﻿118 Journal New York Ent. Soc. [Voi. hi. 



chitinous ridges which stand up from the cuticular hning of the wall of 

 the sac (Plate V, Fig. 6). The secretory cells of the walls of this sac 

 in Centra vimila are said by Klemensiewicz to be large hexagonal cells, 

 resembling those of silk glands, having like them large branched nuclei. 



The fluid thrown out is said by Poulton to be formic acid ; it 

 causes violent effervescence when allowed to fall upon sodium-bicarbon- 

 ate, and colors blue litmus paper red. 



In the caterpillar of Astyanax archippiis (^Limenitis disippus') a 

 dark bladder-like sac is everted, but the lateral tubes appear to be 

 wanting and no spray is sent out; it occurs in the larvae of many 

 Nymphalidce, and other butterflies and moths. 



Scudder tells me that these glands are generally present in the 

 larvae of butterflies, including the present species, but as I observed it 

 repeatedly and with some care in this caterpillar I will record my ob- 

 servations. A larva which had hibernated was found May 1 1 at Provi- 

 dence on a leaf of the wild cherry ; its length was 1 2 mm, I could not 

 but be struck with the protective resembance of the creature when 

 curled up to a mass of birds' droppings. 



While examining the caterpillar, my attention was called to a 

 whitish mass with a black outer edge, situated on the under side of the 

 prothoracic segment just behind the head, and in front of the first pair 

 of legs. On removing this mass with the needle I found under it a 

 large low conical eversible soft tubercle covered with short hairs. On 

 rupturing the gland with a needle a little fluid exuded from it. When 

 at rest the gland is retracted within a transverse oval opening. No 

 odor appears to be given out by the fluid, as tested by four persons. 



The caterpillar when at rest was experimented on, with the follow- 

 ing result. On rudely touching it with the point of a needle, it turned 

 the head on one side and suddenly evaginated the gland to its fullest 

 extent, but no fluid could be seen. On teasing it still further the cater- 

 pillar would angrily turn its head over upon its back, so that the hirsute 

 gland would be directed upwards. It then, on being let alone, gradu- 

 ally, but rather rapidly retracted the gland, the thick, rather swollen 

 lips forming a narrow transversely oval opening, which would be easily 

 overlooked. 



The gland is bladder-like and of simple bag-like shape, without 

 the pair of diverging siphon-like tubes seen in Centra and Pheosia, 

 and it is probable that the fluid is not ejected in a stream or spray, but 

 simply exudes from the gland, in which no opening could be detected. 



The gland is of the same dark brown color as the skin of the cater- 

 pillar itself, and not light in tint as in Centra, Pheosia, etc. 



