Microhexuridae

Bond, Opatova & Hedin, 2020

Pygmy Funnel-web Spiders

Genus Guides

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Microhexuridae is a small of spiders containing only the Microhexura. These tiny spiders are found in montane forests of western and eastern North America. The family was established in 2020 based on molecular phylogenetic studies that revealed its distinct evolutionary position separate from related mygalomorph families. Only two are known, each restricted to specific mountain ranges.

Spruce Fir Moss Spider by U.S. Fish and Wildlife Service. Used under a Public domain license.Spruce-fir Moss Spider found by U.S. Fish and Wildlife Service Biologist Susan Cameron at Mount Craig in July, 2019 in the spruce-fir forest 06 by USFWS/Southeast. Used under a Public domain license.U.S. Fish and Wildlife Service Biologist Susan Cameron visited Mount Craig in July, 2019 to search for the spider in the spruce-fir forest 02 by USFWS/Southeast. Used under a Public domain license.

Pronunciation

How to pronounce Microhexuridae: //ˌmaɪ.kroʊ.hɛkˈsjʊər.ɪˌdiː//

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Identification

Microhexuridae spiders are distinguished by their extremely small size among mygalomorphs. They possess the characteristic features of funnel-web spiders including robust and adapted for silk production. The two can be separated by geography: M. idahoana in the Cascade Mountains and M. montivaga in the Blue Ridge Mountains. Detailed morphological requires examination of genitalia and other microscopic features.

Images

Habitat

Montane forest environments at higher elevations. M. montivaga occurs in spruce-fir forests of the southern Appalachian Mountains. M. idahoana inhabits similar coniferous forest zones in the Pacific Northwest.

Distribution

Restricted to two disjunct mountain ranges in the United States: the Cascade Mountains of the Pacific Northwest (M. idahoana) and the Blue Ridge Mountains of North Carolina and Tennessee (M. montivaga).

Behavior

Constructs small funnel-shaped webs, typical of mygalomorph spiders. The 'Pygmy Funnel-web Spiders' reflects this web-building combined with their diminutive size.

Similar Taxa

  • HexathelidaeBoth contain funnel-web spiders with similar web architecture, but Microhexuridae is distinguished by much smaller body size and restricted North American montane distribution versus the primarily Old World and Australian range of Hexathelidae.
  • DipluridaeAnother mygalomorph with funnel-web building ; Microhexuridae differs in its reduced size and distinct phylogenetic placement based on molecular data.

More Details

Taxonomic History

The was erected in 2020 by Bond, Opatova & Hedin based on phylogenomic analysis. Previously, Microhexura was classified within Dipluridae or Hexathelidae, but molecular evidence demonstrated it represents a distinct lineage warranting familial status.

Conservation Status

Both known have highly restricted ranges in specific mountain systems, potentially making them vulnerable to changes in these limited montane zones.

Sources and further reading