54 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 94 



inologous, while the absence of median lobes between the processes of 

 the eighth segment shows that true gonapophyses are not developed 

 on the gonopods of this segment. Nel concludes, therefore, that the 

 first and third valvulae are developments of the gonocoxae, and that 

 the second valvulae have no morphological equivalents on the eighth 

 segment. As we have seen, however, the valvular processes of the 

 eighth and ninth segments do not have a similar place of origin rela- 

 tive to the sternal regions or plates of their segments, and that a com- 

 parison of the development of the ovipositor of Acrididae with that 

 of Gryllidae and Tettigoniidae shows clearly that the elements of the 

 usual ovipositor that are absent in the acridid organ are the valvifers, 

 which are the true representatives of the coxopodites. It may still 

 be difficult to prove that the first valvulae are gonapophyses homo- 

 dynamous with the second valvulae, and not coxal processes corre- 

 sponding with the third valvulae ; but the identical relations of the 

 first and second valvulae to their respective valvifers in most insects, 

 and the fact that these valvulae constitute the usual blades in the shaft 

 of the ovipositor, to which the third valvulae are mere ensheathing 

 lobes, leaves little basis for questioning the apparent and generally 

 accepted homologies of the ovipositor components. There can be no 

 doubt, at least, that the prongs of the acridid ovipositor correspond 

 with the valvulae of the ovipositor of other insects. 



OVIPOSITION 



The females of Acrididae lay their eggs in holes made by the ovi- 

 positor ; most species dig the egg cavity in the ground, a few bore into 

 decayed wood or into the stems of living plants. The ovipositor, there- 

 fore, is both an excavating and an egg-laying instrument. In pene- 

 trating an even soil the abdomen usually extends downward in a 

 slanting direction from the insect and then turns more or less parallel 

 with the surface of the ground (fig. 23 F) ; the curvature of the ex- 

 tended abdomen is perhaps attributable to the fact that the protractor 

 muscles of the abdominal sterna (fig. 8, 14^204) have no dorsal op- 

 position, since the external muscles of the back are transverse in posi- 

 tion and give a lateral twist to the segments on one another. The shape 

 of the burrow, however, is subject to much irregularity, especially 

 where ovipositing insects are crowded on a small area, or where 

 obstacles are encountered in the soil. When the abdomen is fully 

 extended it may reach a length two or three times that of its usual 

 retracted condition. The great extension of the abdomen is made pos- 

 sible by the size of the conjunctival membranes ordinarily inflected 

 between the sclerotic parts of the segments (fig. 23 A, E). 



