Fringed Jumping Spider

Introduction

Fringed Jumping spiders are specialist spider-eating spiders which have attracted a great deal of interest in recent years due to their extremely varied and adaptable prey capture techniques, their ability to learn from previous experience, and to solve mazes from observation.

Identification

The Fringed Jumping Spider, Portia fimbriata is a web builder and a skilled hunter of spiders. Its body and legs are adorned with fringes and tufts of brown, white and black hairs - at rest it looks like a piece of litter detritus. The web may be a small 'platform' or a more complex, inverted 'cone' of silk enclosing a tangle of threads, with a curved leaf at the top. They are highly cryptic in both appearance and behaviour and are often difficult to find in their habitats.

Habitat

These spiders are found in habitats ranging from savanna woodland to rainforest. They make webs among rocks, buttress roots, bark or foliage. In dryer habitats they are associated with rockpile outcrops and cave entrances.

Distribution

The Fringed Jumping Spider is found across Northern Australia, including Western Australia, Northern Territory, and Queensland.

Feeding and diet

Spiders and their eggs are the preferred food of the Fringed Jumping Spiders. Web building spiders and other jumping spiders are especially targeted. Portia readily invades its victim's webs and is skilled at moving on silk. These webs belong to spiders from at least 11 families and they can be very different (orb, sheet, space and tangle webs; dry, sticky and cribellate silk). Web spiders have poor vision compared to Portia.

Other behaviours and adaptations

The Fringed Jumping Spider walks slowly and jerkily, bursting into action only when seizing prey. It has good vision, with the large anterior eyes that are typical of jumping spiders.

Fringed Jumping Spiders use their behavioural skills to lull victims into a false sense of security. Other jumping spiders seem to be taken in by Portia's slow gait and resemblance to a piece of detritus, allowing it to move fatally close. When invading webs, Portia uses its legs and palps to vibrate the silk in specialised patterns. This may simulate struggling prey or a male spider's mating signals, causing the web's unsuspecting owner to move toward the waiting, or slowly stalking, predator. When the victim is about 5 mm away, Portia suddenly attacks, lunging forward, fangs outstretched to grasp its prey and inject a fast acting venom.

Persistence characterises Portia's hunting strategy. One spider performed vibratory behaviour in a web for 3 days before the host spider finally decided to investigate and fell victim to it. In another instance, when a direct web approach to an orb web spider was unsuccessful, Portia left the web only to re-appear in the foliage above it. From there the hunter lowered itself down on a silk line beside the web until it was close enough to grasp its victim and deliver a fatal bite.

How does this species determine which method of attack or web signal to use with a particular spider? Probably, it is through a sophisticated trial and error procedure, backed up by cues from the victim or its web. Portia's web signalling behaviour seem to be constantly varied until the confused victim finally responds - usually with fatal results. All of this reveals a form of problem solving capacity unmatched by other spiders.

Life history cycle

Females silk their eggs within the hollow of a curved leaf.

Breeding behaviours

Subadult males and females live together in the same web, mating after their moult into adulthood.