in the leaves. (6) A poorly differentiated protective zone. (7) The spherical form of the galls and their attachment to the veins of the leaves.
Beyerinck's analysis (1883) of the development of both the agamic and bisexual galls of Cynips folii are detailed under the variety folii.
In the pages that follow, the bibliographies given for each species include only such papers as I have actually seen and summarized in the account of the species, except in those few cases where the record is given on the authority of (“acc.”) another work which is duly cited. It has been impossible to secure as complete a library of European literature as I have for the American Cynipidae, but the summaries can be offered as fair accounts of our knowledge of European Cynips.
To the student who is confused by the hundreds of European titles on the gall wasps, we may render some service by pointing out that our knowledge of that fauna is largely contained in a short list of eight papers. Hartig in 1840 (Germar Ent. Zeit. 2:176-209) contributed the original descriptions of many species and, more important, gave us the foundation for the generic classification on which we are building today. Mayr in 1870 (Die Mitteleuropaischen Eichengallen), 1881 (Die Genera der Gallenbewohnenden Cynipiden), and 1882 (Die Europaischen Arten der Gallenbewohnenden Cynipiden) extended Hartig's generic arrangement with a noteworthy regard for biologic significances. Kieffer (1901-1903, Les Cynipides in André Hymén. Europe 7 (1-2) gave us a critical compilation of all the then-available taxonomic and biologic data on European Cynipidae. The several compilations which have followed in the last twenty-five years have contributed little to the advancement of our knowledge, if they are not chiefly responsible for having discouraged fresh investigations of the group. Even the Dalla Torre and Kieffer (1910) volume in Das Tierreich can be shown to have been drawn, as far as European Cynipidae are concerned, with few additions and no critical revision from Kieffer's 1901 monograph, or even more literally in places from Mayr's earlier papers.
Two papers on the life histories of European Cynipidae, Adler's 1881 contribution (Zeit. wiss. Zool. 35:151-246) and its confirmation by Beyerinck (1883, Ver. Akad. Amsterdam
