﻿120 TouRNAL New York Ent. Soc. / [voi. iir. 



/ 

 segment is only a single pair of papilla ; the anterior pair being obso- 

 lete, and I cannot detect any opening to a gland. 



On the first thoracic segment, the legs are closely contiguous at 

 their broad expanded bases. Directly behind the legs and in the me- 

 dian line of the body is a minute area bearing two minute tubercles, 

 but no opening near them is visible. 



It is possible, though careful observations on the living larvae are 

 needed, that the openings of the repugnatorial glands in Lacosoma are 

 closed from disuse, and that the glands themselves only exist in a rudi- 

 mentary state. It is interesting, however, to find these glands in this 

 family, and to find that they appear obsolete (at least the external open- 

 ings in Lacosoma), while the glands are functionally active in Pero- 

 pJiora, a genus so nearly allied. It will be interesting to ascertain 

 whether these glands are present in the true sackworms, or Psychidse. 

 We should hardly, however, expect to find them developed, since these 

 caterpillars are in closer quarters, the sacks being smaller and more 

 tubular, and there seems to be little need of active repugnatorial glands 

 in creatures otherwise so well protected from attack.* 



The caterpillars of the swallow-tailed butterflies {Papilio, Doritis 

 and Thais), as is well known when irritated thrust out from a trans- 

 verse slit on the upper part of the prothoracic segment, a large orange- 

 yellow V-shaped fleshy tubular process (the osmeteriion), from which is 

 diffused a more or less melon-like but disagreeable, in some cases, an 

 insufferable, odor; the secretion is acid and reddens litmus paper. The 

 mechanism has been described and figured by Klemensiewicz. 



When at rest or retracted the osmeterium lies in the upper part of the 

 body in the three thoracic segments, and are crossed obliquely by sev- 

 eral muscular bundles attached to the walls of the body, and by the 

 action of these muscles the evagination of the osmeterium is strongly 

 promoted. After eversion the tubes are slowly retracted by two slender 

 muscles inserted at the end of each fork or tube, and arising from the 

 sides of the third segment behind the head, crossing each other in the 

 median line (Plate V, Fig. 7, r. m.). The secretion is formed by an 

 oval mass of glandular cells at the base of the forks ; in the glandular 

 mass is a furrow-like depression about which the secretory cells are 

 grouped. The secretion collects in very fine drops on the side of each 

 furrow opposite the glandular cells. 



According to C. D. Ash the larva of an Australian Notodontid 



* After an examination of microscopic sections of two young larvce of Thyri- 

 dopteryx I am unable to detect them. 



