Page:The Gall Wasp Genus Cynips.pdf/149

 as many as eight galls on single leaves. The galls first appear in June (acc. Mayr 1871; June 30 acc. Connold 1908 for England). They are mature by August or September (acc. Schlechtendal 1870), falling to the ground with the leaves in October (acc. Kieffer 1901). At that season the adults are mature and, just as with most other Cynips, they then chew a passage to the inside of the epidermis of the gall, but it is not until late November or December that the insects break thru the epidermis and emerge from the galls. It is true that Schlechtendal (1870) assigns late August to late October as the emergence time for this species, but many of that author's records are earlier than the experience of other students would verify. Mayr (1882) says the insects come out of the galls late in the autumn; Adler (1881) found the adults emerging in November and December in Germany, and I have German material dated November 15 and 18. My Danish material (Hoffmeyer coll.) is dated November 22 and 30, and December 5, 7, 8, 10, 11, and 17. Kieffer (1901) said emergence was in December in Lorraine.

Adler made the only experiments we have on the alternation of this insect. In 1877 he found that the agamic females oviposited in the adventitious buds of the oak stems (and trunks) in quite the same way as he had observed for folii. But in the first experiments he failed to secure the bisexual galls, and he failed again in 1878. In 1879 he observed several ovipositions from which he secured two bisexual galls in the following April. The insects and galls and biology of this bisexual form are discussed in the following pages on the form similis.

The first histologic studies of this gall were made by Lacaze-Duthiers in 1853 (acc. Kieffer 1901). Fockeu (1889) has given us a more detailed account, noting that the gall tissues are very similar to those of folii—an account of which is given under that variety in the present paper. The subepidermal structures of longiventris are more solid and woody than in folii, as one may directly observe, and this seems to me to represent a fifth layer, a collenchyma layer not found in folii. Kustenmacher (1894 acc. Darboux and Houard 1907), Hieronymus (1890), and Weidel (1911) have given us less extended accounts of the anatomy of this gall.