MO. 6 GRASSHOPPER ABDOMEN SNODGRASS 57 



one can see that the rhythmical movements of the ahdomen, which ap- 

 parently facihtate the work of the spiracles, result in the filling of the 

 sacs with air, in their expansion and in the expansion of the abdomen." 

 In his summary Fedorov definitely states : " Inflation of the air-sacs is 

 the cause of the expansion of the abdomen." 



Without having made more than casual observations on egg-laying 

 female grasshoppers, the writer, after studying carefully the mechan- 

 ism of the ovipositor, has no hesitation in saying that the above ex- 

 planations of the extension of the abdomen during the digging process 

 are not only highly improbable, but are quite unnecessary. It is true 

 that the muscles of the abdomen are entirely inadequate to distend the 

 telescopic abdominal tube to the length observed, and, as we have 

 seen, the protractor muscles that are present are limited to the sternal 

 region. Furthermore, the writer has frequently observed that females 

 of Dissosteira Carolina taken in late summer and fall have all the mus- 

 cles of the visceral part of the abdomen in a very lax and apparently 

 semidegenerate condition, contrary to what is found in the male. There 

 is no reason to doubt the observations of Kiinckel d'Herculais that 

 the alimentary canal contains air during the digging process, or that 

 of Grasse that an inflation of the food tract will distend the abdomen ; 

 nor is there any reason to question the statement of Fedorov that the 

 air sacs become expanded as the abdomen lengthens. It is, however, 

 quite too much to believe that the observed inflation of the alimentary 

 canal or of the air sacs could be the means by which the abdomen is 

 thrust out with sufificient pressure against the ovipositor to drive the 

 latter into the ground. Insects can and do swallow air in sufficient 

 amount to distend the body, as in moulting, but there is no demon- 

 strated mechanism by which they can pump air into the air sacs and 

 distend these delicate vesicles against any considerable opposing 

 pressure. 



An examination of the mechanism of the grasshopper's ovipositor 

 shows that the latter is an organ fully competent to dig its own way 

 into the ground; it is a boring machine, v/hich, once set in motion 

 with its prongs against the soil, must automatically bury itself, and 

 in so doing it will stretch the easily extended abdomen to its full 

 capacity, so long as the insect maintains its hold on the surface of 

 the ground. There is thus no question of the abdomen forcing the 

 ovipositor into the earth ; the ovipositor digs the hole and pulls the 

 abdomen in after it. The extension of the abdomen undoubtedly in- 

 volves a distention of the air sacs, and is probably facilitated by an 

 active swallowing of air on the part of the insect ; in fact, if the ab- 

 domen is actually increased in bulk by the drawing apart of its seg- 



