Flat, ovoid blister... Meunieriella aquilonia Gagné
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The spot is inconspicuous, showing only a little chlorosis until the larva escapes, when it turns brown...Host: G. triacanthos...

Meunieriella aquilonia Gagne, New Species

Females of M. aquilonia deposit eggs on either the upper or lower epidermis, the latter apparently preferred. Of 34 mines examined where empty eggs were found, 25 had been deposited on the lower epidermis. The spot galls are circular to oval, usually measuring 2-3 mm in greatest diameter. Initially the spot is whitish, but gradually turns brown after the larva abandons the leaflet. Only on gall was found per leaflet in all but two of 51 leaflets examined and only one larva was found in every gall, except in one that contained two. The pupal period for two flies reared from field-collected larvae lasted 10 days for one, 11 for the other.

This gall midge appears to be widespread in central Pennsylvania. It was collected on wild honeylocust in Dauphin Co.; at a garden center in Lancaster Co.; in nurseries in Centre, Columbia, and York counties; and in a cemetery in Dauphin Co. where thornless cultivars of honeylocust were infested. The collection of larvae from late June through mid-September suggests the midge has several generations per year.

Host: Gleditsia triacanthos