Psyllopsis fraxini agg.

These species of jumping plant louse cause galls to form on the leaves of Ash. The adult has wings with strong black markings. The gall is on the leaf edge, causing it to swell and roll. It starts green but gradually becomes reddish or purplish, often with a chequer-board pattern. The nymphs are pale green, marked with black, and can be found inside the rolled leaf with a white waxy deposit. The galls on Ash produced by Psyllopsis fraxini, P. discrepans and P. distinguenda are indistinguishable, and must be recorded as this species aggregate . Identifying the adult insect requires close examination of the genitalia of the males; if this has not been done, the adults can be recorded as this species aggregate as well. Psyllopsis fraxinicola is not a gall-causer, but may be found as an inquiline inside the P fraxini agg. galls. The nymphs are pale green, without black markings. Use this species aggregate for all galls - provide a photo of the gall - and for adults that have not be determined by examination of male genitalia. Galls appear in spring and summer with the arrival of the leaves, adult from June to November. The time when the larvae leave the eggs mainly coincides with the beginning of foliation of Ash. Under the influence of toxins from larvae's glands, the edges of leaves swell, folding backwards, towards the middle, turning into loose galls which become brown and wither, but do not fall. The mature forms appear in early July. Believed to be fairly common throughout England and much of Britain, but seems to be under recorded in many areas.