground becomes better
drained or cleared, so that breeding places for the larvae
are lessened in number, the adults will become gradually
less troublesome; and, as a matter of fact, while the in-
sects are sometimes horribly annoying, they are usually
much fewer than they seem because of their active
movements, and it may be quite possible to exterminate
some of the species locally, by persistent collecting on
some especially favored animal, for a few days after
the flies first make their appearance.

The term "stable flies" is rather an indefinite one,
but applies chiefly to one species, Stomoxys calcilrans,
of very general distribution, in appearance like a large
house fly, but with mouth parts produced so as to be
capable of sucking blood. These are often present on
horses and cattle in great numbers, and frequently
cause great annoyance and distress. They rarely attack
humans,- but sometimes in hot, oppressive weather
will get at exposed ankles and bite hard, usually with-
out causing any noticeable swelling. The larvae are
maggots, like those of the common house fly, and de-
velop in excrement, preferably in cow dung. If no better
lodging is found for them, almost any kind of decaying
vegetable matter will be made to answer.

A near ally to this stable fly is a somewhat smaller
species known as the "horn fly" from its habit of

172

INSECTS

clustering at the base of the horns of cattle. This is
an importation of comparatively recent date from
Mediterranean Europe, but it has spread in the few
years since its arrival throughout most of the United
States and into Canada. For a few years after its
first appearance it produced great alarm, and weird
stories were told of its destructive effect on cattle;
the least of which was that the flies attacked the horns

FIG. 75. — Horn fly: a, egg; b, adult; c, d, head and mouth parts.

at base, laid their eggs there, ate off the root of the
horn and then penetrated the brain. As a matter of
fact much injury was caused to dairies from the abund-
ance of the flies, because they kept the cattle in a con-
stant state of irritation and therefore poor in milk flow.
But breeding was always in fresh cow manure, and at
no time did the insects get within the outer surface of
the animal in any stage. After two or three years of
alarm it was noticed that the flies lessened in number,
and finally became less abundant than the native
species, which it seemed at first fated to displace.

RELATION TO OTHER ANIMALS 173

Carbolated fish or a similar oil is used as a repellant,
where flies of this character are abundant; but proper
attention to the manure so as to prevent breeding is
a much more effective and satisfactory measure.

Leading to those species that have been referred
to as parasitic because, in the larval stage, they are
confined to and dependent on the host, are a number of
species that in a sense are intermediate in habit. There

FIG. 76. — Screw-worm, Lucilia macellaria: a, b, c, larva and details; d,
pupa, e, fly; /, its head.

are many species that are true scavengers in the larval
stage; maggots which are found on exposed meats,
fish or vegetable matter, and which in an almost in-
credibly short time dispose of most of the organic matter
of an animal of even considerable size. And in the
determination of what is suitable organic matter, the
adult flies of some species seem to follow the rule
that it is best to "blow" anything that might by any
chance be suitable. Hence while the parent of the
" screw- worm" normally lays her eggs in or on dead
animals or on exposed meats, yet sometimes, when
suitable food is scarce, she will select any raw or sore

174 INSECTS

surface on even a living animal. Most of the flies of
this series are attracted by foul odors which, to them,
is an indication of a suitable place for eggs; hence it
is not altogether unusual to have a female oviposit
into the open mouth or into the nostrils of a sleeping
human afflicted with catarrh or some other trouble
giving rise to foul breath. Eggs of this kind are usually
ready to hatch .when laid and sometimes already hatched
within the abdomen of the female; hence it is a matter
of only a very short time for the young larva to make
its way along the mucous membrane, in which it may
exist for a day or two without giving rise to much dis-
comfort. After this it bores into the soft tissue of the
palate and into the cavities and sinuses of the head,
giving rise to intense pain, high fever and often death,
if the character of the trouble has not been at once
recognized and prompt treatment made. Yet this
form of parasitism is incidental or accidental, and shows
principally how slight and easy is the step from the
beneficial scavenger to the injurious parasite. When
the eggs are deposited on or near an open wound or
sore surface, the larvae bore into the exposed tissue and
feed upon the living flesh, which of course becomes
much inflamed, ulcerates and attracts yet other flies
of the same character, unless the matter is promptly
looked after. The screw-worm flies are common enough
throughout the middle, southern and central states,
but are most troublesome in the south and the south-
west where, during some years, much loss among domes-
tic animals has resulted from their attacks. The adults
are stout flies almost two-fifths of an inch long,
metallic bluish in color, with three blackish longitudinal
stripes on the upper side of the thorax.

A very similar but somewhat smaller species is the
blue-bottle fly, much more common in the northern

RELATION TO OTHER ANIMALS 175

states and more metallic yellow or green in color, which
has similar habits so far as attacking wounds or raw
surfaces is concerned; but it does not, so far as I am
aware, ever actually bore into living flesh nor into the
openings of the face. The nearest approach to this
was in the case of a tramp admitted to the hospital at
New Brunswick, complaining of unbearable headache.
Investigation showed the ear cavities rilled with a dirty

FIG. 77. — Blue- bottle fly, Lucilia casar.

mass in which were found maggots which I believe
were of this species. The ears were cleaned, syringed
and all the maggots removed before they had pene-
trated further into the head cavities.

The large blue "meat-fly" or "blow-fly" has sim-
ilar habits and seems to occur all over the world, at-
tracting attention by its large size, deep blue color
and noisy hum.

The one guard against all these semiparasitic scav-
engers is cleanliness and disinfection. It is the attrac-
tion of foulness that brings them to the attack, and if
by unavoidable accident an attack is made on some

i76

INSECTS

unprotected point, prompt treatment to destroy the
larvae, reduce inflammation and protect the wound,
should be resorted to. Carbolated washes or ointments
are excellent as protectives, and nothing is better than
peroxide of hydrogen to clean and sterilize a suppur-
ating sore.

It is rather an easy step from the sort of elementary
parasitism just described, to the simpler forms of at-
tack by bot-flies, or (Estrida. Bot-flies in the adult
stage are usually large, stout species with a large head,
but no functional mouth parts.
The adults, therefore, though
very highly specialized in some
directions, are merely produced
to provide for the continuance
of the species ; incapable of harm
in themselves and, so far as we
know, not productive of any
distinct good.

In the simplest forms the
adult fly lays an egg on the skin
of the animal that serves as a

host; the larva hatches, bores its way through the skin,
enters the tissue and lodges. It increases in size, some-
times forms a swelling which may or may not suppurate,
and, when full grown, works out through the skin, drops
to the ground which it enters to pupate, develops to an
adult in due course and the cycle is complete. Bots of
this character attack a great variety of animals and even
man is not exempt from them. I have personal knowl-
edge of such a case and there are enough others on
record to make it quite certain that under abnormal
conditions some of the species that ordinarily attack
other animals may attack man. In tropical regions the
attacks on man are much more frequent and are referred

FIG. 78. — Blow-fly, Calliphora
vomitoria.

RELATION TO OTHER ANIMALS

177

to species of Dermatobia. So far as I am aware no
species has been demonstrated that is confined to
human beings.

Almost any part of the animal body may be at-
tacked by bots; but in a general way they are most
likely to appear in regions which the host is least able
to reach with its teeth, e.g., the neck; but they occur
often enough in other portions of the body. Occa-

FIG. 79. — The sheep hot, CEstrus ovis: i, 2, flies; 3, pupa; 4, 5, full-grown
larvae; 6, young larva.

sionally they appear to attack specific organs as those
that destroy the testes of squirrels and chipmunks, or to
be confined to special regions like those that are so often
found around the anal openings of hares and rabbits.

Some species have almost identically the habits that
were observed in the screw-worms entering the head
of man through the nostrils. An example of this is
the well-known sheep bot, the adult of which lays its
eggs ready to hatch or just hatched on the mucus of
the nostrils of the sheep. The larvae work their way up
into the head passages, feeding on the mucus, on the

12

1 78 INSECTS

membrane itself and, if pressed for food, upon the
muscular tissue. When the infestation is a bad one
they work their way, through all the openings between
or in the bones, to all parts of the head cavity, and into
the brain itself, in such cases causing "staggers" and
death. The larvae like almost all bots are set with
short stiff spines, definitely arranged, that enable them
to make their way forward, and there is also a pair of
mouth hooks that enables the grub to fasten itself
firmly to any place selected. This spiny structure and
the definite mouth hooks are not developed in the
"screw- worm," which is a typical maggot, altogether
unlike the highly developed "bot. " The amount of
damage caused by the sheep bot is very great in many
localities, while in others the species seems to be alto-
gether unknown. As to remedies against them, each
locality or herdsman has its or his own, and none is
entirely satisfactory.

An altogether different type of bot is that which
occurs in horses. The fly that produces this has rather
a conical pointed abdomen and a brown hairy body.
The eggs are laid on and attached to the hair, usually
on the forelegs or on some part easily reached by the
horse with its head; and they remain there, unhatched,
although the embryo may be fully developed, until
the horse in licking itself or a companion dislodges
the egg-cap and, freeing the larva, transfers it to the
mucous membrane of the mouth. From this place it
moves at once and makes its way down the oesophagus
into the stomach. Here the young bot finds its proper
conditions and becomes anchored by means of a pair
of mouth hooks into the lining membrane. It feeds
here, absorbing the juices for several months, maturing
in late spring, and then loosens its hold, is carried into
the intestines with the excrement and so on through

RELATION TO OTHER ANIMALS

179

the anus. When it reaches the ground it burrows into
it at once, changes to a pupa, and not until a month
thereafter does it transform into an adult fly. A full
year is thus required for the development of the species,
and there is only one danger season for infection — the
period during July and August when the flies are on
the wing.

FIG. 80. — The horse bot, Gastrophilus equi: a, egg, attached to hair; b, young;
c, full-grown larva; d, adult fly; e, hooks of larva.

A few bots, while not of course an advantage, will
not hurt a horse. More than a few will cause trouble,
in proportion to the amount of infestation. There is,
naturally, the irritation to the membrane to which the
insects are attached, causing digestive derangement;
there is also the positive drain upon the system by the
feeding maggot which is apt to weaken the animal and
to intensify the effect of the digestive trouble; and
finally, when there are many bots, they tend to form a
mechanical obstruction to the passage of food from

i8o INSECTS

the stomach to the intestine. A bad infestation is a
serious matter and may easily become fatal.

On well-cared-for horses bots are not often trouble-
some. The eggs are readily seen and as they cannot
be hatched for several days after being deposited,
they may be easily removed when the animal is groomed.
They are firmly enough attached, however, not to
be easily removable by the horse, and the embryo
develops within ten days after they are laid. If at any
time after that the egg is licked, the cap covering the
top opens and the larva slips out of the shell on to the
tongue, moving actively at once toward the gullet.
A thorough brushing and washing once every week
will therefore be sufficient to keep a horse free, even
when exposed to the attacks of the flies.

It is curious to note how all animals subject to bots
appear to dread the adult flies. They cannot possibly
know the relationship between the flies and the bots,
and it is probably the apparent intention to attack
that arouses the fear that undoubtedly exists.

Horned cattle are subject to the attacks of bots
that form swellings or "warbles" under the skin,
usually on each side of the backbone; and these insects
affect not only the general health of the animal, but
very materially reduce the value of its hide. In fact
the impairment of value so caused has been reckoned
at many millions annually while the impairment in
value of dairy products, due to the poor condition of
suffering cows, can hardly be estimated.

The life cycle of this species is also interesting and,
in a way, decidedly more complicated than that of any
of the species previously referred to. The adult is not
so unlike that of the horse bot ; a little more compactly
built, with a shorter abdomen and a somewhat banded
appearance in black and whitish. Like its ally it lays

RELATION TO OTHER ANIMALS

181

its eggs on the hair of the animal it infests, and here
also further development is dependent upon the in-
troduction of the young larva into the mouth. But
there the resemblance ceases, for the young larva, in-
stead of permitting itself to be carried to the stomach,
attaches itself to the walls of the oesophagus and bores
its way through into the muscular tissue, continuing on
until it reaches the desired position beneath the skin.

FIG. 81. — The ox bot, Hypoderma lineata: a, eggs attached to hair;
b, fly; c, larva.

As with the horse, the well-cared-for dairy animal
rarely suffers from bots; the eggs are so conspicuous
that they readily attract attention, and removal is
easy. If any do escape and bot-swellings are noticed,
they should be lanced and the contained larva removed.
Cattle on the range or beef cattle in pasture suffer much
more, because they are less or not at all looked after,
and the bots are not suspected until the ulcerating
sores attract attention.

A still more highly specialized type is represented
by the "louse flies," sometimes separated under the

182 INSECTS

term Pupipara, or those that give birth to pupae. They
are usually active, flattened, brown or yellow flies,
with small head and rounded abdomen. Some of them,
infesting birds of prey, fly actively, while others, like
the "sheep tick," are wingless, although not there-
fore inactive. They are called pupipara because the
egg hatches within the body of the female and the
larva attains its entire growth before being extruded,
ready to pupate. Of course this means a very slow
rate of reproduction, since the number of young matured

FIG. 82. — A louse fly, Olfersia species.

at one time cannot be great; but, on the other hand,
it is also a safe rate, because the larvae run few dangers
during their early life, and the infant mortality is not
very high. Nestlings become infested from the mother
bird, and the flies are quite active enough to make
short flights from the host and back again when neces-
sary to escape an especially vigorous hunt. When
the host dies or is killed the parasites leave it at once,
and seek shelter on any living thing in the vicinity.
"Sheep ticks" which, as already indicated, are
wingless, do really look very much more like ticks
than like flies; their long mouth parts, small thorax,
long legs and round flattened abdomen giving them

RELATION TO OTHER ANIMALS 183

a peculiarly spider-like appearance. They are some-
times very abundant on sheep, and find no difficulty
in getting on to new animals because of the habit of
congregating into dense masses, peculiar to their host.
The body of these flies is very tough and leathery, and
I am informed by those who handle the raw hides
that they will survive all the preliminary handlings,
cleaning and soakings which the pelts undergo before
being denuded of wool and prepared for tanning.
Herders know of a great variety of "dips" useful

FIG. 83. — Sheep tick, Melophagus FIG. 84. — A bat tick,

ovinus. Nycteribia.

against these insects and "dipping" is a regular prac-
tice wherever sheep are raised in any numbers.

The extreme development in this direction we find
in the bat ticks, which are even more spider-like than
the sheep tick and have similar habits, while infesting
a much-shorter-haired animal. It is distinctly curious
that while there are many species of these louse flies
among birds, there are only a few, very aberrant forms,
that have adapted themselves to live on four-footed
animals.

We find, then, that among the insects there are foes
to almost all kinds of vertebrates and that they are
not at all despicable foes. While the death of the
animal attacked is never sought as a prime object,

i84 INSECTS

it not infrequently follows as the result, and it is not
by any means easy, even for man himself, to guard
against injury in all cases.

We see also that parasitism is not by any means a
primitive condition but an adaptation, frequently
accompanied by specialization of a high order. It is,
in some of its manifestations, of comparatively recent
origin, the greatest diversities obtaining in the highly
specialized Diptera, while the simple forms are all
in the more generalized orders, being there little more
than an adaptation to life on an animal rather than
on a plant.

CHAPTER VIII

THEIR RELATION TO MAN AS BENEFACTORS

INSECTS as benefactors to the human race have
been very little considered, their position on the op-
posite side having been so much more emphasized ;
and yet, if some few species were eliminated, their ab-
sence would be very seriously felt for a time, until a
substitute for them could be discovered. Possibly
the reference to them as benefactors is a little inac-
curate for most of those referred to here — they are
useful to man rather than his benefactors. We might,
of course, class as benefactors those that pollenize his
fruits and other crops; but there the benefit is indirect
as to man, and more direct as to the plants, hence coming
under another head.

Directly beneficial to man are those insects that
act as scavengers, working to reduce to their original
inorganic compounds those animal and vegetable
materials that are dead or dying and of no further use
as living organisms. The extent of the benefit thus
derived is absolutely unappreciated; but were all
insect scavengers removed at one time and all dead
animal and vegetable material left to other decays,
the foulness and noxious odors that would be thus let
loose are beyond all description.

Does a small animal die in the field — within a few
hours burying beetles are working to get it under-
ground; flies have laid their eggs on the body and
numerous other species have begun feeding on the skin,
the hair and the flesh. Within twenty-four hours in
summer, the process of disintegration is well under

185

1 86 INSECTS

way and in a remarkably short time nothing but the
bony framework remains.

Hardly has a cow dropped a mass of excrement
in the pasture, before it is covered with flies absorbing
the moisture, helping to form a dry outer coating and
ovipositing for maggots to help reduce the half-decayed
mass into fragments that may be mingled with or ab-
sorbed by the soil. If, after a dropping has been in
the field forty-eight hours, it is broken up in a pail of
water, the number of specimens and species that will
come to the surface is startling.

Is a forest giant stricken and borne to the ground
by wind, flood or lightning — immediately insects of
many sorts attack and begin to reduce it to dust, con-
tinuing their work until nothing remains. And so of
all organic matter in which life is waning or from which
it has departed — such matter is prey to insects and they
are never backward in fulfilling their duty.

This scavenger function is by no means a "low,"
or "primitive" habit; it does not exist in the lowest
orders at all and is best developed in the Coleoptera
and Diptera, which are among the highly specialized
and dominant types. To be sure the Thysanura are
largely feeders on the products of decay and hence
may seem to be entitled to rank as scavengers; but
they rather come after decay and feed on its products,
hence their presence is merely indicative of moisture
and decay produced by other causes.

The Termites among the Neuropterous orders are
feeders on wood and other vegetable products, but they
invade rather for building purposes and are never
found in really decaying material.

The order Hemiptera contains no scavengers among
either the Homoptera or Heteroptcra and stands entirely
free from even a tendency in that direction.

THEIR RELATION TO MAN 187

In the Coleoptera or beetles there are several families
that are scavengers in whole or in part, and some of
these families contain very large numbers of species.
In a very general way the scavengers may be recog-
nized by the clavate or club-shaped antennae, combined
with five- join ted feet or tarsi, and thus belonging to
the series ll Clavicornia. "

The Stapkylinidos or rove-beetles are found wherever
decaying or fermenting material occurs, although by
no means all the Staphylinids are scavengers. They
are long, slender, somewhat flattened beetles, with
wing-covers or elytra extending over only two segments
of the abdomen. The other segments are free and
flexible, often readily up-curved so that it sometimes
appears as if they intended to sting. Some of these
species are so small and slender that they are difficult
to see and some are of considerable size; sometimes
they are smooth and shining and sometimes densely
covered with short silky pile, both methods serving
to keep the insects clean in their often unsavory sur-
roundings. As an indication of their habits some of the
species have peculiarly sickening odors that in penetra-
tion and volume are altogether out of proportion to the
size of the insect producing them. In animal or vegeta-
ble decay, in excrement, under and in dead animals, in
the fermenting sap of injured or dying trees, in fungi of
all kinds — in all these places our Staphylinids occur and
everywhere do their share of the needed work.

Closely allied to them come several families of
minute beetles, some of them of odd and bizarre shapes;
all of them with the enlargement or club of the antenna
well marked, and all of them feeders on dead or decay-
ing matter. Their names alone would tell us nothing;
to go into their habits and peculiarities would require
another book, for there are literally hundreds of them.

i88

INSECTS

Conspicuous in appearance and habit are the bury-
ing beetles and carrion beetles, their names indicative
of their functions. They are often of moderate or large
size and at the end of the feelers the club is capitate or
shaped like a head, an arrangement that permits the
organization of an extremely sensitive olfactory system.
The sense of smell in these insects is so well developed
indeed, that even a small dead animal is unerringly

located very soon after its
demise. I have seen these
beetles climb to the tip of
a twig, extend the antennae
in every direction with the
leaves of the tip widely sep-
arated, and then fly in a
straight line and without hes-
itation in the direction from
which, apparently, an agree-
able odor was perceived. The
burying beetles are so called
because of their habit of
digging out the soil from
beneath a small animal un-
til it sinks down to or below

the level of the ground, and the powerful head, thorax
and legs are well adapted for this kind of work. The
carrion beetles are quite as prompt in their arrival,
but do not work in the same way. They are content
with ovipositing on or under the cadaver, trusting the
resulting larvae to their own devices. And what a lot
and variety of these carrion beetles there are! Species
so small as to be almost invisible to the unaided eye,
and others an inch or more in length. Species smooth
and shining so that none of the material in which they
live can adhere to them, and species covered with fine

FIG. 85. — A burying beetle, Necro
phorus americanus .

THEIR RELATION TO MAN 189

silky pubescence, or rough and ridged for the lodgment
of any sort of material, serving in some cases to disguise
and conceal. And as with most of the scavenger fam-
ilies, not all of the species are confined to animal foods.
Some are found in decaying vegetation, and yet more
in fungi, which harbor a great number of species.

The Histeridce or "pill beetles" are little, chunky
creatures shining black or metallic in appearance, and
the legs all broad and flattened, fitted for digging.
They occur in decays and ferments of all kinds, but
their habits are more diverse than in some of the other
groups, predatory forms being not uncommon.

And then come those species allied to the Dermes-
tid(B or larder beetles; species that feed upon dead
organic material but which instead of being advan-
tageous are rather the reverse, since they often feed
upon material that man desires for his own use, like
dried and smoked meats, hides and even the animal
fabrics. Here again we note that the matter of use-
fulness is after all only a relative one, since the very
function that makes a species valuable when it affects
something of no use to man, makes it harmful when it
affects something that he wishes to keep.

There are exceptional scavengers in most of the
other beetle families, but none that need mention
here except the "tumble-bugs" and their allies, which
feed on excrementitious material, often rolling large
balls of dung from the place where it was found to a
place where it can be conveniently buried to serve as
food for their larvae. These tumble-bugs are members
of the Lamellicorn series which contains mostly plant
feeders and which are more fully referred to as plant
enemies.

The Lepidoptera contain no scavengers strictly
speaking, although there are some species that feed

1 9o INSECTS

on dried organic matter, animal as well as vegetable,
and in the Hymenoptera only the ants may be classed
as such. Ants, of course, are feeders on a very great
variety of materials. Some species will attack and
devour any living thing that comes in their way ; others

FIG. 86. — A "tumble-bug," Copris Carolina: a, larva; b, the cell in which
it lived; c, pupa; d, female beetle.

confine themselves to vegetable food only and yet
others seem to be restricted to liquid food. Most of
them have quite a range of supplies and some species
may be found almost anywhere, even in our houses.
And yet ants are rarely thought of as real scavengers,
for they are not seen in or on decaying animals or in
or on foul excrements.

In the Diptera, however, we have scavengers in
great number and variety; and yet very much alike

THEIR RELATION TO MAN

191

after all, for in the larval stage they are nearly all mag-
gots, similar to those of the common house fly. -Wher-
ever an animal dies, a mass of excrement drops in the
field, an over-ripe fruit falls to the ground or a pail of
garbage is set outdoors, there we find flies present at
once and in a few hours young maggots. It has been
said that flies will devour an ox more rapidly than a lion
and while that may be a little exaggerated, they will
certainly make a more complete job of it. It is literally

FIG. 87. — Pommace fly; Drosophila ampelophila: a, adult; b, larva;
d, e, pupa.

astounding to note how rapidly a small carcass may be
transformed into a mass of squirming maggots, ap-
parently liquefying the tissues so that they may be ab-
sorbed through the small mouth orifice. And it needs
so little to attract these flies. Lay out a few bruised
apples, pears or other fruit on a table, and in a short
time they will be covered with little yellowish or gray
flies having bright, brick-red eyes — pommace flies —
coming from no one knows where, but attracted by the
odor of the ferment. In the fall when cider or wine is
making, every tub or barrel of must is an attraction,
and in the ferment thrown out of the bung of the wine
cask the larvae occur by the hundred. Not long as

192 INSECTS

larvas either, for in two or three days they have become
full-grown, change to a pupa and then to the adult
condition. And so we find that in this, the most highly
organized series of insects, scavengers are numerous and
effective. So effective, indeed, that their usefulness is
not recognized by the average man, because he has no
chance of knowing what conditions would otherwise be.

Among the insects of direct use to man none are of
greater importance than the silk-worms. Silk is in
such general, almost universal, use, that there is scarcely
a moderately well-dressed individual of either sex
that does not have some of it as part of a garment
or other article of wear. Of the millions who wear or
use silk how many ever know, or knowing, realize, that
every particle of that silk is the product of a cater-
pillar; nothing more than a dried viscid salivary secre-
tion, originally intended by nature as a covering to
protect the pupal stage of the insect? This covering
or case is called a cocoon, and cocoons are spun by
many caterpillars, some of them much larger than the
Chinese silk- worm.

Why, then, if there are many silk spinners do we
use one only, and what particular advantage has the silk
of this species over all others? As to the latter, it has
few advantages over other caterpillar silks: it is not
nearly so strong as some produced by other varieties,
it is not more lustrous, and it is not nearly so great in
quantity. Its one great advantage for our use is that
it can be more easily reeled than any other known
variety. The silk- worm, when ready to make its cocoon,
spins a small quantity of loose, supporting threads or
floss and then starts inside this framework, spinning
with a continuous thread, unless interrupted, until
the entire cocoon is completed — a thread almost a mile
long which, under favorable conditions, can be unwound

THEIR RELATION TO MAN 193

in the same way and without a break! Generally,
other caterpillars that spin cocoons do not work con-
tinuously; or if they do work steadily on, they make
a patchwork affair of it. They may spin a few yards
at one end, break the thread, put in a few yards at an-

\

FIG. 88. — Silk-worm, cocoon and male moth.

other point, and so on until the work is completed,
making a nice even job when everything is done, but
a cocoon that cannot be profitably unwound or reeled
because of the great number of breaks.

Then, too, the particular species, Sericaria mori,

has been domesticated so long that it has developed

some highly desirable qualities. The adult moths are

very sluggish, even the males flying little or not at all,

13

i94 INSECTS

while the females are practically incapable of flight.
They pair readily in confinement, are hardy, and very
fecund, the female producing several hundred eggs.
All these advantages, together with the ease of handling
the caterpillars, are matters in favor of the mori, and
its propagation is largely the work of women and
children who do it as a side issue and hence very cheap-
ly. It is this latter factor indeed that has barred silk
culture in America, where the cost of labor is too high
to make the venture attractive to any class.

It has already been said that the silk is in the nature
of a salivary secretion; but that is only partly true,

^^(/g^J/3^>~
Secreting Glands

FIG. 89. — Salivary gland of silk-worm.

because, although the material is secreted by one pair
of what are usually salivary glands, these glands have
been so enormously enlarged that they extend along
the sides of the body for almost the full length of the
caterpillar, and the material has become so sticky and
viscid that it could not possibly have any digestive
function. The two glands unite into a single outlet
on the lower lip of the caterpillar, and as soon as the
fine thread of liquid issues from the opening of the
spinning organ and comes into contact with the air,
it hardens sufficiently to hold its form, reaching its
full strength and elasticity a few moments later. As
to the value of silk products each year, they must be
figured in millions of dollars, so that the humble cater-

THEIR RELATION TO MAN 195

pillar adds not a little to the wealth of the producing
countries, and to the support of those engaged in textile
industries. The elimination of the silk-worm and its
product, while it would not eventually cause mankind any
serious inconvenience, would deprive it, for all time, of
one of its most valued and widely employed fabrics.

Next in order of value are the bees and bee-products
which seem to have been recognized and employed
almost or quite as long as we have any historic records.
Honey from wild bees is known to every savage nation
and has formed an important item of food. And not
of food alone, for away back in the dark ages it was
found that it made an excellent drink when fermented,
the "meth" of the ancient Saxons being the ancestor
of the "metheglin" of more recent times. The latter
drink is little known now-a-days, especially in cities and
towns where malted and distilled liquors are in use;
but it has still a vogue in a few sections of the country,
where those who first make its acquaintance gain a
wholesome respect for those ancestors of ours whose
capacity for it was measured by "flagons," or "horns."

Wax and honey as products of the bee are uni-
versally known and the organization of the beehive is so
well understood that it need only be referred to. Paraf-
fine has largely supplanted beeswax for many purposes,
while sugar and glucose have replaced honey ; so, even
were the bee now completely eliminated from our fauna,
mankind would still worry along. Nevertheless, bee-
products are on the increase rather than otherwise and
there is no lessening in the demand for them.

The products of the "lac" insects known as "stick
lac," "shell-lac," etc., are yet of considerable impor-
tance although the insect "lac" has now been largely
replaced by cheaper preparations from other sources,
for general use. The lac insect is really one of the "soft

196 INSECTS

scales," allied to the most serious of our tree pests:
indeed it is a tree pest, tolerated only because the insect
is of more value to us than the plant upon which it
feeds. Infested twigs are cut and stored when the insect
has reached the proper stage, and the adherent scales
and their secretions are dissolved off when they are to be
commercially used. Lac is a product of the Orient and
many of the fine polishes and lacquers of Indian, Chinese
and Japanese workmen are based upon it. There are
allied species of Coccidcz occurring in tropical America;
but none that have been made commercially useful.

Cochineal as a source of a beautiful crimson and
scarlet is well known and is also a scale insect or Coccus,
belonging to the mealy-bug series. It infests -certain
kinds of cacti and is cultivated in plantations called
"nopalries. " It is the source of the coloring matter
known as crimson lake, and is a native of Mexico and
Central America. Before the day of aniline colors
cochineal was extremely valuable and important; but
at present the complete elimination of the insect would
cause little if any inconvenience.

It is noticeable that, except in the case of silk, we
have substitutes for practically all the insect products
and even silk has been artificially produced, i.e., a
product so closely resembling it as to be called artificial
silk has been made that could be developed practically
in case of necessity.

In olden days insects had a wider use, and out of
a plague a food supply was sometimes developed.
"Locusts" or grasshoppers as articles of food are known
among barbarous nations of many countries where
the insects are sufficiently abundant. The Indians of
the Rocky Mountain regions in America and the
aborigines of Africa were equally familiar with a grass-
hopper diet and with the methods of preparing them.

THEIR RELATION TO MAN 197

It has even been suggested that there is no reason why
they should not be retained on our modern bills of fare,
and experiments have been made in different methods
of preparation. Fried they are said to have a sweet,
nutty flavor, while in a stew with milk they recall
oysters. It must be confessed that no very great en-
thusiasm has ever been developed for this kind of diet,
and on the whole the use of grasshoppers for food pur-
poses is distinctly on the wane.

In South America a species of water bug of the Corioca
series occurs in great abundance in some localities and
lays its eggs in large numbers on the surface among the
sedges. These eggs are gathered, dried and preserved by
the natives, who mash and bake them into a cake that
is much appreciated. Inasmuch as the eggs have a very
decided bed-buggy odor, it would require considerable
education to make that sort of omelet popular.

The large boring larvse of Coleoptera and even some
Lepidoptera are not unusual articles of food in tropical
countries, and ants or ant larvae and pupae have also
served as sources of food supply to uncivilized man;
but as civilization tends to eliminate the insects in its
advance, their decreased numbers would render them
less available as sources of supply even were better or
more usual articles not more plentiful.

Galls as sources of supply for tannic acid are still
gathered in some localities, and some forests are com-
mercially profitable as gall producers. When inks were
largely dependent upon galls for their black color, there
was a greater demand for them than now, when chem-
istry supplies other if not better sources of more or less
permanent black stains.

Insects have from time to time served as ingredients
in medicaments ; but very few are so used at the present
time. Of these the Cantharides or blister beetles are

198 INSECTS

best known and yet most widely employed. In the
body juices there is secreted an extremely irritating
material known as cantharidin which, when applied
to the skin, produces blisters or, taken internally, pro-
duces inflammatory conditions of the genito-urinary
system. Most of the blister beetles possess this prop-
erty to some extent, and a fresh specimen of any of
the common American species crushed upon the skin
will produce blisters; but the officinal preparations
are obtained from a European species, known as the

FIG. 90. — Spanish flies, Lytta vesicatoria,

Spanish fly, Lytta vesicatoria, from the locality whence
most of the specimens come and from its vesicating
properties. These beetles come in great swarms when
they emerge and are on the wing for a few days only,
during which period the entire country is engaged in
gathering them in sheets on which they are killed and
dried, after which they may be preserved indefinitely.
The blistering property is dissolved out of the powdered
beetles with alcohol.

Broadly stated there are no insects that are indis-
pensable to man; there are a few that are very use-
ful to him, aside from those that are plant pollinators,
and he makes use of a few others for which he has
substitute materials at hand and already in partial use.

CHAPTER IX

THEIR RELATION TO MAN: AS CARRIERS
OF DISEASES

SINCE the development and general acceptance of
the microbian or "germ" theory as applied to many
contagious and infectious diseases, and its absolute
demonstration in plagues like cholera, typhoid fever,
dysentery and other enteric or intestinal troubles, as
well as in consumption, pneumonia, diphtheria and other
affections of the respiratory organs, the question of the
agencies concerned in the distribution of these germs
has come to the front.

The surgeon has long known that suppurations and
pus-producing inflammations might be carried from one
individual to another by almost any sort of carrier; so
when he operates, he sterilizes his instruments, his
hands, the cut or bruised surfaces, and protects the
wounds by antiseptic dressings. That flies were among
the agencies for spreading suppurations was soon
learned, and the readiness with which flies gather on
sores or raw surfaces is matter of common observation.
When it was observed that flies of various kinds gathered
with as much readiness on fecal or excrementitious
matters as on food products in the kitchen, and were
ready to change their diet from one to the other without
much provocation, the conclusion that they might inocu-
late the food products and through them healthy indi-
viduals from the fecal matter was not a difficult one
to draw.

In the cholera epidemic at Hamburg not so many
years' ago, this was absolutely demonstrated as to that

199

20O

INSECTS

disease. It remained for the United States, during its
war with Spain, to demonstrate with equal positiveness
that typhoid and other enteric fevers could be carried
in the same way. More soldiers killed by common
house flies than by Spanish bullets, is the unenviable
record, and the most unsafe places for our soldiers were
the fly-infested home camps where open latrines and
near-by mess tents furnished ideal conditions — for the
flies and the diseases.

FIG. 91. — The house fly, Musca domestica: larva with details at right, puparium

at left.

While flies are not the only carriers of enteric disease
germs and these do not actually depend upon insects as
their sole means of spread, yet the habits and structures
of flies are peculiarly adapted for effective service of this
nature and they are correspondingly dangerous. No
other insects live in such close communion with man, and
so much are they regarded as a matter of course that
their companionship at our table arouses no fear; and
such is their persistence that they gain admittance to
the palace of royalty, as well as the hovel of the peasant.
They breed in all sorts of decaying and excrementitious
matter, in garbage pails and even in neglected corners of

THEIR RELATION TO MAN

201

cellar or store-room; a very little material serving to
mature a large number of specimens. The common
house fly, Musca domestica, prefers horse-manure for its
development and is most numerous in the vicinity of
stables. The eggs are laid in little masses by the adults,

FIG. 92. — Foot of the house fly: a, the last tarsal joint and claws; b, claws and
pulvilli; c, a small section of the pulvillus, showing hooked hairs.

the larvae or maggots hatch almost at once, and a week
later these are full grown and ready to transform.

On the soles of their feet flies have pads of very fine
hair, which serve excellently as gatherers of micro-
organisms from the surfaces over which they travel, and
equally well as distributors on others over which they
may track later. This point has been proved experi-
mentally by allowing flies to walk over cholera excre-

202 INSECTS

tions, and afterward over plates of prepared gelatin.
In the incubator, every footprint developed a flourish-
ing colony of virulent cholera germs.

The mouth parts of flies are almost equally well
adapted for similar purposes. At the end of the fleshy
lips are lobe-like expansions furnished with chitinous
ridges by means of which the pasty masses of food are
scraped into shape to be ingested by the insect. These

FIG. 93. — Lapping organ at the tip of the fly mouth.

ridges are excellent resting places for the minute organ-
isms and, when the flies change their diet, the germs are
directly inoculated into the new food material, what-
ever its character. And flies are not always cleanly in
their habits, but void their excrement anywhere in
small, pasty masses which dry quickly. It has been
shown that the bacilli of intestinal troubles pass through
the digestive tract of the insect unchanged, hence every
"fly speck" may be a source of danger.

This method of transfer for pathogenic organisms is
very simple and direct, and is applicable only to forms

THEIR RELATION TO MAN 203

that undergo no change and which, when implanted in
a suitable medium, will continue their growth and
increase with unabated virulence. We have yet quite a
different class of diseases, also due to microscopic or-
ganisms, but of an altogether different type: minute,
single celled animals in fact, that live in special body- or
blood-cells, but are not capable of completing their en-
tire life cycle in a single host.

The best known example of this sort of infestation is
that due to the Plasmodium parasite which produces
what is loosely known as malaria. It is not so long ago
that almost any sort of indefinite
illness was likely to be classed as a
"touch of malaria:" now-a-days
when a doctor diagnoses "mal-
aria" he refers to an affection

FIG. 94. — Part of one
Caused by One Of tWO Or three of the pseudo-trachea used

specific organisms that have very as scraping organ'
definite life cycles and produce

very definite results. All of them agree in being Spor-
ozoa, i.e., animals that reproduce by means of spores, and
in that they do not complete their entire life cycle with-
in the body of their human host. The parasite producing
the ordinary type of tertian malaria or " chills and fever "
lives in the red blood-corpuscles of the human body and
comes to maturity in such a blood-cell in forty-eight
hours. It then breaks up into a mass of minute spores
which rupture the cell and are liberated into the blood-
serum. In this they float about for a short time, and
then each spore makes its way into a sound red blood-
corpuscle, and in forty-eight hours is itself mature and
in turn reproduces in the same way. As all the parasites
come to maturity and liberate their spores at about the
same time, this causes a disturbance of the body tem-
perature resulting in a chill, followed by a fever when the

204 INSECTS

spores are entering new blood-corpuscles. In other words
the "chills" and "fever" merely emphasize the period
at which the parasite sporulates, and the ill effects of
malaria are due to the gradual destruction of the red
blood-cells.

If some of this infested blood be drawn from a pa-
tient and injected into the circulation of a healthy indi-
vidual, a new case of malaria will result; but in no other
way can there be a direct infection from one individual
to another. Normally this reproduction by means of
spores continues in an infested individual for some time
and then, in addition to the spores, special cells develop
which, when liberated into the blood-serum, make no
attempt to enter new blood-corpuscles. These are the
"gametes," of two types, differing a little in size and
form and termed respectively "micro-" and "macro-
gametes. " They undergo no change in the human body
and may remain in that stage for an indefinite period,
even when the active reproduction of the Plasmodia
has been checked and the patient is apparently well.
Taken from the human body by any sort of blood-
sucker or even drawn on a properly prepared slide,
further development takes place. From the micro-
gametes slender, whip-like processes are produced,
known as "flagellae," and these break off and represent
the male element that unites or conjugates with the
large unaltered " macrogamete " representing the female
element. At this point development stops unless the
blood is in the -stomach of a mosquito belonging to the
genus Anopheles. If it is not only Anopheles, but a
member of the right species, the conjugated gamete
elongates and becomes a "vermicule" which bores into
the tissue of the mosquito stomach, increases in size and
gradually works its way to the outer surface where it
forms a little lump or protuberance, now known as a

THEIR RELATION TO MAN

205

"zygote." In about ten days this form matures and
bursts, liberating thousands of "blasts" or "sporo-
zoits" into the body cavity of the mosquito. In

FIG. 95. — Anopheles and Malaria: a, larva; b, pupa; c, adult; d, the blast
introduced into the blood by the mosquito; e to ;', stages through which the
Plasmodium passes in the red blood-corpuscle; k, the spores which enter new
blood-corpuscles; /, m, the microgamete ; n, o, the macrogamete ; p, flagellae
forming; q, union of a flagellum with macrogamete; r, fusion of nuclei; s, the
vermicule; t to y, formation of the zygote in the mosquito stomach; the fully
developed zygote, y, rupturing to produce blasts d.

206 INSECTS

some way these gather into the salivary glands, and
when that mosquito bites again, it introduces with its
droplet of saliva a large number of "sporozoits" which,
if they find conditions favorable, enter red blood-
corpuscles and set up a case of malaria.

The transmission of this disease, then, is by no means
a simple matter, and the proper species of Anopheles is
absolutely essential to it. The elimination of these mos-
quitoes from any locality would carry with it the elimi-
nation of malarial troubles as well. It may be inter-
esting to note in this connection that the species of
Anopheles live easily in settled communities, enter
houses freely where they can manage it, and that the
female passes the winter in the adult stage in cellars,
coming up occasionally into well-warmed rooms and
even biting. Normally, they do not become active
until well along in May or in June, when eggs are
laid by the female which has been fertilized the
previous fall.

All stages of the parasites causing the various forms
of malaria have been followed in both man and the
mosquito, and no part of the history above given is
guess-work. The connection between the Stegomyia
mosquito and yellow-fever is equally certain, though the
specific parasite has never been made out in either man
or insect. Direct experiment has furnished convincing
proof of the connection, and the treatment of yellow-
fever epidemics has entered a new phase. The efficient
work done in the Panama Canal Zone has demonstrated
that the disease is quite controllable through the insect
and, incidentally, collections made by entomologists
from the U. S. Department of Agriculture at Washing-
ton, have shown that this Stegomyia is never found
away from human settlements. The relation, then, is
extremely close between this insect and man, and they

THEIR RELATION TO MAN 207

are both needful to the continued existence of the
disease.

There are other tropical fevers that are probably as
much dependent upon other mosquitoes, but we know
less about them. We do know that several forms of
bird malaria, due to species of Proteosoma, are also de-
pendent upon mosquitoes as intermediate hosts, and

FIG. 96. — The Tsetse-fly, Glossina morsitans.

how many diseases of other animals are transmitted by
them is as yet matter of conjecture only.

A species of Culex very closely allied to our common
"house" or " rain -barrel " pest is responsible for the
transmission of that tropical disease "filariasis" which
sometimes causes the abnormal enlargement of the
lymphatics and thickening of the skin, known as "ele-
phantiasis." Other species have been charged with
being agents in the transmission of leprosy, but this
must be considered "not proven" as yet.

In all these cases, the mosquito is an intermediate
host: not a mere carrier, but a fellow sufferer with
man, subject to another form of the same disease,

208

INSECTS

and in this respect there is a fundamental difference
from those troubles conveyed by house flies, which
suffer nothing, and are purely mechanical transporters
of the infection — albeit peculiarly well adapted for
their purpose.

There are other flies, however, that seem to be nearer
the mosquitoes in this respect and, among these, are the
species of Glossina or "tsetse" flies of South Africa,

which are known to pro-
duce fatal affections in
horses and have been re-
cently charged with being
agents in the transmission
of the "sleeping sickness. "
All mosquitoes pass
their early or larval stages
in water, and that is about
the only feature that is
common to all of them.
They differ widely in the
character of the waters
which they inhabit, in the

FIG. pT.-Larva^and^upa of the house period of development, and

in the number of broods.

Some pass the winter in the egg state, some as larvae
and a very fair proportion as adults. All the species
that are closely associated with man may breed in
dirty water, and some in such as is absolutely filthy.
Culeoc pipiens, the common "house mosquito,"
breeds in rain barrels, lot puddles, cess-pools, gutters
and sewer basins. It is rarely found in clean water and
almost never in streams or brooks. The eggs are laid
in a mass or raft on the surface and are easily seen when
their character has once been recognized. In forty-
eight hours the larva is ready to hatch, a little lid drops

THEIR RELATION TO MAN 209

from that surface of the egg that rests upon the water,
and the minute wriggler slides at once into its natural
element. This "wriggler" is so named from its peculiar
jerky mode of progression. It has, attached to its
mouth, a pair of very dense brushes of fine hair, and
these brushes are kept in constant motion, combing
from the water and into the mouth the minute organisms
upon which the creature subsists. At the other end of
the body is a cylindrical tube of moderate length, at the
tip of which are the spiracles or openings to the breath-
ing tubes, by means of which air is secured from above
the surface of the water; for the larva although strictly
aquatic as to food and other habits, is yet dependent
for its supply of oxygen upon the outer air, and must
come to the surface at short intervals to breathe. Indeed
the favorite position of this larva is to hang head down
in the water, the tip of the tube at the surface, the
mouth brushes hard at work securing food. This pecu-
liarity of the insect gives us a certain advantage in our
efforts to control their increase, for a film of oil on the
surface of the water in which they live will prove rapidly
fatal, the oil entering into the body through the spiracle
when the insect attempts to get air.

In from five to seven days during the summer, the
larvae are full grown and change to pupae in which the
outline of the future mosquito can be made out hunched
into a comma-shaped mass. This pupa also gets its air
supply from above the surface, through two small,
trumpet-shaped tubes on the thorax, so that it is also
fatally affected by oil. It is active in this stage when
disturbed, and moves about rapidly but erratically, by
means of two paddle-like structures at the end of the
abdomen. When it becomes quiet it rises automatically
to the surface, and there rests until ready to assume the
adult stage, which is in from one to three days in summer.
14

210 INSECTS

In cool or cold weather all the stages are lengthened and,
whereas eight days from egg to adult is perhaps a normal
period, this may be increased to two or even three weeks.
The adult male is incapable of sucking blood; but the
female is ready to bite twenty-four hours after she be-
comes developed, and in three or four days thereafter is
ready to lay eggs. The life period of the male is always
short, since his only function is to fertilize the female.
The life of the female depends upon her ability to find a
place for her eggs. When she has placed them her pur-
pose in life is filled and she also dies. If she finds no
suitable place she may live for weeks and bite several
times. Those females that develop late in fall do not
feed after they are fertilized, but seek some convenient
hiding place in a cellar, barn or outbuilding and remain
there dormant throughout the winter. They become
active again in May, but larvae are rarely found in any
number until well along in June. This species occurs
throughout North America and a close ally occurs in the
old world.

The yellow-fever mosquito, Stegomyia calopus, or
fasciata as it used to be called, is a smaller species, black
in color, with white marking on the body and legs. It is
rather a pretty creature, an inhabitant of the more
southern states and of the tropical and subtropical
regions of America generally. On the Atlantic coast it
does not extend normally north of Virginia, and this
marks the limit to which yellow-fever may extend under
ordinary conditions. I am not unmindful of the fact
that yellow-fever has occurred in New York and Phila-
delphia; but the conditions permitting these epidemics
are now understood and cannot be again reproduced.

In habit, the Stegomyia is not unlike C. pipiens, and
like it breeds in all sorts of dirty water. It is very sensi-
tive to cold, and the first frost puts an end to its activi-

THEIR RELATION TO MAN

211

ties. It is even more domestic than its ally and seems
to be confined to the vicinity of human settlements. It
is as susceptible to oil, in the larval stage, as any other
species and also hibernates as an adult. The eggs are
not laid in rafts, however, but are placed singly, not
even necessarily in water, and may remain dry for a
considerable period without losing vitality. When they
do become water-covered they hatch, and the life period
and stages are similar to those of pipiens.

FIG. 98. — The yellow-fever mosquito, Stegomyia calopus; larva, pupa, adult.

The species of Anopheles are longer and more slender
than the Culex, and the wings are usually more or less
mottled or "dappled." The adult females hibernate in
houses when they can get in, and in May or June lay
eggs on the surface of water, singly or in little groups,
but not in boats or rafts. They are kept afloat by a
peculiar lateral supporting structure and hatch in a day
or two after they are laid. The resulting larva or wriggler
is altogether unlike that of Culex or Stegomyia. It is
flatter, with a proportionately smaller head and a much
shorter breathing tube, and lies flat on the surface of the
water. It has similar mouth brushes but gets its food

212 INSECTS

from organisms that float on the surface film. Its float-
ing habit enables it to live in very shallow water, and in
places where no fish except the smallest top minnows can
follow.

For breeding places the species of Anopheles select
moderately clean water, and prefer the grassy edges of
large pools, ponds or swamp areas, or the eddies or dead
corners of sluggish streams or ditches. They do breed in
lot pools, however, and even in rain barrels, pails or tin
pans. Cess-pools, sewage water or dirty gutters are not
attractive to them.

Despite this difference in habit the larvae are as much
susceptible to oils as are those of Culeoo, and in the pupal
stage the differences are much less pronounced. While
in a general way, the species of Anopheles are referred
to as malaria carriers, not all of the*n are able to serve
as intermediate hosts. The most common and widely
distributed form known to be dangerous is A. maculi-
pennis, which has two fairly well-marked dusky spots
on each wing.

None of the domestic or house mosquitoes are great
travellers, and they rarely fly for any considerable dis-
tance ; but there are species breeding in the salt marshes
along our coasts, both Pacific and Atlantic, that migrate
long distances inland, drifting with the wind twenty
miles or more in a single night. These species lay their
eggs in the marsh mud and winter in that condition.
The larvae, which resemble those of the house mosquito,
develop equally well in salt or fresh water, and mature
in about ten days from the date' of hatching. In the egg
stage they may remain dormant for months and perhaps
for years.

There are many other kinds of mosquitoes important
as nuisances, but not a menace to health, whose consider-
ation here would carry us beyond the scope of this essay.

THEIR RELATION TO MAN 213

The one uniform requirement for development — water in
which they may breed — gives us the clew to the method
of control, and our efforts should be intelligently directed
to eliminating such places by draining or filling rather
than to destroying the larvae after they have begun to
develop.

Sometimes, where it is recognized that mosquitoes
are hibernating in numbers in a house or cellar, it may
become desirable to attempt their destruction during
the winter. This can be accomplished by fumigation
with either stramonium or culicide. Stramonium is
simply the powdered leaves of "jimpson weed," which
grows almost everywhere within the United States, and
it is made up with one-third its weight of saltpetre to
make it burn better. Eight ounces of good stramonium
is sufficient for 1000 cubic feet of space and the fumes
are not poisonous to man. Culicide is a combination of
equal parts by weight of carbolic acid crystals and gum
camphor. Dissolve the carbolic acid crystals over a
moderate heat and pour over the camphor broken into
small lumps; the acid dissolves the camphor and the
solution is permanent when kept in a stoppered jar. It
requires three ounces of this culicide for every 1000
cubic feet of space and it should be evaporated in a
shallow pan over an alcohol or other lamp. This will
kill flies as well as mosquitoes and is not dangerous to
human life. The mixture is inflammable, however, and
must be used with that fact in mind.

Whichever of these materials is used, the room to be
fumigated must be made as nearly air-tight as possible,
and must be kept closed at least an hour to make certain
of a satisfactory effect on the insects.

Fleas are specialized flies, adapted for a particular
mode of life, and their habit of more or less indis-
criminate biting has laid them open to suspicion in

214

INSECTS

FIG. 99. — A home-made evaporating outfit for "culicide," using a section of
stovepipe.

various directions. Their connection with the spread of
the "plague" seems to be demonstrated and that disease
is now fought in the rats from which the fleas transmit
it to man.

THEIR RELATION TO MAN

215

Fleas live in their adult stage on hairy, warm-
blooded animals, feeding on their blood, and their trans-
versely flattened form set with spines all directed back-
ward enables them to move about freely and quickly.
Their eggs are dropped in the dens or nests of their
hosts, and the larvae, which are slender, white and

FIG 100. — The common cat and dog flea: a, the egg; b, adult; c, pupa;
d, larva coiled in silken case; e, lar^a.

worm-like, live on the dead and decaying animal and
vegetable matter always present in such places. In
houses, the common dog and cat flea is able to develop
its larvae in the material accumulating in the crevices
between floor boards and similar situations, and in the
adult stage almost any kind of flea will bite any warm-
blooded animal upon which it may happen to get, even
if not capable of maintaining itself there. So man,
though unfitted because of his hairless skin to serve as

216 INSECTS

a host for fleas, may nevertheless be bitten by any of
those infesting any of the animals that live with him
or in his dwelling places.

In an ordinarily well-kept house flea larvae cannot
develop; but occasionally, when such a house has been
kept shut up during a summer, a brood of larvae may
develop and become annoying. In such case a free use
of gasoline in floor cracks and similar places where the
flea larvae live will generally give relief.

The subject as presented here is a mere outline of
what is known and believed; there are other insects
that undoubtedly facilitate the spread of disease in man,
directly or indirectly, and there are many more that do
this for other vertebrate animals. Their importance
from this point of view cannot be overestimated, and at
the same time it is eloquent testimony that for many
ages man and these insects must have dwelt together, to
permit so close a union as identity in parasitic affections
argues.

CHAPTER X

THEIR RELATION TO THE HOUSEHOLD

SINCE man has enjoyed the shelter of a dwelling, how-
ever simple, he has had in it something in the nature of
furniture and bedding, and he has usually felt the need of
storing, in time of plenty, supplies that might be drawn
upon in seasons of want. And stored products of all kinds
have ever been attractive to those insects that feed upon
dead animal or vegetable matter ; not necessarily decay-
ing or decomposing matter, but simply that which is
without active life and ready to return to its original con-
stituents, whether by way of the human alimentary canal
or in any other manner. Stored seeds are not dead in the
strict sense of that term; but it can stand here for that
inactive condition of vegetable life in which it is not ca-
pable by any process of growth of outrunning or opposing
the attacks of such creatures as attempt to feed upon it.

There is no one species of insect that is confined to
human habitations. All are species that also occur under
normal outdoor conditions, and that could continue even
though every trace of mankind were removed from the
face of the earth; but as to some of them the struggle
would then be very seriously intensified.

We might arrange the species that associate with
man so closely, in the order of the manner in which
they affect us, and that would be the better method
were we intent only on a treatise dealing with house-
hold pests; but I have preferred to follow the general
scheme of dealing with the orders and giving those
general habits that have induced certain of their mem-
bers to frequent man's neighborhood.

217

INSECTS

I begin by stepping outside the insects altogether
and dealing with the common house "centipede" or
"thousand legged worm." It is a frail yet formidable

looking creature with a large
number of long slender legs,
yellowish-gray in color and
mottled with blackish. It has
a pair of long, many-jointed
feelers and the last pair of
legs are unusually extended
so that they give a weird im-
pression of danger that makes
most people hesitate about in-
terfering, except through the
agency of a broom or similar
weapon. It is most commonly
seen in cellars or on damp
walls, but may occur almost
anywhere in the house, and
its mission is quite innocent;
praiseworthy in fact, for it is
predatory on other household
insects, feeding on roaches,
bed-bugs, moths and such sim-
ilar creatures as it is able to
get hold of. The specimens
should really never be inter-
fered with at all ; but few per-
sons like their looks and there
is neither danger nor difficulty
in killing them. At a touch

the thing collapses into a struggling mass of legs, which
continue to wiggle for some little time after they are
separated from the body. The natural habitat of
species of this kind is under the bark of trees, under logs

FIG. 10 1. — A house centipede, Sou-
tigera forceps.

RELATION TO THE HOUSEHOLD

219

or in other damp, sheltered situations. There is a small
poison gland connected with the mandibles which, howr-
ever, are incapable of piercing the human skin. Nor is
the poison sufficient in quantity and character to cause
any appreciable trouble, even if by any combination of
circumstances the jaws could be forced into the flesh.

Among the true insects the lowest or most primitive
order, the Thysanura, are represented in houses by
several species. In the cellar
of the farm-house where veg-
etables and other provisions
are stored in quantity, they
occur wherever it is damp
and wherever the least sus-
picion of decay occurs. There
are here several species of
bristle-tails and spring-tails;
small wingless creatures,
soft -bodied, with indefinite
mouth parts, that feed only
where a way is opened to
them by other things; but
when that way is opened

their feeding promotes the decay that first gave them
entrance, and by their numbers they may become
troublesome. Remembering their fondness for damp
places the free use of lime and thorough ventilation
will serve to disperse them. Some are so lowly organ-
ized that the tracheal breathing system is not fully
developed and oxygen is absorbed through the damp
skin. To such creatures dryness is fatal. In cities
and towns few of these insects are found, and prac-
tically only two species of "bristle-tails," or "fish-
moths" or "silver-fish" occur. One of these species
is quite tough in texture, somewhat convex, evenly

FIG. 102. — A spring-tail or
Podurid.

220 INSECTS

silvery, and found only in cellars or damp places;
the other is very soft-bodied, the silver mottled with
blackish or gray, and found in dry warm places like

FIG. 103. — The silver- fish, Lepisma domestica

kitchens, bake-houses and pantries. They feed on
all sorts of starchy products and nibble preferably at
bits of bread, cake and the like; but at a pinch they
gnaw the calendered surface of paper or book bindings,
and have been known to attack the glossy surface of a

RELATION TO THE HOUSEHOLD 221

shirt front. They are rarely abundant enough to be a
real nuisance, and wherever it is necessary to deal with
them they yield readily enough to pyrethrum or gaso-
line whichever may be indicated; naphthaline serves
very nicely as a repellent wherever one is necessary.
Ordinarily, killing the specimens as they come under
observation answers every purpose.

A little higher in the scale of development come the
"book lice" belonging to the family Psocidce, allies of
and somewhat resembling the
biting lice that have been al-
ready dealt with in their rela-
tions to other animals. Indeed,
as a rule housekeepers when
they notice these little insects
among their stores of linen or
in dusty corners of drawers,
suspect them of being really
parasites or true lice. But all
lice, whether of the biting or
sucking variety, are awkward, FIG. 104.— A book louse,
slow-moving creatures on a

level surface, while these little Psocids are active and
agile, running backward or forward with equal readi-
ness, and so spry as to be not easily captured. When
captured, instead of being tough and leathery in texture,
requiring an effort to crush, they are soft and go to
pieces at a touch. They are never found on animals of
any kind, and what they are after is the little organic
particles that they get from any sort of dry animal or
vegetable matter. A dead fly will be reduced to a fine
powder by them in a few days when they are abundant,
and in collections they are occasionally something of a
nuisance; but almost any pungent odor drives them
away, and besides we have always the resource of not

222 INSECTS

leaving anything about that is attractive to them.
Camphor, naphthaline, oil of sassafras, carbolic acid,
and oil of peppermint have all been employed with good
effect and, really, almost anything answers. Occasion-
ally they infest an old straw or corn husk mattress in
great numbers, and in such case the only real remedy is
the fire. Other members of this group composing the
order Corrodentia or "gnaw^ers," a branch of the great
Neuropterous series, are winged and live outdoors, as
indeed do many of the wingless species; but always
their food is dried animal or vegetable matter, so that
the only reason why any species occurs in our houses is
that the materials that they feed upon are found there.
Scarcely higher in development so far as structure
is concerned are the Termites, or "white ants;" but
though low in physical organization they are most
wonderfully developed en the social side, standing
scarcely inferior to the true ants. Termites are not
numerous in species anywhere in temperate or frigid
North America, and throughout most of our country
only a single species occurs or is at all common — the
Termes ilavipes. In warmer countries and in the trop-
ics, the number of species is much greater, while in
Africa they have their point of greatest development.
In that country the insects themselves are house build-
ers, their habitations rising in many cases ten feet or
more above the surface in turret-like form and clustered
in great villages. But it is not with their peculiar or-
ganization nor interesting social life that we have to do
here; but with their habits when they leave their own
dwellings and invade ours. Yet to fully understand the
creatures and how they come to be with us at all, we
must know a little of their history. The popular term
"white ant" is derived from the pale, yellowish-white
workers of the common species, which are wingless,

RELATION TO THE HOUSEHOLD

223

about one-fourth of an inch long, flattened, with a large
head, small thorax and a rather large, ovate, bluntly
terminated abdomen or hind body. Outdoors they are
usually found in small numbers under flat stones at the
edges of woods, in fallen trees, old stumps or in woody
material generally. When a colony is disturbed most of
them will dive out of sight into galleries underground

FIG. 105. — Termes flampes, — a, larva; b, winged male; c, worker; d, soldier;
e, female; /, pupa.

and seem to be concerned only in getting away as fast
as possible. They are very soft, helpless, without eyes,
and in the day-light are absolutely defenseless. A few
specimens a little larger in size will appear bolder than
the rest, not quite in such a hurry to get away, and when
we look at these more closely, we note that the head is
larger and that they have longer, pointed jaws or man-
dibles. They are indeed the soldiers of the colony, and
developed for its defense; but very helpless soldiers at
that when uncovered, because like the workers they are
wingless and blind. Both workers and soldiers are

224 INSECTS

represented in both sexes, but the reproductive organs
are undeveloped and neither sex is capable of repro-
ducing. If we get at the home of a large colony in an
old tree, in late fall or early spring, we may find with
these white, wingless forms, some decidedly larger,
rusty brownish specimens, which have well developed
long wings lying flat on the back and well developed
eyes. These are the males and females which during
the warm days of spring leave the parent nest in a body
and swarm. They are sometimes seen emerging from
some old fence-post or house timber in great hordes
and for a short time fill the air. Their flight is very
weak, the two pairs of wings being unconnected and
very similar to each other, and when they have mated
they disappear. The majority of all these specimens
die without being able to found a colony and the method
of starting varies somewhat with the species. For our
present purpose it will be sufficient to say that in a
developed colony there is one queen or egg-laying
female, with abdomen so distended that she is helpless,
simply oozing eggs which are taken and cared for by the
workers. Or there may be several " complement al "
females which have never left the nest and never become
fully winged. In any case the colony consists of many
thousands of individuals and from the centre, where the
queen resides, galleries extend in all directions. The
food is usually wood-fibre; but may be any sort of dry
vegetable products even when made up into thread,
paper or other artificial forms. Because they are blind
the workers shun the light and always work in burrows
or galleries, first eating out the fibres as food and then
using the excrement to form cells or chambers where the
raw tissue has been removed. When a nest of Termites
has its centre near a wooden dwelling, the galleries may
at almost any time reach some of the posts or supports:

RELATION TO THE HOUSEHOLD 225

and when they do, the insects work into and through
the wood in concealment, until suddenly there is a
collapse. In the tropics they get into floor boards and
the furniture resting on it, always mining out of sight
until there is a breakdown.

Where the insects are plentiful their habits are well
known and house builders use all sorts of precautions to
keep them out and never leave furniture in one place
very long. In the more northern countries where T.
flavipes only occurs, or is the only common species,
usually fence- or stair-posts only or the timbers of
barns and other out-buildings are attacked and then
the problem is getting at and destroying the central
nest, which is usually in an old stump or log not far
away- Only occasionally do they get into the beams or
timbers of dwellings or other inhabited buildings; but
when they do, they usually work until the timber is
ruined before their presence is suspected. In such
cases there is nothing to do but remove the infested
material and put in iron or, before putting in another
wooden support, treating it with some creosote or other
poisonous preparation unless the central nest can be
found and destroyed. They have been known to get
into a store-house and to ruin large quantities of sup-
plies before their presence was even suspected, and
into a masonry vault containing records, leaving the
pile of books and records fair to all outward seeming,
but a mass of cells and excrement behind it.

Yet a little further up come the members of the
order Orthoptera, including some of its most unlovely
fellows, the roaches; but also a few that have appealed
more to poets and dreamers in the chimney corner —
the crickets, including of course those on the hearth.
Crickets are generally accidentals and their presence is
usually due to their search for shelter. They are suffi-
15

226 INSECTS

ciently catholic in their tastes to exist for some time on
such scraps as they can find indoors and so the cheerful
chirp is not infrequently heard in some country locali-
ties. But there are other species, with other habits.
In sandy districts and often along the coast where
crickets are very abundant outdoors, they are apt to
get into houses in their general wanderings and develop
an inordinate fondness for woollen goods, especially if
they are at all damp. It has been my fortune to accom-
pany a fisherman on an early spring trip to the club-
house at the seashore, after it had been closed since the
preceding fall, and I watched him open the drawers of a
bureau containing his store of clothing, and then I
listened to his expression of regard for the crickets
that had found the garments so toothsome; and I
grinned in no holy joy, for that same fisherman had
always regarded insects as unworthy of consideration,
and knowledge concerning them as of no account what-
ever. And lo, now he was forced to appeal to that
knowledge and ask advice! It was all very easy and
meant simply have everything perfectly dry when put
away, and have things put into a trunk or chest rather
than a drawer. Where crickets do get annoying, pieces
of soft bread dusted with Paris green or white arsenic
will soon rid the house of them.

As for roaches, there are a few that have been dis-
tributed by commerce throughout the civilized world
and, in addition, some localities have species of their
own which, while living chiefly outdoors, rather com-
monly get indoors as well. In the tropics roaches are
most numerous, and in the warmer parts of our own
country even the common species are more abundant
and troublesome than they are further north.

All roaches have much the same appearance and
general habits. They are flattened, soft -bodied with

RELATION TO THE HOUSEHOLD

227

long spiny legs, long slender feelers, and the head bent
down so that the mouth comes almost between the
front legs. Some are winged and some are not; but
even the winged species do not as a rule fly readily and
some never at all. They hide in crevices during the day
and roam abroad at night seeking what they may de-
vour, and they are not at all particular what it is; dry
scraps of animal matter, moist vegetable matter — almost
anything indeed that can be eaten. Moist articles are

FIG. 106. — The "Croton bug," Ectobia germanica: a, first; b, second; c, third;
d, fourth stage; e, adult; f, female with egg case; g, detached egg-case; h, adult
with wings spread.

preferred and a warm wet dishrag which was not washed
after using has almost irresistible attractions. If there
was only one roach in a kitchen and I wanted that roach
I would place just such a rag on the middle of the floor
soon after dark, and I. would expect that roach there
before ten o'clock. This applies more particularly to the
large oriental roach or "black beetle" which is very
heavy, does not climb much, and prefers moist places.
The " croton bug" or "German roach" is a much
smaller species, climbs readily, and favors drier places.
It is much bolder than the oriental species, and is not
infrequently seen during the day.

228 INSECTS

How to get rid of roaches is a question frequently
asked, and judging by the number of infallible roach
powders and foods on the market is one frequently and
satisfactorily answered. Most of the dry powders
depend on a mixture of sugar or chocolate with borax,
the latter being the killing agent, ihe sugar or chocolate
merely to attract. Mix equal parts of sweet chocolate
and borax in a mortar, so as to mingle thoroughly, and
spread where roaches abound, removing, so far as
possible, all other food particles.

Roach pastes usually contain phosphorus or arsenic
and are applied on pieces of soft bread which is a favor-
ite food. An ingenious Australian scheme is to mix
one part of plaster-of-paris with three or four parts of
flour and set it on a small saucer easily accessible to the
insects. Feeding on this makes the roaches very thirsty
and they seek water; dishes of this should also be
placed near by and when this is added to the flour and
plaster, the latter sets and clogs the intestines. This is
a very simple, safe and inexpensive method, and once
the flour and plaster are set out, needs only attention
to keeping up the supply of water. In any case when a
house is once badly infested by roaches and it is desired
to clean them out, it means a campaign. No one appli-
cation will ever be successful, but persistence will be
victorious in every instance.

There are many interesting peculiarities about
roaches, but none greater than their egg-laying habits.
The entire egg supply of the female develops simul-
taneously in a sac or case attached at the end of the
body, technically known as an ootheca. As the eggs
develop this case enlarges, until all have attained full
size and the eggs are almost ready to hatch. Then the
female drops it in some sheltered corner, the seam along
one side splits, and all the young roaches come out at

RELATION TO THE HOUSEHOLD 229

about the same time. As a matter of policy it is always
well to begin a roach campaign before the egg cases
have been fully developed, as there are then much
fewer specimens to be dealt with.

The Hemiptera as an order are always difficult to
place in a linear series among the mandibulata, but
they contain one species that must be referred to among
the forms dwelling with man — the "bed-bug," Cimex
lectularius . It has local names in different parts of the

FIG. 107. — The bed-bug from above and below and egg.

country, but "bed-bugs" are always recognized even
where they are commonly referred to as "chinches."
There are quite a number of the Hemiptera that are very
much flattened and fitted to live in narrow crevices;
but none more than this bed-bug which occurs now-a-
days only in connection with human habitations. An
allied species lives in the nests of swallows, sometimes
in great numbers, but does not infest houses.

The pest is found all over the world and has been
recorded ever since there were any records; so there is
an immense fund of information concerning it — some
true, some more or less imaginary, like the tales of the

230 INSECTS

ingenious measures adopted to reach sleepers in beds
which had been isolated so that they nowhere touched
the wall and had the posts set in pans of water. The
bugs are normally red brown in color, but when first
hatched or when compelled to go without food for a
long period, they are almost transparent whitish.
Just how long they can go without food seems to be
not definitely determined, but it is certain that houses
entirely uninhabited for a year have been found infested
with very hungry bugs when again put to use. The
insects moult five times and normally feed only once
between moults, a period of five or six days. Nor,
when the insects have fed, do they always or even usually
stay in the bed occupied by the victim. On the con-
trary, especially where there is a metal bed, they are
very apt to leave it and seek some other piece of furni-
ture or get behind base-boards, picture mouldings,
trimmings or even behind the backing of picture frames.
In one case the resort for a considerable colony was
found in the large old-fashioned lock on the room door.
In the large wooden bed of the older type there was
usually abundant chance to hide and these beds were
difficult to get and keep clean, especially before the days
of gasoline. In such cases a large percentage of the
bug population might be confined to the bed; but the
life of the "chinch" becomes ever more difficult under
modern conditions, and with a little care, practical
exemption is securable in a well-ordered household.
Their occasional introduction is almost unavoidable
where public conveyances are used. I have seen them
in railroad cars, trolleys, boats, omnibuses and carriages,
and have noted them crawling on the clothing of well-
dressed fellow passengers who probably did not bring
them in. It means, therefore, in the average house-
hold, a more or less continual vigilance on the part of

RELATION TO THE HOUSEHOLD 231

the housekeeper, and one of the first and most charac-
teristic signs of their presence is the round black spot
produced by their excrement on the bed linen or other
places where they have rested. Some extremely sen-
sitive persons recognize their presence by the peculiar
buggy odor, which is not ordinarily noticeable until the
insects are handled. Eggs are laid in the crevices in-
habited by the adults, in small batches, and oviposition
extends over a considerable period. They are whitish,
oval, reticulated, and, like most hemipterous eggs, of
rather large size, so that they are easily seen and recog-
nized. The total life cycle, from egg to adult, is about
forty-five days, and the insects do not breed during the
winter, except under unusual conditions.

Given an ordinary infestation in an ordinary bed-
room, thorough work would mean taking out all bedding
and taking apart and examining the bed. With a large
bulb pipette force gasoline into every crevice however
small, and drench the binding and tuftings of the mat-
tress, wherever there is a folding over that might serve
as a hiding place. Force gasoline through the pipette
behind and under the base-boards, under the picture
moulding, behind all the trim of the room, and into all
other possible hiding places. Treat the wash-stand,
bureau and all other furniture to liberal doses, and
carefully examine all pictures for signs of either eggs or
"spots." If necessary remove the back to see whether
the insects have made their way under it. The gaso-
line will kill every insect it touches; but not the eggs,
so that a second treatment must be made to reach the
insects that hatched after the first. It will require
about one gallon of gasoline for a bedroom of good
size, with a normal amount of furniture, and the ma-
terial will hurt neither fabrics nor paper. Bad infesta-
tions in hotels, boarding-houses or tenements are best

232 INSECTS

reached by fumigation with hydrocyanic acid gas,
which will be described later on.

In the southern and southwestern states there is
another, much larger species that has also developed
the house habit and is known as the "big bed-bug," or
the "blood sucking cone-nose," Conorrhinus sanguisu-
'gis. It belongs to the family Reduviidce or "assassin
bugs," all of which are predatory in habit, and its bite
is a serious matter, causing much swelling and often
inflammatory and febrile symptoms. These insects
are so large and so little fitted for hiding that ordinary
care in looking after beds and rooms will detect them
and prevent trouble.

Among the Coleoptera or beetles there are a large
number that live with us and cause trouble. All, how-
ever, are species quite capable of taking care of them-
selves outdoors and come to us only because we have
in our possession or in the building some of the products
upon which they normally feed.

A good illustration is found in the species belonging
to the family Dermestida, nearly all of which are feeders
upon dried animal products. The term "dried animal
products" is a broad one and includes little scraps of
meat left on an old bone, a bit of hide remaining where
an animal has decayed, or a pile of hair or wool, no
matter where found. A dead insect found in the field
serves as a nidus in which an egg is deposited, and if
the dead insect is in our collections that is not a matter
of concern to the beetle, provided it can be gotten at.
We have, therefore, larder beetles, leather beetles,
museum beetles, carpet beetles, and a variety of others
of the same type, all seeking in our dwellings that dried
animal food which they require, and whose presence is
indicated to them by the discriminating sense of smell
with which they are fitted.

RELATION TO THE HOUSEHOLD

All the members of this family are dull brown or
blackish, clothed with gray, white or colored scales ar-
ranged in more or less distinctive patterns. They are
more or less oval, without conspicuous head, and with
short legs and feelers that can be retracted and folded
close to the body, so that the insect, playing 'possum,
looks like a bit of dirt or other fragment among the
mass in which it lives. The larvae or grubs that do the
real damage are .stumpy, worm-like creatures set with
brown hair, often with a longer
brush at the end of the body,
sometimes with a series of tufts
at the sides.

The carpet beetles are best
known and least liked of all
these species, and in the adult
stage when they frequent the
flowers in our gardens, are
rarely recognized. The so-
called "buffalo-moth," in the
adult stage, is really very pret- FIG. io8.—c. the larder bee-

. .. ., «. /• 1 MI- tie; a, its larva; b, larval hair.

ty, with its lines of brilliant
red and white scales. This in-
sect is a feeder on animal hair, and that accounts for
its attacks on woollen goods and feathers. Its close
ally, the black carpet beetle, has similar habits, and
both sometimes get into a feather pillow and create
havoc. Where the cover to the pillow is of the right
texture, the feather fragments are occasionally worked
into it so as to form a soft, felt-like covering, that
puzzles the enraged housekeeper when she discovers
the condition of her feather stuffing. All woollen and
feather fabrics are attacked and fed upon, and the
best way to prevent trouble is to keep those things
not in actual use shut up until midsummer. After

234

INSECTS

that there is no further danger from these species.
Of course the usual repellents, camphor, naphthaline
and the like are useful, and gasoline is an excellent
destructive agent; but after all, care and protection by
tight boxes or paper bags is best. When carpets on
the floor are attacked and it is not convenient to take
these up, a liberal use of gasoline is indicated, until no
further traces of the insect work are noted.

FIG. 109. — d, the carpet beetle; a, its larva, the "buffalo moth"; c, pupa.

Almost every museum and every collector of speci-
mens of organic natural history has to do with two or
three species that attack such dry products by prefer-
ence, and here again the ordinary repellents are brought
into use, supplemented by a free use of bisulphide of
carbon, ether or chloroform. None of these is advisable
in ordinary household use because pf either expense or
danger, so there is no necessity for going into details.
The larger species such as the larder beetles are usually
controlled by screening or keeping the provisions prop-
erly covered. The leather beetles that occur more
commonly in manufacturing establishments must be

RELATION TO THE HOUSEHOLD

235

dealt with according to the conditions as they exist in
each individual case.

Quite a different series of species attack our stored
grains and other vegetable products. The largest and
most conspicuous of these are the meal worms — long,
yellowish, slender worm-like grubs with a brown head

CL

FIG. 1 10. — a, the meal worm; b, pupa; c, adult beetle, Tenebrio molitor; d, its egg;

e, antenna.

and anal segment, reaching the length of an inch or
more. These live in meal of all kinds and are more
common in the barn and stable than in the house
though not unknown there by any means. The parents
are oblong flattened black beetles nearly three-quarters
of an inch in length, and are usually found in the same
places as the larvae. Incidentally these meal worms
are great favorites with our feathered friends, and they
are raised in great quantities as food for cage birds of
various descriptions.

236

INSECTS

Allied in appearance but very much smaller, come
the various species of flour and grain beetles; the larvae,
very slender whitish grubs, not much over an eighth of
an inch in length, the adults equally slender, flattened
brown beetles, less than that length, or scarcely attain-
ing it. They accumulate wherever meal or grain prod-
ucts of any kind are kept open and allowed to stand for
any length of time. In pantries or closets where jars or

FIG. in. — The confused flour beetle, Tribolium confusum: a, adult; b, larva;

c, pupa.

receptacles are never entirely cleaned out before re-
plenishing, they find their best opportunity for multi-
plying, and the best method of checking them lies, in
consequence, in cleaning out thoroughly every recep-
tacle for such products before putting in a new supply.
In peas, beans, lentils and the like, "weevils" often
make their appearance, and that is manifested when in
such seeds one or more round holes about one-sixteenth
of an inch in diameter may be noted. Now while, ordi-
narily, these insects breed outdoors, and simply pass the
winter in the seeds that were attacked in the field; yet

RELATION TO THE HOUSEHOLD

237

in the artificial warmth of our houses the beetles emerge
in late fall or during the winter, and lay their eggs on
the dried peas, etc., so that what may be a pretty fair
lot of legumes in fall, may be an utterly useless lot of
vegetable debris, in the spring following. The grubs
in this case are chunky, white creatures, curled up
inside the seeds, and the beetles are small, very chunky
gray forms, with very stout hind legs and the hind part
of the abdomen very abruptly terminated. The ordi-

FIG. 112. — The drug beetle, Sitodrepa panicce: a, larva; b, pupa; c, d, adult.

nary householder sees little of them because, as a rule,
only a small stock of such products for almost imme-
diate use is at hand; but to the farmer, the seedsman,
the grocer or other dealer, the matter is sometimes
serious. Fortunately we can reach the insects even
inside the seeds by the fumes of bisulphide of carbon,
in a manner to be pointed out a little later.

Then come those species that get into more solid
vegetable fibre, like roots, stems or even wood, and
many of these belong to the little family Ptinidcz which
contains a mixture of odd and bizarre forms, very
different and yet very similar in general character and

238 INSECTS

habits. The drug beetles, Sitodrepa panicea, and the
cigarette beetles, Lasioderma serricorne, are examples of
such forms and, in the adult stage, are little, brown,
more or less cylindrical species, not much if any over
one-tenth of an inch in length. The eggs are laid in or
on almost any kind of wood or leaf tissue, and the larvae
which are very small, curved, white grubs, bore into this
tissue reducing it to powder. Cigarettes, cigars and
plug tobacco are often attacked and little round holes
through the surface tell the tale of the destroyer. So
the roots of licorice and hellebore are equally favorites,
and may be reduced to powder, while occasionally
willow- and rattan- ware is seriously injured.

The somewhat larger species of Hadrobregmus, and
the species of Lyctus or powder post beetles belonging
to the same family, occur in the woodwork of houses
or in furniture, and may create serious trouble. They
live and bore in the seasoned wood, mining it in every
direction and in time reducing it to a mass of powder.
Little round holes, from which sometimes little masses
of sawdust are ejected, declare the character of the
insects at work here, and for them there is no one
method of treatment. Creosote, gasoline, tar, paint
and similar penetrating or covering mixtures are ap-
plied with more or less good effect, and which of them
is to be used depends upon the especial conditions of
the attack.

In the order Lepidoptera, the "clothes moths" have
become adapted to a life in our dwellings and are rarely
found elsewhere. They belong to the great group of
Tineid moths in which the early or primitive characters
of the order are yet well marked, and as a relic of their
ancestral habits they retain the practice of making cases
or shelters in the larval stage. This serves as a protec-
tion to the caterpillar and as a means of concealment;

RELATION TO THE HOUSEHOLD

239

for being made of the material among which the insect
feeds, it is not usually conspicuous. The divergence
from the usual vegetable feeding habit of caterpillars
is a specialization that is quite marked, because it is
not only a feeding upon animal tissue but upon dried
or dead animal tissue. In Chapter VII it was pointed
out that some moths lived in the heavy fur of certain
animals so that they became literally moth-eaten dur-
ing their lifetime, and this habit of feeding upon such

FIG. 113. — A clothes moth, Tinea pellionella, with its caterpillar in and
out of case.

material when removed from the animal is only a little
further specialization in the same direction. It fur-
nishes, also, an explanation of why woollens and ma-
terials made of animal hair or fibre, in whole or in part,
are subject to moth attacks, while linens and cottons
are practically exempt.

The "moth" itself, or " miller, " is a small, glisten-
ing, light yellow creature, with very slender, long
fringed wings, and it may be seen fluttering about in
the dusk of early evening in our rooms during late
spring or early summer. If when a closet door is opened
at this period a number of these moths flutter out,

240 INSECTS

there is a probability of damage already caused, and
very great danger of more damage to come. Not that
this moth itself has done or is capable of doing any
injury. Its mouth parts are such that it is practically
incapable of feeding at all, and altogether incapable of
feeding on solid tissue of any kind. But it lays its little
whitish eggs in the woollen or similar tissue wherever it
finds a chance to do so, and from these eggs hatch the
little caterpillars whose mouth parts are formed of
sharp jaws, quite fitted for cutting the animal fibres
among which they live. Almost the first work of the
caterpillar after hatching from the egg is to form a
little case from the tissue among which it finds itself,
held together with silken threads of its own produc-
tion ; and this case is enlarged from time to time as the
insect grows. It is curious how these individuals differ
in habit. Sometimes the cases will be made up of fibres
of all colors, indifferently put together without pattern
or system. At other times, and that is rather the rule,
the color first selected will be adhered to, so that in a
carpet one pattern may be completely eaten out, while
others, of a different color, will be untouched. In my
own experience I have observed a very decided prefer-
ence for reds where such were obtainable, and in rag
and brussels carpets I have seen the red stripes and
flowers eaten, while the blue stripes and green leaves
were untouched.

The period of development depends on the tem-
perature. In the more northern United States there is
only a single brood; in the middle and southern states
there are two and in the extreme south and on the
Pacific coast there may be more. But the insect is
sensitive to cold and does not grow or develop unless
the temperature is above 60°, even though it is not
killed by a much lower degree. Hence has come the

RELATION TO THE HOUSEHOLD 241

practice of placing furs and other valuable articles of
apparel or drapery in cold storage where, even if already
infested, no development can take place. The ento-
mologists of the U. S. Department of Agriculture
have determined that a temperature of 40° is low
enough to prevent any development, and my own
experience in the household is that until a daily average
of 60° is reached, little danger is to be apprehended;
but this, of course, does not mean that in closets so
placed that a higher average temperature is main-
tained, breeding would not go on even though the
outside temperature was not above 60°.

To prevent infestation, nothing is better than to
brush all the clothing to be protected and then pack it
into tight boxes. They need not be heavy nor large
boxes, but they must be tight. Pasteboard boxes will
answer every purpose if the covers are fastened at the
point of junction with gummed strips and such boxes
are now obtainable of almost any size, for garments of
all kinds. Heavy paper bags answer the same purpose,
and these are now sold for that purpose in the larger
cities. They can be easily made where they cannot be
bought. Even carefully wrapping in newspaper, using
plenty of paper and covering joints, will answer, where
the garments are packed away in trunks or moderately
tight drawers. But there should be no doubt about the
freedom of the garments thus put away from "moths"
or their eggs. When a fabric is once infested and the
insects cannot be reached by beating or brushing, a
drenching with gasoline is effective, and when a closet
becomes infested, it should be thoroughly sprayed with
gasoline so that every crevice is reached and penetrated.
Fumigation with sulphur will kill them if properly made,
but there must be no metal and no fabrics in the closet
when it is done. Formaldehyde vapor is ineffective.
16

242 INSECTS

As for the various repellents like camphor, naphthaline,
tar, etc., these are all of some value and in proportion
to the tightness of the drawer, trunk or other recep-
tacle in which they are used; but none are implicitly
to be relied upon if the fabric is already infested, or if
the container is not reasonably tight. Gasoline will
kill every caterpillar that it touches and is the best
material to use where rugs, carpets, hangings or drape-
ries that cannot for any reason be removed are to be
dealt with.

We have further, among the Lepidoptera, and in
this same group of Tineids, other moths and their
larvae that feed on our stored products, but hardly in
our houses, and such are the Indian meal moth, Plodia
inter punctella, the Angoumois grain moth, Gelechia
cererella, the meal snout moth, Pyralis farinalis, and the
like. They scarcely come under this head for detailed
consideration; but should be mentioned to call atten-
tion to the fact that they may be found among products
often stored yet hardly to be considered as inhabi-
tants of the household itself.

In the order Hymenoptera the ants are not infre-
quent invaders of our domestic economy. Sometimes
they come in merely on exploring expeditions from
outside, with no thought of remaining. It is merely
part of the hunt for food, and if something is found, a
squad is soon at hand to clean it out. Among such
visitors comes the large black carpenter ant, which
nests in partly decayed logs, branches of trees and the
like, and forages for a considerable distance round about.
A house near a large nest is likely to be so frequently
visited as to make them a nuisance, and to abate this
the colony should be located and their home destroyed.
This general recommendation applies to any species
which comes in as a visitor in this same way.

RELATION TO THE HOUSEHOLD 243

Sometimes ants make their nests just outside of our
houses, on the lawns, and while this does not bring
them strictly under this chapter head, we may digress
for a moment to consider them as a nuisance. With a
cane or other stick poke a few holes to the depth of
about ten inches near and about the centre of the nest,
and into each hole pour about one ounce of bisulphide
of carbon, covering the hole by stepping on it. The
fumes will penetrate throughout the- galleries and kill
all the ants and their Iarva3 that are
reached. Usually one application is
enough; if by any chance there is
renewed activity about the nest a few
days later, repeat the application.

Within our houses three or four
much smaller species make their
homes, and establish colonies. There
is a small red ant, a larger black ant,
a very small black ant and, more
occasionally, a very small red ant.
They differ materially in their habits
and somewhat in their life cycle, but for our purpose
are enough alike to be considered together. Like all
ants the colonies consist of a queen, a large number of
workers and, in the late summer and early spring, also
the males and females that will at the proper time
leave the nest to swarm. Only the workers are seen as
a rule, and these swarm over everything in the nature
of food, and cart it off to their nests which are situated
behind base -boards, in crevices behind the plaster or in
the masonry , or anywhere in the shell of the house where
they can establish themselves. Once a house is thor-
oughly infested the task of getting rid of them becomes
a serious one and can be accomplished only by persistent
work ; but it can be accomplished. In the first place lo-

244 INSECTS

cate the nests if possible and destroy by injecting gaso-
line or bisulphide of carbon with a syringe. Both of these
are highly inflammable and should only be used where
there is no fire nor open artificial light of any kind.
Many colonies may be reached in this way and greatly
weakened or destroyed. Others will be so situated that
they cannot be reached, and the insects will simply seek
less exposed openings into the rooms. The systematic
campaign then consists of keeping all food products un-
der cover so far as possible, or protected by belts of cre-
osote or oil of lemon, which the insects will not readily
cross. Set out, easily accessible in their ordinary lines of
march, all the raw bones with small particles of adher-
ent meat that come from the kitchen, and when these
become covered with ants throw into the fire and
burn. Or with a knife scrape the surface of a piece of
meat and spread the scrapings thinly on a piece of
paper. Burn this when covered, in the same way,
always taking care to let none escape. Keep this up
consistently and persistently, and no matter how
numerous the ants may seem to be, they will become
so greatly reduced in numbers that the nests are dis-
organized for lack of workers. There will be no one to
feed or care for the young and the colonies will perish.
Instead of the meat and bone method the sugar-sponge
method may be employed. This means two moderate
sized sponges, saturated with sugar water and pressed
nearly dry. Place one near the run until the ants
swarm in all its cells; then remove and drop into boil-
ing water, substituting the second sponge in its place.
The boiling kills the ants, of course, and the sponge
should then be thoroughly washed to get rid of the
dead insects, again dipped into the sugar water and
prepared to replace the second sponge when that is
ready to be boiled. It is sometimes a matter of weeks and

RELATION TO THE HOUSEHOLD 245

it may be necessary to change the location or even the
character of the traps several times; but, faithfully car-
ried out, I have never known this plan to fail, and I have
personally employed it in two houses occupied by me,
when the insects threatened my collection and ate the
fresh specimens on the setting boards when not protected
by carbolic acid belts. This plan is of no avail against
those ants that come in merely as foragers from the out-
side, like the black carpenter ants already referred to.

Of recent years a species of ant has been introduced
into one of the southern states from Argentina that is
far more troublesome than any of our American species.
It bids fair to spread and to become a first class pest so
far as it extends; indeed it has been already reported
from California and may be more wide-spread than we
now believe. It is known as Iridomyrmex humilis, and
is as ready to establish its colonies indoors as out.
It is under investigation by the entomologists in that
section of the country and we may hope that before it
gets much further, efficient methods for its control will
have been developed.

In the order Diptera there are no species that are to
be considered as guests except the common house-fly,
and that is dealt with in the previous chapter in its
relation as a carrier of disease. So the flea, which gets
into houses not infrequently, does so as a parasite of
the dog or cat, and not because of any love for man
himself. Other flies there are in the house not infre-
quently, but in most cases as scavengers, when at-
tracted by decaying or fermenting material, hence not
strictly to be dealt with here. To be sure we have
"skippers" occasionally, in cheese, especially of -the
odorous sorts, and sometimes in bacon and other fat;
but they come very decently under the classification of
scavengers and need not be further considered here.

246 INSECTS

And now, it sometimes happens that a house or a
room long neglected gets into such a condition as to be
almost uninhabitable by reason of insect pests of all
kinds — from scavengers to parasites — and the question
arises whether there is any method by which all these
things can be reached at one fell swoop, or at least by
two swoops; the second being made necessary by the
fact that there are always some forms in the egg state
and not to be reached even by fumigation with hydro-
cyanic acid gas, which is usually recommended under
such conditions.

Hydrocyanic gas is formed by the action of dilute
sulphuric acid upon cyanide of potassium, and is one of
the most penetrating of poisonous vapors, fatal alike to
man and insects and even to plant life when long enough
exposed to it ; but harmless to fabrics and not injurious
to metals. The formula for each 100 cubic feet of space
to be treated, is

Cyanide of potassium, 98° pure, by weight. . i ounce

Sulphuric acid, sp. gr. 1.83, by measure 2 ounces

Water 4 ounces

Break the cyanide into small lumps and put the
necessary amount in a thin paper bag. Put the water
into a glazed earthenware vessel — a wash basin, slop jar
or other bowl will answer — then add the acid slowly.
The water will heat as the acid is added and will fume
or bubble. When all the acid is added, drop in the bag
containing the cyanide and get out. The formation of the
gas will be retarded for a few moments while the acid
gets through the paper and this will give opportunity to
close the door and seal it as tightly as possible. The
order of doing this is important, for if it were attempted
to pour water into the acid, the first drops would cause
a boiling so violent as to spatter the entire volume in

RELATION TO THE HOUSEHOLD 247

every direction. It is also well to have the vessel large
enough to hold at least twice the amount of liquid
required, and if more than one pound of cyanide is
necessary, it is better to have two or more jars.

Where only a single room is to be treated make it as
tight as possible by sealing windows and other exits,
but open all closets, furniture drawers and trunks so as
to give free entrance to the gas. When the exit door is
closed, place a damp towel or other cloth at the bottom,
plug the key-hole with cotton and leave the room
tightly closed for at least two hours. Then open a
window or transom from the outside into the open air
or into a well- ventilated hall, and allow the gas to
escape for at least ten minutes before entering the
room. Open all windows for at least an hour before
attempting to re-occupy the chamber.

When an entire house is to be treated, first of all
close and seal all windows and openings to the outer
air as tightly as possible, except those through which
the operators expect to leave, and those should ^be on
the ground floor. Put into every room and into every
hall the basins or jars containing the necessary amount
of water; place alongside in a bottle or tumbler the
necessary amount of acid and in a bag the cyanide.
Begin at the top of the house, because the gas is light
and rises; first pour the acid into all the jars, then add
the cyanide and repeat on the floors below until the
entire building is treated. Two men can work better
than one in a building of any size, and in such cases the
number of fumigating vessels should not be multiplied
more than absolutely necessary. If everything has been
properly prepared it is a matter of only a few minutes
to start fumigation in a building of considerable size,
and such a building should then be kept tightly closed
for twenty -four hours if possible. At the end of that

248 INSECTS

time no living creature not in the egg state will remain,
and the house can be opened to admit fresh air and
permit the escape of gas. If windows can be opened
from the outside or a through draft can be obtained, a
few minutes will answer, and if a scuttle can be opened
from the roof, the entire house will be safe in half an
hour if all the doors in the halls are open.

The directions for use here are much more formi-
dable than the actual work ; but the danger to life is so
great if proper care is not exercised, that undue pre-
cautions are recommended rather than general direc-
tions that might promote carelessness.

CHAPTER XI

THEIR RELATION TO THE FARMER AND
FRUIT-GROWER

IT was emphasized in another connection that insect
species that are naturally abundant are so because
they have made good their position and relative num-
ber as against all their checks, and so long as natural
conditions prevail they will maintain that abundance
with such slight seasonal variations as may be caused
by temporary favorable or unfavorable conditions.

When civilized man enters the field, serious changes
in environment are produced and these changes are
produced faster than the insect and other life can adapt
itself to them. In a decade a wilderness is transformed
to a farm or an orchard, and the balance which it has
required centuries to establish is rudely upset. Those
species so nicely adjusted to their surroundings as to
barely maintain themselves under normal conditions
may be completely crowded out by the destruction of
some one factor that permitted survival, and, on the
other hand, conditions may be changed to favor such a
species, so as to permit it to increase out of all propor-
tion to its past history.

The Colorado or zo-lined potato beetle, universally
known as the "potato bug," Doryphora io-!meata, was
not always the pest that it is at present. When first
discovered in the foot-hills of the Rocky Mountains it
was accounted rather a rare species, that barely main-
tained itself on the scattered indigenous solanaceous
plants. But when civilization brought in the cultivated
potato, the species that had been so rare that it had

249

250

INSECTS

practically no specific natural enemies, found condi-
tions so materially changed in its favor that it increased
by leaps and bounds, followed the trail of its food plants
to the east, and in a few years over-ran the entire area
of potato cultivation.

It was first described in 1824; it had become abun-
dant enough to demand the attention of the economic

FIG. 115. — Colorado potato beetle: a, egg; 6, larvae; c, pupa; d, adult beetles.

entomologist in 1869, when Riley wrote concerning it
and the methods to be adopted for its control. I still
remember the joy that possessed me when, for the first
time, in 1874, I found on Long Island a patch of pota-
toes with the insects present in all stages. They had
arrived earlier, but I had not been fortunate enough to
get within their range previously. As nature works,
all this is so very recent that nothing has yet developed
in the way of an effective natural check. It is rarely,
however, that an insect is so marvellously favored by
the changed conditions produced by man. Usually it

RELATION TO THE FARMER 251

is a more local species already abundant and vigorous,
that derives a moderate advantage through the re-
moval of certain of its natural checks and the greater
facilities for getting food.

We must remember that an injurious insect, as
generally understood, is not necessarily one that seriously
injures plants, but one that causes notable harm to any
plant or part of a plant that man wants for his own use.
The farmer looks with equanimity upon weedy plants
devoured by slugs or caterpillars, but raises an outcry
when his cabbages are much less seriously eaten. Yet
any insect feeding on a cruciferous weed is likely at any
time to take to cabbage, and so the innoxious species of
to-day may become the scourge of to-morrow.

Among the factors that are changed by the farmer
in favor of the insect, none is of greater importance
than the elimination of the necessity for seeking a food
supply. In nature, plants and shrubs of one kind do not
often grow in large numbers or on large areas crowded
together by themselves. Insects are therefore com-
pelled to seek their food and the difficulty of finding it
makes a very important check. The farmer removes
that when he plants orchards and fields many acres
in extent and puts on the same or similar crops year
after year. Clean culture, important as it is in some
directions, destroys the shelter of ground beetles, of
snakes, toads, lizards, tortoises and similar creatures
that feed on species that go underground to pupate,
like the plum curculio, or hide just below the surface
during the day, like the cut- worms. The war on small
rodents is especially favorable to insects, because shrews
and mice are great devourers of such things. Culti-
vated areas are not sought by birds if they can find
other quarters, and some species will simply not go
into such places at all, even if they are never disturbed.

252 INSECTS

Hiding places for parasites are also limited and that is
a matter of great moment, for some species seem to be
dormant or in hiding for very long periods. Alto-
gether, it may be said that in all that he does on the
farm and in the orchard, the farmer and fruit-grower
favors those species that feed upon his cultivated
crops, and turns the natural scale against their enemies.
That he does not suffer more, is merely an indication
that these bird and animal friends that he eliminates,
and even the predatory beetles, are not the most im-
portant checks of the injurious forms.

Another way in which man interferes with the
orderly course of nature is in the introduction of plants
from other countries, well adapted to live in the new
locality but unable to resist the insects native to that
place, and so giving them an undue advantage. But
this is not a circumstance to the mischief done when
an adaptable insect is introduced into a new country
where it is unknown to the parasites and predatory
forms native to that country! The wine-growing dis-
tricts of Europe imported from America some of our
vigorous American stocks and with them the Phylloxera
as well. Now the Phylloxera in its native home is not a
serious pest and there was no reason to believe that it
would or could ever become such. But the European
vines proved absolutely non-resistant and succumbed
to injuries where the American vines would have shown
no sign. The attempt to control this insect in Europe
has cost millions of dollars and it is still an annual
charge of many thousands on the various governments
and growers. The difference between the American
and European stocks is merely a matter of adaptation,
our native varieties having become used to the insect
when present in normal abundance. There is no specific
native enemy to the Phylloxera and conditions in Euro-

RELATION TO THE FARMER

253

pean countries are not unduly favorable to its rapid
multiplication. Their vines are simply not used to the
attack and sink under it.

So on the other hand, we have a long list of insects
in North America introduced from foreign lands. The
Hessian fly, the cabbage butterfly, the asparagus beetles,
the elm-leaf beetle, the cottony cushion scale, the black
scale and the San Jose scale, are only a few of the
well-known pests that have been with us for some time.

FIG. 116. — Vedalia cardinalis, the destroyer of the cottony cushion scale:
b, larva; c, pupa; d, adult.

Most of our troublesome forms have come to us across
the Atlantic: the cottony cushion, black and San Jose
scales came to us across the Pacific. The former never
got away from the western coast ; the latter has covered
the entire country and has become the most generally
troublesome pest of the horticultural industry. The
cottony cushion scale was eliminated by a brilliantly
successful experiment, resulting in the introduction of
the specific check to the species from its native home.
It was an experiment that we can duplicate at any time
with the same factors. It is quite a different matter to
import parasites and predatory forms hap-hazard to

254 INSECTS

control or affect insects with which the imported species
is not familiar in its native home. Here we are not
making use of an adaptation, but are rather attempting
to create one. Such experiments may be crowned with
success, but it will be a success which cannot be pre-
dicted and it will depend on factors not apprehended
by the experimenter.

While we have, undoubtedly, introduced into our
country numerous first class pests — the brown-tail and
gypsy moths among the latest — it is equally true that
dozens of species have been introduced on imported
stock or in other ways, that have never secured a foot-
hold; and we have a few species that have started out
as if to sweep all things before them and have gradually
died out so as to become almost extinct. Two such
species have been enemies to pear trees — the pear midge
and the sinuate pear borer; the latter of which never
got much beyond New Jersey, after destroying nearly
all the pear trees in one district. One species, the
"horn-fly," created enormous alarm among owners of
cattle for a few years, swept over a large part of the
United States and Canada in less than a dozen years,
and is now so rare where it first appeared that speci-
mens are at a premium for collectors. In none of these
cases are specific natural enemies to be credited with
the disappearance of the species. Conditions simply
were not suitable in all respects, and the insects failed
to adapt themselves with sufficient completeness to
survive in the long run.

The important point is that those species that do
survive the introduction are exceptional in vitality and
adaptability, and are therefore naturally abundant and
able to maintain a lead over all their enemies. If the
specific parasite or other check of such a form does not
exist in the new country, and is not introduced with it,

RELATION TO THE FARMER

25S

a destructive increase under cultural conditions is almost
inevitable.

Now in what ways do insects injure the crops
and cause injury to the agriculturist? This might
be answered by a reference to Chapter III, but it
may be useful to take up some features more in detail,
with the injury rather than the insects as the prime
objects of consideration.

Plant lice do their mis-
chief in part by directly
exhausting the plant of
sap, partly by causing dis-
tortions of growth, and
partly by preventing the
proper maturing of the
fruit, be it on shrub, tree
or vine. If on the roots,
the plants are weakened
or often killed and even
trees are sometimes seri-
ously injured. A secondary
cause of injury is due to

the production of honey-dew by the lice. This serves as
a culture medium for a black soot fungus which often
disfigures tree fruit to such an extent as to make it un-
salable. Some of the scales have a similar habit and so
do some Psyllids and Membracids. The enormous re-
productive powers of plant lice render them especially
dangerous, and very often the farmer does not even
see the nucleus from which come the hordes that he
finds on his wheat, his cabbages or his melons, a few
days later.

During a spell of dry weather it may be noticed
that the oats or the grass is showing white spots or
becoming silver-tipped; or the onions begin to show

FIG. 117. — Thrips, with antenna and
tarsus.

256 INSECTS

yellow spots, turning white later, and often killing the
tops. This the experienced grower will recognize as
the work of Thrips, which scrape the surface so as to
break the leaf-cells and exhaust the sap, leaving a dead
spot. When these dead spots become sufficiently
numerous, the leaf fails to fulfil its function and dies, or
is only a burden to the plant.

Leaf- and tree-hoppers do similar work and a com-
mon example is found in the vineyard, where leaves
often turn brown in summer before the fruit is ripe,
because of the injuries done by the grape leaf-hopper.

Scales, soft .and armored, attack trees of all kinds,
in the orchards, in the forests and on the city streets.
Sometimes they are so small and inconspicuous that it
requires close scrutiny to find an isolated individual;
sometimes they are large and showy, flaunting their
numbers and threats as far as the tree itself is clearly
visible. The honey-dew and soot fungus produced by
the soft scales have been already referred to. Many of
the armored scales produce a specific effect on the tree,
besides exhausting its juices. In some cases distinct
pits or depressions are formed on the surface of the bark ;
in others the bast is discolored and poisoned where the
puncture is made, and when the punctures are suffi-
ciently numerous the bast simply fails to do its work.
Peach trees infested by the San Jose scale sometimes
reach such a condition in fall that, after growth is
completed, the bast has lost all vitality. During the
winter the poison does its work; in spring the tree
starts from the supply stored in the buds, blossoms
and even begins to leaf out, but when demand is then
made upon the roots for fresh nourishment the bast
fails and the tree dies.

This poisoning effect is not peculiar to scales, but
is a feature in many other of the Hemiptera. Some of

RELATION TO THE FARMER 257

the plant bugs of the Capsid series have it very strongly
developed and Coreids like the common squash bugs
are well known for the poisonous effects of their punct-
ures on vines and other plants.

Some plant lice form galls, sores or cankers on
branches, trunk or even the roots, like the woolly louse
of the apple; and some of these canker sores offer
excellent points of entrance for germs of disease and
decay. Indeed it has been charged against some of the
species that certain plant diseases are either carried or

FIG. 118. — Woolly apple-louse at c, showing galls made on roots at a,
the woolly wingless form at b.

given points of entrance by them. The root-feeding
forms are particularly dangerous, because until the
tree or other plant begins to show bad condition there
is no way of recognizing their presence.

Not all the injury done by these various forms of
sucking bugs is obvious, and so used does the farmer
become to the loss that very often he does not appre-
ciate it. A simple experiment made by one of our
economic entomologists proved that leaf-hoppers in
grass fields in his state were so numerous that they
shortened the crop one-half. Demonstration of this
was made by dividing a meadow into two equal parts,
pasturing cattle on both, but collecting the leaf-hoppers

2 S8 INSECTS

by means of hopper-dozers on one part only. This part
supported exactly twice the number of cattle during
the season that could be maintained where the hoppers
were left undisturbed.

It is comparatively easy for the farmer to estimate
his loss when the green-fly drains his wheat so that
instead of the expected twenty bushels he harvests
only ten or none at all. The drain upon all sorts of
crops by the myriad of specimens constantly sucking
plant juices and reducing the yield to a less obvious
extent, is rarely capable of estimation, but varies from
ten to fifty per cent, almost every year on most of our
staple crops. This sounds like an exaggeration, but
every person who has ever studied the problem at all
carefully will agree in the estimate, I think.

And then come the host of species that feed directly
upon leaf tissue. They come from many orders: grass-
hoppers, locusts, crickets and their allies of many
kinds; slugs and grubs as well as adult beetles in great
variety; caterpillars of the most diverse appearance
but always great devourers; saw-fly larvse from the
Hymenoptera and a few maggots from the Diptera or
fly tribe. Perhaps no kinds of insects do more obvious
injury than those that feed openly on the foliage and
yet the real harm that they cause is not always in
proportion to their feeding, because many plants and
trees will support the destruction of a great percentage
of leafage without material impairment of crops. This
does not apply where the crop consists of the leaves
themselves as in cabbage, spinach and other vege-
tables, all of which have their own particular insect
friends.

Unfortunately some of these foliage feeders modify
their habits somewhat, on occasion, and attack more
important parts of the plant, e.g., when the rose-chafer

RELATION TO THE FARMER 259

eats by preference the flowers of the grape and thus at
once destroys the crop without injuring the plant
itself. Some cut- worms, hiding out of sight during
the day, cut off the stalk at base for convenience of
feeding, leaving the tops on the surface to dry and
perish. Or they climb on the shrub or tree and eat
out the buds or growing tips, destroying the crop if
not the plant.

This brings up the. fact that in his method of culti-
vation the farmer frequently forces upon himself an
injury which the insects wrould not under normal con-
ditions inflict. If a field be left fallow or in grass for a
year or two, it will almost inevitably attract the night-
flying or owlet moths of the family Noctuida, whose
larvae, the cut-worms, feed normally on grasses and a
great variety of low plants. These cut- worms, or many
of them, winter half grown in sod or rubbish on the
surface of the ground, coming out to resume their
feeding in spring. If now, in early spring, the farmer
plows this infested sod and plants corn or potatoes,
or sets out cabbages, tomatoes or sweet potatoes, he
deprives the cut-worms of their natural food and prac-
tically forces them to take what he has set in its place.
Furthermore, while a population of one cut- worm per
square foot would not be a very serious infestation in
grass land, it would be destructive in a cornfield, or in
a cabbage patch. And not only are cut- worms favored
in this way: there are weevils known as bill-bugs,
attacking corn planted on timothy sod or following
certain other grasses, and there are wire- worms and
white grubs that attack cultivated crops when they are
put in after grass or other infested plants. Of course
this means bad farm practice from the standpoint of
the entomologist; but not until quite recently have the
farmers been willing to consider any modification

26o INSECTS

merely because it would produce conditions less favor-
able to insect increase.

Besides those species devouring foliage above ground,
there is a large subterranean population of wire- worms,
white grubs, maggots, slugs, and the like that attacks

FIG. 119. — A bill-bug, its larva and work in root of Scirpus.

the roots of plants. The underground work of plant
lice has been already mentioned; the species now
referred to are those that actually devour the root
tissue or dig into the underground stem so as to destroy
or weaken the overground plant. Cabbage, onion,
radish and other root maggots, wire- worms, grub-
worms, grape-root worms, root-borers — all are familiar

RELATION TO THE FARMER 261

terms to the farmer, and represent sources of injury
that he has learned to dread.

And when his plants have developed well, his fruits
have set and all looks fair and free from any of the
pests already enumerated, the farmer is by no means
certain that he will get either seed or fruit. There are
numerous midges that develop in the ovaries of fruits
and flowers, and either feed directly in the seed or
suck its juices so as to shrivel it. We have species that
attack the kernels of wheat, rye, oats, sorghum and
other grains; others that get into the ovaries of the
clover flower and destroy the seed — so thoroughly,
indeed, that in some localities, while it is easy to get
good crops of clover hay, it is impossible to get any
seed at all. Midge larvae, indeed, are found under the
most divergent conditions and their injuries are by no
means appreciated as yet to their full extent. Not
that the midges are alone in this work, for among the
beetles there are a large number that infest special
crops. There are, for instance, the BruMda, contain-
ing the bean and pea weevils that infest seeds of all
sorts of legumes, from the pods of the locust tree to
those of the lentil. Sometimes only a single larva
develops in a seed as is the rule in peas, or there may be
up to half a dozen or more in a single bean. And the
worst of it is not the infestation that comes in the
field alone, but the likelihood that without great care
it may be brought and continued in the barn or store-
house. Even after harvest the wheat is not safe, for
if it be left in shocks in the field, the Angoumois grain
moth is apt to find it and start its work of destruction.

Further, among the snout beetles we have species
that confine their attacks to the buds or developing
seed capsules. The boll-weevil of the cotton is perhaps
the most conspicuous example, and this species alone

262 INSECTS

has demanded the expenditure of hundreds of thousands
of dollars in its study and attempted control, and has
injured the value of the crops in the affected states by
many times that amount. Less conspicuous but equally
destructive on a smaller area is the strawberry weevil,
which develops in the bud, preventing the formation
of fruit.

This habit of placing the eggs in a protected position
or with reference to the food supply of the larva is
quite a trick among the snout beetles, and some of their
habits are very interesting as well as economically
important. The nut- weevils have the snouts very
much elongated and very slender so that they are
enabled to pierce the growing burr or husk and place
the egg in the developing nut, long before there is a
shell to be reckoned with. The plum curculio cuts a
little flap from the surface of the fruits that it infests
and in this bit of loosened tissue lays its egg, safe from
the pressure that might otherwise be exerted upon it
by the growing fruit. And so it is with other of the
Rhynchophora that attack our fuits, large and small.

Even tree fruits are not exempt from midge attack,
one form depositing its eggs in the pear bud that the
young larvae may be in position to get down into the
seed capsule while yet the passage-way into the ovary
is wide open. Other flies attack growing fruits of many
descriptions and are furnished with a horny ovipositor
of considerable length for puncturing the skin. Apple,
orange, olive and plum, all have their "fruit-flies" that
demand toll of varying importance.

Among the Lepidoptera, none is better known than
the codling moth, the larva of which feeds in apple,
pear and quince. Where no active measures are taken
for its control, it is no unusual matter to find from 90
per cent, to 95 per cent, of all the fruit on a tree wormy

RELATION TO THE FARMER

263

and of inferior value. This species seems to be dis-
tributed wherever the apple is grown. Other species
attack grapes in a similar manner and there are feeders
among the smaller caterpillars in or on almost every
fruit that grows. Besides feeding on or in the fruits,
many of them are also miners in leaves and even in
twigs and branches. There is, of course, a great deal of

FIG. 120. — Codling moth and its work: a, the injury done; b, place where
egg was laid; c, larva; d, pupa; i, cocoon; /, g, adults.

difference between the amount of injury caused and
usually a species is confined to either one kind of plant
or to the members of one plant family. There are a
few, however, that are obnoxious to a variety of crops
and none that occurs to me at present is much worse
than the corn-worm, boll-worm or tomato-worm, as it
is variously named. It winters, usually in the pupal
stage, underground, and early in the season emerges as a
yellowish, inconspicuous owlet moth, which during the
month of May in the middle states seeks a place to lay

264

INSECTS

its eggs. At this time the most attractive things seem
to be the early peas, and very soon the greenish cater-
pillars will be found boring into the forming pods.
As the young corn makes its appearance this becomes
attractive to the moths of the second brood, and the
caterpillars, now usually with a pale reddish-gray tinge,

FIG. 121. — Heliothis armiger: a, b, eggs; c, larva, ("corn- worm", "boll-
worm", and " tomato- worm "); d, pupa in cell; e, f, moths.

appear as stalk-borers. As the sweet corn advances the
caterpillars find the forming ears, and many a barren
stalk is so because the ear has been eaten even before
it appeared between the leaves. About this time, too,
the earliest tomatoes become of nice size and offer
another outlet for the caterpillars, which bore into the
fruits when they are nearly ready to color and take
those specimens which would otherwise have sold for
fancy prices. In the southern states the cotton at this

RELATION TO THE FARMER 265

time begins to offer an attraction in the shape of form-
ing buds, and a little later the "boll- worm" makes its
appearance. When corn is plenty, that forms an at-
traction superior to everything else and then come the
"corn- worms" so common and objectionable in the
"roasting ears." Sometimes there is only one, usually
of good size; sometimes there are several, usually
smaller, and the explanation is that the insects are very
pugnacious and when they meet they fight. When
there are two or more full grown larvae in one ear, it
simply means that they have never chanced to meet.
The caterpillars continue in the corn until it is cut and
stacked, and some may yet be found at husking time;
but from the time the kernels begin to harden they go
underground as they mature and change to that pupal
stage in which they safely pass the winter. After they
once get started in spring they can be found almost
continuously in some one or the other of their food
plants.

There remains yet one more way in which growing
crops are attacked and that is by borers, and these
also are of many kinds and all sizes. The stalk of wheat
and the fruit tree fifty years old are equally subject to
this kind of injury, and larvae of Coleoptera, Lepidopterat
Hymenoptera and Diptera all contribute to the mischief.

Some of these stem feeders really do not deserve
the name of borers at all, as for instance the larva of the
Hessian fly , which attacks wheat stalks at the base and
produces a gall that checks growth, or the joint- worm
which works into the stem at a joint; but for conven-
ience we may class as borers all forms which feed out
of sight in stems, twigs, branches or trunks. And it is
astonishing what a variety of borers there are and how
generally plants are infested. Not cultivated plants
only, but arrant weeds like burdock, thistle, rag- weed

266 INSECTS

and the like. We find among Dipterous larvae maggots
in some variety, often producing swellings or galls in
herbaceous stems, besides the numerous midge larvae
already so often mentioned. Hymenopterous borers
are comparatively few in number and chiefly members
of the saw-fly or horn-tail divisions. Some of these are
in grasses including grains, and are slender, white,
caterpillar-like forms which often hollow out the entire
length of a stalk. Pithy stems like those of blackberry
and raspberry are favorites with this kind of borers,
not many of which belong to the seriously injurious
class. The horn-tails attack woody plants more gen-
erally, but are also comparatively few in number, both
as to species and specimens.

Lepidopterous or caterpillar borers we have in great
variety and in all kinds of plants and trees. The largest
of them belong to the Cossids and Hepialids, the giants
among the so-called Microlepidoptera. Most of these
are confined to forest trees, and it is notable that our
only really troublesome species is an imported one —
the wood-leopard moth — that attacks shade and orchard
trees. In this connection it is interesting to observe
that the boring habit among Lepidoptera is an ancient
one, not even confined to terrestrial vegetation, and
that by far the greatest number of the borers of the
present day are members of the simpler and earlier
types of Microlepidoptera.

Wood-feeders largely we find in the Sesiid clear-
wing moths, among which are some of our most trouble-
some species, e.g., the peach borer, cherry borer, cur-
rant borer, blackberry borer and the like. Some live
in the solid wood of trunks and branches, like the cherry
borer and those that live in oak, maple and other trees:
some live just beneath the bark and make chambers
rather than galleries, like the peach borers: others are

RELATION TO THE FARMER 267

in roots like the blackberry crown borer and the grape
root borer; while yet others feed in the centre of a
stern, like the currant borer or lilac borer. Among the
Pyralid moths there are numerous borers in herbaceous
plants and among the Noctuid or owlet moths there is
quite a series in which the boring habit is well devel-
oped; such plants as potatoes, tomatoes, corn and
wheat being among the victims. A few are twig borers
on trees, like those working in the terminal shoots of
peach and plum.

It is among the Coleoptera or beetles that boring
habits are especially well developed. There is almost
no sort of tree or plant among our cultivated species
that is not more or less infested by coleopterous borers
of some kind, and in a very general way that same
assertion might be made of all trees and plants. So
general is this habit that except in the predatory and
scavenger forms, there is scarcely a series that does not
have some sort of boring species included in one or
more of its families. The Longicorns and Buprestids
are almost all borers in woody tissue; among the
Rhynchophora or snout beetles there are numerous
borers in herbaceous plants and a goodly representation
that works in woody tissue. Apple, pear, quince, peach,
plum, nut and citrus trees are all more or less subject
to attack, and grape, blackberry and other vine and
small fruits are equally apt to be infested. Potatoes
have weevil borers in the stem, many grasses have
similar borers in the roots, and even cabbage has its
leaves and stem more or less riddled. Among the
tree borers there are two rather well-marked types
represented by the round-headed and flat-headed bor-
ers. The former quite usually do most of their work
in solid tissue, the latter are more apt to make channels
in the bast or between bark and sap-wood, getting into

268 INSECTS

the solid wood only to pupate. Some of the round-
headed borers have similar habits but on the whole
they are more diverse in their methods of feeding than
the flat-headed borers. With both we have species
that attack only dead or dying tissue, and others that
will feed in or on perfectly healthy trees. Some of them
must have matters just exactly right, like the twig-
girdler which lays an egg and then girdles the twig
below the point of oviposition, so that in the first high
wind it may break off and fall to the ground. Others
like the oak-pruner demand living wood as food for
the larva, but a dead twig for pupation; so the larva
girdles the twig from the inside, leaving only a thin
shell, makes itself comfortable beyond this point, and
waits the time when it is blown to the ground to com-
plete its transformations.

Another important series contains the bark beetles
which, while they do not so much affect the horticul-
turist, do most seriously affect the forester and the
lumberman. It would hardly pay to go at much
greater length into the different kinds of borers, be-
cause the fact of general infestation has been suffi-
ciently brought out.

We see from this brief review that from the time the
plants first show above ground until the harvest is in,
they are subject to the attacks of sucking and chewing
insects in all their parts, and that neither root, stem,
leaf, fruit nor seed is free from liability to infestation
and injury. Some of this liability is increased by inju-
dicious farm practice, some of it is the consequence of
past carelessness, and a portion is due to the inevitable
change in the balance of nature caused by culture and
by planting large areas in one sort of vegetation.

It follows that the agriculturist and horticulturist
is always at war with insects, either actively or pas-

RELATION TO THE FARMER 269

sively, and he always suffers some injury, large or
small in proportion to the activity of his campaign
against them. What is not always realized by the
passive resistant is that what he loses is all profit.
It costs about so much to prepare, plant and harvest
an acre of corn, wheat, potatoes, cabbage or other
crop, and if the insects eat 10 per cent, of what would
have been produced had they been destroyed, that 10
per cent, is directly out of the farmer's pocket. And
if in two orchards of the same variety, producing exactly
the same number of barrels of apples, those from the
one are clean as the result of an active campaign and
the latter gnarled and wormy from curculio and codling
moth, the difference in price between the fancy fruit
selling at the top of the market, and the other fit only
for the cider mill, is the measure of loss, since the cost of
handling and growing is practically identical.

It has been attempted again and again to calculate
and estimate the annual loss of agricultural products
due to insect ravages in the United States and Canada,
and no one has fixed it in figures of less than hundreds
of millions. As a matter of fact, the money loss is
difficult of estimation, because any material addition to
the amount of a crop might have a decided influence
on its price. It is not uncommon, for instance, for a
farmer to make more money on a short crop than out
of an excessive one, and this factor has been- previously
noted by Dr. L. O. Howard, in his discussion of the
same subject. A better basis, perhaps, is the percent-
age of crop destroyed, and that has been estimated at
anywhere from 10 per cent, to 25 per cent, of the total.
The careful student will be inclined to consider the 10
per cent, estimate too low; it is doubtful whether, in
actual lessening of crop, it will reach the 25 per cent,
mark; but if we take into consideration the lessened

2 7o INSECTS

value of much of the crop actually harvested and
marketed, I believe that 20 per cent, depreciation in
value of farm products is not too high an estimate of
the losses annually caused by insects in the United
States and Canada. As the value of such products
was estimated in the Report of the U. S. Department of
Agriculture for 1907 at $7,412,000,000, the estimated
loss, due to insect ravages in the United States alone
should be put at $1,500,000,000 at least.

CHAPTER XII

THE WAR ON INSECTS

HAVING detailed the character of the injury done
by insects and given some idea of its extent, the question
arises; what can we do to prevent such loss, and what
has been done in this direction? There is yet, in the
older settled portions of our country a rather widely
distributed feeling that as insects exist and feed on
plants, they were created for that purpose and that it
is meddling with a divine institution to attempt their
destruction or limit the amount of injury done. It is
the same sort of spirit that protests that "it can't be
done" whenever any attempt is made to better sani-
tary conditions, to control the spread of disease or to
limit the agencies that make for the spread of infection.
Supplemented by the equally wide-spread conviction
that any grown man that engaged in so trifling an
occupation as the collection and study of insects must
of necessity be deficient in intellect or of unsound
mind, this condition was responsible for retarding the
development of economic entomology to the middle of
the last century, and even then it developed slowly
and failed of general appreciation.

With the establishment of agricultural experiment
stations under the Hatch Act of 1887 conditions began
to change. Entomologists were appointed in several of
them; their work began to make itself felt, its im-
portance began to be appreciated, arid now there is
scarcely a state or territory in which there is not at
least one working economic entomologist. In 1889 an
Association of Economic Entomologists was formed

271

272 INSECTS

with about a dozen members. In 1907 there were
enrolled among the active and associated members,
most of them in official positions, no less than 211
names; and that does not include all of them. Of
foreign associates interested in the same line of work
there are forty-five, and that includes most of those in
official positions. In 1888 there were less than half a
dozen makers of pumps or machinery suitable for
insecticide work, while nozzles were difficult to obtain
and poor. At present there are numerous makers of
machinery and each of them presents a long line of
pumps, nozzles and fittings for applying insecticides
and fungicides. On the Pacific Coast the problems
were somewhat different from those of the Atlantic
Coast and the line of development in the production of
insecticides and spraying machinery w^as also different.
Fumigation with hydrocyanic acid gas, the lime and
sulphur and resin-washes are Pacific Coast contribu-
tions; the development of the arsenical sprays and the
mineral oil preparations are to be credited to the Atlan-
tic Coast, or at least to the territory east of the Rocky
Mountains, for much of the pioneer work with insecti-
cides was done in Illinois and Missouri, by Walsh
and Riley.

In 1889, every ounce of kerosene emulsion was
home-made, and Paris green, London purple, helle-
bore, tobacco and pyre thrum were practically the only
insecticides on the market. There was whale oil soap
also, but expensive and an unknown quantity as to
its ingredients. Now there are a large number of
manufacturers throughout the country, producing com-
mercially -every preparation that has proved useful in
the hands of experimenters, and chemists everywhere
are seeking to improve and cheapen the known combi-
nations or to devise new and more effective ones. Mis-

THE WAR ON INSECTS 273

cible oils and lime and sulphur combinations are made
and shipped in car-load lots, while arsenate of lead,
absolutely unknown as an insecticide in 1888, is sold in
ton lots to individual purchasers.

This development in the face of at least passive
opposition could not have taken place in so short a
time as twenty years had it not been promptly dem-
onstrated that the fight was a paying one. And when
the reader who remembers the fruit markets of that
earlier period, compares them with the magnificent
productions in our markets at present, he will realize
the advance that has been made. Farming and fruit
growing has been developed as a science, along scien-
tific lines. The soil is a chemical laboratory, with
elements ready to be combined into organic compounds
under proper conditions. The plants produced in this
soil and from these elements serve naturally as food
for man and other animals, including insects. Man
wishes to get it all for his own use and, of course,
therefore desires to eliminate the insects as partners.
Can he do it, and if so, how?

To the first part of the question we answer yes, to a
very great extent; to the second there is a less definite
answer since every group of species must be dealt with
according to its kind and no one application will serve
for all kinds of species. Often, indeed, where insecti-
cides cannot be used at all, we can circumvent by plant-
ing at proper times, rotating crops so as to prevent
undue increase, and by harvesting so as to destroy the
insects before they mature. In the garden and in the
greenhouse where conditions are more under our
control, injury from insects can be reduced to a mini-
mum, and the records from our orchards show that
wormy fruits are not necessary features in a crop.

We have learned that as against practically all
18

274 INSECTS

insects that chew their food and feed openly upon
plant tissues, arsenical preparations may be used with
good effect. Up to within a few years Paris green was
practically the only satisfactory material of that char-
acter, and even that could not be used on tender foliage
or on conifers without extreme caution. Recently, the
manufacture of arsenate of lead has been developed to
a point that we have now a satisfactory killing agent
that can be safely used at any strength on foliage of
any kind. It has the further advantages of remaining
well in suspension without constant stirring, and of
sticking to the foliage indefinitely after it has once
dried. In the garden and greenhouse no other stomach
poison should be used and it will be found effective
against all caterpillars, saw-fly slugs, beetles and their
larvae and generally against insects that actually eat
foliage; it is useless against sucking insects such as
plant lice, scales, plant bugs and the like. It contains
less actual arsenic than Paris green and at least three
times as much must be used to obtain the same results.
One pound in 10 gallons of water will kill potato beetles
and their larvae; i pound in 50 gallons of water will
kill slugs and small caterpillars; i pound in 25 gallons
of water is a good general strength for ordinary cater-
pillars and other similar species. Paris green is perhaps
a little more economical in orchard work and can be
used at the rate of i pound in 50 gallons of water for
potato beetles, i pound in 125 gallons for orchard work
and i pound in 150 gallons on sensitive foliage or against
young caterpillars. It should never be used on peach or
conifers and should be very cautiously used in the
garden. It is well to slack one pound of quick-lime
with every pound of Paris green to combine all the
water-soluble arsenic in the insecticide, especially when
used at the greater strengths.

THE WAR ON INSECTS 275

Arsenate of lead comes in paste form only, at present
writing, and cannot be applied dry.* Paris green can be
mixed with air-slacked lime or dry hydrate and applied
with a bellows, and for cases where a powdery dusting
will form as satisfactory a coating as a spray, the appli-
cation in that manner is just as good. There are cases,
however, as where an insect feeds only on the under-
side of a leaf, where a dust does not and cannot cover as
well as a spray, and others where the material must be
forcefully applied so as to get into a crevice or cavity
in order to secure a maximum effect.

There are preparations of white arsenic which can be
made at home, forming combinations with lime which
are stronger and cheaper than either Paris green or
arsenate of lead; but these are dangerous in unskilled
hands and require so much care in preparation that
they are not advised, save when very large quantities
of material are needed.

It is very often desirable to combine an insecticide
and a fungicide so as to prevent injury from disease as
well as insects, and Bordeaux mixture is the fungicide
generally used with either Paris green or arsenate of
lead. This Bordeaux mixture is in itself very offensive
to many insects and some of the flea beetles will scarcely
touch a plant protected by it. If the arsenical insecti-
cide is added to the fungicide in the same proportion
as if it were water, an extremely effective material is
obtained. The Bordeaux mixture is prepared as follows:

Copper sulphate 4 pounds

Quick-lime, stone or shell, good quality .... 4 pounds
Water 50 gallons

Dissolve the copper sulphate in one gallon of hot
water, slack the lime in water sufficient to do it well,
and strain. These are the stock mixtures and will

* A dry powder has been produced, but is still in the experimental stage.

276 INSECTS

keep a long time if tightly covered. To prepare for use
dilute each of the stock mixtures with ten gallons of
water, combine them in a barrel of sufficient size, and
then add water to make up the full amount. Never
combine the concentrated stock mixtures as it pro-
duces a heavy coarse precipitate that is much less
effective. The above mixture is the full strength that
is reasonably safe for general use. The tendency is to
use only three pounds of copper instead of four on
orchard trees, and on peach it should be even weaker,
if used at all.

Against plant lice, scale insects and other sucking
insects our battery is much larger, much less satisfac-
tory, and applications must be much more carefully
made. We can spray a tree with arsenate of lead to
reach an insect which we expect will make its appear-
ance to-morrow; but a contact insecticide must be
applied when the insects are actually present and must
be brought into actual touch with the specimen before
it can be effective.

Contact poisons kill either by direct corrosive action
on the skin of the insect, as where dry hydrate of lime
is dusted on a soft slug, or by clogging or entering the
body through the spiracles or breathing pores. Soap
mixtures clog by forming a film over the openings and
matting up the hairy guards that as a rule protect
them; a soap that makes a rather thick slimy suds is
therefore preferable to one that forms a clean, thin
suds. Mineral oils are very penetrating and kill by
getting into the body cavity through all openings.
Decoctions like those of tobacco and hellebore get into
the spiracles and perhaps also through the mouth into
the stomach and set up a convulsive affection that re-
sults in death. Dry powders like hellebore and tobacco
are effective in proportion as they are finely ground, and

THE WAR ON INSECTS 277

even fine road dust has some insecticide value. The
fine dust particles get into the trachea and there set up
specific irritation, but they must get there to do any
good at all. Coarse particles are no better than so
much coarse dust and insects with covered spiracles are
not affected at all. It is quite possible, therefore, to
have an insecticide which is very effective against one
series of a species, but which, against another series,
will be entirely useless: any material for which it is
claimed that it will kill everything, should for this
reason be looked upon with distrust from the start.

Plant lice are among the most common of all the
insects to be dealt with in a practical way, because
there is almost no vegetation not more or less infested
by them. In a small way on house plants, insect powder,
i.e., pyrethrum, is the cleanest and simplest remedy.
It can be dusted on through a sieve, put on with a little
powder puff or bellows, or it can be made into a decoc-
tion or tea, using an ounce to two quarts of hot water.
This can be put on with an atomizer and, when fresh, it
is very effective against all kinds of plant lice, against
most small caterpillars and slugs, and against the
larvae of scale insects. It loses strength rapidly when
exposed to the air, and in corked bottles the decoction
ferments and moulds after a day or two. It is alto-
gether too expensive for general use in fields, but in
gardens or greenhouses its cleanliness and absolute
safety to plants are in its favor.

Tobacco has a much greater range of usefulness.
When very finely powdered it may be dusted on and
will kill about the same sorts of insects as the pyre-
thrum. It may be worked into the soil of pots and
benches to kill root lice, besides discouraging many
other underground insects. It is also a fertilizer and
stimulates the plants to which it is applied. If a spray

278 INSECTS

is preferred, one pound of chopped tobacco stems may
be boiled in one gallon of water until a dark brown
extract is obtained, and this will control white fly,
mealy bugs and most of the other greenhouse pests,
provided it be frequently and thoroughly applied. It
stains delicate flowers and is apt to cause a little injury
to very delicate foliage, but in general it is safe on all
ordinary plants. The cost of tobacco dust or ground
tobacco is low enough to warrant its use in gardens
and fields, and we have no better remedy for root lice
on trees and plants; even the woolly apple louse suc-
cumbs to a liberal application. To reach such insects,
the soil must be removed to a depth of at least six
inches in a circle from eighteen to twenty-four inches
around the trunk, varying according to the size of the
tree, before a layer of ground tobacco is put on, and the
trench must be then filled up. The soil moisture and
rains extract the nicotine and bring it into contact
with the root lice. Stems, whole or coarsely chopped,
are of very little use, since the nicotine is extracted so
slowly as to be ineffective. Tobacco is also used in
greenhouses as a fumigant and is quite effective against
a great variety of pests. It may be burnt on a layer of
hot coal in an open stove, an extract may be smeared
on the pipes for slow evaporation, or paper-rolls soaked
in the extract may be burnt on wires suspended in
different parts of the house. And that brings up the
point that there are now on the market commercial
extracts under various names which, when only small
quantities are to be used, are cheaper and better than
can be made at home. They must, however, as a rule
be used at greater strength than recommended on the
labels in order to be thoroughly effective.

Soaps are also used against plant lice and other
sucking insects and these have a much greater range of

THE WAR ON INSECTS 279

effectiveness than the extracts just mentioned because
of their greater penetrating power. All soaps have
some insecticide value, and so washing the leaves of
house plants with soapsuds is always good practice
provided the suds be not too strong. An ounce of soap
to one quart of water is ordinarily quite sufficient to
kill green lice and young scales, especially if whale oil
soap is used. At twice that strength it kills even the
more resistant forms of plant lice, but becomes danger-
ous on tender plant foliage. While soapsuds may be
freely used on house plants, the suds should not be
allowed to accumulate on the surface of the soil for the
alkali may easily become detrimental to the plant roots.
For greenhouse and garden use, whale oil soap is much
improved by an addition of tobacco and such a combi-
nation is now obtainable from most seedsmen.

In the field, whale oil soap is much used against
plant lice, and is effective at varying strengths de-
pending on the insects to be reached. Against most
green lice i pound to 4 or even 6 gallons of water may
be satisfactory; against brown or black Aphids twice
that strength may be required, and against young scales
i pound in 2 gallons is the weakest mixture that can be
effectively used. For winter work against armored
scales like the San Jose', 2 pounds in i gallon of water
are applied.

In all dealings with plant lice and similar insects
that multiply rapidly, prompt action is essential for
best results. It is sometimes easy to destroy a slight
infestation and to get rid of a few specimens on leaves or
stems. If they are allowed to multiply unchecked
until the plant begins to show signs of suffering, it will
be necessary to make much more thorough treatments,
and as many species tend to curl or otherwise to dis-
tort the leaves, hiding in the shelter thus caused, it

280 INSECTS

becomes also more difficult to reach them. It must
always be remembered that no contact poison can be
effective unless it actually touches the insect aimed at,
and covering the top of a leaf no matter how thoroughly,
when the insects are feeding on the underside, is of
little or no use. More ill success results from a failure
to recognize this fact, than from any deficiency in the
material applied.

There are a large number of "patented" or pro-
prietary insecticides on the market for killing plant
lice, scales and similar insects, and some of these are
really meritorious; but they are usually expensive and,
in the long run, no better than the materials we have
just enumerated.

While it is comparatively easy to reach and control
plant lice on most ordinary farm crops and in the
garden, it is decidedly more difficult to reach scales
whether soft or armored, and even mealy bugs are
difficult to kill, in spite of the fact that they are com-
paratively unprotected.

There is only one period in the life of such insects
when they are within reach of mild applications and
that is when the young have just hatched and are
moving about without protective covering. Theoreti-
cally that is the best time to reach them and with some
species it is practically the only time. The oyster
shell scales and some others that attack our trees and
shrubs winter in the egg stage under the mother scale,
practically safe from all our known mixtures. Early
in the season, depending of course on latitude as to the
exact time, these eggs hatch, all at about the same time,
so that for two or three days there is a great swarm of
naked larvae, and for a week there are newly set scales
with the thinnest sort of protective covering; that is
the time for whale oil soap, kerosene emulsion, miscible

THE WAR ON INSECTS 281

oils or whatever else is depended upon to reach the
insects. After the scale has once hardened, none of
our summer applications that are safe on foliage can be
relied upon to kill. A large number of scales, soft as
well as armored, come under this general rule as to
development and treatment, and the gardener or farmer
who has insects of this kind to deal with, should know
their life cycle sufficiently well to know when to make
his applications.

Scales that bear living young usually winter in the
partly grown condition and may be reached by appli-
cations which either penetrate through or under the
protective covering to the insect beneath. When repro-
duction begins the larvae are born singly, a few each
day, and this may continue for two or even three weeks.
By the time the last young emerge, the earliest are
already well grown and covered with scales, so there is
no time when a single application will reach more than
a small proportion of the infestation. If sprayings
could be made every third day so long as reproduction
continues, satisfactory results could be gotten; but
while this may be feasible in the garden and green-
house, it is not practical in the field and orchard. In
large greenhouses this method is often resorted to and
the scales on palms and other hot-house plants are kept
under control by frequent application of weak material.

In the orchard much more drastic measures must be
resorted to, and in winter when the plants are dor-
mant, very caustic or very penetrating materials are
used. For caustics nothing is much better or more
generally effective than the lime and sulphur wash,
formed by combining one pound of ground or flowers
of sulphur with one pound of unslacked stone or shell
lime in three gallons of water. This combination is
made by boiling the lime and sulphur with just enough

282 INSECTS

water to do it properly and afterward diluting to spray-
ing strength. It usually requires about one hour's
boiling to get the proper combination and, when re-
duced with warm water and applied fresh on peach
and plum trees, there is no more effective remedy
against the pernicious or San Jos^ scale. The material
is, of course, quite as effective a killing agent on other
trees as well; but on pear and apple it is more difficult
to reach all the specimens in their hiding places behind
or under bud or bark scales, in crevices or, in the case
of apples, among the hairy clothing of the terminal
shoots. On such trees the wash should be applied with
great force and as thin as possible so as to aid its pene-
tration. On peach, plum and apricot trees it exercises
also a beneficial effect in checking certain fungus dis-
eases and improving the general health of the tree.
On trees in foliage this wash should never be used, nor
on conifers of any kind. As to the practical work of
making the wash, place the lime and the sulphur in an
iron kettle over a brisk fire, pour in hot water enough
to cover and start slacking, which will bring the mass to
the boiling point at once. Add hot water slowly, stir-
ring to prevent burning and to facilitate the combination
of lime and sulphur. One part of good lime is a little
more than enough to combine one part equal in weight
of sulphur and any excess of lime remains as white-
wash and adds nothing to the effectiveness of the
material. If the lime is poor, a little more should be
used to make sure that all the sulphur is combined.
If flowers of sulphur are used, three-quarters of an
hour's boiling is sufficient if hot water is used as a
starter. Otherwise an hour is better. If ground sul-
phur is used boil half an hour longer.

Where large quantities of the wash are to be made
up, live steam is quite generally used, and the mixture

THE WAR ON INSECTS 283

is made in barrels into which live steam is led from a
central boiler. These plants vary so greatly that only
the principles upon which they are built can be stated.
In all cases there is a drop from an elevated steam pipe,
reaching to the bottom of the barrel, where there are
usually cross arms of perforated iron pipe to permit
the steam to get to all parts of the mass and prevent
irregular cooking. The proper amounts of lime, sulphur
and water are put into the barrel, and the steam is
turned on for an hour or longer, until the combination
is completed.

It is also possible to make a good combination of
lime and sulphur by the heat of slacking lime alone, or
by using potash in addition to the lime to produce the
proper degree of heat. It requires heat to combine the
lime and sulphur and it matters little whence this heat
comes; whether from burning wood or coal, from steam,
or from slacking lime, soda or potash. The wash is
effective in proportion to the completeness of the
combination and the thoroughness of the application.

To make the lime, soda and sulphur combination
put into a barrel 22 pounds of best quality stone lime
and add hot water enough to start slacking. While
this is in progress sift in 10 pounds of flowers of sul-
phur, stirring and adding hot water as needed until
the mass is well reduced. Then add n pounds more of
lime with more hot water, and sift in 7 pounds more of
sulphur while this is slacking. Before it is done steam-
ing, stir in ij pounds of caustic soda which will cause a
violent boiling, and when this begins to subside add an
equal amount and then again another ij pounds,
making 4^ pounds altogether. Keep stirring and
adding hot water slowly until the combination is com-
pleted. Then add hot water to make 50 gallons and
apply at once.

284 INSECTS

To make the self-boiled lime and sulphur combina-
tion, place forty pounds of best quality stone lime in a
barrel, sifting in twenty pounds of sulphur flowers with
it so that it is well mingled. Add boiling water enough
to start a brisk slacking and cover with a heavy blanket
to confine the heat. Add hot water as needed to keep
up the slacking, and stir occasionally to aid the combi-
nation. Keep this up until the lime is fully reduced and
mixed with the sulphur. Then let the combination stand
covered for an hour to maintain its heat, after which hot
water enough to make fifty gallons should be added.

The objection to these mixtures is that unless they
are very carefully made there will be a considerable
percentage of uncombined sulphur which is of no value,
and there is so great an excess of lime forming white-
wash, that it makes the wash too thick to get into
crevices or through plant hairs. But even this wash is
now made commercially and there are several brands
on the market which, when thinned down for use, cost
very little more than the home-made wash, and much
less to the man who has no plant available for making
up small quantities. Some of these brands have been
tried in comparison with the home-made wash and,
when reduced no more than nine times, they were
quite as effective. The gardener who has only a few
trees to be treated will save time and money by using
the commercial preparations.

This wash is extremely caustic and corrosive. Ma-
chines in which it has been used should be thoroughly
washed out and oiled before being put away, the hands
should be protected by gloves while spraying, the face
should have a coating of vaseline, and if there is much
wind the eyes should be guarded by goggles.

As already indicated this wash was developed on
the Pacific coast, and it is undoubtedly more uniformly

THE WAR ON INSECTS 285

effective there than it is on the Atlantic coast. A
variety of reasons for this difference have been sug-
gested, but for our purpose it is enough to recognize
that the fact exists.

Sulphur by itself is not a mean insecticide if we
stretch the term insect just a little so as to include the
mites. In the greenhouse, against red-spider there is
nothing much better than flowers of sulphur dusted on
the surface, where the slow decomposition generates
fumes that are fatal to the mites and not conducive
to the multiplication of other parasitic organisms.
In the citrus orchards of Florida a similar practice is
adopted to prevent injury from the rust mite; lump or
ground sulphur is used, and here the hot, moist
atmosphere favors effects that are unobtainable in the
dry climate of the Pacific Coast regions.

A barrel half full of lump sulphur set in a warm
corner of the greenhouse and kept filled with water is
an excellent spraying solution for general use on the
benches. There is very little sulphur in the solution,
but there is enough to keep down mites, check mildew
and destroy many other spores of disease organisms.
As the water is used, more is added, so that half a
barrel of sulphur may last a year or more. It needs a
warm corner to start decomposition.

Combined in a soap, sulphur is used as a wash for
mangy animals, and as true mange is due to a mite,
good effects are obtained. Better yet are the results
when sulphur is administered internally. It is one
of the materials eliminated through the skin, and is
therefore brought into direct contact with the skin
parasites.

Among the penetrants the mineral oils rank highest.
A light crude petroleum of the paraffine series, testing
43° or over on the Beaume scale, will penetrate and

286 INSECTS

kill every scale it touches, and it spreads so well that it
will get under every protection, into every crevice and
through every covering of plant hairs. Unfortunately
it goes further and, if carelessly used, is just as likely
to get through the outer bark into the bast, and to kill
the tree as well as the insect. Nevertheless the material
has been and is even yet quite extensively used, and is
the reliance of a large number of good fruit-growers.
I do not advise its general use, but mention it for the
benefit of those willing to try it. In the garden and
conservatory it has no place.

Kerosene is a derivative from the crude petroleum,
with the lighter volatile oils, the vaseline and the par-
amne eliminated. It can be safely applied to trees
even when in full foliage, in a very fine spray, under
conditions which favor rapid evaporation. I have
frequently applied it with excellent effect late in summer
on very scaly trees, killing off most of the insects with-
out appreciable harm to the tree itself. Apple and
pear trees are most resistant to the mineral oils; peach
and other stone fruits are most susceptible. Citrus
trees stand kerosene very well under favorable condi-
tions; but on the whole this is another material which
needs a thorough appreciation of all the factors in-
volved to make it safe. As a winter application it is
not nearly so effective as crude oil because it evapo-
rates so much more completely, leaving nothing in the
way of a coating to continue its work; but that very
feature makes it safer to use.

The good points of kerosene as an insecticide were
long ago recognized, and nearly thirty years ago methods
of emulsifying it with milk and afterward with soap
were worked out under the direction of Dr. C. V. Riley
then U. S. entomologist, by Mr. H. G. Hubbard. The
milk formula was soon abandoned; but the soap emul-

THE WAR ON INSECTS 287

sion stands to this very day, much the same as Mr.
Hubbard worked it out.

Kerosene 2 gallons

Water i gallon

Hard soap \ pound

Shave the soap fine and dissolve in boiling water;
warm the kerosene and add to the boiling suds; churn
with a force pump by pumping back into the pail
through a fine nozzle until a thick white cream is formed.
This hardens into a butter-like mass when cold and
may be diluted to any desired extent with water. If
both kerosene and suds are hot, five minutes' churning
will bring the proper combination. In making and
diluting the emulsion, soft water should be used and
only a little water should be mixed in at first to get
the butter into soluble form. A well-made emulsion
will keep for weeks in a dark cool place; but event-
ually the oil will separate and come to the top.

Diluted with from twelve to fifteen times its own
bulk of water this is an excellent summer remedy for
plant lice, young leaf -hoppers, mites, thrips and other
insects liable to be killed by contact poisons. The pene-
trating qualities of the oil and clogging effect of the
soap are combined; but the soap prevents the rapid
evaporation of the kerosene, holds it longer in actual
contact with the vegetation to which it is applied, and
thereby increases its danger. Most plants will stand
an application of i to 15; few plants will safely stand
anything stronger than i to 10, and i to 12 is the more
usual limit. As a summer wash against scale larvae
the i to 10 mixture is an excellent combination on all
save stone fruits, and even i to 15 must be carefully
used on such. For winter work it is not advised, because
at a dilution strong enough to kill scales, it is actually

288 INSECTS

more dangerous to the trees than the undiluted oil
itself. Nevertheless, kerosene emulsion shares with
whale oil soap the burden of the fight against plant lice,
with the advantage of cost in favor of the emulsion.

A more recent development in the use of petroleum
oils is found in the miscible or "soluble" oils, sold
under special names such as "Scalecide," " Kill-O-
Scale," "San-U-Zay," or simply as "soluble petro-
leum." These are preparations of petroleum, crude or
partly refined, so combined with vegetable or animal
oils, rosin oil and sulphonated oil, as to be readily
miscible in water to any extent, forming a perfectly
homogeneous spraying mixture of even effectiveness
throughout. None of these oils contain over 75 per
cent, actual petroleum and few contain over 10 per
cent, of water, which is actually necessary to form the
emulsion. They are, therefore, approximately equal
in their effect and are extremely useful as winter washes
against scales hibernating in the partly grown condi-
tion. Against the pernicious or San Jose scale a dilu-
tion with fifteen parts of water is the weakest mixture
that should be used in general practice. Good results
have been obtained with a solution of 20 to i, under
exceptional circumstances; but I would rather recom-
mend a dilution of only twelve times if I were anxious
to secure definite effects. These oils have no vaseline
or paraffin e residue, hence can be safely applied for
successive years, even peach showing no appreciable
injury within my experience. It is on large old apple
and pear trees that these miscible oils find their most
effective field of use, for they spread and penetrate
well and when applied with proper force can be made
to reach wherever a scale can go. This quality makes
them effective against such species as the pear psylla,
which hibernate as adults in crevices and under rough

THE WAR ON INSECTS 289

bark scales, and against such mites as hibernate under
bud scales or in similar positions. They are not espe-
cially effective against insect eggs, and have little
fungicidal value. In all cases where the oils and the
lime and sulphur are equally effective, the latter is
preferable because of its influence on plant diseases.
"Soluble" oils are not safe as summer washes at effec-
tive strengths, although when carefully applied on
mature foliage of hardy trees, no serious injury is caused.

Miscible oils can be made at home and formulas
have been published minutely describing the process;
but it requires skill, absolutely uniform materials and
an outfit that only the user of large quantities can
afford. Furthermore it is an unpleasant and even
somewhat dangerous process which can hardly be
recommended to ordinary farmers and fruit-growers,
and certainly not to gardeners using only a few gallons
or even barrels.

There is another field for kerosene emulsion and the
like when it is necessary to reach certain leaf-miners
which, while feeding on plant tissue are never exposed
to the action <of arsenical coverings, but live entirely in
the leaf tissue. There is usually, however, an opening
to the surface, or the tissue above the mine is so thin
as to be readily penetrated by the oil; hence a contact
insecticide against a leaf-miner is indicated.

It is with the mineral oils as with the lime and
sulphur; the effects are not equally satisfactory under
all climatic conditions. Applications that are entirely
safe in one locality may be distinctly injurious to plants
in another, and a little caution must be observed when
the material is used for the first time in localities differ-
ing from those in which it has been tested.

Another combination with both caustic and pene-
trating qualities as well as a specific feature of its own

290 INSECTS

is found in the resin washes which have had a wide use
on the Pacific coast, but have not been much exploited
in the east. Two formulas for summer and winter
washes are given:

SUMMER FORMULA.

Resin 20 pounds

Caustic soda, 70 per cent, or over 5 pounds

Fish oil 3 pints

Water sufficient to make 100 gallons

WINTER FORMULA.

Resin 30 pounds

Caustic soda, 70 per cent, or over 9 pounds

Fish oil 4$ pints

Water sufficient to make i oo gallons

These are really very thin varnishes, readily soluble
in water and therefore more effective in a dry climate.
The second or winter wash contains so much resin that
its application to foliage would choke and thus destroy
it and is also much more caustic. The summer wash is
effective against scale larvae, recent sets, plant lice and
similar species, clogging their spiracles.

To make these washes, boil all the ingredients
together with about twenty gallons of water until
thoroughly dissolved, adding hot water from time to
time as needed, but never enough to stop the boiling
after it has once begun. Three hours will be required
for a complete mixture, hot water being gradually
added to make up fifty gallons, stirring continuously.
After this, the balance of the 100 gallons may be added
in cold water. It may be that the work of preparing
these washes has something to do with their present
lack of popularity.

It frequently happens that we have underground
insects such as root maggots to deal with, and none of
the soap or petroleum washes heretofore considered is

THE WAR ON INSECTS 291

of any value in this direction. The petroleum mixt-
ures, indeed, usually kill the plants primarily and
the maggots consequentially. We derive some help
from carbolic acid emulsified with soap, so as to be
soluble in water. To make this, dissolve one pound of
hard soap shaved fine, in one gallon of boiling water,
add one pint of crude carbolic acid (50 per cent.), and
churn the whole into an emulsion with a force pump.
This emulsion is diluted for use with thirty times its
own bulk of water, and applied to the soil at the base of
infested plants. The mixture, to be effective, must
come into direct contact with the insects, hence the
earlier it is applied when cabbages and onions are
infested, the more effective it will be; there must be
enough material to penetrate down to the lowest point
reached by the maggots. On cabbages this may be
three or even four inches and may require half a pint of
material; on onions it would not be over an inch or
two, and would of course require much less. Wire-
worms and white grubs are also affected by this emul-
sion and driven away or killed. On growing foliage it
cannot be safely applied, and it is unsuitable for use
against maggots infesting radishes or beets.

Carbolic acid is sometimes used to increase the
effectiveness of whale oil soap and an ounce of the
acid in a gallon of spray mixture does improve it to
some extent, but not enough to balance the extra cost
and labor of working it in. It has been added to air-
slacked lime for use as a repellent around melon and
other cucurbit vines to keep off the melon beetles. It
forms an ingredient in tree washes and preparations
intended to prevent the entrance of borers, and is
somewhat effective in this direction. But insects are
not often adversely affected by unpleasant odors unless
they are also directly poisonous.

292 INSECTS

Another use that has been proposed for the acid is
to paint a band around the trunks of fruit trees with
the idea that it would be absorbed by the bark and
carried into the circulation, poisoning the sap to such
an extent as to kill all the scales and other insects feed-
ing on the tree. The theory is a very plausible one at
first sight, but unfortunately the acid as it penetrates
strikes first the down-current that carries it to the
roots, and when there is enough of it to get into the
active cells, these promptly die and refuse to do any
carrying. If the acid gets still further and really does
strike the up-current, then the girdling is complete
and the tree itself dies. Rarely, however, is there
enough acid applied to cause this mischief.

This suggests the fact that there are always a num-
ber of philanthropic gentlemen ready to aid the farmer
— for a consideration — and willing to insert into his
trees a compound of which they only possess the secret,
which will infallibly kill all the insects infesting the tree
and cure all its diseases. They are even willing to give
a written guarantee to that effect. Many a farmer
and tree owner even in cities and towns falls victim
to the persuasiveness of these benefactors, who bore
holes two inches deep into the wood, fill them with
their compound and fasten it in tightly with a wooden
plug, absolutely beyond reach of those cells of the
tree engaged in carrying sap. Even were the material
soluble and active, it is imbedded in tissue which serves
only as a support to the tree, and has absolutely nothing
to do with its nourishment. Its absorption into the
surrounding cells would therefore mean precisely as
much as if it were absorbed into the tissues of the
nearest fence or hitching post.

Caustic potash and caustic soda have a limited use
on the farm, but in the orchard and garden are fre-

THE WAR ON INSECTS 293

quently used as winter washes for tree trunks. In a
solution of one pound in one gallon of water we have. a
mixture which kills lichens and mosses on tree trunks
as well as many spores of fungi, and leaves the bark
in a nice, clean, shining condition, vigorous and free
from all clogging organisms. It is astonishing what an
improvement a wash of this kind will often produce on
fruit and shade trees, and where a clean healthy bark
is a desideratum, there is no better way to obtain it.
Besides cleaning the bark, this material will also corrode
and destroy many of the thinner scales such as the
species of Chionaspis of which the scurfy scale is an
example. That species hibernates in the egg state, and
the egg is not affected by the caustic; but the scale
covering is thin, easily corroded, and the eggs are then
washed out and scattered by rains. Those larvae that
hatch from them will rarely be able to find their way
back to the tree, and in most instances the eggs them-
selves perish under the unnatural conditions. A ma-
terial so caustic as this should be carefully handled,
for sores caused by it frequently ulcerate badly and
heal very slowly, because of the destruction of tissue.

Lime is one of the most useful materials on the
farm from a great many points of view. Few insects
care to rest voluntarily on a lime-covered surface;
only hunger will induce most species to eat through it,
and some will not touch it under any circumstances.
Lime in its various forms is about the only material
used by most European orchardists, and whitewashed
trees form a characteristic feature in many localities.
As a whitewash on fences and farm buildings generally,
inside and out, it covers over or fills crevices and cavi-
ties that would otherwise serve as hiding places for
insects. It seals up and destroys the eggs of such insects
as may be present when the wash is applied, and on

294 INSECTS

tree trunks it prevents the setting of young scales. A
continuous coat of whitewash will absolutely prevent
the setting of all scales and will keep many of them
from hatching; but it requires rather a thick coating to
effect this, for the lifting of the scales when the young
are ready to emerge, will usually break the coating.
In chicken-houses the wash should be applied with a
spray pump so as to force it into cracks and crevices,
and the addition of a little carbolic acid is here a dis-
tinct gain to the wash. The same may be said of it in
stables and out-buildings generally. Instead of the
crude carbolic acid, which is not readily soluble or mis-
cible with watery liquids, one of the many soluble tar
or cresol preparations may be used in liberal quantities.
Tree trunks are often white-washed to prevent borers
from entering, and with good effect so long as the
coating is thick and well put on. But the egg-laying
instinct is among the strongest, and the parent beetles
of round, flat-headed and bark borers will hunt for a
broken point, an unfilled crevice or a loosened bark
scale, to find a place where they can safely deposit an
egg, while the clear-wing moths will lay their eggs
anyway, and trust the minute caterpillar to find' a bare
place or a crevice through which entrance may be
obtained to the sap-wood below.

On foliage, whitewash is not an advisable applica-
tion; its brittle character makes it quickly imperfect,
even where the tissue itself is not harmed.

In its dry condition the range of usefulness of lime
is much greater. Air-slacked lime mixed with Paris
green for application through a blower or powder bel-
lows is well known, and as a driver in fields of cucurbs
invaded by the cucumber beetles, it is relied upon in
many parts of the country. As a dry hydrate, that is
slacked with just enough water to crumble it into a dry

THE WAR ON INSECTS 295

powder, it is useful against a great variety of viscid or
moist slugs, like those of the asparagus, potato, pear and
the like. When slacked in this way the fine particles of
lime are still very caustic and need another particle of
water to complete the slacking. If, in this condition, the
lime is dusted on the moist slugs, each particle of lime
gets the desired particle of water from the body of the
slug, and in doing so burns a little hole into the skin.
The effectiveness of a dry lime application, therefore,
depends on the moist condition of the insect to be
dealt with, and in consequence early morning appli-
cations when there is a little dew are always most
effective. In the asparagus fields where once the slugs
have gotten a start after the cutting season is over,
there is nothing better than a cloud of dry hydrate of
lime put on with a powder gun just at sunrise or a little
before.

This reference to the time of application in order to
reach the insects in the best condition brings to mind
that there are some plants and insects that by reason
of a waxy or powdery surface or covering repel or shed
water particles. The woolly lice and mealy bugs are
insect examples and the cabbage leaves are good plant
examples. When cabbage plants are attacked by
Aphids which have a covering of fine waxy powder,
ordinary watery applications are of little or no use,
and even soap washes or kerosene emulsions must be
applied with considerable force and in a fine spray to
really wet and be effective. When on cabbage or simi-
lar plants arsenical applications are required, the
matter becomes even more difficult and some sort of
adhesive is needed. Molasses, glucose and soap add
materially to the sticking qualities of arsenical sprays
other than arsenate of lead; but in extreme cases a
resin soap is needed. Such resin soap may be pur-

296 INSECTS

chased, or may be made up according to the following
formula:

Pulverized resin 5 pounds

Concentrated lye i pound

Fish oil i pint

Water 5 gallons

Boil resin and oil in one gallon of water until the
resin is thoroughly softened, then dissolve and add the
lye slowly, stirring continuously until thoroughly mixed.
Then add four gallons of water and boil for about two
hours or until you get a clear amber-colored liquid which
dissolves readily in cold water. This liquid resin soap
may be added at the rate of one gallon to every 100
gallons of any arsenical spraying mixture other than
arsenate of lead, or at the rate of one gallon for every
fifty gallons of any spray used on cabbage or similar
waxy leaves. The adhesive should be placed in the
entire amount of water to be used and, when thor-
oughly dissolved, the Paris green or other poison should
be added.

Powdered white hellebore was at one time almost
the main reliance against saw-fly larvae such as the
currant worm, and is even yet the • favorite for this
purpose with many gardeners. It may be applied as a
dry powder, pure or mixed with two or three times its
own weight of cheap flour; or it may be used in the
form of a decoction, using one ounce, steeped in two
quarts of hot water. This is also effective against
certain small caterpillars and naked slugs, but is not so
reliable and is more expensive than some of the other
materials already recommended.

Sometimes we can make use of certain abnormal
tastes among insects to secure their destruction. Thus
cut- worms prefer wheat bran to their normal food,

THE WAR ON INSECTS 297

and will eat it by choice even when a corn plant grows
near by. We take advantage of this habit by making
up a mixture of white arsenic one pound, to wheat
bran seventy-five pounds; mingle thoroughly, moisten
with sugar water enough to make a soft mush and put a
spoonful in the hill of plants to be protected. There
will be dead cut-worms next morning, and no further
cutting of plants. Sometimes, where a field of grass
has been plowed down and cut-worms are known to be
present, rows of the dry bran and arsenate mixture are
drilled at ten-foot intervals across the field to attract
and destroy the worms before the crop is set out or is
up, as the case may be. Paris green may be used in-
stead of arsenic, but the latter is cheaper. Chickens or
other farm animals liable to eat this poisoned bran
should of course be kept out of fields so treated.

Grasshoppers of certain injurious species have an
abnormal fondness for moist horse manure and great
numbers can be killed off by mixing one pound of
arsenic with three gallons of droppings and spreading
where the insects are most numerous. It is better to
use small quantities several days in succession than
large quantities at one time, because as the material
dries out it loses its attraction.

To keep borers out of fruit and shade trees, all sorts
of mechanical protections have been devised. The use
of lime-wash has been already referred to, and that is
most wide-spread. Sometimes soap, carbolic acid and
arsenic are added, and help a little toward its effective-
ness, because the poison may kill the parent beetles
when cutting a place for the egg, or the young larvae
when attempting to enter. Sometimes the entire trunk
is cased in wire mosquito netting held at a distance of
at least half an inch from the bark at all points, and
sometimes only the lower portion of the trunk is so

298 INSECTS

protected. The round-headed borers of pomaceous
fruits like apple and quince, and the boring caterpillars
infesting peach and its allies, usually enter near the
surface and work in just at or below the ground. A
wTash of hydraulic cement mixed with water, or better,
with milk, is often used to protect trees at this point
and on peach trees a band of newspaper or tar paper is
tied so as to extend a little below the surface and for a
distance of eighteen inches above. Other mixtures have
been recommended and all are more or less effective.
It means simply coating the bark with anything that
the insects cannot or will not penetrate in their efforts
to get to their place of feeding.

Gas tar is safely used in some localities as a protec-
tion, but in others is fatal to the trees, and it is better
not to use tar paper or any black paper, since that
seems to cause a scalding of the bark beneath it. So,
while paints mixed with linseed oil are tolerably safe,
those in which turpentine is used should be avoided,
as they are almost always dangerous.

A great variety of protective devices are in use on
trees to prevent insects from getting up or down the
trunk, or to attract them as shelter for larvae and
pupae, and some of these are effective in special cases,
as when a band of fluffy cotton or of a sticky material
bars the ascent of female canker-worm moths or the
ascent of caterpillars of the tussock moths, from egg
masses laid below them. The larvae of codling moths
can be attracted to burlap bands when they leave the
fruits to pupate, and many of them can be there gathered
and destroyed. Finally, on field crops we can use, very
effectively, tar paper discs to protect cabbage plants
from root maggots.

The direct campaign with poisons is a most impor-
tant feature of the war with insects, and to carry it on

THE WAR ON INSECTS 299

we need a great variety of machinery for applying pow-
ders and liquids, and such machinery is now obtainable
almost throughout the civilized world, to meet the needs
of the man who wishes to protect one plant as well as of
him who farms ten thousand acres. There is every
range from the little atomizer to the steam pump, and
from the little powder bellows to the rotary fan blower
capable of enveloping a large tree in a dust cloud. Spe-
cific description of such machinery would be of little
avail, and he who has the selection need keep in mind
only a few fundamental points. The apparatus should
be so simple as to be fully understood by the pur-
chaser; it should be well made and of the most durable
material; it should be more than equal to the utmost
demands ever made on it; it should be able to give
great force to the material issuing from spout or nozzle,
and there should be a nozzle or spout capable of bring-
ing the dust or liquid into actual contact with all the
insects to be reached, under all the circumstances
under which they occur. Thoroughness of application
is always essential to success, and careless work is al-
ways wasteful and expensive work.

We are not confined in our work to insecticides
merely. Modifications of the primitive method of col-
lecting potato beetles in tin pans with a scum of kero-
sene are still in use, and in some cases form our only
practical line of offense. Leaf -hoppers and grass-
hoppers are collected by means of hopper-dozers drawn
by man or horse power over infested fields, gathering
up the insects on a bed of soft tar or petroleum. We
have similar contrivances to run under grape vines
into which we jar rose-chafers, and wheeled, umbrella-
like structures to capture plum curculios. In a few
cases when large, conspicuous caterpillars like those of
the hawk-moths infest low plants like tobacco or toma-

300 INSECTS

toes, hand picking is the best and most reliable method.

So, when borers get into our peach trees, the only
really effective way is to go after them with a knife,
and if apple or similar round-headed borers are in
fault, a soft wire is added to the outfit to reach such
insects as have gotten into the heart wood.

Against species that march we erect barriers of one
kind or another. Army -worms and chinch-bugs, for
instance, may sometimes be stopped by running a
ditch across their path or a couple of plowed furrows
with steep sides to prevent their easy ascent. At
intervals in these furrows post holes are driven and as
the insects crawl along the bottom of the furrow or
ditch seeking a way out, they fall into the post holes
and are treated to a dose of kerosene. Myriads of
specimens are often killed off in such campaigns, and
the farmer saves his crops, without perceptibly de-
creasing the number of his foes for the year to come.

Some species we are able to circumvent by a little
adaptation of our farm practice. For instance, where
corn is raised continuously on the same land in the
middle west, the corn-root worm soon becomes a serious
pest; but if every third year the land is put into some
other crop, no harm ensues because the insects in the
old cornfields are starved out. We have learned that
rotation of crops is a good thing, and "try to avoid plant-
ing two successive crops of a similar kind; or if that
cannot be avoided, planting or plowing so as to avoid
harm. For instance, corn following old timothy is bad
practice where the latter is liable to be infested with
bill-bugs. Corn belongs with the grasses, and the bill-
bugs finding no timothy when they emerge, attack the
corn. If the succession cannot be avoided, the soil
should be plowed in fall and the corn planted as late as
may be. Similar practice is to be followed where root

THE WAR ON INSECTS 301

web-worms occur and, as a rule, old sod is better fall-
plowed if insect injury to the next following crop is to
be avoided. Most wire-worms and white grubs require
two entire years to come to their full growth, pupating
or even changing to an adult in the late fall of the
second year, and coming out as adults during the
spring of the third. Fall plowing at the end of the sec-
ond year will expose these pupae or recent adults and
kill them, whereas if delayed until the land is fit the
spring following, the beetles would be sufficiently mature
to survive.

The corn-worm and many similar pests also pupate
in the fall, making cells in which they lie safely in all or-
dinary winters. Fall-plowing breaks up those cells and
brings the soil into direct contact with the pupae, which
are killed by the contractions and expansions of the
soil about them, under the influence of frost and thaw.
Of course fall-plowing is not always good farm prac-
tice from other points of view, and the grower must
decide what he had better do after balancing all the
factors of his problem. But in the control of under-
ground pests this practice is important. Sometimes,
indeed, our efforts are indirect, as when in late fall we
plow land infested with root-lice very deeply, to destroy
the nests of the ants that shelter them or their eggs
during the winter.

Frequently the time of planting or the time or
manner of harvesting determines the question of in-
jury. We have learned that in regions subject to Hes-
sian fly attacks, late-sown wheat may be almost en-
tirely free from infestation, while that sown early may
be almost totally destroyed. This is because the early
fall rains bring the adult flies to maturity and they lay
their eggs on wheat or other grasses very soon there-
after. Anything that comes up later is exempt from

302 INSECTS

attack. It is impossible to fix an arbitrary date, for
that varies with latitude, and even in the same latitude
the time at which the flies appear on the wing is deter-
mined by weather conditions: a drought may delay
them until the very latest period for safe sowing has
passed, and in that case early and late sown are apt to
be equally infested. Sweet potato growers in regions
infested by flea beetles have learned that if they delay
setting out their plants until the middle of June they
have little to fear from the insects; but if plants are
set in May, they are almost certain to be seriously
injured. Other cases might be cited, but it is sufficient
to show that by a careful study of the habits of a species
we can often avoid injury without a direct fight. Wheat
harvested in July and left in shock is very likely to
become infested by the Angoumois grain moth. Carted
from shock to mow the infestation spreads until, in
September or October when threshing time comes round,
a large percentage of grain is defective and "flies" or
"moth" are numerous. If instead of being left in the
fields and then mowed, the grain had been at once
threshed and binned, there might have been a little
surface infestation, but there could have been no serious
spread in the bulked grain.

Occasionally an insect can be diverted from a more
to a less valuable crop, as in the case of the squash
borer which prefers late squashes like the hubbard or
marrowfats when it can get them, but will accept sum-
mer varieties like the crook-neck if the others are not
present in equal attractiveness. The grower therefore
plants crook-necks early, and on the same ground puts
in the other varieties late. The early vigorous growers
attract the moths, the plants become infested but are
vigorous enough to produce a crop that pays for the
labor, before the late varieties need the ground and the

THE WAR ON INSECTS 303

borers approach full size. Then the infested plants are
taken out and destroyed, borers and all, leaving the
others free with prospects for only a very small brood
of moths for next season.

That introduces the matter of clean culture. It
has been shown, elsewhere, that some of our well-known
pests pass a portion of their life, and sometimes an im-
portant one, on wild plants allied to the crop grown,
and these serve to tide it over from one season to an-
other. Clean cultivation rids the farm or garden of
these wild plants and makes it more difficult for them
to survive. So a great many species live through the
winter on the remnants of the crop they infested, and
were these destroyed, the hibernating forms would be
destroyed with them. It is a good general rule, when
you are done with a crop, get it off as soon as possible
and burn all left-overs that might shelter injurious
insects. Stems of cotton, cucurbs, potatoes and toma-
toes are among those with insects so controllable.

If in all orchards all dropped fruit could be kept
picked up and destroyed, injury from codling moth
would be at once reduced more than one-half; plum
curculios would soon cease to be important, and fruit
flies would lessen materially. Some work is done along
this line in large orchards, but as a rule the insects in
dropped fruits are allowed to develop at will.

Farm animals can be utilized much more exten-
sively than they have been. Sheep and hogs in an
orchard are great helps in disposing of dropped fruits
and of such insects as come to the surface. A drove
of hogs in a sod field infested with wire-worms and
grubs will tear it up and dispose of a very large number
of the specimens if aided by a few shallow furrows to
give them a start. Chickens, turkeys and guineas are
great insect feeders and can be trained to follow the

304 INSECTS

plow and pick up every specimen brought to view.
Once a small number of fowls has been trained to this
work, the flock will continue the training; the new
members following the older without additional trouble
to the farmer.

In the selection of fertilizers considerable benefit
is sometimes derived in the use of minerals rather
than barn-yard manure. Many insects require the
shelter or presence of decaying vegetable material,
and do not thrive in soils impregnated with mineral
fertilizers. This is a point, however, where the question
of farm practice is eminently one for the cultivator, and
no general recommendations can be given.

There are still among our battery of insecticides
the gases and vapors, and these are of great impor-
tance. Sulphur fumes have been used for many years
against household insects but these are being superseded
by the hydrocyanic acid already described.

Bisulphide of carbon is a clean, water-white liquid,
very foul in smell, volatilizing rather slowly at ordinary
temperatures, the vapor heavier than air and very
inflammable. This vapor is fatal to most insects ex-
posed to it in a confined space for an hour or more,
and it destroys the vitality of seed germs exposed to
it much over twenty-four hours. It is rarely used in
the field, but for insects infesting stored products is
extremely useful. Where entire plants infested by plant
lice can be covered by a tight cone, jar or box, one
drachm or, roughly speaking, a tablespoonful to every
cubic foot of space will kill the insects in one hour.
In melon or cucumber fields in which plant lice have
just made a start, it is sometimes possible to check their
spread by treating the infested hills under hay-caps
or similar covers, or even under tubs or large pails.
Large clam-shells make good receptacles for the liquid,

THE WAR ON INSECTS 305

and as the vapor is heavy, the shell should be put on
top of the mass of vines.

A much more usual employment for the material
is to destroy insects infesting seeds like peas, beans,
lentils, wheat or corn. In such cases the infested seeds
should be put into a tight box or other receptacle, and
bisulphide at the rate of one drachm per cubic foot
of space should be placed in a shallow dish on top of
the mass, the box or jar being tightly covered, of course.
In twenty -four hours all the insects will be killed with-
out injury to the germinating power, but if the seed
is to be used for planting, it must then be aired out be-
fore being again put away. Eggs are not killed by this
vapor, hence it may be necessary to treat a second time
in case of badly infested material. If the grain or other
seed is to be used for food only, it may be kept covered
indefinitely, as no injury is caused to its milling or cook-
ing qualities. In large spaces one pound may be counted
for 100 cubic feet of space, or for one ton of binned
grain. Shallow vessels should always be used for evap-
orating dishes to expose as large a surface as possible,
and the heavy nature of the fumes must be taken into
consideration. Under no circumstances should the
material be used near a light of any kind, and if the
person using it has any regard for his safety, he will
not smoke while handling it even in the field.

Before the development of the hydrocyanic acid
gas, bisulphide of carbon was used to treat even large
spaces like houses, barns and mills; but its cost and
dangers are so great compared with the newer material
that it is not now employed in this way. Purchased
in small quantities at drug store prices, this is rather
an expensive material; but there is a special much
cheaper grade known as "Fuma" bisulphide, which
answers every purpose for agricultural use.

20

3o6 INSECTS

Hydrocyanic acid gas is produced by the action of
dilute sulphuric acid on cyanide of potassium, and is
intensely poisonous to all animal life. It effects vege-
table life to a somewhat less extent and more slowly,
so that there is usually a fair margin of safety between
its effectiveness on insects and the danger of injury on
plants. For the destruction of insects on dormant
nursery stock, and for the treatment of rooms and
buildings to destroy household or other pests, the fol-
lowing formula answers for 100 cubic feet of space:

Cyanide of potassium, 90% pure (by weight) . . . i ounce

Sulphuric acid, sp. gr. 1.83 (by measure) 2 ounces

Water 4 ounces

The gas is lighter than air and is generated in an
earthenware jar, pot or basin as follows: First pour in
the water, add the acid slowly, and finally drop in the
cyanide broken into small lumps in a thin paper bag.
The order of mixing is important, for if the water be
poured into the acid, the amount of heat suddenly
developed will be so great as to spatter the material
in every direction. The cyanide is dropped in, bag
and all, to somewhat delay the development of gas and
permit the operator to escape or close the fumigating
chamber. The method of dealing with household pests
has already been given. Greenhouse fumigation forms
a study by itself, because of the difference in effect on
the many sensitive plants there raised, and for which
no generally applicable directions can be given.

Orchard fumigation is not much practised in the
east where most of the trees have a dormant season
permitting their treatment with sprays. On the Pacific
coast, fumigation of citrus and olive trees is quite largely
practised and elaborate apparatus for covering trees
with gas-tight tents is in use. But even there the prac-

THE WAR ON INSECTS 307

tice is not yet finally settled, and an extensive series
of experiments is in progress to determine the most
effective methods. Under these circumstances no
more is needed here than a reference to the matter,
emphasizing its extent and importance.

By no means all the materials used in the fight against
insects have been enumerated here; a few, like gasoline
and Delphinium are of very limited application and
have been referred to in other connections. But enough
has been said to show the chief weapons in our battle
with the tiny foes that influence us so much more than
is generally known. What is not told is the number
of materials and combinations that have been tried
and rejected, before those here enumerated were fully
tested out and approved. In the reports and bulletins
of agricultural departments and experiment stations,
almost every year brings records of trials made of new
combinations; some originated by the experimenters,
some produced by inventors or manufacturers who
believed they had discovered something better than
was ever known before. Out of all these experiments
very little is annually added to our battery; but
the limitations of the older materials are becoming
ever better understood and the number of effective
combinations is larger now than ever before.

And so in the machinery for applying insecticides
and fungicides there is an enormous and continuing
progress. A collection of dusters and sprayers dating
only ten years back now seems antiquated and ineffec-
tive, and as our methods of application become perfected,
the benefits derivable increase.

From the practical standpoint man now carries on
his war against insects absolutely without regard to
the natural checks of that insect, if it be a native. If
it be an introduced species his attempt is to restore the

3o8 INSECTS

natural balance by introducing the natural checks as
well, and beyond that he relies on his own efforts.

We have learned to take advantage of the weak
points in the life cycle of a troublesome species, and
we know that there is at least as much in the proper
application of insecticides as in the insecticides them-
selves. As there is a continuous specialization in the
raising of crops, so each grower learns to deal with the
pests of that crop by experiment and observation.

It is beginning to be realized that numbers of speci-
mens are not a measure of the difficulty in dealing
with pests. Mosquitoes are abundant enough in exam-
ples, but their life cycle is simple and the methods of
control are obvious. The old cry "it can't be done"
has not even yet ceased, in the face of the results ob-
tained in Cuba, Panama, and New Jersey. And yet,
after all, it is simply a matter of dealing with many
breeding places in the same way, and when a problem
is reduced to a mere matter of amount, it is a matter
of time and dollars only to get it done.

Flies are even more universally distributed than
mosquitoes, and from the sanitary standpoint yet
more dangerous; but even they will not escape man's
efforts at control. The campaign has been already
begun and no doubt it will be continued until practical
measures for checking fly development are universal.

To one in the forefront of the battle progress some-
times seems distressingly slow, and results small out
of all proportion to the efforts made; but, after all,
a review extending back a decade or two shows that
neither the entomologist nor those for whom he has
labored need be ashamed of the advances made. At
all events the importance of insects in their relation to
man has come to be fully realized.

INDEX

Adhesives, 295

Air-slacked lime, 294

Angoumois grain moth, 242,
302

Animal feeders on insects, 131

Anopheles and malaria, 204
habits, 211

Ant guests, 128
lions, 89

Ants and plant lice, 125
and Scutellista, 127
as scavengers, 190
domestic economy, 125
in houses, 242

Aphelinus on scales, 119

Aphis lions, 89

Apple borers, 65

Argentine ant, 245

Arsenate of lead, 274

Arsenical poisons, 274

Asiatic lady-bird, 107

Asilidae, no

Balance of nature, 249
Banding, uses of, 298
Bark-beetle injury, 70, 268
Barriers to canker worms, 298
Bat-tick, 183
Bean weevils, 66, 261
Beaver parasite, 161
Bed-bugs, 229
Bee disease, 151

flies, no

habits, 26

products, 195
Bees as pollenizers, 25

Beetles as borers, 267

as parasites, 96

as pollenizers, 36

injury by, 58
Bill bugs, 259
Bird lice, 160
Birds vs. insects, 133
Bisulphide of carbon, 304
Biting lice, 159
Black beetles, 227

flies, 167

Blastophaga on figs, 31
Blister beetles, 97, 197
Blood of insects, 10
Blow-fly, 175
Blue-bottle fly, 174
Body louse, 156
Boll-worm, 263
Bombyliidae, no
Book lice, 221
Bordeaux mixture, 275
Borers as food, 197

protections from, 297
Boring caterpillars, 266
Bot-flies, 176
Bran and arsenic, 297
Breathing of insects, 10
Breeding of insects, 1 5
Bristle-tails, 219
Bruchidae, 66, 261
Buffalo gnats, 166

moth, 233, 234
Bumble-bees and clover, 25
Buprestidae, 60
Burying beetles, 188
Butterflies as pollenizers, 34

3°9

3io

INDEX

Cabbage maggot, 82
Caddice-flies, 91
Cantharides, 197
Carbolic acid, 291
Carbon bisulphide, 304
Carpenter worms, 74
Carpet beetles, 233
Carrion beetles, 188
Caterpillar diseases, 149
Cattle bots, 180
Caustic potash, 292

soda, 292

Cecidomyiid injury, 81
Centipedes in house, 218
Cerambycidae, 64
Chicken flea, 165

lice, 1 60
Chilocorus bivulnerus, 106

similis, 106
Chinch-bug disease, 145

injury, 53
Chitin, 1 6

Cholera and flies, 199
Chrysanthemum fly, 37
Chrysomelidae, 64
Chrysopidae, 89
Cicada disease, 148

injury by, 52
Cigarette beetle, 237
Circulatory system, 10
Clavicorn beetles, 187
Clean culture, 251, 303
Clerids vs. Scolytids, 108
Click beetles, 59
Climate and insects, 138, 144
Clover pollination, 25
Clothes moths, 238
Coccinellidae habits, 102
Cochineal, 196
Cockroaches, 227
Codling moth, 262
Coleoptera, 18

Coleoptera, as parasites, 96
as pollenizers, 36
injury by, 58
Coleopterous borers, 267
Complete metamorphosis, 17
Contact poisons, 276
Corn bill-bugs, 259

worm, 263

Cossids, injury by, 73
Cotton-boll weevil, 141, 261
Cottony cushion scale, 105
Crab louse, 158
Crane-flies, 80
Crickets in house, 225
Crop remnants, 303
Croton bugs, 227
Crude petroleum, 285
Culex and disease, 207
Culicide, 213
Currant worm, 77
Cutting out borers, 300
Cut -worm injury, 259
Cynipid injury, 78

Deer flies, 169
Dermestidae, 189
Dermestids in house, 232
Destroy crop remnants, 303
Digger wasps, 1 1 6
Diptera, 20, 190

as pollenizers, 37

injury by, 80

predatory, 109
Diseases and insects, 199

of insects, 138, 144
Dragon flies, 92
Drug beetle, 237
Dry hydrate of lime, 294

powders, 276

Ears of insects, 13
Earwigs, habits of, 53

INDEX

Egg stage, 15
Elateridae, 59
Ephemeridae, 87
Eyes of insects, 13

Factors favoring insect injury,

251

Fall plowing, 301
Fallen fruits, 303
Farm animals, use of, 303
practice, 300

and insect injury, 259
Fecundity of insects, 84
Feeling, sense of, 13
Fertilizers for insect control,

3°4

Fifteen-spotted lady-bird, 104
Figs, pollination of, 30
Filariasis and mosquitoes, 207
Fish-moths, 219
Flat-head borers, 60
Fleas, 162

as disease carriers, 213

development of, 215
Flies and sleeping sickness, 208

as disease carriers, 199

as pollenizers, 37

as scavengers, 190

blood-sucking, 166
Flour beetles, 236
Fly disease, 144
Foul brood in bees, 151
Fowls vs. insects, 137
Fruit flies, 83
Fumigating dwellings, 246
Fumigation, 306

for mosquitoes, 213
Furrows as barriers, 300

Gall midges, 80

wasps, 77
Galls, uses for, 197

Gas-tar protectors, 298
Geographical distribution, 139
Golden-eyed flies, 170
Grape phylloxera, 252
Grasshopper disease, 144, 147

injury, 54

Grasshoppers as food, 196
Green-heads, 169
Ground beetles, 101

Hand picking, 299
Head louse, 156
Hearing of insects, 13
Heart of insects, 10
Hellgrammite, 88
Hellebore as insecticide, 296
Hemiptera, 18

as animal parasites, 1 53

feeding habits, 41

habits of, 93
Hepialid injury, 74
Hessian fly, 81
Heteromera, food habits, 67
Histeridae, 189
Honey bees, 195

dew, 256

Hopper dozers, 299
Horn-fly, 171, 254

-tails, injury by, 77
Horse bot, 178

flies, no, 169

manure and arsenic, 297
House ants, 242

fly, 200

mosquito, 208
Household insects, 217
Hydrocyanic acid gas, 246, 306
Hymenoptera, 20

injury by, 75

predatory and parasitic,

H5
Hyper-parasitism, 124

3I2

INDEX

Incomplete metamorphosis, 1 7
Indian-meal moth, 242
Injury caused by insects, 269
Insect powder, 276, 277
Insecticide machinery, 299
Insects as disease carriers, 199

as food, 196

as medicine, 197

denned, 10
Instars = stages, 15
Introduced insect pests, 252

plants, 252

Jigger flea, 1 63
June bugs, 63

Katydids, 57
Kerosene, 286

emulsion, 287

Lace-wing flies, 89
Lace-insects, 195
Lady-bird beetles, 102
Lamellicornia, 62
Lampyridas, 108
Larder beetles, 1 89
Larval stage, 15
Leaf -feeding insects, 258

hoppers, injury by, 257
Lepidoptera, 20

as parasites, 161

as pollenizers, 34

injury by, 72

predatory, 109

Machinery, 299
Malaria, how carried, 203
Mantids, habits of, 95
Mantispidae, 90
May beetles, 63
flies, 87

Meadow grasshoppers, 56
Meal snout-moth, 242

worms, 235
Mecoptera, 90
Meloidae, habits of, 97
Metamorphoses, 15
Midges, 167

injuries by, 261
Migration of insects, 140
Mineral oils, 285
Miscible oils, 288
Moisture, effect of, 142
Moulting of insects, 1 5
Mosquitoes and malaria, 204

and yellow fever, 206
Moths as pollenizers, 34
Muscles of insects, 12
Museum beetles, 234
Myrmeleonidas, 89

Neuroptera, 18, 88

feeding habits, 41
Nervous system, 12
Nut weevils, 67, 262
Nymph, 17

Odonata, habits, 92
(Estridas, 176
Onion maggot, 82
Oriental roach, 227
Orthoptera, 18

injury by, 53

Ox-bot, 1 80

Pain, sense of, 14
Paper disks for root maggots,
298

protectors for trees, 298
Parasitic flies, 113

hymenoptera, 120
Parasitism on vertebrates, 153
Paris green, 274

INDEX

Pea weevils, 66, 261
Peach-tree borer, 72
Pear midge, 81, 254, 262
Perception, sense of, 14
Periodical cicada, 52
Phasmids, injury by, 53
Phylloxera, 252
life cycle, 46
on grape, 46
Pill beetles, 189
Pirate bugs, 94
Plague and fleas, 214
Plant-beetle injury, 63
lice and ants, 125

and weather, 143
development, 43
disease, 148
injury by, 42, 255
parasites on, 119
remedies, 277
sexual parts, 21
Planting, time of, 301
Plasmodium, 203
Platypsylla, 161
Platyptera, 87
Plecoptera, 87
Plum curculio, 262
Pollination by insects, 22

by wind, 22
Polyembryony, 122
Pommace flies, 191
Potato beetle, 249
Potter wasps, 1 1 6
Powder-post beetles, 238
Predatory beetles, 100

insects, 86

Pronuba and yucca, 24
Protective resemblance, 131
Psorophora, 109
Psocids in house, 221
Ptinids in houses, 237
Pupal stage, 16

Pupipara, 182
Pyrethrum, 277

Raphidiidae, 90
Reason in insects, 14
Reduviids, habits of, 94
Reproduction, organs of, 15
Resin soap, 296

washes, 290
Rhynchophora, 67
Roaches, habits of, 95, 226
Robber flies, no
Root lice, 46

maggots, 82
Rose-chafer injury, 258
Rotation of crops, 300
Round-head borers, 64
Rove-beetles as scavengers,

187
habits of, 102

San Jose" scale, 51
Saw-fly injury, 76
Scale-insect disease, 147

injuries, 49, 256
Scale insects, development, 49
Scales, parasites on, 119

remedies for, 280
Scavengers, insects as, 185
Scolytid, injury, 70
Scorpion flies, 91
Screw-worm fly, 173
Senses of insects, 13
Sesiids, injury by, 72
Sheep-bot, 177

ticks, 182

Sight of insects, 13
Signate lady-bird, 105
Silk-worm disease, 151
Silk-worms, 192
Silver-fish, 219
Simuliidae, 166

INDEX

Sinuate pear borer, 254
Skin of insects, 16
Smell, sense of, 13
Smilia misella, 106
Snout -beetle injury, 67
Soaps as insecticides, 278
Soldier beetles, 108
Soluble oils, 288
Squash borer, 72, 302
Structure of insects, 9
Stable flies, 171
Staphylinidae, 187

habits of, 102

Stegomyia and yellow fever,
206

habits, 210
Stem borers, 265
Stone flies, 87
Stylops, habits of, 96
Sulphur as an insecticide, 285

soap, 285
Syrphids vs. plant lice, 1 1 1

Tabanidae, no, 169
Tachinid flies^as parasites, 113
Tactile structures, 14
Taste, sense of, 13
Temperature, effect of, 140
Termites in house, 222
Thalessa, habits of, 121
Thripids and dry weather, 142
Thysanura, 17

feeding habits, 40
Thysanurids in house, 219
Time of planting, 301
Tobacco, 277
Tracheae, 10

Transformations, 15

Trap crops, 302

Tree -hoppers, injury by, 52

protectors, 298
Trichoptera, habits, 91
Tsetse flies, 207
Tumble-bugs, 189
Typhoid fever and flies, 200

Vedalia cardinal! s, 105, 253
Vertebrate enemies of insects,
130

Walking sticks, 53
War on insects, 271
Warbles, 180
Warning colors, 132
Wasps, predatory, 115

social, 118

solitary* 115
Weather vs. insects, 138
Whale-oil soap, 279
Wheel-bug, 94
White ants in house, 222

fly in California, 141

grubs, 63
Winter, effect of on insects,

M3

Wire -worms, 59
Wood-boring beetles, 60

-leopard moth, 73
Woolly apple louse, 257

Yellow fever and mosquitoes,

206
Yucca pollination, 23

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