22:1-198) are the bases of our knowledge of alternation of generations among the gall wasps. Such studies as Fockeu's (1889, Hist. Galles) and several others in gall histology are superior to the work we have done in America. Beyerinck (1883) and Paszlavzsky (1882-1883) studied the early development, or what might bé called the embryology of the gall structure, an aspect of our problem which has hardly yet been considered in America.
If the present review of European Cynips serves to clear the way for further work on the group, or if it serves to awaken interest in a reconsideration of the Central European fauna in the light of the more northern and the more southern faunas, and even of the related American subgenera, then this part of our study shall have accomplished its purpose.
Cynips (Cynips) folii Linnaeus
agamic and bisexual forms
AGAMIC FEMALE.—The entire insect rich rufous and piceous (Mediterranean and Central Europe) to entirely black (more northern Europe); the head distinctly narrower than the rather robust thorax (Mediterranean and Central Europe) or practically no narrower (more northern Europe); the mesonotum largely punctate and hairy (Mediterranean and Central Europe) or largely smooth and naked (more northern Europe); the abdomen not more than twice again as long as high, the tip of the second segment approaching the tip of the abdomen dorsally; the tip of the second abscissa of the radius not bent, with or without a distinctly triangulate enlargement; length 2.1 to 4.4 mm. in three varieties.
The central European variety folii (q.v.) is nearly identical with C. longiventris longiventris and close to the other varieties of Cynips in the same region; the more northern variety atrifolii is very near C. longiventris forsiusi and C. divisa atridivisa of that region.
BISEXUAL FEMALE AND MALE.—As described for the genus and subgenus (q.v.). Very similar to the bisexual forms known for other species of European Cynips. Differing in having the legs a brighter, clearer yellow and the mesonotum and mesopleuron entirely smooth and shining.
AGAMIC GALL.—Rather large, spherical, filled with soft and spongy fibers. Up to 30. mm. in diameter. Externally smooth and naked, or set with small, irregular papillae; fresh specimens green, yellowish, or red in color, becoming yellowish brown or russet brown on drying; the outer shell rather thin, readily distinguished from the spongy interior of the gall; this spongy material filling all the gall, but consisting large-