BSS) Pi SwSjigl
SEL VEVEE hap

VA
BG;

NATURAL HISTORY.

SLUG WORM.

NATURA NUSQUAM MAGIS QUAM IN MINIMIS TOTA EST]
Plin. lib. x1. ca ramet cll
RS: cant Tae lug ~

0283 Fe > 5
fi tan FS
fy A he 2 ~

ri Of \\
x =AUG 1 ; 39 *)

3108800. Oeee — if
on —— us fe

ONAL MUSE
——
By Wit.iam Danpaibe

5
Member of the Agricultural and Hiftorical Societies and A. A. Ss

By ORDER OF THE MAssAcHUSETTS AGRICULTURAD
SoclETY.

Boffo :

PRINTED By Younc & MINNS, PRINTERS TO THE STATE;

1799s

, " ! a” =
} ty : t
” ie
5 e
*
SR RRY OF CANA ip
TA ‘o%

DEC10193g.

DUPLICATE Je
EXCHANGE .

git fae) i the Loe , ton

0000¢90090000000860000000009¢00000000000200000090¢ 08
By WILLIAM DANDRIGE PECK,
MEMBEROfthe AGRICULTURAL aud HisTORICALSOCIETIES, & A.A,S,

ecro0CONNSDCONaDDONDONOAOC Ss00000 DNDN CNNNCRNSCOB000cS

‘Natura nufquam magisin minimus tota ef

PEIN, LIB. XK, GAR. Ss

Addreffd to JonatHan Mason, Efg. Correfponding
Secretary to the MassaAcHUSETTS AGRICULTURAL
SOCIETY,

SZR,

ie evety branch of agriculture, and particularly
that which comprifes gardening, we cannot but
take notice of infeéts, which inhabit the plants we raife :
The variety oftrees which you cultivate, muft have pre-
fented to your obfervation many infe€ls, that the dili-
gence of your gardener is {carce able to repel.

Mosr infe&s, from the time of their being excluded
from the egg, till they ceafe from feeding, wear a different
form from that which they put on in their perfeét flate.
The name of Larva,has been given to the form under '

which they firft appear, and in which they are moft injurt-
ous to trees and plants. At the termination of this firft
period, they become contra&ied, fome before, and others
after, they have formed around them a covering, with ma-
terials furnifhed by themfelves. In this fecond period
they have received the name of Pupa and Chryfalis. In
this ftate the infe&t remains, till every part of its new form
has acquired its full growth, and atthe end of this period
it leaves its narrow prifon, and may be figuratively faid to
have arrived at the age of puberty.

CATERPILLABS

£ NATURAL HISTORY

CATERPILLARS are exceedingly numerous and gener-
ally known ; there are however other larve, which bear a
-confiderable refemblance to them; but are transformed
to infeéts widely different : Naturalifts have ealled them
falfe caterpillars. The largeft of thefe that I have feen,
were upon the White Birch and the Willow. ‘Thofe
which inhabit the willow are common enough: They
‘are f{mooth and black, with a feries of yellow fpots on
each fide, along the whole length of the body. They feed
in ranks arranged along the edges of the leaves, and throw
themfelves into very odd attitudes. Examined with a
magnifier, they are found to have the fix firft feet, armed
with a fingle claw, like the caterpillar; but the other
feet are more numerous, and inftead of being furnifhed
with a number of little hooks, as in the caterpillar, are
only retra€tile prominences terminated by a foft, {mooth,
and rounded furface. , )

I cive you this defcription, Sir, and refer you, for the
obfervation of the feveral particulars of it, to the black
jarva which infefts the willow, as itis large enough to be
eafily examined, becaufe the Slug, which feems at prefent
to threaten the deftruétion of fome' of our beft fruit-trees,
is of the fame family.

Ir is faid tobe about eight or ten years, fince the Slug
was firft obferved in gardens, in the county of Effex, from
whence itis fuppofed to have fpread. ;

Havine been in the habit of frequently vifiting my
. trees, in crder to deftroy the canker and web-worms, or
other infe&ts which infefted them, I think I fhoald have
feen the Slug if it had been in my garden; but it was not
tillthe 8th of July, 1796, that I faw any on my trees:
I wilt not however affert, that it did not inhabit them be-
fore, infuch fmall numbers as to elude obfervation.

On the 12th of July I plucked fome leaves on which
the Slugs were feeding; and having filled a glafs vefflel
with light earth, laid the leaves upon it ; by the 19zh thefe
had all ceafed to feed, and having thrown off the flimy
{kin, appeared in a yellow one, and defcended into the
earth. A few which had entered the earth at the a

: ; or

or tHe SLUG WORM. 5

of the veffel, afforded me an opportunity to obferve, that
when they had attaineda certain depth, they, by moving
their body, prefled the earth equally.on all fides, and thus
fmoothed the cavity, which they then lined with an adhe-
five fubftance, refembling Lac in colour, and ofthe na-
ture of filk ; though not fibrous. To this fubftance the
earth clofely adheres. The cellis rather ofan oval form,
externally of a rude appearance, internally {mooth, and in
fome degree glofly. :

As foon as the cel] was compleated, they remained
contraéted for fome time, till the yellow fkin was thrown
off and the pupa fate fucceeded. In fixteen days after
their defcent, one end.of the cell was broken off tranf-
verfely, and through the opening, thus made, the perfeé&
infect arofe.

Ir was a {mall black fly, a little more than a quarter of
an inch in length, with four tranfparent wings. It is to
be noted, that this was the firft hatch of the year 1796,
which had now paffed through all its ftages. The fly is
reprefented at fig. 8. a. and magnified at fig. 8. d.

On the 7th of Auguft the eggs, placed in the leaves
by the flies of this firft hatch, began to be feen, and on the
16th I firft faw the larve of the fecond race. A number
of the fmalleft of thefe were colle&ted, and I found that
they began to ceafe from feeding on the 11th of Septem-
ber ; a term of 26 days from their being hatched; and by
the 1gth of the fame month there were none any where
to be feen,

Tuese are the principal obfervations I was able to
make that year.

Havine acquired a certain knowledge of the fly and
the eggs, I determined in the {pring of 1797, to watch their
progrefs very carefully. Some young cherry trees, five
or fix feet high, afforded me good fubjeéts for this pur-
pofe. From the firft unfolding of their leaves, I examined
them every day. It was the 2d of June before I fawa
fly ; but eggs had been depofited the day before.

On the 6th, as I was ftanding by a {mall tree, a fly
came and reftedon a leaf before me, and while I was look-

ing

6 NATURAL HISTORY

ing at.it, fhe raifed her head a little, bending down the
hinder part of her body, reclined alittle on one fide, and
throwing out a {mall fling, pierced the leaf obliquely, and
by degrees feparated the upper membrane from the flefhy
part of the leaf ; making a circular incifion of about half
a line in diameter : then withdrawing the fting a little,
forced an egg into the aperture. I marked this leaf, by
putting a thread loofely round it, in order to determine
the precife time which would elapfe before the egg was
hatched. Examining it from tine to time with a magni-
fier, Ifound it encreafed in bulk, and from a long oval,
approached a fpherical. form, as reprefented at fig. 1. a.
<r.

Own thetenth day I could perceive, through the mem-
branes of the leaf and egg, the eyes of the larva, as at jg.
1. 6; and on the goth of the month it appeared on the »
leaf and began to feed. This was the fourteenth day from
the depofite of the egg, and the refult accorded with the
appearance of the other Slugs that firft fhewed themfelves
on the 15th of the month from eggs depofited on the ift.
From the 11thtothe 19th the flies appeared in the great-
eft numbers, fo that [caught 50 or 60 ina fhort time while
ftanding by the trees. They have not the timidity of other
infe@s, and may be taken with very little trouble. When
the fly is about to place an egg in a leaf, after the has be-
gun to make the incifion, the leaf may even be cut off,
and with a magnifier of about 3 4ths of an inch focus, this
very amufing operation, which 1s performed in lefs than
a minute, may be diftin@ly obferved through the tran{-
parent fkin of the leaf. The incifion is generally made
on the under fide of the leaf, without wounding the fkin
of the upper fide ; the egg being forced in raifes the up- |
per fkin, and the fpot appears like a fmall blifter ; the
health of the leaf and the circulation of its fap, appear to
be in no wile injured; the egg is kept moift, and defend-
ed from the a@tion of the air and rain ; but has all the
benefit of light and heat.

Tue fkin of the egg is foft and fufceptible of diftention,
and in order to preferve thefe qualities, it feems aaa se

: that

OF THE SLUG WORD 7

that it fhould be placed in contaft with the fap-veffels of
the leaf, which may, perhaps, in fome fort, contribute to
the nourifhment of the embryo larva. Ifthe cuticle of
the leaf is carefully raifed, the young larva may be feen,
rolled in a fpiral form, as at jg.1. 2. and white ; a flip of
a leaf in the vial, with the affiftance of a glafs, will afford
you an opportunity to obferve it in this flate.

Soon after emerging from the blifter a vilcid exuda-
tion takes place which covers the whole upper furface of
the larva with a flimy coat of an olive colour. In this,
as well as inits tardy motion, it refembles the Slug or Snail
whofe name has been applied to it. This coa* retains its
humidity although expoled to the fierceft heat of the fun:
it is probably a defence againft its enemies, and anfwers
the further purpofe of fupport when removed from its na-
tural pofition. The olive colour in fome is very decp, in
‘others more dilute and inclining to adirty yellow.

On firft quitting the egg the larva is nearly white, the
head brown and apparently large in proportion to its
body, as in fig. 1. c. where it is delineated both of its
natural fize and magnified.—In the courle of twenty
days it throws off four fkins at nearly equal periods ; it
remains in the fifth or laft vifcous fkin fix days, and ac-
quires its full growth (fig. 2. a.) ; it then quits this fifth
{kin which is left adhering to the leaf (jig. ¥. c.), and ap-
pears in a clean yellow one, entirely free from vifcidity,
and has fo different an afpeé that it would not be fup-
pofed to be the fame larva (jig. 2. b. and fig. 5.)

Arter refting fome hours, it proceeds flowly towards
the earih, creeping down the leaf-f{talk and along the
body of the branch—I did not watch its tedious progrefs
to the trunk ; but believe, when they arrive at the rough
bark, they lofe their foot-hold and fal] ; as I have never
feen any on the trunk, which muit be covered with them
at the feafon of their defcent if they were able to move
on rough furfaces.

Tuey do not all proceed thus regularly; for I have
obferved, that if the leaf on which they reft, receive the
leaft fhock, they roll themfelves up and fall off. They

‘enter

e | NATURAL HISTORY

enter the earth to the depth of from one to four inches,
and the procefs of transformation goes on as related a-
bove.

FREQUENTLY as foon as the fkin is fhed, they are feen
feeding upon it; this appears to be an inftinétive aét, and

perhaps contributes to furnifh a more copious fupply of

the vifcous exudation; but the laft mucous fkin which is
thrown off remains extended on the leaf, as at fig. 2. Cc,
and fuch fkins have been miftaken for dead flugs.

On the 12th of July, perceiving many in the yellow
fkin, I dire&ted cloths to be fpread on the ground and
the trees to be fhaken; About 170 were colleéted which
I threw into a veffel filled with light earth. Onthe goth,
or in eighteen days after their defcent into the earth they
began to rife in the form of flies.

I was then unexpettedly called from home, and was_
abfent through the months of Auguft and September.
At my return, in Oober, the flugs of the fecond hatch
were in plenty on the trees, and fome of them remained
till the 21 ft, amonth later than in the preceding year,
when almoft all the leaves had fallen and after having
furvived feveral frofts.

Tuey had been far more numerous in the firft hatch,
than they were in 1796; but according to the beft infor-
mation I could colle¢t, their numbers in the fecond great-
ly exceeded the firft: the fmall trees were covered with
them; and a breeze of air paffing through the trees,
became charged with a very difagreeable and almoft fick-
ening odour.

In order to determine, with fome degree of precifion,
the time when the fly firft rifes in the fpring, I filled a
box with earth taken from the foot of a cherry tree, from
one to four inches deep, in the month of February of
the prefent year. It contained about two cubic feet.
This earth I caufed to be fifted, and by this means 190
cells were colleGed, which were put with fome of the
fifted earth in a garden pot. At the fame time I exam-
ined the earth in which the larve of the firft hatch
of the laft year had paffed their transformation; and

finding |

or THE SLUG WORM. 9

finding many cells whole, fuppofed the larve within them
had perifhed; but on opening fome of them, I found
they were alive, and in the fame {tate as on their firft en-
trance. I examined both parcels of earth again on the
6th of May: the larve had then juft entered the pupa
ftate in both. It appears hence that if all the Slugs of
the laft hatch of 1797 had been deftroyed on the trees,
there would have remained in the earth a fufficient num-
ber to have continued the fpecies.

On the 21{t of May they began to rife and depofite
their eggs. About the 5th of June the young Slugs be-
gan to fhew themfelves, and continued to do fo in great
numbers, till towards the end of the month; and it ap-
peared, that the flies not only rofe earlier; but that they
continued to rife and depofite their eggs longer this year
than in the two former years.

In the beginning of July, the larve began to defcend ;
about the 23d, the flies from thefe began to rife, and by
the 7th of Auguft the Slugs of the fecond hatch began to
appear on thofe trees which had any green leaves remain-
ing, in fuch abundance that by the t5th there were from
twenty to thirty on a fingle leaf. Inthe mean time the
trees which had been ftripped, had thrown out new leaves,
at the ends of tnofe branches that had not perifhed, from
buds, which fhould not have unfolded, according to the
ufual courfe of vegetation, till the next fpring; thus anti-
cipating the growth of one year, and cutting off the prot-
ped of fruit.

As the flies continue to depofite their eggs about three
weeks, and the period of hatching is as long, the Slugs
ave confequently of different fizes: the larger difappear
leaving the fmallieft on the leaves. Hence, fome perfons
have f{uppofed there were three or four hatches in a
year; but there are certainly only two.

Heavy fhowers are faid to deftroy them, and it is pof-
frble that a few may be wafhed off; rain appears to be
difagreeable to them, and, in fhowers, I have obferved
that they make a fafe retreat to the under fide of the
leaves,

THAN

30 NATURAL HiIsTORY

Tury feem.to prefer different trees in different places.
In my neighbourhood the common red Cherry was more
attacked, than the Plumb or Pear: ina garden about a
mile diftant, they feemed more pleafed with the Quince,
than with the Pear, Cherry or Plumb: In another place
the Button-Pear was preferred to any other. I have alfo
found them on the wild Black-Cherry and wild Pear.

Tue largeft flugs that I have feen, were about g-20ths
of an inch in length. The head of a dark chefnut colour,
is bent under and entirely concealed (fig.3 & 4.) This
conformation is neceflary as the dire€ton of its bite is in
the plane of the leaf; but when it has aflumed the yellow
coat, its head is more prominent and ,difcernible (fig. 2.
b. & fig. 5.) The fix firft feet are terminated with a lit-
tle hook ; befides thefe there is a Jimb on each fide, be-
tween the firft pair of feet and the head, which is unarm-
ed, and alwavs laid over the fide of the face juft below
the eyes. I have not obferved any thing analogous to
thefe in any other larva; they are fhewn at fig. 4. a:
their ufe may perhaps be to regulate the depth of its bite,
and to wipe off any extraneous particles that may adhere
to the jaws.or antenna. ‘The other fourteen feet are en-
tirely unarmed (jig. 3. 5.) It is mechaincally fupported
by the former; but its fupport by means of the latter ap- |
pears to depend on the preffure of the atmofphere.

Tuer body is largeft towards the head, and diminifhes
gradually toward the tail. They have the faculty of
{welling out the anterior part of the body (as in fig. 2.4.
& fig. 3.), and they moft frequently appear in this man-
ner with the tail a little turned up (fig. 2. a).

Tue cell is reprefented at fig. 7; the pupa is yellowifh,
the eyes brown and is delineaied at fig. 6.

Tue fly is of a full gloffy black except the legs which
are of a brownifh afh colour : the antenne black with nine
articulations. It is reprefented at fig. 8. a, of its natural
fize, and magnified at fg. 8.5. The wings are tranfpa-
rent, with a footy tinge, refleéting the prifmatic colours
when held in certain direétions tothe light. They area
little tumid or convex on the upper fide, which 1s one
charafteriftic of this genus; but a more certain one is

the

or rue SLUG WORM. -g2

the fling, or inftrument with which the female makes the
incifion for the reception of her eggs. This refemblesa
faw,and from this circumftance they are called by Englifh
writers Saw-flies. One of the anterior and pofterior wings
is fhewn at fig. 9. The male refembles the female in
colour; but is confiderably lefs and has no fting. A part
of the abdomen of the female, containing the fting, is
fhewn at fig. 10; and the correfponding part of the male
at fig. 11.

In the thirteenth edition of the Linnean Syftem, by
Profeflor Gmelin, there are 142 fpecies of this genus, of
which the Tenthredo Cerafi or Saw-fly of the Cherry-tree,
has the greateft affinity to the Slug-fly ; and is deferibed
as being “ black, with the legs and triangular part on the
66 bach, between the infertion of the wings, yellow. Thé
“ larva flimy and black, inhabits the leaves of the Cherry
& tree, which it rolls up.’*

Tue Slug-fly has no yellow about it, neither does the
larva roll up the leaves: it may, notwithftanding, be a
variety of the Ténthredo Cerafi, as it agrees in fize and
in the flimy covering.

An eminent French author, on the fubje& of infeéts,
has a figure of the fly and of the larva; but defcribes only
the latter, which he calls the Falfe Caterpillar of the
Pear-tree. In his defcription he fays, “ Another kind of
“¢ falfe caterpillar, which differs very much from the com-
6 mon kind in form and which it is difficult to character-
6: ize is found on various fruit-trees, as the Plumb, the
s Cherry, but efpecially on the Pear-tree. Fruit-trees
6 however are not the only ones on which they are found ;
« for I have alfo feen them upon Oaks. In both they
“ live on the upper furface of the leaves, and there con-
¢ fume the parenchyma; their fkin is always mucous,
6 which would make them to be taken for fnails, if one
did not perceive their feet. Their colour isa brown-
& green. They are rarely ftretched out like the Cater-
6: pillar, and can at pleafure {well a certain part of their
“ body: they frequently {well the fore part for a third

Kot
* Syftema Natura, pa. 2659, No. 20.

12 NATURAL HISTORY.

* of its length or more, and narrow the reft. They have
« but twenty feet and none in the laft fegment. Thefe
infeéts fometimes multiply exceedingly on the Pear-
“ tree, fo that four or five are found on the fame leaf.
« I have feen of thefe trees in the month of July without
“a green leaf.’T

Tus defcription, according fo exa&t!y with the Slug,
and the author’s mentioning it as a fingular f{pecies, in-
cline me to believe that it is the only fpecies of this ge-
nus which has a mucous coat, and that our Slug-fly is a
variety of the Tenthredo Cerafi. The. form of the faw
in the European fpecies will determine this point.

Tuis inftrument is a very curious obje&, and in order
to defcribe, it will be proper to compare it with the tenon-
faw ufed by Cabinet-makers; which being made of a very
thin plate of ficel is fitted with a back to prevent its bend.
ing. The back is a piece of iron, in which a narrow and
deep groove is cut, to receive the plate, and is fixed; the
faw of the Tenthredo is alfo furnifhed with a back, but
the groove is in the plate and receives a ‘prominent ridge
of the back which is not fixed, but permits the faw to flide
forward and backward as it isthrown out or retracted.
The faw of artificers is fingle, but that of the Tenthredo
is double, and confifts of two diftin&t faws with their backs;
the infe&t in ufing them, firft throws out one, and while
it is returning, pufhes forward the other, and this alter-
nate motion is continued till the incifion is effe€ted;
when the two faws receding from each other, condué the
egg between them into its place. In the artificial faw the
teeth are alternately bent toward the fides, or out of the
right line, in order that the fillure or kerf may be made
fufficiently wide for the blade to move eafily: to anfwer
this purpofe in fome meafure, in that of the Tenthredo the
teeth are a little twifted fo as to ftand obliquely with re-
{peé to the right line, and their points, of courfe, proje& a
little beyond the plane of the blade, without being lateral-
ly bent, and all the teeth in each blade thus proje& a lit-
tle outward ; but the kerf is more effe€tually made, and a

a

+ Reaumur in Mem. des Infettes. Tom, 5. Mem. des Mouches a fcie.

“or tuz SLUG WORM. ig

free range procured for the faws, by fmall teeth placed
On the outer fide of each; fo that while their vertical ef:
fe&t is that of a faw, their lateral effeét is that of a rafp,
In the artificial faw the teeth all point outward and are
fimple ; but in the faw of the Tenthredo, they point in-
ward or towards the handle, and their outer edge is be-
fet with fmaller teeth which point outward. Some idea
of the faw as conneéted with its back may be formed
from fig. 12, and ofthe faw alone from fig. 13. The
lateral teeth in the faw of the Slug fly are very minute, and
the want of light, when the greateft magnifiers are ufed to
examine a flat furface, has prevented my feeing them fuf-
ficiently well defined, to be able to exprefs them accurate-
ly, though the contour of the objeét is very diftin@, but
viewed edgeways they are plainly feen. I have there-
fore given fig. 14. of one from another fpecies inhabiting
the cherry-tree, which fhews this part of the ftruéture very
- plainly.

I xnow not how long the flies continue to live after
their firft appearace; though plenty about the trees, in
the time of depofiting their eggs, they become, afterwards,
very fcarce. I am equally uncertain as to the number of
eggs from a fingle fly. Ifall in the ovaria come to per-
feétion, a fingle fly may depofit between two and three
hundred; but probably not more than half thefe are ex-
cluded by the fly. The ovaria are compofed of feveral
tubes, about fix on each fide, which occupy a great part
of the abdomen, flowing from a common point, enlarging
in their courfe and uniting again on each fide, ina canal
Jeading to the oviduét. (fee fig. 15.) The eggs in thefe
tubes are of all intermediate magnitudes, from a {fcarce
_ vifible fpeck to thofe ready to be excluded, of which laft
_ I have frequently counted fifty, though the feafon of de-
pofiting was advanced.

Tue flies do not feed like ry infe&is of this clafs,
on the honey of flowers; but upon the moiflure which
they lick up from the leaves, moift with dew or fhowers.

Tue vifcous coat of the Slugs feems to be their fuffi-
cient defence in the larva flate ;_ they are not, however,

without

44 oe SNATURAL HISTORY,

ag , %
without enemies, and fuch as I hope will be a confidera-
ble check upon the increafe of this very difagreeable and
deftructive infeét.

In profecuting my inquiries the laft year, I obferved
fome eggs in the leaves of the Cherry-tree,which were not
femitranfparent ; but opaque and black ; concluding they
were abortive, and defirous to know the caufe, 1 examined
them and found each egg occupied by two or three white
fpecks: thefe were fo many infeéts in the pupa ftate, one
of which is reprefented at fig. 16, and I afterwards found
the perfeét infe&t which is fhewn at fig.17. This is an
extremely {mall fly of the genus Ichneumon, which depo-
fits its eggs in thofe of the Tenthredo and other infeéts.
It is of a pale ruft colour ; the eyes and three fpots (fiem-
mata) on the top of the head, of a bright red; the wings
tran{parent, fiudded and fringed with fine briftles, the pof-
terior wings very narrow; the antenne confifting of §
articulations. I obferved this year that great numbers of
the eggs of the Slug-fly, efpecially of the fecond hatch,
were rendered abortive by this atom of exiftence. The
out line of the egg of a Slug fly at fig. 18, magnified to the
fame degree as fig. 16 & 17, will enable you to judge of
their comparative magnitudes.

I cannot but remark here, how juft was the obferva-
tion of a naturalift who lived in thefrft century, and how
amply it 1s confirmed by the microfcopes of the moderns,
‘that the author of nature is no where more perfect than
in the minuteft of his works !”

To make this account as perfe& as I was able, I have
noted every particular which has come to my knowledge ;
this has renderedit prolix : but I hope the fatisfa&ion you
may receive, will,in fome meafure, compenfate for the
fatigue of going through it.

I sec you to believe me to be, with much refpeét,

Sir, your moft obedient fervant,

Maffachufetts, Augufi—1798— RURICOLA.

N. B. The above Hiftory obtained the Agricultural Society’s premium
of Fifty Dollars and the Gold Medal. $= The preferved fpecimens, ree
ferred to inthe Hiflory, may be feen by calling on the Corr’g. Secretary.