March, I9I2.] NeWCOMER : RELATIONS OF AnTS AND CATERPILLARS. 35 



bottom, the cuticula is modified into the tubercles or papillse bearing 

 the setae (s). The hypodermal layer (hyp) is composed of smaller 

 cells than in other parts of the body, except about the base of the 

 organ. Here the cells are enlarged and somewhat pyriform. The 

 function of these cells is to produce the setae, and each cell tapers out 

 through the cuticular layer to one of these (Fig. 4). No cells were 

 discovered which might secrete an odor-producing liquid. Attached 

 to a thickening of the cuticula at the base of the organ is a retractor 

 muscle (r.m) which extends to the ventral wall of the larva, where 

 it passes through the hypodermis and is attached to the cuticula 

 (Fig. 5). It is probable that the body-tension is sufficient to evert 

 the organs whenever the retractor muscles are relaxed, and a con- 

 traction of these draws them in again. 



The skin of the larva is rather thickly set with spreading, stellate 

 spines, from the center of each of which arises a toothed seta. These 

 (Fig. 3, t.h) are hypodermal in origin, and without doubt are tactile 

 in function. Viehmeyer (8) states that according to Thomann's theory 

 these hairs serve to notify the caterpillars of the return of the ants. 

 They are scattered over the whole surface of the body, but are most 

 numerous dorsally, and perhaps a little more thickly distributed about 

 the glandular opening. 



This paper was written in the entomological laboratory of Stan- 

 ford University. 



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2. Klemensiewicz, Dr. S. (1882). Zur Naheren Kenntniss der Hautdriisen 



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