planidium, planidia

From Greek planos wandering (compare planet), plus -idion diminutive (1).

planidium noun, plural planidia - 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. All Strepsiptera have planidial larvae. The first instar larva in Meloidae has three claws on each foot, and is therefore called a triungulin , but otherwise they are typical planidia. (Definition based on Wikipedia article Planidium, retrieved 19 January 2008.)

Note that the terms triungulin and triungulid are sometimes used to refer to other planidial beetle or Strepsipteran larvae, though this is, perhaps, imprecise.