HETEROGONY, MOULTING AND DIMORPHISM 75 



the imaginal stage with its cessation of growth supervening 

 before this point is reached. (This is perhaps supported by 

 the fact that the double-logarithmic plot for all forceps taken 



7 



to 



20 

 15 

 10 



& 5 



K 



I 020 



15 



10 



5 



10 11 12 13 14 15 16 17 18 



body -length, mm. 



•St 



5 



35 4-0 5-0 60 7-0 



forceps-length, mm. 



B 



80 



90 9-5 



Fig. 42.— Different types of changes produced by unfavourable conditions 

 (D — D) as against favourable conditions (C — C) on (A) body-length and 

 (B) forceps-length in male earwigs. The modal body-length is reduced ; the 

 frequency of forceps of low or high modal lengths is altered, but the modal 



length remain the same. 



