﻿Sept. 1S95] Packard. Scent Glands of Insects. 117 



tailed larva of Cerura has been known to throw out a secretion, which 

 was described by Bonnet in 1755 ^^ a true acid, sharp, sour and biting. 

 This spraying apparatus in Cerura (^Harpyia) viuula has been well de- 

 scribed by Klemensiewicz (Plate V, Fig. 4), though Rengger in 181 7 

 noticed the general form of the secretory sac, and that it opens out in two 

 muscular evertible tubes, out of which the secretion is ejected. 



The fork-tailed larva of Macritrocampa marthesia, which is much 

 like that of Centra, when teased sends out a jet of spray to the distance 

 of nearly an inch from each side of the neck. While examining the 

 very gaily colored and heavily spined caterpillars of Schizura concinna 

 I observed that when a fully grown one was roughly seized with the 

 forceps or fingers it sent out a shower of spray from each side of the pro- 

 thoracic segment, exactly like that of Cerura and Macrnrocampa. 



In the European Cerura vinu/a the apparatus consists of a single 

 sac, which opens by a narrow transverse slit on the under side of the 

 neck, out of which is rapidly everted four lateral tubes, two on each 

 side (Plate V, Fig. 4/), which are withdrawn within the opening by the 

 contraction of several fine muscles. The apparatus in the American 

 C. multiscripta is as in the European C. vinula. In a living specimen 

 the large secretory sac was seen to be of the same size and shape as in 

 Macrnrocampa, and of the color of raw silk. The sac when disturbed 

 extends back to a little behind the middle pair of legs, and is nearly 

 two-thirds as wide as the body. The caterpillar sent out the fluid when 

 handled, but I could not make it spray. 



In the larva of Macrurocampa marthesia the cervical or secretory 

 gland (Plate V, Fig. 5) is situated in the first and second thoracic seg- 

 ments, extending to the hinder edge of the latter and lying between the 

 nervous cord and the oesophagus and proventriculus, and when empty 

 the bulk of it lies a little to one side of the median line of the body. It 

 is partly held in place by small tracheae, one quite large branch being 

 sent to it from near the prothoracic spiracle. The short large duct 

 leading from it to the transverse opening in the membrane between the 

 head and prothoracic segment is a little narrower than this opening, and 

 is kept distended by t^enidia or a series of short spiral threads which 

 are pale, not honey-yellowish in color. This duct lies on one side of 

 the prothoracic ganglion resting just under the commissures passing up 

 to the brain ; it is also situated between the two salivary ducts. 



The very distensible sac (Plate V, Fig. 5) is rendered elastic by 

 a curious arrangement of the cuticle, the ttenidia of the duct itself be- 

 ing represented by very thickly scattered irregular separate, sinuous 



