This week, the question was: Which brassica-feeding caterpillar is commonly found in groups on a single leaf, as shown here?
These are cross-striped cabbageworms (CSCW). CSCW moths lay eggs in clusters of 3 to 25 rather than singly like most other brassica caterpillar pests. Because there are numerous caterpillars feeding on a single leaf once the eggs hatch, they can extensively damage the host plant in a short amount of time. As these caterpillars grow, they will develop the black and white transverse stripes on their back that is a unique identification feature. Learn more about cross-striped cabbageworms here.