‚ÄčThe Mygalomorphae are a diverse group of spiders and most species (except the Microstigmatidae) live in silk-lined retreats. The retreats could be either vertical burrows or chambers made under rocks or under the bark of trees. The retreats can be left open or be closed by a trapdoor. Extensions of the entrance are frequently found in the form of lids, signal threads, collars, turrets or catch webs. This structure extend the range of the spider and help the substrate vibration receptors located on the palps and legs of the spiders to detect prey. Most of the prey is usually captured at or close to the entrance of the retreats. The construction of trapdoors and other structures around the retreats have evolved many times independently.

The Microstigmatidae are the only free-running mygalomorph spiders in Southern Africa that do not living in a burrow or web. Mygalomorphs are usually nocturnal and hide during the day in their retreats. At night some species wander around in search of food while most of the burrow living spiders lay and wait for prey in the entrance of their retreats.

Why a burrow?

Burrows provide spiders with the following protection:

  • against predators and parasites

  • for the eggs and developing spiderlings in the brood chamber

  • during the moulting process

  • during mating

  • while intercepting or ambushing prey

  • during inactive periods, especially during winter

  • against flooding as the silk used is waterproof

  • against field fires when spider withdraw deep into the burrow

  • against thermal stress as temperature and humidity stay relatively stable in the burrow

  • against fungal and bacterial attacks due to the antibiotic properties

 

Burrows

FAMILY

TYPE OF RETREAT/BURROW
AtypidaeSilk-lined burrow entrance an excavate chamber covered with a silk layer that are used to trap prey
Barychelidae Variable silk-lined burrows with one or more entrances or entrance with leave and/or grass turret or shallow retreat under stones with one or two trapdoors or arboreal tubular retreats.
Ctenizidae Silk-lined burrows usually with rigid cork-like trapdoors either circular or D-shaped.
CyrtaucheniidaeSingle silk-lined burrows or burrows with side passages; frequently Y-shaped with flexible wafer trapdoor or closed with mud pellets.
DipluridaeTubular or funnel-shaped silk retreats made between crevices with entrance extending outwards to form irregular interconnected funnel- or sheet-like webs.
Idiopidae Silk-lined burrows or chambers closed with wafer- or cork-like trapdoors.
MicrostigmatidaeFree-running wanderers, hide below debris on forest floor.
MigidaeBag- or sac-like arboreal retreats or terrestrial silk-lined burrows closed with flap-like trapdoors.
NemesiidaeSilk-lined burrows either single or Y-shaped or silk-lined tunnels and chambers made under rocks.
TheraphosidaeSilk-lined burrows or silk-lined chambers made under rocks usually without a trapdoor but entrance covered with a thin layer of silk when not active .