DESCRIPTION: Up to 12 mm in length this spiralled gall is found on the petioles of the host plant and is made up of 2 to 3 spirals. The surface is smooth with the odd raised pimple and starts green in colour before becoming reddish and finally brown. The causal agent is a newly hatched aphid whose feeding activities result in the distorted growth. Inside the gall the aphid gives birth to approximately 30 wingless young which grow and produce a winged second generation a month or so later. These second generation aphids leave the gall and lay eggs on the twigs and bark of the host. DISTRIBUTION: Frequent throughout Britain. HABITAT: Found on Poplars, especially Black and the hybrid Lombardy.
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