Cynips gemmula variety gemmula
agamic form prinoides
Cynips prinoides
Philonix prinoides
Philonyx prinoides
Acraspis prinoides
GALL. — Averaging nearer 8.0 mm., altho up to 11.0 mm. in diameter; always monothalamous ; on leaves of Quercus prinoides, Q. Michauxii, Q. Muhlenbergii, and possibly other chestnut oaks. Figure 327.
RANGE. — Massachusetts: Springfield (gall, acc. Stebbins 1910). Eastern part (bisex. form, Thompson in Bost. Soc. coll.). Connecticut: Waterbury (bisex. form, Bassett coll.). New York: Oriskany Falls (galls, J. A. Douglass acc. Felt 1912). Vicinity of New York City (acc. Beutenmiiller 1904). Staten Island (acc. Weld 1928). New Jersey: Lakehurst (Beutenmiiller and W. T. Davis in Kinsey coll.). Toms River (Beutenmiiller, types). Richland (Kinsey coll.). Virginia: Cape Charles (Kinsey coll.). Ohio: Cincinnati (gall, Braun in Amer. Mus.). Indiana: Bloomington (C. M. Kinsey coll.). Benham (G. F. Hyatt in Kinsey coll.). Aurora (Kinsey coll.). Kentucky: Lebanon (Kinsey coll.). Tennessee: Tazewell (gall, Kinsey coll.). Missouri: Ranken (Kinsey coll.). Occurring in the northeastern United States from Massachusetts to southern Indiana and Missouri, south in the mountains to Kentucky and Tennessee, confined to areas in which chestnut oaks are found. Figure 62.
This is the common variety of the species over the northeastern quarter of the United States. I find no appreciable difference between the northern Coastal Plain material on Q. prinoides (the source of the type) and our Middle-Western series of the insect on Q. Michauxii and Q. Muhlenbergii. In this failure to differentiate a Coastal Plain variety gemmula is matched by Cynips fulvicollis.
In common with all the other Cynips of this part of the country, gemmula shows an extreme degree of individual variation that may indicate a hybrid origin of the variety, possibly dating from the Pleistocene glaciation which projected northern varieties into the ranges of southern varieties and which ultimately, upon the glacial retreat, left a great territory where the hybrid individuals developed into hybrid populations deserving taxonomic recognition (see pp. 55 to 60) . The Ozark variety fuscata would appear to be the southern parent of gemmula, for gemmula intergrades into fuscata in southern Indiana (and probably elsewhere). Unlike the other species of Cynips involved in this area, the northern parent of gemmula is not known from any pure population in the north, possibly because most of the chestnut oaks, which are the hosts of our insect, do not range as far north as other white oaks. If they did extend further north in the former day, there may have been a northern parent of gemmula which does not now survive. Nevertheless, in the line series of gemmula which we have from Bloomington, in southern Indiana, there are a few individuals that are much smaller and darker, with smoother and more naked body surfaces. Since these are the very characters which distinguish the most northern varieties of Cynips pezomachoides, C. fulvicollis, C. hirta, C. folii, C. divisa , and C. longiventris, it is possible that these small insects of gemmula are Mendelian segregates from the hybrid stock, and that these represent the northern parent of gemmula. It is, on the other hand, possible that these small individuals represent local mutants. We have described them as variety suspecta. Out of the 606 insects we have bred from Bloomington material, we find 23 (= 3.8%) have this small and dark form, 22 (=3.6%) seem characteristic fuscata, and the remaining 92.6% are the variable hybrid series which is gemmula.
The galls of the agamic gemmula are to be found late in August (acc. Beutenmuller) but they probably appear much earlier than this — perhaps late in June as with other species of Cynips. The galls were of full size at Lakehurst, New Jersey, on September 14 (1904, W. T. Davis in Kinsey coll.), and at Bloomington, Indiana, early in September (1928). The insects had not yet emerged from the galls I collected at Rich- land, New Jersey, on October 13, at Cape Charles, Virginia, on October 17 (both in 1919), and at Ranken, Missouri, on October 29 (in 1926). Material in the American Museum records unemerged adults in the galls on an October 26. Our emergence dates for this insect are December 1, 2, 4, 6, 8, 10, 16, 18, and 21.
