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A planidium is a specialized form of first-instar insect larva, seen in groups that are parasitoids; they are generally flattened, highly sclerotized, have legs, and are quite mobile. Some species have eyes, others not. The function of the planidial stage is to find a host on which the larva may feed until it attains adulthood. ==Etymology== The name "planidium" is derived from the Greek language ''πλάνος'' (planos) meaning "roaming", and also, for similar reasons, the root of planula. Accordingly, it is the general term for such an adaptation, and not limited to any particular species or morphology. Planidia in different species may differ greatly in form. The first instar larva in the beetle family Meloidae has three claws on each foot, and is therefore called a triungulin (plural ''triungula''). The term is derived from the Latin ''tri'' meaning "three" and ''ungula'' meaning a claw. Note that an obsolescent variant form from the same root as "triungulin" is ''triungulus'', plural ''triunguli'' and sometimes it still is encountered.〔(Webster's international dictionary 1895 )〕 For practical purposes of uniformity, unless there is some special reason for the use of the term, it is best to use only the term "planidium". ==Function and occurrence== Planidia occur among subsets of the members of several orders, including Neuroptera, Hymenoptera, Coleoptera, Strepsiptera, and Diptera; examples include the neuropteran family Mantispidae, the beetle families Meloidae and Ripiphoridae, and the fly families Acroceridae, Bombyliidae, Nemestrinidae, and Tachinidae Among the Hymenoptera examples include the parasitic wasp families Eucharitidae and Perilampidae. All Strepsiptera have planidial larvae. The term "triungulin", originally coined in referring to the planidia of the beetle family Meloidae, is commonly applied to similar-looking planidial larvae of other families of beetles or Strepsiptera. It is purely descriptive and of no theoretical importance as differing conceptually from other planidia. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「planidium」の詳細全文を読む スポンサード リンク
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