|
The Tridactylidae are a family in the order Orthoptera. They are small, mole-cricket-like insects, almost always less than 20 mm long when mature. Generally they are shiny, dark or black, sometimes variegated or sandy-coloured. They commonly live in short tunnels and accordingly are known by common names such as Pygmy mole crickets, though they are not particularly closely related to the true "mole crickets", the (''Gryllotalpidae''). ==Description== The Tridactylidae are small members of the Orthoptera, most species being less than 10 mm in length, though some approach 20 mm. They have a wide, but patchy, distribution on all continents but Antarctica. Being so small and inconspicuously coloured, while living in shallow burrows in moist sandy soil, they are not generally familiar to non-entomologists. They have several unusual features, for example, the posterior femora are greatly enlarged, being strongly adapted for leaping; in some species those hind femora actually are larger than the abdomen. Correspondingly, in support of their powerful jumping capabilities, the hind tibiae bear movable plates towards their distal ends. These vary in number according to the genus, and they are called natatory lamellae (meaning literally "swimming plates"). Ordinarily the insect keeps the plates closely pressed against its tibiae but it can fan them out for swimming, which most species can do very well, some even being able to dive and swim under water. Apart from scrabbling over the water or swimming, some species actually can jump off the water surface. It is probable that the natatory lamellae are what makes such implausible leaps possible. The plates also may aid jumping on land, which Tridactylidae certainly can do impressively. The posterior tibiae also bear articulated spines near their tips, plus spurs longer than the hind tarsi, which may be entirely absent or else are at best vestigial, having only a single segment. The insect uses its hind tibial spurs for digging, which is unusual for an insect's hind leg. The anterior four tarsi, in contrast to the posterior two tarsi, generally have two segments each.〔Comstock, J. H. An Introduction to Entomology, Comstock Publishing. 1949〕 The tegmina are reduced in size, rather as in the Tetrigidae, but there is no corresponding extension of the pronotum. The vestigial tegmina are horny, almost without veins, and without stridulating organs. In keeping with the lack of stridulatory adaptations, the fore tibiae do not bear tympanal organs such as those found in many Orthoptera. Rear wings generally are present, often longer than the abdomen, but their presence in any particular species need not imply that the insect is capable of flight.〔 Tridactylidae give the impression of having two pairs of cerci; this is because, in addition to the true cerci, the two podical plates (comprising the divided sternum of the eleventh abdominal segment) are greatly elongated and each bears a terminal segment that looks like a stylus or cercus. The antennae are fairly short, typically filiform or moniliform, with eleven segments. Some species have vestigial ovipositors, whereas others have ovipositors similar to those of the Acrididae, suited to depositing the eggs in sandy soil.〔 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「Tridactylidae」の詳細全文を読む スポンサード リンク
|