Druon ignotum (Bassett, 1881), comb. nov.

Cynips ignota Bassett, 1881: 106, female, gall.
Andricus ignota (Bassett): Ashmead, 1885: 295.
Dryophanta ignota (Bassett): Ashmead, 1887: 127.
Diplolepis ignota (Bassett): Dalla Torre & Kieffer, 1910: 360. [NOT Diplolepis ignota Osten Sacken, 1863]
Rhodites ignota (Bassett): Dalla Torre, 1893: 127. [NOT Andricus ignota Bassett, 1900 (junior homonym).]
Diplolepis ignota (Bassett): Weld, 1926: 26.
Andricus ignotus (Bassett): Weld, 1951: 634.

Gall. Asexual galls (Fig. 99). Small (2–3 mm long) brown, thin-walled and gregarious ovoid galls firmly attached to the underside of the leaf midrib in clusters of up to 30 or more. The entire cluster is covered with a dense coating of long woolly hairs, which is initially cream-coloured or pink but fades to brown over the winter, and sometimes wears away.

Biology. Alternate asexual and sexual generations are known (see comments). See Bassett (1881) and Weld (1926) for the biology of the asexual generation. Asexual galls have been recorded on leaves of Q. bicolor and Q. macrocarpa (Section Quercus, Series Prinoideae), mature in October–November, adult females emerge very early the following spring (late March to late April in Edmonton, Alberta, Canada), often on the first warm days after accumulated snow has melted and fallen leaves bearing galls are exposed. Emerged females fly up to buds and oviposit. The sexual generation adults emerged in Edmonton in early June. Females were observed ovipositing multiply along the midrib on the upper leaf surface in a zipper-like pattern, suggesting that asexual females in a given gall cluster are sisters. Galls of the asexual generation first became apparent on leaves in Edmonton in late July.

Distribution. USA: Massachusetts, Connecticut, Illinois, Minnesota (Burks 1979), Nebraska (Weld 1926); Canada: Alberta, Manitoba.

Andricus ignotus

Quercus bicolor
Leaf galls, detachable
Woolly, 2.5 by 1.25 mm, single or in groups along midrib or main veins, on under side, dropping with the leaves after which the hairs weather away.

Quercus macrocarpa, stellata
Leaf galls, detachable
Woolly midrib cluster on under side of leaf in fall.

[Photo caption]
On Q bicolor. Also on Q macrocarpa. Galls drop with the leaves in the fall and wool weathers away during the winter as shown in photo. Adults out Mar 24-Apr 27 and oviposited in buds.

Diplolepis ignota [distinct from the rose gall of the same name]

The galls on Quercus bicolor are common about Evanston and Wilmette, IL., becoming full grown by middle, of September and dropping with the leaves. During the winter the woolly covering weathers away more or less exposing the tan-colored galls which in shape and size resemble a cluster of cocoons of the braconid genus Microplitis. They contained pupae March 10, 1909, and adults emerged April 1-15. The next spring the flies began to emerge March 24. Similar galls on Q. macrocarpa were noted at Evanston and Algonquin, IL., and Nebraska City, Nebr.

Cynips ignota, n. sp.

Small oval cells, found singly or in small clusters of from two to eight together on the under side of the leaves of Q. bicolor. They are sessile on the midrib and principal veins, and usually lie in a position nearly horizontal to the surface of the leaf They are at first covered with short woolly hairs, but when ripe become more or less denuded. The naked surface when examined with a microscope shows numerous minute papillae, and between these a fine and regular reticulation. They are .10 of an inch in length and . 05 in diameter, and might easily be mistaken for the cocoons of some species of Microgaster.

About fifteen years ago I found a few of these galls on the fallen leaves of a large oak and also on a small tree a few rods distant. The next year the greater part of the leaves on the large tree were covered with galls, a hundred or more being sometimes found on a single leaf I gathered a large quantity after the leaves fell, and the flies came out the next spring. I have examined this tree every year since and have never found any of these galls, nor have I ever seen them on other trees.

There are some specimens of this species in the Museum at Cambridge, which Dr. Hagen informs me were found on oaks in the University grounds. I examined some oaks of the same species in the borders of the Botanical Garden at Cambridge last fall, and found several species of galls, but none of these. Can it be that the species has disappeared entirely?