314 The Structure and Action of a Butterfly's Trunk. (May, 
When not in use the trunk is coiled into a close spiral, and lies 
beneath the insect’s head, hidden between the large and hairy 
feelers of the lower lip— 
the labial palpi—which are 
specially developed for this 
service, 
Now although, as just 
said, these facts have long 
been known, the mechan- 
ism for sucking liquids 
through the trunk seems 
q never to have been noticed, 
and it has been supposed 
the inner gee with stiff bristles; #4, base of that the po of suction 
the trunk. lay in the “sucking stom- 
ach,” so called, or perhaps in the peristaltic contraction of the 
trunk, or that simply the capillary action of the latter might be 
sufficiently powerful to dispense with any special sucking appa- 
ratus. The anatomy of the trunk has been equally neglected and 
misunderstood. Thus even Burmeister believed that each half 
had a canal of its own, and Newport described non-existing hori- 
zontal muscles, and otherwise mistook the muscu- 
lar mechanism, 
Having been for some time engaged in studying 
the anatomy of the “emperor,” as Mr. Scudder has 
christened Danais archippus, our largest and very 
common butterfly, I will describe the mouth or- 
gans of this species, the same plan of structure 
prevailing through the whole group of Lepidop- 
tera, at least wherever I have examined repre- 
sentatives. 
Bik rE ici of In the “emperor” then, the trunk is about fif- 
chippus from out. teen millimeters long, with a width at the base of 
girene mas- about 24 mm., from which it gradually tapers to a 
are really black point at the tip. Externally a sort of coat-of-mail 
py fip apa 2 appearance is given by its composition of an im- 
spaces delicate mense number of rings (Fig. 2) (or rather portions 
ae a rings, the inner segments being of course wanting) 
which being united by more yielding parts of the cuticle, evidently 
permit the rolling up of the whole organ, while imparting at the 
