Phylloteras poculum (Osten Sacken, 1862), sexual generation

Synonyms: Cecidomyia poculum Osten Sacken (1862: 201), galls. Xystoteras poculum combination and description of adult females by Weld (1922a: 7); Phylloteras poculum combination by Lyon (1993: 133).

Gall. Galls of the asexual generation (Fig. 224) on Q. alba are as described by Osten Sacken (1862) and Weld (1922a).

Biology. See Weld (1922a) for the biology of the asexual generation. Galls of the asexual generation became evident on bur oak leaves in Edmonton in July, and were fully mature in September, when many separate easily from the leaf lamina, falling to the ground. Galls are susceptible to drying, and rearing experience suggests that desiccated galls produce no emergents. Females of the asexual generation overwinter and pass the entire subsequent summer in their galls, emerging in late autumn and winter – generally from late October to December with a peak in mid-November, but when a large number of galls was reared over winter 2016-2017 in Edmonton, a small number of females emerged in all months from January through April 2017. Weld (1922a) reared adults in Evanston, Illinois, in March. The brachypterous females were observed in Edmonton to crawl up through any accumulated snowpack, climb bur oak stems, and oviposit in buds. Emergence and adult female activity appeared delayed in autumn during periods of warmer weather, and was observed during a period of sustained temperatures ranging from -10°C to -17°C during early January 2017 in Edmonton. Galls of the sexual generation became apparent in early May in Edmonton, with adults emerging from mid-May through mid-June. This species has not been previously recorded from Q. macrocarpa; earlier records are from Q. alba and Q. montana. Another congeneric species, Phylloteras volutellae (Ashmead, 1897), is also found on Q. macrocarpa.

Distribution. USA: Virginia, New York, Vermont, New Hampshire, Illinois, Missouri (Burks 1979). Canada: Manitoba, Alberta.

Xystoteras poculum

White oak spangle gall. Button-shaped, 3-4.5 mm. in diameter, with a heavy rounded ring of tissue on under side between pedicel and rim, concave above with a slight nipple in center, covered with a whitish bloom. In large number on under side of leaves of Q. alba, dropping in the fall. The flies emerge in late March the second spring.

Xystoteras poculum

Quercus alba, prinoides, prinus [montana]
Leaf galls, detachable
Spangle, 3-4.5 mm in dia with a whitish bloom, on under side leaf in Sept.-Oct.

[Photo caption]
On Q alba. Also on Q prinus [montana], prinoides. Full-grown in early Sept. Adults emerged in Jan, the second spring and some came out the fourth spring.

Xystoteras poculum, new species

Host. — Quercus alba.

Galls. — Popularly known as "spangle " galls and first described by Fitch in 1859, these common objects have an extended literature under the name of Cecidomyia poculum, with good figures by Glover, Beutenmueller, Stewart, Thompson, and Felt, but they have not hitherto been reared. Osten Sacken suspected that they were due to a Cynipid.

The galls are attached in groups on the underside of mature leaves, and they are found in September and October. They are button-shaped, 3-4.5 mm. in diameter, covered with a whitish bloom, slightly concave above, with a low elevation in center, the edge sharp and becoming less upturned as the larval cavity develops, attached by a short slender pedicel, between which and the rim on the under side is a prominent heavy rounded ring of tissue. The larval cavity is centrally placed, transverse, with no false chamber.

Habitat. — The type material was collected at Ironton, Missouri, on October 5, 1917, and living flies were found in the out-of-door breeding cage at Evanston, Illinois, on March 24, 1919, indicating that the emergence is very early the second spring. This delayed emergence probably accounts for the failure of other students to rear it. The writer has seen these galls in Virginia, New York, and Illinois also and museum specimens from Vermont and New Hampshire, indicating a widespread distribution of the species. There is a precisely similar gall in Q. prinus, which will no doubt prove to be due to this species.

Cecidomyia poculum, n. sp [mistakenly identified as a midge gall]

The so-called oak spangles (Fitch, Hop., vol. II, No. 40), small, circular, somewhat saucer-shaped scales, from 0.1 to 0.2 in diameter, reddish or purplish, covered with a white efflorescence, attached to the leaf by a short pedicel, common in autumn on different kinds of oaks, are generally found empty. In the beginning of August I found a similar gall, yet succulent and greenish, on the post oak {Q. obtusiloba [stellata]), and inside of it a small whitish larva having all the appearance of the larva of a Cecidomyia, although, on account of its minuteness, I did not succeed in discovering the breast-bone. Dr. Fitch is in error when he states that these palls are " perfectly the same" as those noticed by Westwood, Introd., II, p. 130. The European galls of this kind are pilose externally, as stated by Westwood and figured by Reaumur (Mom., vol. Ill, Tal). XL, f. 13); the American ones, at least those which came under my notice, are smooth.

Phylloteras poculum

Hosts: Quercus alba, prinus [montana], prinoides

Button-shaped spangles on underside of leaves of Quercus alba, prinus [montana], prinoides

Distr: CT, IN, KS, MD, MO, NY, VA, DC