DESCRIPTION: An impressive bladder is caused by the feeding activity of an aphid. These galls can reach up to 8cm across and usually have a grooved basal area. The gall contains many aphids and starts off green in colour with a mealy surface. With age the gall takes on a reddish tinge before becoming browner and smoother. The aphids leave the gall in late summer and go to feed on the roots of Pear and Quince. The young of the colony return to the Elms in autumn where they will lay their eggs.  DISTRIBUTION: Widespread but far from common, becoming scarcer in the north. HABITAT: On the leaves of Elm.