Animal Species:Tube spiders
Tube spiders build aerial tubes, open at the top, that are supported against rocks, stems, tree trunks or buttress roots.
Tube spiders are large brown, burrowing spiders. They are unexceptional apart from their remarkable habit of building aerial tubes that extend their burrows well above the ground. Their numerous relatives in the genus Misgolas build burrows with ground-level openings that are commonly seen in bushland and gardens in eastern Australia.
body length 15 - 25 mm
Tube spiders are found sporadically in moist forest habitats, especially in rainforests and their margins. Southern Tube Spiders are known from highland and coastal forests in New South Wales from the Macleay River to the Illawarra region. Northern Tube Spiders range from the Dorrigo region of New South Wales into south eastern Queensland.
Tube spiders can be found in considerable numbers in suitable habitats. They were recorded as far back as 1922, in an article published in the Sydney Mail newspaper (they were not taxonomically described until 1974). The report noted that the tubes were present in thousands on damp ground sloping down to creeks in coastal rainforest patches of the Myall Lakes region of New South Wales. Such abundance is rare today.
The aerial tubes, open at the top, are supported against rocks, stems, tree trunks or buttress roots. Sometimes they occur in clusters 'like miniature organ pipes'. Each tube is attached to its supporting structure only by the silk collar at the tube's mouth - the rest simply lies alongside the support or even hangs free of it. Tubes can reach 30 centimetres in height, although one older report has a tube extending 'up to three feet' (about 90 cm). The tubes are made of thin, parchment-like silk, often admixed with soil particles and adorned with moss. The tube wall thickens at ground level but it is only weakly attached to the finer silk of the burrow below, which descends 15 to 20 cm to a sock-like, silken retreat chamber. When hunting, the spider usually sits in the tube mouth waiting to ambush any prey passing nearby.
Why build these curious aerial tubes? Tube spiders are found in moist forest habitats that may be prone to waterlogging or flooding, such as rainforest creek banks and gullys. Consequently, one function of the aerial tube may be to provide an above ground retreat for the spider during rainfall-induced sheet flooding or creek overflows. In addition, the tube elevates the spider into a feeding niche above the forest floor. This would allow these spiders to intercept insect and other prey moving across rocks or between ground and foliage along stems, so avoiding direct feeding competition with ground dwelling spiders. Prey animals can even use the tube itself as an aerial walkway. The tube may then act as an early warning system that alerts the spider to the presence of prey, as well as a means of delivering prey directly to the spider waiting above.