162 



ANATOMY. 



abdominal segment ; it is frequently minute and indistinct, but occa- 

 sionally, as, for example, in the Capricorn beetles, it is very large, indeed 

 larger than the first. The following spiracles, six or seven in number, 

 lie always between every two of the successive abdominal segments, so 

 that the two last segments alone have no spiracles; we thus obtain ten 

 spiracles upon each side, twenty together, a typical number which is 

 never exceeded, but often also not attained. 



In the Orthoptera the spiracles are not differently situated. The first 

 which is in the connecting membrane between the pro and meso-thorax is 

 very large, particularly so in Gryllotalpa (PI. XI. No. I. f. 2. a, a); 

 the second, between the lower wing of the scapula and the dorsal piece 

 is here quite free and uncovered (the same, fig. 8. /i). The third 

 spiracle, which properly should lie between the meta-thorax and the 

 first segment of the abdomen, approaches more closely to the latter, 

 and lies in Gryllus, F. (Acri/dium, Lat.) in a half moon-shaped hollow, 

 which upon one side is partly closed by the projecting cover-shaped 

 margin. All the succeeding ones are placed in a similar situation, 

 namely, at the lower margin of each dorsal plate of the abdomen. In 

 the B/attaria, on the contrary, the spiracles are always placed in the 

 connecting membrane between two segments, and precisely where the 

 dorsal and ventral plates meet ; the same is the case in Forjlcula ; in 

 these also the third spiracle lies at the anterior edge of the dorsal plate 

 of the first segment of the abdomen, where it is very distinct although 

 but small. 



In the Hemipfera, which, by the structure of their thorax, approach 

 closely to the Orthoptera, the first spiracle likewise lies in the connect- 

 ing membrane between the pro- and meso-thorax ; it is tolerably large, 

 and narrow, and is only apparent upon the removal of the pro-thorax. 

 A second spiracle is found between the meso- and meta-thorax, and 

 resembles the former in being a rather long, half moon-shaped, or 

 straight incision, and is covered by a posterior projection of the margin 

 of the meso-sternum. This spiracle consequently cannot be seen from 

 the exterior from the preceding projection (PI. XIII. No. 5. fig. 2. /3) 

 lying over it, and above it is concealed by the elytra. The succeeding 

 spiracles are in these insects, as in the Ortlioptera, more approximate 

 to the ventral segments, a spiracle being placed in each abdominal seg- 

 ment, whereas by analogy it should lie between every two segments. 

 In the male Cicada the first is very large, free, and always beset with 

 strong setae at the margin, the following are smaller and indistinct. 



