140 SEX INHERITANCE 
reduction divisions is supressed when a worker’s 
egg gives rise to a female. Such a supposition 
finds some support in the fact that in other groups 
of Hymenoptera (saw flies and gall flies) females 
arise regularly from unfertilized eggs. In some of 
the species of gall flies, males are unknown; in 
others they appear very rarely. 
The female of Dinophilus apatris produces large 
and small eggs in equal numbers. From the former 
arise females, from the latter males (Korschelt, 
von Malsen, Shearer, Nachtsheim). The small eggs 
may predominate in some of the earlier laid batches, 
so that at this time sons are in excess, but if the 
mother remains alive, so that the full output is 
produced, the sex-ratio becomes 1 to 1 (Nachtsheim). 
If the mother dies early, there may appear an excess 
cf males. What factor determines whether an egg 
is to become a large female-producing egg, or a 
small male-producing egg is not known. The sug- 
gestion, that the difference in size is due to the 
number of yolk-bearing cells that are absorbed by 
the egg during its growth period, has been disproven 
by Nachtsheim; for he finds at the end of that 
period that all the eggs are of the same size and the 
difference in their size comes in later. 
