Article beginning on page 387.
Psyche 3:387-401, 1880.

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PSYCHE.
ON SOME GLANDS WHICH OPEN EXTERNALLY ON INSECTS. BY GEORGE DIMMOCK, CAMBRIDGE, MASS.
The following paper consists, for the
most part, of compiled material bronght
into connected form in consequence of
idea's suggested to me in studying odor- iferous glpds of the larvae of Attcicus
cecrupiu, to which I have already called the attention of the C:m~briclge Entomo- logical Club, at its ineetiiig of 13 Oct. 1882. Since that time I have made see-
tions of the above-mei~tionecl glands of Attactis cevnipiu, and of those which I
fonnd later in the larvae of a pterophorid. Aciptihis lobitlactylus; the glands of the larvae of these two species have furnished the original descriptive matter of this
paper.
The peculiar odor of the larvae of Atta- czis cecropia, when tlie~- are rongI11~- ban- died, tias probably escaped the notice of but few persons who have reared these
moths through their larval stages. If a
larva be examined carefully the black
spines upon its red, blue, and yellow
knobs, or tubercles, will be seen to break easily from the tnliercle, ancl :i clear yel- low fluid of disagreeable odor to ooze
from each openingleft by the i~ljury.
By cnishing the tubercle with a pair of
forceps the snme strong odor is very
noticeable, and by this mode of treat-
ment one has no difficulty in proving that each tubercle, small or large, -blue,
yellow or red,- contains the oclorous
fluid. The red tubercles are seen, in
sections cut with the microtome, to be
divided into con~partments, the cavities of each spine opening into a compartment at its basal end. The spines themselves
are quite rigid ancl very brittle, so that they break away at a slight touch and
leave a hole in the tnbsrclii, out of which the odorous fluid ponrs, unshed by inter- 11a1 pressure. This fluid, which I have
not examined carefully, but which I hope later to study chemically, is strongly acid to litinns paper, but causes a purple
precipitate in carmiu solutions. Larvae
of Attuciis cecropia are provided with
these glands and the odorous fluid as
early as the third larval stage-perhaps
earlier-and apparently shed the glands
in the tubercles when moiilting tlie last larval skin iu order to enter tlie pnpal state.
The odor given out by the glands of
the larvae of Attaciis cecropia suggests at once their protective function, and, after having w:itcliecI a sparrow (Passer domes- ticm) drag a spliiugid larva abont, seiz- ing it usually by the horn, it seemed
likely to me that the disagreeable acid
fluid in the tuoereles of the larva of
dttcicus cecropia was a protection to the larva from similar rough treatment.




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388 PSYCHE,
Having found these interesting glands
American species -of lepidoptera which
on the larvae of Attaws cecropia, glands are known to sting. Lintner has experi- coneei'tiidg which I can find no mention nabntcd further tipou the stingiug power in entomological literalure, my attention of the larvae of Lagoa crispatu, and Miss was drawn further to the subject of ester- Mdrtfeldt8 upon that of the larva of,
na1 glands of insects, many of which are Lapa opercularis. That the sting of protective or defensive in fmiction. some of these larvae can do lasting in- Glands similar to those of the larva jury ia certain, for my mother, when of Attvicusceeropia, in that they liare no twenty-seven years old, received SO outlet until one is produced by external severe a sting in the middle finger of one agency, are not rare in the larvae of ham1 iu brushing away a larva from her boinlycidae. The severe poisoning pro- neck that the distal joint, healing only dnced by the hairs of certaiu larvae of after seveial months, remains somewhat bambycidae, of which the so-called pro- stiff<it~ect and slightly deformed, now thir- cessioiiary caterpillar of Europe is an
ty-seveu years. For a time the stinging
example, find obaervcd, according to of these bombyeid larvae was attributed Monfet,l by Uioscorides and oilier early to the action of the hairs in entering writers, is caused by the secretion from a and wandering dwut in the ficsli, nu!, minute glaud at the base of each hair. even as late as 1881. long after the dis- The secretion of these glands fills the cover;. of the glands at the base of the ,
hollow central portion of the hair, and
hairs, Gooseens advances the idea that
when the sharp, often barbed, hairs are
the poisou of the processiounry etiterpil- broken iu the flesh of attacking animals, lar of Europe comes from other glands
the broken parts carry with them the
which I shall mention more in detail
poisonous aecrption. Tins setiretion is, later. Keller,7 in 1883, discusses the perhaps, formic tieidor a formate in soln- mode of urtication in the processiouiiry tion. Karste~i,~ in 1848, described the ctitei'pillars (larvae of Oastropacka) and . anatomy of the poison glands it the base figures the glands at the bases of their of the hairs of an American species of hairs. Siitun~h. Fine illustratious of this kind Still another form of gland witho~t of gland are to be found hi the stinging a111 outlet until broken open, but 11 gland hairs of tire larvae of Bype~c1iIriu~ $0 and which can scarcely be classed with those I/emileucct niaia, both common insects
previoniil~ mentioned, is that at the an- in parts of the United States.
Li~itner*
tenor end of certain bombycid pupae,
and Rilev4 have recorded their experi-
which breaks when the imago spriugs
ments on the stinging power of these
the chitinuns pupal akin, and leaves its two apedes of larvae, and the latter
secretion, which has been termed bornby- writer has given a list of the larvae of cic acid. on the lieiid of the moth, the hitter using the secretion to moisten the 'For literature referred to throughout this paper see the end of the article.
threads of the cocoon so that they cau




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P~%HB. . 889
be cut or pushed aside to allow the ea-
Second are hairs (fiorn 0.08 to 0.14 mm. -
cape of the imago within. I have never
long) more or less ditmb-bell or club
studied this gland and will refer for fur- formed, which are filled with granular
ther notice to the easily accessible papers matter, and seem to be set usually only of Trouvel~t,~ Pachard? McLai'enm and
upon the surface of the chitiuous cover- Worthington," wherein references can ing of the larva. Third are the longer be found to earlier European writers on hairs (from 0.8 to 1.3 mm. long);linear this subject.
or aliglitly davate, usit?lly burst at the It is an easy transition from the glanda tip, or sometimes along the sides, and
of the larvae of AttWUs, Byperchiria
where burst surrounded by a drop of
and Hemileurn, closed by 1-u-We, hollow
exuded gummy matter. Tlieae last hairs
spines or hairs, to the glandular hairs are mounted, by a kind of joiufc such as of certain larvae of pteropltoridae, where is often present at the base of insect the hairs are apparently burst open at haire, upon or near the summit of little their tips by the pressure of the secretion conical elevations, wliicli rise about 0.2 within them, the liquid then oozing out mm. above the surface of the dorsal and to form a dew-like drop upon each hair. lateral parts of the larvae. Theae Zelleru mentions glandular hairs ("dm- hairs are arranged systematically and aenh~rchen") on the larvae of Mimeseo- symmetrifially upon tlni different seg- pti/uspha,eodactylus and M. mictodmtylva, ments of the larva, the most prominent but says nothing of the stt'nctnre or use of them being a pair upon a conical of these hairs.
Miss Murtfeldt1' writes elevation just at each side of the median of the larva of Lewptilus sericisactylus dorsal line of each ~egnicnt. A corn- "Dorsal hairs proceeding from prominent parison of the arrangement of these hairs tubercles, and of two sizes in each tuft, and prominences with the arrangement each of the shorter ones tipped with a of hairs and warts upon other lepido- minute pellucid bead of viscid fluid, to pterous larvae, espacially of those upon which pollen and bits of leaves often ad- the larvae of tortrfci-due, would be an here." I have found the larva of Acipti- iuterestiug study. The interior of hairs lus lobidactylus to be covered, in like of this third form opens at the base into manner, with glandular hairs. the conical prominence or wart on which Upon making transverse sections of
the hair is situated. The prominence is
the larva of Aciplilus lobtdactylus, its ex- probably entirely filled by the gland terual surface is found to bear three which secretes the viscid matter that hinds of appendages. First are the very finds outlet through the hair. minute, but obtuse spines (about 0.01
The specimens of the larva of which
mm. long) which clotlie most softer and I made microtomic sections were not more flexible portions of its external
quite welt enough preserved to admit of
covering, and which are found on many
carefully studying the glaud at the bass larvae of different orders of insects, of the hairs. The hairs of the second



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and third form seem to be modificationa
of each other, for, in the longer and
more clavtite hairs of the second form,
the granular matter in the hair extended without, interruption 'into the larva,
and these haira often burat and give out viscid fluid. The larger hairs. of the
second form are often upon the sides of
the conical warts which bear at their
summits hail's of the third form. Hairs
of similar nature, but smaller and with- out viscid 011id, clothe the larva of Oxy- ptiltts periscelidactylu.8 and Pterophow no no dactyl us.
Sfheseoptiltis phaeod~~-ctylus feeds on
Unonis regem, M. mictodactylus on Saxi-
frqa grunuluta, Lioptilua seitcictmty??ts on Vei'nonia wveboracensis and Aciptilus lobidach&s on Solidup fcmadensis :
thus, as will be noticed, all the species of pterophoridae rnent.ioned above feed
ou plants clothed with glandular or long hairs.* The glandular hairs of the larva protect it, probably, by causing it to re- semble the surface of the plants on which it feeds, a kind of resemblance not rare iu insects ; but it is also probable that ' the secretion of the glandular hairs also protects the larva, to some extent, from the attacks of ichneumons and of other
parasites, for I obtained no parasites
from over .fifty specimens of Aciytilus
*Miss Murtfeldt writes me its Follows: ''3 had not thought to tncntlon it in connection with my description of titioptitus siricidactyius but there i$ a very dosi; imitation in the dermal clothing of the larva to that of the young leaves of Vtmonia, on which the spring and early summer broods feed." . . . "Later in tilt season, when feeding chiefly on the flowers, the larva acquires a purplish tbge which, with the particles of the flowers that adhere to its giandular hairs, isa sufficient disguise from any but the eye practised in its detection." lobiciwstybts, reared from larvae taken
,
when nearly full-grown, while I have al- ways obtained, in rearing a much less
number of Oxyptihts pevisceliductylus
under similar conditions, several para-
sites. It is noticeable that the viscid
secretion upon the larvae of Aciptilws
lubidactylus is alkaline to litmus paper, while the fluid from the tubercles of the , larvae of Attam cecropia is acid.
Turning from the study of insect-hairs
which furnish more or less temporary ef- ferent ducta for glands, there are forms of haire-leaving out of account, a8 un-
proved, "Weisma~m's curious, but not
improbable, view1* that S C ~ ~ B of lepi- doptera may be sometimes ducts for an
odorous fluid secreted by cells at their bases-which are regularly and perma-
neutlv the outlets for glands at their
bases. An interesting example of this
kind of open hair duct is furnished by
the hairs upon the foot of the common
house-fly (Musca ciomesfica), through
which hairs, as recently shown by De-
witz,la a sticky secretion is poured, the fly being enabled by the adhesion of this secretion to rest upou smooth vertical
surfaces. Le~flig,1~ in 1859, describes
and figures glands in the tarsi of several coleoptera ; West," in 1862, descrilies
and fignres the tarsal hairs of the fly and of many other iusects ; and dew it^,'^ in 1882, discusses the function in locomo-
tion of the viscid secretion wliic'h is dis- charged by the glands of the foot through the tarsal hairs, both in flies and in
coleoptea.
Defensive glands of another kind, the
duets of which open into spines, are the



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glands which furnish the poisonous se-
cretion for the sting of bees and wasps. I have not discussed these glands further in this paper, because they are rather
internal than external glands; for like
reasons I have not referced to the silk- glands of lepidopterou~ and hymenopte-
rous larvae. The literature of impor-
tance upon the subject of the silk-glands of lepidoptera can be found in a disser- tation by Helm," in 1876 ; and papers
by Dewitz, *", in 1875 and 1877, and
by Fo~el,~ in 1878, give a clue by which to trace the literature upon the stinging organs of hymenoptera.
The glands of the larva of Attacus
cecropia and Byperdihia io, sealed
until broken open by some external
agency, may be termed passive glands,
while those glands which pour out their
secretion in direct response to some vol- untary or reflex action of the insects, as do the foot-glands of Musca, the sting
of the bees and many other glands,
may be termed active glands. But there
are glands characterized by still greater activity than those already mentioned.
If the larvae of certain species of Ciw- hex are suddenly disturbed, they will jet out, as observed by Bonnetm (v. 1, p.
470, 473, 485), a clear yellow fluid, of disagreeable odor, from opening6 along
their sides. In the case of a German
species of Cimbex I have Been this fluid thrown by the larva to a distance of
several centimetres, altho Frisch,'" who first mentions this secretion, in 1736,
apparently only ssm it flow from the
openings.
Upon disturbance, the larva of the
European bornby cid , ffa.pyia winula,
raises its head and jerks it from side to side, throwing a strongly acid fluid from a gland, the opening of which is on the
ventral side of the first thoracic segment. The propulsion is here partly produced
by the rapid jerking of the head, and
partly by pressure upon the receptaculum or lumen of the gland within the body.
This gland, or at least its secretion, was noticed by de Geer^ in 1750, and more
fully in 1753 by Bonnet," who described
the secretion as a true acid, sharp, sour, and biting. Later, besides many brief
notes on this gland, may be mentioned
more extended descriptions by Muller,"
Amoreu~,~ Jorden~,~~ and Eengger.^
I have not observed whether the larvae
of the common American species of
Harm/ia (Cerura) possess this power of
throwing a defensive fluid or not, and
Lintner,81 as well as French,win descrip- tions of the American larvae, make no
mention of such power. The soft skin
of the larva of Edruyiu vinzda evagiu-
ate8 itself about the orillice, on the first thoracic segment, where the gland die-
charges its fluid, forming four points
which are well figured by Mulier and
Jordens, in the books cited above.
"Within, the duct of the gland passes to A the right of the displaced central nervous system, as described and figured by Mrs. Dimmock, in PSYCHE, v. 3, p. 340-341.
I pass by, with mention only, the
openings which pour out an odorous
yellow fluid from the joints of the legs of species of coccinell-ida.e, chrysomelidae and meloidae, for further notice of which I
refer to papers by Leydigm (p. 37-38)




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CUE.
who thought the fluid to be only the
1 of the insect ; the glands opening
between the prothorax and head and
tween the mesotliorax and metathorax
, of which the nature of the
lateaus; the anal glands of Brachinva
id other carnivofous coleoptera, the
ploaive mode of whose discharge in
-ae/unus has given rise to its popular
glish name of bomburdier, for the
rattire of which I refer to Leydigl@
, 46-49), and to a late paper by
gementM; the cornicles of the sixth
ominal segment of aphidae, which
supposed to pour out a sugary mate-
songtit by ants, but which material
laczi18* writes, in a paper LO which
ill refer for further literature of the
tomy of aphidae,
comes from the
us of these insects ;* the sacs, proba-
glandular in function, found by
en" noon the larvae of certain ueu-
era ; the odoriferous glands of hem-
ramentioned by Landoisw and others ;
he acent-glands which AubP1 mentions
n the elytra and thorax of E~tmolp~ts
etbauq the wax-secreting glands found
ertain insects, treated of by Claus,"
67 ; and the odoriferous glands of
midae described by Scudder, in
h e suck the secretion of the cornicles of older ones is anticipated by Morrem,m in 1836, and Mnrren adds to his stAtement *&fAt' observd d4jh par Wonnet"-fact already observed by Bonnet,
to some papers which will guide further
to the literature of the stihject, in order to come directly to forms of which the
morphology is more interesting in this
connection, or of which the function is
not so well understood. -
An interesting economical provision is
evident in the odoriferous tiiburcles of the larvae of Attacus cec1-0p;'a and in the urti- eating spiuea of Hilperchiria io. There
is no waste of the secreted material by
either of these larvae; it is sealed up
until its use is necessary and then it is applied exactly where it will accomplish most.
But what shall one say of the ,
novel mode of avoiding waste, to which
attention was called by Ciau~,'~ in the
larva of the European chrysomelid, Liy
pop&? Along the dorsal side of this
larva .ire rows of short black spines, not noticeably different from the spines often fouud on larvae of wleoptera, but if the larva is disturbed it will suddenly press out upon the tip of each of the s1)iues a spherical drop of milly liquid. Watch
these drops for a momeut. As the dis-
turbance which has caused their appear-
ance subsides, they become smaller,
sometimes suddenly, sometimes gradu-
ally, but always iu unison, until finally. when the larva no longer feels itself in danger, the drops entirely disappear:
the fluid has been drawn back into the
spines to be used again in case of need- , Claw ha^ suspected that salicylic acid exists in the secretion from the larva of Linapopull, which is very prrtbable, since the larva feeds upon leaves of Salix and Popuh, that contain salicio, of which




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PSYCHE.
salicylic acid is an oxiiliition-pftiduct. Clans says that the larva of liinci ppuU has been used as ft source of salicylic
acid in mail quantities. The odorolis
secretion of the glniids of the larva of Lh a protcct not only the larva, but, as Lyoiiet noticed, also the pnpa, from the attitcks of birds. Clans slims bow tins
protection of the pupa is accon~plished : the glands, with their contents, are shed with the last lwval skin, diicli reinaiiis around the point of attachment of the
nhdomen of the pnpa, and, when the
latter wriggles about on acconnt of any
disturbawe, tbc odorons fitiid is squeezed from the molted glands. De GeeP de-
scribes and figures the spines of the
larva of Litm p~pdi in 177.). Ly~iiet,,~~ probably sonwwliat eariior, describes and fgnres the larvae of Lhm pr>pn.li and L. dwi-ah, and mentions the proti'nsiou
and retraction of the milky drops.
EatzulHirg49me~~tioiis briefly the glan- tliiiiir stiwiitioii of L. pr,pf<U^ and Wcst- wood47 collccts together notes on the
larvae of different species of Lina.
Cliapnis and CanciSze^ write that the
larva of Lina (Plagiodera} scripts from
the fiiitid States is similar to that of L. jpupdi.
Clansda was the first to study the in-
ternal anatomy of the glands aid spines
of JLiinn populi, and lie shows that the liqnid is pushed out of the spines by
a cmti'aclion, which I may be allowed to term an ilieipknt evaginntivii, of the
walls of the gland. This leads one to
search further in order to find if this