150 A. S. SHULOV AND M. P. PENER 



achieve a morphologically more advanced state at stage XIV, 

 than species which do not as a rule show any diapause. We have 

 been able to demonstrate that in Schistocerca gregan'a^^ as well 

 as in Locusta migratoria migratorioides and Nomadacris sep- 

 temfasciata (Shulov and Pener, manuscript in preparation), eggs 

 deprived of the full quantity of water needed for completing 

 development reach stage XIV only, and then enter into a develop- 

 mental pause which may be broken in the same way as in the 

 above group, i.e. by addition of water (see Table II, part B). 

 However, the morphological stage in which this interruption 

 occurs is significantly less differentiated than is the stage XIV of 

 eggs which interrupt their development at the fourth type of 

 diapause almost always under natural conditions (Table IIA)^. 



Two further types of interruption may be added to the four 

 types already mentioned. 



One has been observed in Melanoplus dijferentialis, where the 

 break of diapause is connected as a rule with low temperatures^ 

 under natural conditions. This type of interruption of develop- 

 ment occurs at the end of anatrepsis. Resumption of develop- 

 ment generally takes place when the eggs are transferred from 

 low temperature conditions to higher ones, but it is still possible 

 that the upper limit of the lower temperature range responsible 

 for the break of diapause merges with the lower limit of that 

 temperature range which allows renewal of slow development 

 after the end of the diapause. 



This type of interruption is manifested in the northern form 

 of Locusta migratoria^'^, in CaUiptamus palaestinemis^ and 

 possibly in Austroicetes cruciata^ and Chorthippus bnmneus^^. 

 It is typical of temperate regions. 



A sixth type of interruption of development has been stressed 

 by Slifer^^ regarding those Acrididae which enter a diapause 

 shortly before hatching. This type of diapause appears in some 

 species of the genus Melanoplus such as M. bivittatus and its 

 duration seems to be shortened by the influence of low tempera- 

 tures, near 5°^^. 



Another group seems to exist in which the development of 



