galls of Pontania vesicator on willow

© J.-P.Kopelke

The characteristic blister-like galls of Pontania vesicator are located between the midrib and the leaf edge. Green when young they become reddish when mature. Like other Pontania species, only one larva develops in each gall. P. vesicator is widespread and common throughout Europe, even in the subalpine ares, only missing in Scandinavia and Scotland.

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