Local feeder (Diptera: Cecidomyiidae) in petioles etc. of Quercus

Larvae were found singly in smooth-walled, ovoid chambers beneath sunken and blackened areas in the bases of leaf petioles or in first-year twigs of the host. The blackening appears to be the result of a fungus, presumably an intentional associate of the gall midge, affecting the plant tissue. The base of one petiole examined by the author contained four larval chambers, three of which had already been evacuated and one of which still contained a larva when the plant material was collected in late October. Other petioles contained just one or two chambers each. Affected petioles no longer inhabited by this insect may show a small round exit hole within the sunken, blackened area, opening from the empty chamber beneath; it has not been determined if the exit hole is from the gall midge emerging or rather from one of its parasitoids emerging. Affected first-year twigs were found to be inhabited by larvae in late July. One example of a blackened, sunken area on a twig appeared to extend into the base of a leaf petiole, which made the author wonder if the petiole and stem feeders might belong to the same species. They are treated in a single account here, although it is unknown how many cecidomyiid species are involved. The typical overwintering stage and location is unknown.