INTERNAL ANATOMY OF THE MOTH. 53 



just the tip, to sliow its peculiar outline and the spine-like structures, 

 which probably have a sensory function. They are present in all Lepi- 

 doi)tera, but under a great variety of forms 5 in Danais they are reduced 

 to small warts, but in many other genera they are large and conspicu- 

 ous,* for details the reader may consult Darwin and Breitenbach.* The 

 spines are evidently modified hairs, for they are each placed over a wide 

 pore-canal of the cuticula, and are themselves pointed chitinous tubes, 

 as shown in the figures (Plate XI, Figs. 6 and 8). The spines consist 

 of two parts, a cylindrical basal joint and a double outer portion, com- 

 poi^ed of two tapering horns (Plate XI, Eig. 8). In some of the larger 

 spines one of these horns is much the greater of the two, and seems to 

 be a direct, spur-like continuation of the base, while the shorter fork is 

 articulated to the proximal joint. In the smaller spines the inequality 

 of the two forks is much less j the long fork is most developed on the 

 spines of the dorsal side of the maxilla. There is difficulty in making 

 out these characteristics in all the spines, as they often lie on the slide 

 in positions unfavorable to microscopic examination, and there remain 

 many points undecided. The largest spines are found a little way from 

 the tip; on the very tip of the trunk they are a little smaller, and to- 

 Avards the base of the proboscis they gradually grow smaller and smaller, 

 and lie further apart ; they are not found on the basal half of the organ. 

 Ul)on that edge of the maxillse which is dorsal when they are extended, 

 are hairs such as are represented in Plate XI, Fig. 7. These hairs are 

 for the most part inclined away from the tip-like barbs. Whether they 

 are stiff, so that they Si^rve to lacerate the flowers attacked by the moths, 

 we were unable to determine ; that this function is performed by thq 

 large spines is, we think, improl3able, although Professor Comstock has 

 suggested this view. 



INTERNAL ANATOMY OF THE IMAGO. 



The digestive canal of Aletia closely resembles that of the Milkweed 

 Butterfly, Danais archippus, as described by Burgess. We shall therefore 

 follow his account. 



The canal traversing the proboscis opens into a large muscular pha- 

 rynx, which occupies much of the lower part of the head, Plate YII, Fig. 

 2. The pharynx is oval, and is suspended by at least two pairs of mus- 

 cles, one dorsal, ??i^, and one frontal, m?. At the anterior border of 

 the pharynx is a triangular muscular flap, the epipharynx, m^, overly- 

 ing the opening of the proboscis, and serving as a valve to close the 

 latter. The pharynx shows two layers of muscles, an outer, thicker one 

 of longitudinal fibers, and an inner of transverse fibers. The pharyngeal 

 cavity extends obliquely upwards from front to back, and is much 

 broader than high. 



" The pharynx, as is evident from its structure, serves as a pumijing 



■» F. Darwin, Quart. Journ. Micros. Sci.,XV, 385. Breitenbach. Arch, fiir mikros. Anat., XV, 8, and 

 XVI, 308. Jena, Zeitschr, f. Nat. - Wiss. 



