Taxonomy

Opisthoncus is found in Australia, New Guinea and New Britain. Australia has thirty species (see Appendix 1), however several of these are of doubtful status or may be misplaced (Gardzińska and Żabka, 2013; Whyte and Anderson, 2017). The genus is part of an Australasian clade (Maddison et al 2008) including Abracadabrella, Apricia, Clynotis, Holoplatys, Huntiglennia, Ocrisiona, Paraphilaeus, Paraplatoides, Pungalina, Tara, Trite and Zebraplatys (Maddison 2015).  Further information on the genus and described species in Australia can be found in Richardson and Żabka (2017) and Whyte and Anderson (2017).

Description

Opisthoncus spp. are medium-sized to large spiders, ranging in body length from 5 to 13 mm, their morphology varying quite markedly between species. The carapace is high, with a bulge on the midline between the posterior lateral eyes in most species. The head, viewed from above, varies in shape, from roundish, almost rectangular to trapezoid. Chelicerae in the female have a subdivided (fissident) retromarginal tooth and two promarginal teeth. The pattern in the males is variable. Though primarily fissident, species can also be unident or plurident, sometimes with additional spurs. The shape and size of the chelicerae is extremely variable. The first pair of legs is longer and stronger than the others.

The male’s palp has an embolus, in some species, slender and curving clockwise around the tegulum, in others, short and thick. The tegulum is small and round, or large and elliptical. The palpal tibia has a single, hook-like or straight, somewhat conical retro-lateral tibial apophysis.

The female has two poorly-sclerotised epigynal atria with copulatory openings on their lateral sides. From these, coiled insemination ducts lead postero-laterally to rounded spermathecae near the midline. The epigastric fold has a median cleft or uptucking of varying size.

Biology

Found on grass, shrub and tree foliage in forests, woodlands, mangroves, heathlands and grasslands, occasionally in houses. Bites have been reported, without medical consequence.

Distribution

The genus has been collected across Australia, except for extremely arid parts of the interior. It is also found in New Guinea and New Britain.

References

Davies, V.T. & Żabka, M. 1989. Illustrated keys to the genera of jumping spiders (Araneae: Salticidae) in Australia. Memoirs of the Queensland Museum 27, 189-266.

Gardzińska, J. & Żabka, M. 2013. Redescription of the genus Opisthoncus L. Koch, 1880 (Araneae: Salticidae). Zootaxa 3717, 401–447.

Maddison, W.P. 2015. A phylogenetic classification of jumping spiders (Araneae: Salticidae). Journal of Arachnology 43, 231-292.

Maddison, W.P., Bodner, M.R. & Needham, K.M. 2008. Salticid spider phylogeny revisited, with the discovery of a large Australian clade (Araneae: Salticidae). Zootaxa 1893, 49-64.

Richardson, B.J. & Żabka, M. 2017. Salticidae. Arachnida: Araneomorphae. Canberra, Australian Faunal Directory. Australian Biological Resources Study, at https://biodiversity.org.au/afd/taxa/SALTICIDAE.

Whyte, R. and Anderson, G. 2017. A field guide to the spiders of Australia. Clayton: CSIRO Publishing 451pp.

* The information sheet should be read in the context of the associated diagrams and photographs. Diagrams explaining anatomical terms can be found in the ‘Salticidae’ pictures at the beginning of the list of genera.