56 REPORT 4, UNITED STATES ENTOMOLOGICAL COMMISSION. 

 TERMINAL BODY SEG-MENTS 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 YIII, Fig. 2, and Plate X, Figs. 1 and 3, where the hook 

 is marked with the figure 9). This hook covers the anal opening (a.), 

 and in some ]N'octuids 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, e left, c' 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 acrceoj 

 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 Jjeticarctia and the Koctuids. The retractor 

 muscle found in Danais we have not succeeded in finding in Aletia. 

 Mtiller 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.^^ 



The male organs of reproduction consist of a very large testis, two 

 vasa defer entia, in each of which a tubular gland opens, a ductus ejacu- 



*■ Morrison, H. K. Psyche, I, 21. 



