Seasonal life cycle and biology of Lepidiota mansueta (Coleoptera: Scarabaeidae): a serious root-feeding pest in India

The seasonal life cycle and biology of a white grub beetle, Lepidiota mansueta Burmeister (Coleoptera: Scarabaeidae), were studied on Majuli river island and in the laboratory during 2005–2010. This species has become an extremely serious pest of many field crops on Majuli river island, the largest mid-river deltaic island of the world. L. mansueta has a biennial life cycle, the first of its kind in North East India, and the duration of egg, grub, and pupal stages varied from 12 to 17, 635 to 671, and 28 to 35 days, respectively. Third instar grubs as heavy as 6 g caused heavy damage to crops and had a prolonged developmental period ranging from 545 to 563 days in the laboratory (27 °C). L. mansueta can be regarded as a rare species, because it spends its entire life cycle under the ground except for a short period during which adults emerge from the ground for mating. There was no evidence that the adults fed on plants either in the field or in the laboratory and hence this species has the unique distinction of being the first Indian phytophagous white grub species with nonfeeding adults.