Page:The Gall Wasp Genus Cynips.pdf/40



It seems warranted to conclude that insects differing as thoroly as these long-winged and short-winged Cynips may be among the most closely related species in existence. Or, interpreting this statement, we may believe that diverse species may originate directly—that is, by direct mutation—from each other. It should be apparent to anyone familiar with the laboratory Drosophila melanogaster that these subapterous Cynipidae are quite comparable to the subapterous mutants which geneticists have shown to have arisen by direct mutation in the laboratory from long-winged Drosophila stock (e.g., see the summary publications of Morgan, Bridges, and Sturtevant cited in our bibliography). The explanation that will suffice for Drosophila will probably need no essential modification for the gall wasps, but the Cynipidae may establish the importance of the laboratory mutations as materials from which species populations actually arise.

Among none of the Cynipidae is there evidence that the modified wings have developed by the sort of fluctuating variation and the essentially orthogenetic selection conceived by the Neo-Darwinians. Altho there are many short-winged species which occur directly beside their long-winged relatives, there are no intermediate forms as we might expect from fluctuating variation, with the possible exception of Cynips bifurca which appears to be hybridizing today with the long-winged, parental stock.

There seems no basis for believing the shortened wings or any of the concomitant variations of any adaptive value to any of these insects. The short wings are not confined to warmer or colder climates, and long- and short-winged forms of various species are active at the same season in the same localities. The field data suggest nothing as to the survival value of these outstandingly basic modifications of structure.