INTERNAL ANATOMY OF THE MOTH. 
53 
just the tip, to show its peculiar outline and the spine-like structures r 
which probably have a sensory function. They are present in all Lepi- 
doptera, but under a great variety of forms ; 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. G and 8). The spines consist 
of two* parts, a cylindrical basal joint and a double outer portion, com- 
posed of two tapering horns (Plate Xr, Fig. 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. Iu the smaller spines the inequality 
of the two forks is much less; 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- 
wards the base of the proboscis they gradually grow smaller and smaller, 
and lie fmtlnT apart ; they are not found on the basal half of the organ. 
Upon that edge of the maxilla.' which is dorsal when they are extended, 
are hairs such as an- repiv>euted in Plate XI, Fig. 7. These hairs are 
for the most part inclined away from the tip-like barbs. Whether they 
are >t iiY, so that fchej s, rve to lacerate the flowers attacked by the moths, 
wo were unable to determine ; that this function is performed by the 
large spines is, we think, improbable, although Professor Comstock has 
suggested this view. 
INTERNAL ANATOMY OF THE IMAGO. 
The digestive canal of Aletia closely resembles that of the Milkweed 
Butterfly, DanaLsarchippus, as described by Burgess. We shall therefore 
follow his account. 
The canal tra versing the proboscis opens into a large muscular pha- 
rynx, which occupies much of the lower part of the head, Plate VII, Fig. 
2. The pharynx is oval, and is suspended by at least two pairs of mus- 
cles, one dorsal, mi 1 , and one frontal, m 2 . At the anterior border of 
the pharynx is a triangular muscular flap, the epipharynx, ?n 3 , 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 libers, 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 pumping 
*F. Darwin, Quart. Journ. Micros. Sci., XV, 3So. Breitenbach. Arch, fur rnikros. Anat., XV, 8, and 
XVI, 308. Jena, Zeitschr. t Xat.- Wiss. 
