Larvae of the canegrub Lepidiota reuleauxi have become pests of commercial sugarcane in Papua New Guinea. The biology of L. reuleauxi was studied under field and laboratory conditions. The species is univoltine. Adult activity commenced soon after the onset of the rainy season. Adults emerged just before dusk for mating. Males aggregated, probably in response to pheromonal cues from females. The adults (both sexes) lived for 3–4 weeks but did not appear to feed. Larvae require live root material as an essential dietary component. Other larval food plants were Imperata cylindrica, Saccharum spontaneum, Panicum maximum, Pennisetum purpureum and Zea mays. The biology of L. reuleauxi is compared with those of other Lepidiota spp. attacking sugarcane.