Cabbage white butterfly larvae (caterpillars) a few hours after hatching. The cabbage white butterfly (Pieris brassicae) lays its eggs on brassica plants, in this case a pak choi leaf. Eggs are laid in batches of up to 100 to 150, hatching after about 10 days. Once hatched, the caterpillars initially feed on the empty vacated egg case (seen here). They are gregarious (feeding together) until they have moulted at least once, after which they feed individually on the leaves. As they feed, they grow in size until they are ready to metamorphose into the butterfly stage that will lay eggs and start the life cycle anew.