What Bug Is That? The guide to Australian insect families.

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These little insects usually frequent the margins of water bodies, where they construct galleries in sandy ground. However, they spend much of their time crawling about on the surface and are active day and night. The hind legs are kept flexed during walking; they are used only for making extremely powerful jumps when disturbed, and for swimming on and beneath the surface of the water, when the tibial lamellae presumably come into action.


Tridactylids are very small, usually smooth and shiny, black or variegated. Eyes well developed. Pronotum overlapping mesonotum, its lateral lobes well separated by broad prosternum. Fore femur little expanded, tibia moderately so, tarsus 2-segmented. Messner (1969) described a glandular opening on the mid tibia of Tridactylus. Hind legs saltatorial, with greatly enlarged femur; tibia long and slender, with 4 terminal spurs long, especially ventral pair, and several more distal spines along dorsal edges often replaced by articulated lamellae; tarsus sometimes greatly reduced. Fore wing tegminised, falling well short of abdominal apex (even when hind wing much surpasses abdomen), bearing 2 veins (probably Sc and R) and sometimes a third (probably 1A). Hind wing, when fully developed, with remigium reduced to narrow sclerotised band, all veins unbranched, except Cu; C weak, supporting proximal part of anterior margin; R, M and CuA fused or closely associated in basal third of wing; anal fan large, with very numerous anals, traversed by single arc of cross-veins. Putative stridulatory mechanism sometimes located ventrally on fore wing, along distal part of Sc. Cercus 2-segmented in all Australian species. Paraproct bearing cerciform appendage. Karyotypes with 2n [male] = 13 (XO) and 15 (XO) have been reported (John and Rentz 1987).


Both subfamilies occur in Australia. The Tridactylinae include the cosmopolitan genus Tridactylus (2 widespread spp.) and Xya (5 spp.)( one of which has been segregated into subspecies). Dentridactylus ( Dentridactylinae ) occurs in Australia (2 spp.) and Brazil (1 sp.).

  • Tridactylus australicus

  • Tridactylus australicus