ire x CELE. 
ON SOME GLANDS WHICH OPEN EXTERNALLY ON INSECTS. 
. 
BY GEORGE DIMMOCK, CAMBRIDGE, MASS. 
The following paper consists, for the 
most part, of compiled material brought 
into connected form in consequence of 
ideas suggested to me in studying odor- 
iferous glands of the larvae of <Aitacus 
cecropia, to which I have already called 
the attention of the Cambridge Entomo- 
logical Club, at its meeting of 13 Oct. 
1882. Since that time I have made sec- 
tions of the above-mentioned glands of 
Aittacus cecropia, and of those which I 
found later in the larvae of a pterophorid. 
Aciptilus lobidactylus; the glands of the 
larvae of these two species have furnished 
the original descriptiye matter of this 
paper. 
The peculiar odor of the larvae of Atta- 
cus cecropia, when they are roughly han- 
dled, has 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 tubercle, and a clear yel- 
low fluid of disagreeable odor to ooze 
from each opening left by the injury. 
By crushing the tubercle with a pair of 
forceps the same 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 odorous 
fluid. The red tubercles are seen, in 
sections cut with the microtome, to be 
divided into compartments, the cavities 
of each spine opening into a compartment 
at its basal end. ‘The spines themselves 
are quite rigid and very brittle, so that 
they break away at a slight touch and 
leave a hole in the tuberele, out of which 
the odorous fluid pours, pushed by inter- 
nal pressure. This fluid, which I have 
not examined carefully, but which I hepe 
later to study chemically, is strongly acid 
to litmus paper, but causes a purple 
precipitate in carmin solutions. Larvae 
of Attacus 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 moulting the last 
larval skin in order to enter the pupal 
state. 
The odor given out by the glands of 
the larvae of Attacus cecropia suggests at 
onee their protective function, and, after 
having watched a sparrow (Passer domes- 
ticus) drag asphingid larva about, seiz- 
ing it usually by the horn, it seemed 
likely to me that the disagreeable acid 
fluid in the tubercles of the larva of 
Attacus cecropia was a protection to the 
larva from similar rough treatment. 
