Thistle caterpillar: Biology and ecology

Thistle caterpillar leaf webbing: The thistle caterpillar, Vanessa cardui, will web together soybean leafs to form a protective case within which it will feed and grow.Thistle caterpillar leaf webbing: The thistle caterpillar, Vanessa cardui, will web together soybean leafs to form a protective case within which it will feed and grow. (Photo Marlin E. Rice)

The painted lady butterfly will lay eggs singly on soybean where they will develop about 7 days until hatching (Pedigo 1994a). They will feed for 2-6 weeks until pupation which will last about 7-17 days. This insect is bivoltine in Iowa.