abstract:A planidium is a specialized type of first-instar insect larva, seen in groups that are parasitoids; they are generally flattened, highly sclerotized, have legs, are quite mobile, and sometimes have eyes. They occur in the orders Hymenoptera, Coleoptera, Strepsiptera, and Diptera; specifically the beetle families Meloidae and Ripiphoridae, the fly family Acroceridae, and the parasitic wasp families Eucharitidae and Perilampidae.