Range.—Massachusetts: Marthas Vineyard. Rhode Island: Providence (Thompson). Connecticut: Waterbury (Bassett). New York: Ellenville (in Coll. Amer. Mus. Nat. Hist.).
Cotypes.—Forty-five females, seventy-four males, in the collections of The American Museum of Natural History, the Boston Society of Natural History, the Museum of Comparative Zoology, in the author's collection, and elsewhere. The adult material was bred by Millett T. Thompson, No. 185 of his collection which is at the Boston Society of Natural History. The galls of the Thompson Collection are in poor condition, so I should designate my Marthas Vineyard material of galls as type galls for this species.
Thompson found the adults emerging late in June.
The type material of Bassett's Andricus cicatriculus in The American Museum of Natural History contains one female of A. concolorans, and a number of specimens of an inquiline. The description of the adult cicatriculus agrees with the inquiline to which that name must be applied; it would appear to be a Ceroptres. The material from the Thompson Collection matches the single female (undescribed) of the Bassett types. Thompson also bred the same inquiline.
Inquiline species are very often quite similar to their gall-maker hosts, and consequently most students of Cynipidæ have repeatedly described inquilines as true gall makers. But Homer F. Bassett was a careful enough worker to have avoided almost entirely such mistakes, and to find the instance here described lends emphasis to the fact that in Andricus concolorans and Ceroptres cicatricula the identity is unusually remarkable. The generic differences are quite apparent, but the specific details show few differences. The main points of difference, all generic (or even family) characters are:
| Cynipid | Inquiline | |
| Radial cell | Open | Closed (not open as Bassett stated) |
| Radius, first abscissa | Angulate | Arcuate |
| Antennæ, female | 14-jointed | 13-jointed |
| Abdomen, first segment | Insignificant | One-fifth the length of the abdomen (separation from segment 2 not always visible) |
The two species agree quite closely (though of course not exactly) in the following respects: general color of head, thorax, abdomen, antennæ (part), legs, wing-veins; length of body and of wings; sculpture of thorax (not exactly); relative prominence of wing-veins. This leaves very few specific characters of difference.
Contemplating such close resemblance of species of different genera, we are wont to consider again how such "mimicry" may have arisen. Mimicry among inquilines in cynipid galls is of especial interest because of the absence of anything like a struggle for existence between the two
