How do caterpillars acquire chubby legs? Scientists trace the origins to a genetic program associated with crabs

Adult insects, including butterflies and moths, typically have only three pairs of legs. But the existence of extra legs in caterpillars—chubby abdominal appendages also known as "prolegs"—has long posed an evolutionary mystery to biologists. A recent study by researchers from the National University of Singapore (NUS) linked this novel trait to crustaceans.