T. nigricomis Boheman (= T. regius Nees). Emerges in March and May of the following year (acc. Mayr 1874).
Cynips disticha seems poorly represented as far as the number of specimens in the collections is concerned, altho it is known from a goodly number of localities in Central Europe. Hartig's report of its abundance in his region in Germany in 1840 was later corrected to apply to Cynips divisa (Hartig, 1843, Germar Ent. Zeit. 4:398). Disticha remains, then, as the most poorly-known Cynips of Central Europe.
The young galls of disticha appear early in the summer, probably earlier than Schlechtendal's records (1870) for early July, reaching maturity by the end of August (acc. Connold 1908) or in September (acc. Kieffer 1901). The insects are mature by October, usually delaying emergence until later in October or in November. Bignell (1898) did breed adults on October 1 and 3 in Cornwall. Schlechtendal (1870) gives October and November for the emergence in southeastern Germany, Cotte (1912) says the same for Provence, and Mayr's dates (1882) agree for Austria. Kieffer (1901) found November emergence in Lorraine. Schenck (1865: 227) gave the following spring as the time of emergence for disticha, but, considering the other records for this insect and the biology of the genus as a whole, Schenck's records must certainly be an error or an instance of abnormal factors delaying normal emergence.
There seem to be no further data on the biology of disticha, the alternating bisexual form being unrecognized. This spring generation may prove to be similar to the bisexual generations of the other species of European Cynips.
The known range of disticha parallels the ranges of other Central European Cynips, except for the absence of records north of more Central Germany. Perhaps this deficiency will be filled in by further collecting. The species is poorly represented in the collections from Mediterranean Europe, even being absent from the coast of Provence in France. There are several records for the Iberian peninsula, which, considering the localities and the distinct hosts represented, may apply to distinct varieties. This question can be settled only from good series of insects from the region. The published records for this material are as follows:
