Effects of Castration in Insects 405 



are sometimes connected by intermediates In ants the soldiers 

 and desmergates represent the intermediate forms. ^ 



But no one, to my knowledge, has studied the testes of beetles 

 with dimorphic males, with a view to ascertaining whether these 

 organs are more imperfectly developed in the low than in the high 

 individuals. The low males undoubtedly approach the female in 

 form, and might, therefore, be said to assume the secondary char- 

 acters of this sex, were it not for the consideration that in a large 

 number of scarabaeid and lucanid species and genera both sexes 

 have the same simple form. Thisindicates that thelowmalesimply 

 fails to develop its secondary sexual characters and hence returns 

 to the ancestral type of the species in which these characters were 

 either very feebly manifested or were altogether absent. G. 

 Smith ('05a) has shown that in the Scarabaeidae and Lucanidae, 

 as well as in certain Crustacea (Tanaidae), "the differentiation into 

 high and low males within the limits of a species has widely in- 

 fluenced the progressive differentiation among the different 

 closely related species of many groups." This is somewhat more 

 clearly expressed by saying that there are also high and low species 

 in certain groups, the larger species of certain genera having a 

 more pronounced male dimorphism than the smaller closely allied 

 species. This is also true of the sexual dimorphism of female ants, 

 as is seen in such genera as Solenopsis and Camponotus and among 

 the genera of the subfamilies Dohchoderinae, Camponotinae and 

 Mymicinae. It will be shown in the sequel that there is also another 

 way of accounting for the "high" and "low" forms of some insects. 



In this connection, I may briefly consider tvv^o cases which, if 

 correctly reported, would appear to represent a complete loss of the 

 reproductive organs by alimentary castration carried back in to the 

 early larval or embryonic period. Adlerz ('86) and Miss Bickford 

 ('95) failed to find any traces of ovarian tubules in workers of the 

 common pavement ant, Tetramorium cespitum. If this negative 

 observation be correct, the workers of this ant must be regarded as 

 utterly sexless. In my opinion, however, renewed investigation 



" For a fuller account of the conditions in these insects the reader is referred to my paper on poly- 

 morphism ('07). 



