
THE BODY SENSE HAIRS OF LEPIDOPTEROUS 
LARV:.! 
WILLIAM A. HILTON. 
Ir is well known that, as a rule, all arthropods have their 
bodies and appendages clothed with hairs, or sete, which are 
simply modified parts of the cuticle. 
These hairs vary in form and in structure. In the most 
common type the hair is hollow, and its lumen communicates 
with the body cavity by means of a “pore canal" in the cuti- 
cle (Fig. 1). Through this pore various structures may extend 
into the lumen of the hair, as a prolongation of a hypodermal 
cell, gland ducts, and nerves. 
There are published references to solid hairs of insects; but 
if we except certain minute elevations of the cuticle, such as 
are represented in Fig. 2, and which are more or less hairlike, 
I found none in the insects studied. It should be said, how- 
ever, that certain scalelike appendages of the cuticle of the 
larva of Corydalis (Fig. 3, 2) appear to be solid; but as these 
occur, each at the end of a pore canal, they may prove to be 
hollow. 
The most commonly observed structure that passes through 
the pore canal into a hollow hair is a prolongation of a hypo- 
dermal cell, which is much larger than the ordinary cells of the 
hypodermis (Fig. 4, 7). Such a cell was named a *trichogen," 
by Graber, as it is believed to be the element that produces the 
hair. In many cases there are associated with the trichogen 
one or more gland cells, which discharge their secretion through 
the hair; the stinging hairs of certain larvae are examples of 
this type. Such hairs may also have a nerve extending to 
them, and perhaps they always do. 
A type of hollow hair which occurs much more commonly 
than does the glandular hair is one into the lumen of which 
! Contribution from the Entomological Laboratory of Cornell University. 
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