14 BURGESS ON THE ANATOMY 



The claspers are articulated to the ventral arch on either side and above the process. 

 In profile, the clasper shows a rather large rectangular body, with a small triangular pro- 

 jection from its posterior edge above; while lower down there is an inwardly curved stout 

 and hard process, which is continuous with a stout rib on the internal surface of the 

 clasper. The lower edge of the clasper is tumid, and in thickness the clasper is here over 

 a third of its width. The upper edge is on the contrary only a thin plate. The concave 

 side of the process is turned outwards (see fig. 16), and at its tip, which is black and hard, 

 is a transvei"se series of file-like ridges, while the inner surface of the process is smooth. 

 Powerful muscles lie in the interior and are attached to the ventral arch. The muscular 

 connection between the latter and the preceding segment is also powerful. From its struc- 

 ture it seems as if the claspers were probably inserted within the copulatory vestibule of 

 the female, and then pressed outward against the walls of the latter, the two sexes being 

 held in this way instead of by the ordinary pincer-like action of the claspers in most insects. 



Yet another apparatus distinguishes the male Danaids among butterflies. A brush or 

 pencil of long delicate hairs lies on either side between the eighth segment and the upper 

 portion of the clasper, piercing the membrane between the eighth and ninth segments. 

 These hairs are attached to the bottom of a sac-lilve sheath (see figs. 14-16 h. s.), which 

 can be everted at will, as the drawn in finger of a glove may be extended by blowing into 

 the interior, thus projecting the hair pencil out beyond the tip of the abdomen. A muscle 

 (r. m.) is attached to the bottom of the sheath and runs downward to the anterior ventral 

 edge of the seventh segment ; this muscle retracts the pencil into its quiescent position. 

 The uses of this apparatus are unknown ; a somewhat similar one has been noticed in some 

 other Lepidoptera, but needs anatomical study. 



The false claspers, though immovable, have a greater resemblance to the ordinary form of 

 genuine claspers, than do the latter themselves in Archippus. They are formed by the 

 production of the lateral edges of the sternum of the eighth segment. In shape they are 

 oblong and the posterior edge is emarginate, leaving at the corners two processes or teeth 

 of considerable size, the upper of which is rectangular and the lower rather triangular. 

 Both are strongly incurved. The sternum between and below the false claspers is deeply 

 emarginated and its edge carries out the regular sweep of the lower edge of the false 

 claspers. The edge is rendered stiff by its shape, which in section is much like that of a 

 T-raU of a railroad. 



Respiratory Apparatus. The air tubes, or tracheae, present no peculiar features in the 

 Lepidoptera. The very short main trunk into which the stigmata open soon divides into 

 branches which run to the special organ to be aerated and there often branch abruptly 

 into a great number of fine tubes, as shown in the tracheae of the testis (fig. 18). Air sacs 

 such as are found in the Orthoptera, etc., do not occur. The stigmata of the first pair lie 

 in the sides of the prothorax behind the prothoracic lobes. Succeeding jsairs of stigmata 

 are situated in the pleurae of the first seven abdominal somites, the pair in the first seg- 

 ment being rather hard to find owing to the folds in the integument of its sides. 



