1922] 
The Mating of Diacamma 
207 
Fig. 4. Gasters of worker and male Diacamma rugosum geometrician 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. Muller (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 
(aclelphogamy), 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 
iculpture 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 are 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. 
