unidentified caterpillar on knapweed

unidentified caterpillar on knapweed

Observation - unidentified caterpillar on knapweed. Description: Fairly certain the plant is common knapweed but no-idea what the caterpillar is. Taken a few years ago so can't be certain of date taken.

Fairly certain the plant is common knapweed but no-idea what the caterpillar is. Taken a few years ago so can't be certain of date taken.