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Infraorder: Insidiatores
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As of January 2024 the Infraorder: Insidiatores consist of 513 species in eight families, four each within two superfamilies. Most Insidiatores are somewhat similar in appearance; many have a pearshaped cepahalothorax with or without adornments such as short spikes, hairs or a pattern of clusters of both. Colours do vary but shades of light ochre to orange-brown to nearly black are most common. Their pedipalps are often quite large and spiked. Some have long legs about 4 - 5x the bodylength but many have legs 2 - 3x the length of the body. Spiked legs are fairly common.
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Of the two superfamilies the larger Triaenonychoidea in the Southern Hemisphere only. The other, the much smaller Travunioidea is limited to certain regions in the Northern Hemisphere. Of all the Harvestmen in Australia (as well as New Zealand) the Insidiatores are arguably the most common. In particular species from the Family: Triaenonychidae which are most frequently encountered along the and hinterlands of the stretch between Adelaide and Brisbame, the south-west corner of W.A. and Tasmania. Another hotspot is the Cairns/Atherton area in northern Queensland.
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Of particular interest is the species, Promecostethus unifalculatus. (Family: Triaenonychidae, Infraorder: Insidiatores) This is the only Harvestman found on the Crozet Islands. These islands are located well south-east from South Africa in the sub-Arctic region of the southern Indian Ocean. These islands, whereas not of volcanic origin, started forming a mere 9 Mya. Considering that dispersion of the Triaenonychidae occurred before the Gondwanan landmass break-up and the remarkably young age of the Crozet islands, it would appear that the species could only have arrived at its location by means of oceanic dispersal which is quite a rarity in the natural world.
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References and links:
> Baker, C., Sheridan, K., Derkarabetian, S., Abel, P.G., Velez, S. and Giribet, G., (2020). 'Molecular phylogeny and biogeography of the temperate Gondwanan family Triaenonychidae (Opiliones : Laniatores) reveals pre-Gondwanan regionalisation, common vicariance, and rare dispersal.' Invertebrate Systematics. 34. 10.1071/IS19069.
> Willians, P. and Abel, P.G., (2020). 'Redescription of Promecostethus unifalculatus, the only known harvestman from Crozet Islands (Opiliones: Triaenonychidae).' Zootaxa. 4861. 120-130. DOI: 10.11646/zootaxa.4861.1.8.
https://www.catalogueoflife.org/data/taxon/5RM
https://en.wikipedia.org/wiki/Crozet_Islands
https://inaturalist.ala.org.au/taxa/526083-Insidiatores
> Baker, C., Sheridan, K., Derkarabetian, S., Abel, P.G., Velez, S. and Giribet, G., (2020). 'Molecular phylogeny and biogeography of the temperate Gondwanan family Triaenonychidae (Opiliones : Laniatores) reveals pre-Gondwanan regionalisation, common vicariance, and rare dispersal.' Invertebrate Systematics. 34. 10.1071/IS19069.
> Willians, P. and Abel, P.G., (2020). 'Redescription of Promecostethus unifalculatus, the only known harvestman from Crozet Islands (Opiliones: Triaenonychidae).' Zootaxa. 4861. 120-130. DOI: 10.11646/zootaxa.4861.1.8.
https://www.catalogueoflife.org/data/taxon/5RM
https://en.wikipedia.org/wiki/Crozet_Islands
https://inaturalist.ala.org.au/taxa/526083-Insidiatores
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