Abstract
Among the higher Hymenoptera it is now generally assumed that females arise from fertilized eggs, males from unfertilized. Exceptions to this have, however, been claimed in certain ants (Wheeler, W. M., 1903). Among the lower Hymenoptera conditions are much more irregular. Some species of saw-flies are exclusively or predominantly female-producing, thelytokous; others male-producing, arrenotokous; while others, amphitokous, produce both sexes parthenogenetically. Gall wasps with their alternation of sexual and parthenogenetic generations have in the latter both male-producing and femaleproducing females. Polyembryonic Chalcidoids produce male broods from unfertilized eggs, female broods from fertilized, but Patterson (Patterson, J. F., 1917) has shown that certain broods, predominantly female, may contain a few males, presumably derived from mitotic irregularities in the polygerm. Among the Ichneumonoids, to which group Habrobracon belongs, arrenotoky is the rule but some species are thelytokous. In a species that is predominantly arrenotokous it has been shown (Hunter, S. J., I9o9, and Webster, F. M., I909) that the tendency to produce females is probably inherited. The irregular forms discussed in the present paper have 89
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