1922] 



The Mating of Diacamma 



207 



Fig. 4. Gasters of worker and male Diacamma rugosum geomelricum from the right side x7. 



bases suggests that the workers may thus prevent the escape 

 of members of the opposite sex from the nest. The same mu- 

 tilation is also practised on the males of Eciton, as noticed by 

 W. Miiller (1886) and the senior author (1921, p. 312). And 

 since the other males taken in the same Diacamma nest were 

 not dealated, it would seem that the workers do not mate with 

 the males of their own colony, that is with their sons or brothers 

 (adelphogamy), but with males that have come from other 

 colonies. The very long sensitive antennae of these insects, so 

 like those of the Ichneumons, may enable them the more easily 

 to seek out alien colonies of their own species. The small size 

 of the Diacamma colony, moreover, indicates that only a single 

 worker is fecundated and assumes the role of a queen, for if 

 several or all of the workers laid fertilized eggs the colonies should 

 be much more populous. 



Externally the worker found in copula differs neither in 

 size nor in structure from any of her sisters. Examination of 

 the materials in the senior author's collection shows that both 

 in rugosum and its varieties and in the various other species of 

 the genus all the workers taken from the same colony are singu- 

 larly uniform in size and structure, even to the minute details of 

 sculpture and pilosity. As will be seen from Fig. 4, which shows 

 the gasters of the mating individuals from the right side, the 

 male and female genital orifices arc in broad and very intimate 

 contact. The powerful sting of the female is extruded and is 

 held down by the finger-shaped process of the right external 

 genital valve of the male. 



