56 



SMITHSONIAN MISCELLANEOUS COLLECTIONS 



\0L. 94 



Kiinckel d'Herculais says, the muscles play only a secondary role in 

 the expansion of the abdomen. It has been suggested also that the 

 abdomen is distended by blood pressure created by a contraction of 

 the thorax, but Grasse (1922) observes that there is no external evi- 

 dence of any such contraction. A contraction of the tergosternal 

 abdominal muscles might be supposed to extend the abdomen length- 

 wise, but these muscles could not in-oduce the extreme elongation 



E flJ F 



Fig. 23. — ^Oviposition of Acrididae. 



A, Schistoccrca percgrina, showing extent to which the female abdomen can 

 be pulled out without tearing the conjunctival membranes (from Vosseler, 1905). 

 B, C, two attitudes of Chrysochraon dispar ovipositing in cut ends of raspberry 

 stems (from photographs by Ramme, 1927). D, E, diagrams showing relative 

 lengths of retracted and extended abdomen of Chrysochraon dispar (from Ramme, 

 1927). F, grasshopper ovipositing in the ground, showing usual position of ab- 

 domen (from Walton, 1916). 



attained during the digging process. Grasse maintained that the ex- 

 planation of Kiinckel d'Herculais is correct, since he was able to 

 demonstrate the extension of the abdomen by gently inflating the ali- 

 mentary canal with a pipette inserted into the mouth of the insect and 

 ligatured in the oesophagus through a hole at the back of the head. 

 However, a different explanation of the abdominal extension has been 

 proposed by Fedorov ( 1927) , who says : " When the abdomen is fully 

 extended it becomes obvious that the expansion is due to the air-sacs ; 



