butterflies. They also differ 



HETEROGONY, MOULTING, AND DIMORPHISM 71 



or the genetic polymorphism of the females of various mimetic 



from the environmental di- 

 morphisms, the best-known 

 case of which is that of the 

 wet-season and dry-season 

 forms of certain tropical 

 butterflies, where the differ- 

 ence between the two types 

 is elicited by different envir- 

 onmental conditions bring- 

 ing out different expres- 

 sions of the same gene- 

 complex. 



O 



I I 



J_Jj. 



■ ■ -- 1 I I 



J-.. 



All 



L 



a 



I I- 1 --T . 



,_L 



17 



16 



15 



14 



m m 

 8 



13 



,+ 



4 



12 



h 



+JL 



3-5 4-5 



—r- 



5-5 



6-5 7-5 8 



forceps-length, mm 



■5 9-5 10-0 



10 



10 11 12 13 14 15 l6 17 18Mm 



Fig. 40. — Bimodality and hetero- 



gony of the male forceps in the 



earwig, Fovficula. 



Left, absolute frequency of different forceps- 

 length at various body-lengths in a random 

 sample of 445 specimens. Right, logarithmic 

 plot of means of ' high ' forceps {h — h), ' low ' 

 forceps (I — I), and both together (dotted), 

 against body-length in 1,519 specimens, k 

 for all specimens, about i-6. 



Can we apply the results found in the abdomen of female 

 spider-crabs to the classical cases of dimorphism in holometa- 

 bolous insects — those of the earwig Forficula and the beetle 



