Andricus lustrans (agamic)

Andricus impositus, sp. nov. [This may be a mistaken synonymy; see ID Notes]

Gall. On the under sides of the leaves of post oak (Quercus minor [stellata]) in clusters from about 4-40 individuals closely packed together, on the mid-rib and lateral veins, September to November. Monothalamous. Green, sometimes tinged with red. Elongate, rounded at the sides, narrow at the point of attachment and concave at the apex with a small central nipple. Outside it is rather densely covered with small pustules. When young, the gall is almost solid, but as it grows older the larval chamber gradually occupies the entire interior. After it drops to the ground, late in the fall, the gall gradually changes its shape to almost globular (berry-like) with the concave apex flattened and the surrounding rim less prominent. The crystal-like pustules change, the gall becoming evenly rugose. The point of attachment becomes long, narrow and sharply pointed. The entire inside becomes hollow with the outer wall thin and brittle. Length, 2.50 to 5 mm.; width, 2 to 4 mm.; length of clusters, 5 to 35 

Habitat: Westchester, New York City. 

My observations on the galls were made from at least 500 clusters. At first I considered it to be that of Zopheroteras vaccinii Ashm., which it resembles when immature. But the flies are different, the female of vaccinii being apterous. The gall of A. impositus when mature resembles somewhat, those of Cynips dimorphus and C. vacciniiformis. My galls were collected during September and until November 1st, 1915, but they evidently also occur earlier in the season, because some of the flies emerged in June and July and others in September, 1916. But the majority remained over until 1917, the flies emerging indoors in January and February. My specimens were collected on a small rocky elevation in a, swamp, close to the Bronx River, near Westchester, New York City. This locality is gradually being filled in for streets and other improvement and soon will become extinct. I have also taken the gall at Lakehurst, New Jersey, and it probably will be found in other places where Quercus minor grows. 

Notes on Cynipidae, with description of a new species (Hym.)