Page:The Gall Wasp Genus Cynips.pdf/97

 The distribution maps of the European species of Cynips will offer material for thought even if they are obviously incomplete summaries of what European collectors may have stored away in their local collections. The records that have been published are often unsatisfactory, for two reasons: they may name the country without giving more precise localities, and tho there may be a dozen such records for a given species in a given country, they can be represented on the maps by only a single dot; or, in a few cases, the published lists carry such precise locality records that a dozen collections may be cited from an area of not more than a few miles in extent. The maps as published may serve to show where it is most desirable to make additional collections or to make available the data from collections already in existence.

The six European species of Cynips represent three wellmarked groups. One of these includes folii and longiventris, species which have insects that are practically indistinguishable in Central Europe, galls that are built on fundamentally the same plan, and bisexual forms which are almost identical as regards both the insects and their small, cell-like, bud galls. Three other species, divisa, agama, and disticha, are a unit in having lengthened abdomens (with agama nearer folii in this respect), more naked mesonota, smaller galls with much reduced spongy parenchyma, and bisexual galls (known for divisa only) located primarily on the leaf. Cynips cornifex represents a third group, its very distinct gall indicating some unique origin or divergence along the evolutionary path, altho its insect is close to the divisa-agama-disticha group of species.

All the Central European insects of Cynips, both in their agamic and bisexual generations, are strikingly alike, altho their galls are distinct enough. The group thus offers a good example of physiologic species, i.e. of species in which a physiologic quality (the gall-producing capacity) has mutated faster than any of the morphologic characteristics of the insects. An even more interesting situation is presented by the striking similarities which exist among the northern varieties of folii, longiventris, and divisa. If agamic insects alone were available, we would recognize the northern material as one species and the Central European as the only other species of European Cynips. With the help of the bisexual insects,