Page:Phylogeny of cynipid genera and biological characteristics.pdf/17

 is to some extent evolutionary, but it should be emphasized that, though a strictly agamic group is in that respect more specialized than one only partially agamic, it need not necessarily be derived from the next less strictly agamic group. Thus, though Diastrophus is undoubtedly derived from Aulacidea or related forms, as indicated by the consideration of reproduction in the group and as confirmed by several other sorts of evidence, and though Rhodites is undoubtedly a more highly specialized group than Diastrophus, it is not to be believed that Rhodites originated from Diastrophus. Other considerations indicate distinct origins of Diastrophus and of Rhodites from Aulacidea, rather directly in each case. That is, the agamic condition has arisen independently at least three times among the Cynipidæ, not to mention its further occurrence among the forms which have an alternation of generations. And, though we do not have the transitional conditions for each of the lines of development, it seems clear that this agamic condition is the result in each case of the gradual disappearance of the males and the gradual appearance of parthenogenetic reproduction, first as an occasional phenomenon, finally as the regular and only method of reproduction.

This condition is not in the least surprising, for parthenogenesis has undoutbedly arisen independently at very many different times among a great number of the groups of the Hymenoptera.