In brief, folii and flosculi are distinct enough where there are considerable barriers that isolate them, but in the few regions in which they do come together one finds some of the individuals looking like hybrids of the two.
Concerning the gradation of folii into the northern variety atrifolii, the insects which I have from Denmark (Hoffmeyer coll.) include 329 which are typical folii, 8 which are atrifolii, and 32 which intergrade between the two. Atrifolii is nearly black and very small, with a naked mesonotum and a naked spot on each mesopleuron.
Schmidt (1907) records the rearing of one specimen of folii from southern Silesia “with very short wings.” Whether this represented a deformed specimen or a true mutation matching the many short-winged insects of this genus in America, is not determinable from the published record.
The life history of the variety folii is known in considerable detail. The alternate generation of the variety flosculi has been recognized by analogy with folii. The detailed data are given under each variety. The alternate form of the northern atrifolii is not yet available, but it undoubtedly will prove similar to that of folii.
There are numerous records for galls “resembling” folii on southern European oaks that are in many cases distinct from the Central European, Q. Robur group of oaks. Our experience with American Cynipidae would justify the prediction that there are several host-limited varieties of folii still to be recognized in Mediterranean Europe, eastern Asia, and northern Africa. The published references which I believe should be re-determined on the basis of good series of insects (as well as on galls) are as follows:
Dryophanta scutellaria Rolfe, 1881, The Ent. 14:56 (Q. lusitanica Turneri at Kew Gardens).
Dryophanta folii Kieffer, 1901, André Hymén. Europe 7(1):87 (Q. fastigiata). Darboux and Houard, 1901, Zoocécid. Europe: 297, 354, 355 (Q. fastigiata, Q. toza, Q. virgiliana). Darboux and Houard, 1902, Zoocécid. Hilfsbuch: 39, 43. Houard, 1906, Marcellia 4:143 (Q. toza record only). Houard, 1908, Zoocécid. Europe 1:265, 268, 278, 318 (incl. Q. macranthera record).
Diplolepis quercus-folii Dalla Torre and Kieffer, 1910, Das Tierreich 24:346 (certain hosts only), 776, 792. Houard, 1922, Marcellia 18:9 (Q. Mirbecki in Algeria). Houard 1922, Zoocécid. Afrique, etc. 1:130, 133, 136 (Q. Mirbecki, Q. macranthera, Q. infectoria). Hedicke, 1922, Konowia 1:35 (Q. haas at Dahlemer Bot. Garten).
