Life-cycle of Some Hymenopterous Insects 357 
of which were males, but two queens also appeared. Reichen- 
bach started with eleven workers of Lasius niger. They laid 
eggs that became typical workers. In August, when the sexual 
forms appeared in the out-of-door nests, about a dozen males also 
developed in the artificial nest, although none had developed 
before. After a few weeks the ants continued to increase in 
numbers, and in the following year produced two to three dozen 
males and as many as 300 workers. The same appearance of 
males took place in the third year. 
Another case has been given by Mrs. Comstock for Lasius 
niger in which. workers appeared in an artificial nest containing 
only workers. The queen of this species is so much larger 
than the workers that a mistake as to the character of the 
individuals was not possible. 
In another group of the Hymenopterous insects, the Tenthre- 
dinidz, or sawflies, some curious cases of parthenogenesis are 
known. Asarule, in this group the males are much less numer- 
ous than the females. The common currant sawfly, Nematus 
ribesii, produces parthenogenetic progeny which is nearly always 
of the male sex. It is said that on rare occasions an unfertilized 
egg becomes a female, a point of some interest in connection with 
the case of the bees. 
Doncaster has recently given some observations of his own, 
and reviewed the results of others in regard to the sex of saw- 
flies from parthenogenetic eggs. He points out that according 
to all observers females alone arise from virgin eggs of Croesus 
varus and Pecilosoma luteolum, only one observer ever having 
seena male. He quotes Mrs. Chawner to the effect that she has 
bred thousands of the latter species for several years in succession 
without obtaining males, and without finding any diminution 
in the fertility of the females. Hemichroa rufa “‘is known to 
give chiefly females from virgin eggs, but occasionally males are 
produced.” On the other hand, certain species produce males, 
as a rule, from parthenogenetic eggs. Cameron states that Ne- 
matus pavidus yields only males from unfertilized eggs. In 
Nematus ribesii (N. ventricosus of von Siebold) it has generally 
