Cecidomyia? parthenocissi n. s.

On under side of midrib of woodbine Parthenocissus quinquefolia, opening by slit on upper side of leaf. About 9 mm. long, 6 mm. wide, others about 5 cm. X 7 mm. Highest in middle. Red and green.

Green and succulent fold gall on the midrib of the leaf. Midrib Gall on Virginia Creeper.

Dasyneura parthenocissi Stebb.

1906. Jarvis, T. W., Ent. Soc. Ont., 32d Rept., pp. 68-69, PI. D, fig. 7 (without name). 910o. Stebbins, F. A., Springf. Mus. Nat. Hist. Bull. 2, p. 44 (Cecidomyia).

Gall. -Length about 1.5 cm., diameter about i cm. The upper surface of the leaf, usually along the midrib, is slightly contracted, while on the lower side there is a turgid lateral swelling usually originating from the midvein and generally (in specimens collected in I912) showing distinct ridges or carinae. In some instances series of galls attain a length of 6 or 7 cm. and in a number of cases all of the leaflets of one leaf were infested. In a few instances the attack developed so early as to practically prevent the formation of foliage, though in most cases the leaves attained nearly full size.

Dasineura parthenocissi

[The platygastrid parasitoids Platygaster munita and Trichacis virginiana were reared from galls induced by Dasineura parthenocissi on Parthenocissus quinquefolia.]

From the 69 midge larvae that emerged from the galls and burrowed between the collection date and 30 June 2016, 14 adults of Dasineura parthenocissi emerged from 26 April to 1 May 2017, in addition to the seven of Trichacis virginiensis that had emerged two weeks earlier.

[A photo of this gall is included in the paper]

Swellings are thick-walled, turgid, usually about 15mm long, and can be found throughout the summer. Larvae are gregarious within the folds and reportedly drop to the soil when full grown. Host: P. quinquefolia. Distr.: Massachusetts to Ontario, south to Maryland.