Gall on Centaurea ?nigra

Gall on Centaurea ?nigra

Observation - Gall on Centaurea ?nigra. Description: Gall on knapweed stem; growing on roadside in longish grass;looks like C nigra rather than C scabiosa;several chambers inside; fat white larvae about 1mm long; Gall itself c 15mm long

Gall on knapweed stem; growing on roadside in longish grass;looks like C nigra rather than C scabiosa;several chambers inside; fat white larvae about 1mm long; Gall itself c 15mm long