GENEBAL EXTERNAL STRUCTURE OP INSECTS. 



25 



ing (fig. 7, -?(r, ^(x, and 3G). At first there is only one pair of these 

 processes on each of the two segments, but those on the ninth soon 

 split each into two, thus producing two pairs on this segment. The 

 opening of the aviduct {OvO) is on the 

 eighth segment between the bases of the 

 first gonapophyses. 



The ovipositor of the longhorned grass- 

 hopper, shown by figure 8, may be taken as 

 a typical example of this organ. The 



median pair of gonapophyses on the ninth 

 segment {^G) remain slender and fuse at 

 their bases into a small bulblike swelling 

 open below {ShB). The pair from the 

 eighth segment {IG) form two long blade- 

 like pieces, which fit by sliding articula- 

 tions upon the lower edges of the corre- 

 sponding second gonapophyses {2G). The 

 first can therefore be worked back and 

 forth while they are braced and held in 

 position by the second pair. The third 

 gonapophyses {3G)\ or the outer pair of 

 the ninth segment (the left one in figure 8 is shown as if cut off near 

 its base), form two long flat blades which are closely appressed 

 against the outer surfaces of the others. In the detailed study of 

 the bee it will be shown how closely the structure of the sting corre- 

 sponds in every way with that of this ovipositor. 



Fig. 7. — Diagram of terminal 

 abdominal segments of a fe- 

 male insect and early stage in 

 development o£ gonapophyses 

 (10, 20, and 30), from 

 which is formed the ovi- 

 positor of most Insects and 

 the sting of wasps and bees. 



Sp jG 'G 



Fig. 8. — Example of a swordlike ovipositor, from a longhorned grasshopper (Cono- 

 cephalus sp.), illustrating the fundamental similarity of structure with the sting of the 

 bee, flg. 36. 



Some entomologists have supposed that the original two pairs of 

 gonapophyses represent the embryonic appendages of the eighth and 

 ninth segments, and they would thus establish a homology between 

 the ovipositor or sting and the legs and mouth parts. It has been 

 shown, however, that the true appendages of the abdominal segments 

 disappear in embryonic life while the gonapophyses appear much 

 later, during early nymphal or larval life. Furthermore, each pair 



