Feeding and diet

The prey-catching method of net-casting spiders is unique. At night they build a rectangular, postage-stamp-sized web, made with wool-like, entangling silk threads. These little nets are made among low vegetation, usually above a surface across which prey animals are likely to walk (e.g. a broad leaf , a tree trunk or even a house wall). After spinning its web the spider deposits some spots of white faeces on this surface to act as aiming points. The spider hangs head down from a trapeze of silk, holding the net in its front pairs of legs;and there it waits, its enormous eyes watching for prey movement across the white aiming spots. When an insect passes over the white target spots, the spider opens the stretchy web to two or three times its resting size and lunges it downward over the unsuspecting prey. The clinging silk net envelopes the insect, which is then rapidly bitten and wrapped. While eating its catch, the spider may start making a new net for its next meal. Prey animals include cockroaches, ants, spiders and even moths - net-casters seem sensitive to air currents and will lunge the net towards aerial prey. Prey as large as male trapdoor spiders and gryllacridid wood crickets are taken.

Other behaviours and adaptations

The Net-casting spiders' large eyes provide outstanding low-light night vision. Their compound lenses have an F number of 0.58 which means they can concentrate available light more efficiently than a cat (F 0.9) or an owl (F 1.1). The image is focussed onto a large, light-receptive retinal membrane (which is destroyed at dawn and renewed again each night).

Life history cycle

Net-casting spiders mature in summer, with mating and egg-laying taking place into autumn. The male attaches a mating thread to the female's net support lines and jerks it to entice her onto it for mating. The egg sacs are round balls, 9-10 mm in diameter, covered with a tough, closely woven layer of salmon-brown silk flecked with black. The sacs are suspended on vegetation and disguised with twig and leaf litter detritus. Up to four sacs may be produced. The dark brown spiderlings emerge in spring and look like a cloud of little anchors (narrow body and extended front legs) hanging in silk lines above the egg sac. In a few weeks they start building their own tiny nets.

Danger to humans

No interactions with humans or threats to net-casters have been identified.

References