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SUMMARY
Nguyen Thanh-Xuan: Investigation on the morphology and the biology of Psyllopsis fraxini (Homoptera, Psyllidae
Every distinctive characters of adults, egg and five instars were described.
Psyllopsis fraxini, a pest of ash (Fraxinus) has two generations a year, in France. Young nymphs was appeared at the end of April. The adults of the first generation laid eggs which got a short incubation (about 12-15 days). Whereas the adults of the second generation laid eggs which presented a long and obligatory period of embryonic diapause (more 200 days).
The hibernating-eggs was laid around the buds, in the bark-fissures. Under the natural conditions, 79% bugs was counted with 6-7 eggs, more particularly those which recolted between 80-100 cm of the ground. 30% eggs can be hatched in Spring, 70% was killed by intemperateness, predators.
It is also prouved that does not exist a close relation between the two phenomenons: the breaking-off of the sleeping-buds and of the hibernating-eggs.
Galls were instigated only by the old-instars.