Page:The Gall Wasp Genus Cynips.pdf/52



The most interesting aspect of fulvicollis is its earlier emergence in northern varieties and its later emergence in southern varieties. If, as our data show, the emergence date is not determined by direct response of the individual insects to environmental factors, then how may we explain this apparent correlation of emergence dates with the latitudinal range of each species? If Lamarckian effects enter here, they must come as the result of influences continued over numerous generations. Is it more probable that Darwinian selection has helped adjust these species to climatic conditions? Or is it possible that the apparent correlation is fortuitous?

All but two of the groups of species of Cynips complete their agamic lives within six to eight months. In Cynips mellea emergence is spread from the seventh to the tenth month (December thru March) with most of it in March. This is a departure from the ancestral tradition, but one specific for mellea. Cynips fulvicollis is a further departure, for most of its emergence is delayed until the eighteenth to twentieth month. This is particularly true of the more northern varieties of the species. The Kansas variety, vorisi, which is nearest the point of origin of the group, has the most normal life history, most of the individuals emerging during the first winter with only a few of them delaying emergence until the second season. The northern variety canadensis gives no emergence in the first year, most of it in the second year, and some stray emergence in the third year. The varieties ranging between vorisi and canadensis show a gradual shift from the one to the three-year cycle. It is an interesting case of new specific characters developing out of physiologic materials that have remained constant in other groups of Cynips for millions of years.