Trachypachus gibbsii

The Trachypachidae are a species-poor family of beetles within the Adephaga. The family comprises two genera and six species.

  • 4.1 Notes and references
  • 4.2 Literature



The beetles are 3.8 to 7 mm long, black, and have a more or less smooth and shiny body surface. The genus Systolosoma has a shiny metallic surface structure. The beetles beetles look similar and have between pronotum and elytra a distinct constriction. The head has forward facing mouthparts and is relatively short. The compound eyes are well developed and slightly prominent. The antennae are filiform, the last segment has a faint fuzz. The wing covers are in the genus Trachypachus smooth for the most part and are only weakly structured punctiform. The genus Systolosoma has on them irregular patches with metallic luster. On the third and fourth abdominal sternite are grown, the last, seventh sternite is broadly rounded.


The larvae are flattened elongated and easily. Your margins are almost parallel. The sclerotized parts of the body are brownish. The after head has forward facing mouthparts and bears six simple eyes ( ocelli ). The antennae are four members. The mandibles are relatively short. The stipes is short, the lacinia lacking. The Galea is bipartite. The pronotum is greater than the subsequent segments. The legs wear double claws. The ninth abdominal segment is normally developed, the horn-like Urogomphi associated with it either or absent, as in Systolosoma breve.

Way of life

Little is known about the life of this family. Roy Crowson described the family as residents of moist habitats, however, both the larvae and the imagoes of all Trachypachus types xerophilic and this independently of adjacent waters. From Trachypachus gibbsii is known that he inhabits sandbanks of rivers with poplar growth in dry gravel and fine sand, which is covered with foliage. Trachypachus holmbergi lives on open or slightly shaded sites that are covered with leaves or needles. Systolosoma breve inhabited rainforests, Systolosoma lateritium was detected in forests with vegetation of coihue southern beech ( Nothofagus dombeyi ) and lenga southern beech ( Nothofagus pumilio ).

The beetles and their larvae are predators and feed on their victims by means of extra-intestinal digestion. About the prey and the hunting behavior is not known. Also the number of larval stages has so far not known.

Systematics and occurrence

The monophyly of the Trachypachidae is mainly supported by autapomorphies of the larvae. This includes among others the absence of sensory hairs on the side of the third sensor element, instead there is a sense field on the ventral side, the tip of the third Maxillartasters has additional hairs and the ninth tergite bears eight bristles. The adults are distinguished by the shape of paramere of the other families of beetles.

The genus comprises four species Trachypachus. Trachypachus zetterstedtii is widespread Palaearctic, the other three species occur in western North America. Trachypachus holmbergi is from California to Alberta, distributed Trachypachus gibbsii of the southern Sierra Nevada to the southern tip of British Columbia and Trachypachus slevini in western Oregon and Washington. The genus Systolosoma covers two types which occur in central and southern Chile: Systolosoma breve and Systolosoma lateritium. The subfamily Eodromeinae with six species is only known from fossil finds from the Triassic, Jurassic and Early Cretaceous of Asia and probably the late Jurassic of Europe.