ORTHOPTERA 



231 



Fig. 237. — Side view of a locust with the wings re- 

 moved: /, tympanum. 



The segmentation of the abdomen and the development and 

 structure of the genitalia or gonapophyses in the jumping Orthoptera 

 are of especial interest ; as, on account of the generalized condition 

 of these parts in these insects, they can ser\-e as a type with which the 

 corresponding parts in more specialized insects can be compared. In 

 some members of this group of families all of the abdominal segments 

 are preserved more or less distinct, and in nearly all of them the 

 genitalia are well-developed.* 



The segmentation of 

 the abdomen can be seen 

 best on the dorsal aspect 

 of this region; for in 

 some cases the tergum of 

 a segment is well-pre- 

 served while the stemnm 

 is vestigial. Figure 237 

 represents a side view of a female locust with the wings removed in 

 order to show the segmentation of the abdomen. The first eight 

 segments of the abdomen of this insect are very distinct; but the 

 caudal segments are much less so. Figure 238 represents the caudal 

 part of the abdomen of the same insect more enlarged, in order to 



facilitate the lettering of the parts. 



In this insect the eighth abdominal 

 tergum resembles the preceding ones. 

 The ninth and tenth abdominal terga 

 are shorter and are joined together on 

 each side ; but in many other jtimping 

 Orthoptera these terga are not thus 

 united. Caudad of the tenth abdomi- 

 nal tergiun there is a shield-shaped part, 

 which is commonly known as the 

 Fig. 238. — Side view of the caudal supra-anal plate; this plate is divided 

 fil'^.^A^o^^^^^"^!^.^^^/-*^™^^^ into two sclerites by a transverse su- 

 ture; the first of these sclerites is be- 

 lieved to be the tergtim of the eleventh 

 abdominal segment, and the other the 

 telson (Fig. 238, t). Thus all of the 

 abdominal segments are preserved, in 

 part at least, in this insect. 

 The last two abdominal segments, the eleventh and the telson, are 

 even more distinctly preserved in the early instars of some orthopterous 

 insects than they are in the adult (Fig. 239). In many adult Orthop- 

 tera there is no suture between the eleventh tergum and the telson. 

 On each side of the body, in the angle between the supra-anal 

 plate and the lateral part of the tenth tergum, there is a 

 triangular sclerite (Fig. 238, p) ; this pair of sclerites has long been 



*T he genitalia are vestigial in Tridactylus and are entirely wanting in Gryllo- 

 talpa. In these genera the reduction or loss of the genitalia is probably correlated 

 with the subterranean life of these insects, they having no need for an ovipositor. 



locust: 8, 9, 10, II, the tergites 

 of the eighth, ninth, tenth, and 

 eleventh abdominal segments ; /, 

 telson; pj podical plate; c, cer- 

 cus; d, i, V, dorsal, inner, and 

 ventral valves of the oviposi- 

 tor. 



