Diptera - Zesshirui

This refers to the order Zoraptera, which belongs to the group Exoptera of the class Insecta of the phylum Arthropoda. This group is found mainly in tropical regions, except for the Palearctic and Australia, and includes small insects with a body length of 3 mm or less. Currently, only about 20 species are known. They have nine bead-shaped antennae, a downward-facing mouth with strong mandibles, a Y-shaped meeting line on the skull, two-segmented tarsus segments, short tail hairs, and a degenerate female ovipositor. Adults usually come in two types: dark-colored with compound eyes and ocelli, and wings with few veins, and pale-colored with no eyes or wings. These are found in clusters under bark, in rotting wood, or in termite nests, and are thought to feed on fungi, but mites have also been found in their stomachs. There are two theories about their phylogenetic relationship: one that says they are closely related to booklice, and another that says they are more similar to cockroaches and termites, but the latter is more likely.

[Takehiko Nakane]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

節足動物門昆虫綱外翅(がいし)群に属する一目Zorapteraのことをいう。旧北区、オーストラリアを除く、おもに熱帯域に分布する一群で、体長3ミリメートル以下の小形の昆虫を含み、現在20種余りが知られるにすぎない。触角は9節で数珠(じゅず)状、口は下向きで強い大あごをもち、頭蓋(とうがい)はY形の会合線があり、脚(あし)の跗節(ふせつ)は2節、尾毛は短く雌産卵管は退化している。成虫には普通、濃色で複眼と単眼、脈の少ないはねをもつ型と、淡色で目もはねもない型がある。これらは樹皮下、朽ち木中、あるいはシロアリの巣の中で集合して発見されており、菌食と考えられているが、胃中からダニも発見されている。系統的にはチャタテムシに近縁とする説と、ゴキブリやシロアリに近いとする説があるが、後者が有力である。

［中根猛彦］

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