Andricus exiguus n. sp.

Visiting West Rock, near New Haven, Conn., several years ago in June, I found among the dry but still adherent aments of Q. obtusiloba [stellata] a number of very minute, dark colored, oval galls. The insects had escaped, but the species was new to me. Three or four years later i visited the locality in May and found galls in abundance, and the flies were very near maturity. I collected plenty of galls by breaking off small flower-covered branches. Placing these in water and keeping them under glass, a large number of very small gall-flies soon appeared. The galls were thin, short, oval larval cells, merely the modified sterile florets of the oak. Of galls affecting the sterile flowers of different kinds of oaks there are several species, but these were smaller and otherwise different from any I had seen. The effect of the sting of the fly was often to check the extension of the floral stems to a degree that reduced the florets to a close bunch or mass. This glomerate condition did not prevent the development of the gall-flies, and probably ten times as many flies appeared as there were galls in sight These galls are hardly black, but rather of a very dark slate color; they are not quite smooth. In size they measure nearly .05 of an inch in length and almost .04 in breadth. The apex is bluntly pointed. They are so very thin shelled and brittle that it is almost impossible to remove one when dry from the ament to which it is attached. After rearing several thousand flies from these galls I noticed that there were at least two species in the box. They differed little in size or general appearance as viewed with the naked eye, but the magnifying glass showed that there were two genera. I examined the galls very carefully, but found but a single species, and from this the Andricus surely came, as I found a specimen in the unopened galls. The other fly belonged to the genus Neuroterus.

- HF Bassett: (1900) New Species of North American Cynipidae (1900)^©

Reference: https://www.biodiversitylibrary.org/page/7522373#page/342/mode/1up