Planidium

"Planidia" redirects here. For the genus of beetles, see Planidia (beetle).
Planidia and larva of a parasitoid wasp of the Perilampidae family.
Triungulin, later larval, and other instars of a Meloid beetle.
Planidia of a Meloid beetle in opportunistic phoresy on a male solitary bee (Andrena carlini), awaiting contact with a female, whose nest they then could invade.

A planidium is a specialized form of insect larva seen in the first-instar of a few families of insects that have parasitoidal ways of life. They are usually flattened, highly sclerotized (hardened), and quite mobile. The function of the planidial stage is to find a host on which the later larval instars may feed, generally until the insect pupates.