INTERRUPTED GROWTH OF ACRIDIDAE EGGS 151 



eggs is interrupted by temperatures below their developmental 

 thresholdi^. w^ ^re unable to classify them into the above 

 proposed scheme, as the stage or stages at which the embryonic 

 development is interrupted are not known to us. 



Apart from environmental factors such as temperature and 

 humidity, it seems that the structure of the egg envelope, and 

 especially that of the hydropyle, is of essential importance at 

 least in Melanophis differeutiaJis type of eggs. Weathering and 

 other changes in these structures play an important role in 

 breaking of diapause, according to Slifer^'* and Lees^"^. 



The intrinsic factors connected with appearance and breaking 

 of diapause in Acrididae are still unknown. It is quite possible, 

 however, that their influence is not less important than that of 

 the extrinsic influences. 



It is unnecessary to stress the survival eff'ect of diapause and 

 its importance in the adaption of the species, cf. Acrididae, to 

 their environment. We should like only to point out that, in the 

 case of CaUiptamiis palaestinensis, in which interruptions in de- 

 velopment of the fourth and fifth types combined take place, we 

 have been able to show recently^ how well the way of the develop- 

 ment fits the climatic conditions of the geographic region of its 

 distribution. The eggs of CaUiptamus palaestinensis are laid in 

 autumn and develop slowly in moist as well as in dry soil. For 

 their successful development both cold temperatures of the 

 local winter and the rains occurring late in spring, are essential. 



REFERENCES 



1 E. H. Slifer, /. MorphoL, 53 (1932) 1. 



•' H. V. Steele, Trans. Roy. Soc. S. Australia, 65 (1941) 329. 



^ F. S. BoDENHEiMER AND A. Shulov, Bull. Research Council Israel, J 



(1951) 59. 

 -> A. Shulov and M. P. Pener, Locusta, 6 (1959) 73. 

 '" A. Shulov, Proc. XIV Intern. Congr. Zool., Copenhagen 1953, No. 6, 



1956, p. 395. 

 6 A. Shulov, Bull. Research Council Israel, 2 (1952) 249. 

 ■^ E. M. Shumakhov and L. A. Jakhimowitch, Zool. J., XXIX, 4 (1950) 



327. 



