Wednesday, 6 April 2011

Fascinating jumping spiders

ResearchBlogging.orgWe had a very warm day today - for April - the sun hit the brick walls and this is something that brings jumping spiders out. I spot one on the wall, quite high up, she moves in a typical jerkily fashion on to a wooden plank and I take a few shots with my arms outstretched and a poor view of the LCD display, but I am happy when manage a few focused front shots (above). I think this is Salticus cingulatus, a close relative of the zebra jumping spider, Salticus scenicus. Jumping spiders, or salticidae - the family latin name - are the largest spider family, with 5,000 species. They have a highly acute visual sense, with their large and forward facing antero-median being responsible for the visual acuity, and the remaining 6 eyes - with the posterior pair facing almost backwards - acting as motion detectors. Although the external lenses are fixed, the internal eye tube can move to precisely look towards an object. Some species have been shown to have colour and UV vision (tetrachromatic vision) and correspondingly, jumping spiders include some of the most colourful spiders. Their mating rituals are mesmerising: they include synchronic front leg movements, abdomen vibrations and percussion, yes, percussion! They remind me of flamenco dancers with their tap shoes and castanets. Something that cannot be imagined and have to be seen:

I often come across feeding jumping spiders. Then they are preoccupied and they are much easier to approach. This male S. scenicus had caught a fly and came to inspect me, before returning to its oversized prey.
The following one, a tiny, possibly immature specimen still poorly marked, was preying on an aphid in my conservatory bougainvillea.
Jumping spider are extremely agile and their hunting has been compared to a cat stalking its prey. First the spider moves its "head" fixing its eyes on the potential prey, then the abdomen is aligned and then the spider moves slowly towards prey. When the prey is within jumping distance, the spider ties a line of silk to the substrate and pounces on the prey. Surprisingly, jumping spiders can detour when jumping, and approach does not need to be in a straight line, with the spider losing sight of prey in occasions, suggesting remarkable planning for a tiny invertebrate. Salticids show a range of predatory strategies from extreme sit-and-wait species which only move to jump into passing prey to specialist ant predators, to cleptoparasitic species, which specialise in robbing spider webs or deceptive prey-mimics, who imitate the movement of prey that has fallen on a web to lure the spider out and the eating the spiders themselves. There is even a herbivorous jumping spider, the just so named Bagheera kiplingii, from Mexico, which exploits an ant-acacia mutualism, mainly  feeding on specialised leaf tips produced by the acacia for its mutualistic ant, and nectar, complementing its diet with a few ant larvae. What amazing animals they are.

Richman, David B., & Jackson, Robert R. (1992). A review of the ethology of jumping spiders Bulletin of the British Arachnological Society, 9 (2), 33-37

Meehan CJ, Olson EJ, Reudink MW, Kyser TK, & Curry RL (2009). Herbivory in a spider through exploitation of an ant-plant mutualism. Current biology : CB, 19 (19) PMID: 19825348

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