56 REPORT. 4, UNITED STATES ENTOMOLOGICAL COMMISSION. 
TERMINAL BODY SEGMENTS AND ORGANS OF REPRODUCTION. 
In the state of rest the eighth and ninth segments in the abdomen of 
both sexes lie concealed within the seventh, the intersegmental mem- 
branes in these cases being long enough to admit of this telescoping 
action. The eighth segment of the male does not differ from the preced- 
ing, except in wanting the spiracles and in its smaller size. It has, how- 
ever, on its under side a thick shock of long hairs or scales parted down 
the middle, which, when this segment is retracted within the seventh, 
serves to form a soft cushion between the two, although this may not be 
its only purpose. The brushes of hair, to be described below, borne by 
the ninth segment act in the same manner as a cushion between the 
eighth and ninth segments. 
The dorsum of the latter or terminal segment is produced backwards 
into a slightly curved hook, often compared with the telson of the Crus- 
tacea (see Plate VIII, Fig. 2, and Plate X, Figs. 1 and 3, where the hook 
is marked with the figure 9). This hook covers the anal opening («.), 
and in some Xoctuids is greatly developed. Beneath it is a chitinous 
finger (Fig. 3,/) which is movable, but its function is obscure. 
The ventral portion of the ninth segment forms a broad trough-shaped 
process (Plate X, v.pr., Figs. 1-3), with upturned lateral edges, the penis 
lying in the bottom of the trough so formed, and hinged to each side 
of this segment are the "claspers," which are narrow triangular pieces 
with a slender, slightly incurved apex. Their exact shape will be more 
readily understood by referring to the lateral, dorsal, and ventral views 
given in Plate X, Figs. 1, 2, and 3, c left, & right clasp. 
There is still another and singular organ attached to the ninth seg- 
ment. This is a sac with delicate membraneous walls thickly covered 
with slender, long-stalked scales (Plate IX, Fig. 3). The sac is very 
elastic, and may be protruded like a long finger and again retracted at 
will. The long hair-like scales give the organ the appearance of a 
brush. It is shown in various positions on Plate X, Figs. 1-3, the 
scales being removed in all the figures. This brush-sac is attached to 
the base of the claspers. 
Morrison * first called attention to similar organs in Leucarctia acrcca, 
and states they are protruded by being filled with fluid from within. He 
also noticed them in Danais, Agrotis, and Euplexia. Burgess (loc.cit.) 
described their structure in Danais, where, however, they are not placed 
in the same position as in Leucarctia and the Xoctuids. The retractor 
muscle found in Danais we have not succeeded in finding in Aletia. 
3iiiller has also noticed these appendages, and regards them as scent 
organs. At all events it is probable they are organs for sexual excita- 
tion. They are not found in the female. 23 
The male organs of reproduction consist of a very large testis, two 
vasa dcferentia, in each of which a tubular gland opens, a ductus cjacu- 
"MoiTi.son, U. K. Tsycho, I, 21. 
