42 Forty-first Report on the State Museum. 



known to me) was taken by me on August 22, 1883, in the Adiron- 

 dack mountains, at Elk Lake, Essex county, N. Y. ; altitude, 2,000 

 feet, ajDiDroximately. 



Ampliibolips prunus (Walsh). 



The Oak-plum Gall Cynijjs. 



(Ord. Hymenoptera: Fam. Cynipid^.) 



Walsh: in Proceed. Eut. Soc. Phila., iii, 1864, p. 639, note. 

 Walsh-Eiley: iu Amer. Ent., i, 1869, p. 104, figs. 80, 81 (as Cijnips). 

 AsHMEAD : in Trans. Amer. Ent. Soc, xiv, 1887, p. 130. 

 Cresson: Synop. Hymenop. N. A., 1887, pp. 175, 178. 



Galls of this insect, growing from the cup of an acorn, were sent 

 for name and information, October 2Gth, by Mr. Augustus Floyd, from 

 Moriches, N. Y., where they have been numerous this year. From 

 ridges within the cup, looking like elongate blisters, and from a rup- 

 ture or disarrangement of the scales on its outer side opposite to 

 these, it appears that six galls had been attached to the one cup. Five 

 were received, which measured from four-tenths to five-tenths of an 

 inch in diameter, of a dark brown color, and wrinkled like a dried 

 plum, except somewhat finer. They were of a leathery texture, but 

 could be cut through without difficult}^ disclosing the suboval, smooth 

 cell within of labout one-tenth of an inch in diameter. The first one 

 opened contained a number (perhaps ten) of white larvse, closely twisted 

 together in a ball, and filling the cell. They were evidently parasitic 

 on the cynips larva, and apparently dipterous. But one other of 

 the galls was opened for examination, and that showed the cj^nips 

 larva. 



The gall was first described by Mr. Walsh, as Quercus prunus, in the 

 Proceedings of the Entomological Society of Philadelphia, for 1864, from 

 specimens found in August and September, on Quercus rubra and Q. 

 tinctoria. 



In an extended valuable paper on " Galls and their Architects," 

 published in the American Entomologist for February, 18G9, by the 

 editors, Messrs. Walsh and Riley, this peculiar gall and the insect pro- 

 ducing it, are noticed and figured. Their brief account (omitting the 

 scientific descrijjtion of the insect) and the figures are herewith 

 given. 



"The oak-plum gall is remarkable for being the only American gall 

 that is known to grow out of the acorn. It occurs indiscriminately 



