Bold Jumping Spider

Lore & Background

Portia spiders are known for their intelligent hunting tactics. All members of Portia have instinctive hunting tactics for their most common prey, but can improvise by trial and error against unfamiliar prey or in unfamiliar situations, and then remember the new approach. They exhibit spatial memory and object permanence, and are capable of trying out a behavior to obtain feedback regarding success or failure, and they can plan ahead, as it seems from their detouring behavior.

Portia species can make detours to find the best attack angle against dangerous prey, even when the best detour takes a Portia out of visual contact with the prey, and sometimes the planned route leads to abseiling down a silk thread and biting the prey from behind. Such detours may take up to an hour, and a Portia usually picks the best route even if it needs to walk past an incorrect route. Nonetheless, they seem to be relatively slow thinkers, as is to be expected since they solve tactical problems by using brains vastly smaller than those of mammalian predators.

Portia has a brain significantly smaller than the size of the head of a pin, and it likely has less than 100,000 neurons (for comparison, a mouse brain has about 70 million neurons and a human brain has 86 billion). Portia can distinguish their own draglines from conspecifics', recognizing self from others, and also discriminate between known and unknown spiders.

Reader's Guide

The 17 described species of Portia are found in Africa, Australia, China, Madagascar, Malaysia, Myanmar, Nepal, India, the Philippines, Sri Lanka, Taiwan, and Vietnam. Portia are vulnerable to larger predators such as birds and frogs, which a Portia often cannot identify because of the predator's size. Some insects prey on Portia, for example, mantises, the assassin bugs Nagusta sp. indet. and Scipinnia repax (that is, Scipinia rapax). When not hunting for prey or a mate, Portia species adopt a special posture, called the "cryptic rest posture", pulling their legs in close to the body and their palps back beside the chelicerae ("jaws"), which obscures the outlines of these appendages.

When walking, most Portia species have a slow, "choppy" gait that preserves their concealment: pausing often and at irregular intervals; waving their legs continuously and their palps jerkily up and down; moving each appendage out of time with the others; and continuously varying the speed and timing. When disturbed, some Portia species are known to leap upwards about 100 to 150 millimetres (4 to 6 in) often from the cryptic rest pose, and often over a wide trajectory. Usually the spider then either freezes or runs about 100 millimetres (4 in) and then freezes.

Did You Know?

• Portia fimbriata has been observed performing vibratory behavior for three days until the victim decided to investigate.
• Some specimens found trapped in Oligocene amber were identified as related to Portia.