Portia (genus)

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Portia
female P. fimbriata
female P. fimbriata
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Arachnida
Order: Araneae
Family: Salticidae
Subfamily: Spartaeinae
Tribe: Spartaeini
Genus: Portia
Karsch, 1878
Diversity
17 species
Type species
Salticus fimbriatus
Doleschall, 1859
Species

see text

Portia is a genus of jumping spider which feeds on other spiders (araneophagic).

Contents

[edit] Distribution

The 17 described species are found in Africa, Australia, China, Malaysia, Myanmar, Nepal, India, Sri Lanka, the Philippines, and Vietnam.

[edit] Hunting techniques

male P. fimbriata
male P. fimbriata

Most jumping spiders prey mainly upon insects, only taking other spiders if the opportunity arises. Portia, however, is different, using deception and mimicry to catch and eat other spiders, which is known as araneophagy. On rare occasions, it will capture and consume an insect as well. It is a cryptic spider and an aggressive mimic, meaning that it imitates something its intended victim finds harmless or even attractive. The mimicry is of two kinds: first, it resembles a fragment of litter detritus. This is a camouflage against other jumping spiders that have relatively superior vision. This way, it can get very close and kill the other spider. Second, it shows a kind of behavioral mimicry: Portia enters a spider's web and creeps up on its victim almost imperceptibly, though it moves quickly when the wind blows. It then plucks the web to imitate a captured insect or a male mating call which will attract the female spiders which is fortunate for the portia spider, but sometimes the prey of the portia spider does not respond and the portia spider resorts to alternative tactics (much like the Pirate spider). If the Portia spider is successful the resident spider approaches, Portia lunges in for the kill.

Portia preys on just about every kind of web-building spider, if it is from 10% up to double its own size. It varies its web signals to suit its specific victim. If it encounters a new spider species, it tries different signals rather randomly. Should one signal elicit a response from the victim, Portia will stop the random signals, and focus on the successful one. [1] Portia fimbriata has been observed to perform vibratory behavior for three days until the victim decided to investigate.

female P. fimbriata in its web
female P. fimbriata in its web

Philippine Portia species approach eggless spitting spiders from the rear, whose preferred prey are jumping spiders.[citation needed] Egg-carrying spitting spiders are approached head on.

Although taxonomically in the jumping spider family, it does not jump, because then it would lose its detritus camouflage.

Unlike other jumping spiders, Portia sometimes builds a web which it fastens to the web of a future victim. Should the web catch insects, Portia will wait for the other spider instead of feeding on the insect.

Their two-lens camera eyes allow them the accurate vision necessary for such complex behavior. They can see as clearly as a pigeon, but only a minute piece at a time. They are, for example, unable to discern the shape of a praying mantis, because it is too big for its field of vision. They have six eye muscles to move the field of vision around.

[edit] Reproduction

Portia exhibits a different mating behavior and strategy compared to other jumping spiders. In most jumping spiders, males mount females to mate. In Portia the female drops a dragline after the male mounts her, mating in mid-air. Before this happens the male shows off his legs and extends them stiffly and shakes them to attract the female. the female then drums on the web. Mating with Portia spiders can occur off or on the web. The spider also practices cannibalism before and after copulation. The female usually twists and lunges at the mounted male (P. fimbriata however, is an exception; it does not usually exhibit such behavior.). If the male is killed before completing copulation, the male sperm is removed and the male is then eaten. If the male finishes mating before being killed, the sperm is kept for fertilization and the male is eaten. A majority of males are usually killed during sexual encounters.

[edit] Species

[edit] Footnotes

  1. ^ Harland & Jackson 2000

[edit] References

  • Harland, D.P & Jackson R.R. (2000): 'Eight-legged cats' and how they see - a review of recent research on jumping spiders (Araneae: Salticidae). Cimbebasia 16: 231-240 PDF - vision and behavior in Portia spiders.
  • Harland, D.P. & Jackson, R.R. (2006): A knife in the back: use of prey-specific attack tactics by araneophagic jumping spiders (Araneae: Salticidae). Journal of Zoology 269(3): 285-290. doi:10.1111/j.1469-7998.2006.00112.x
  • Platnick, Norman I. (2007): The world spider catalog, version 8.0. American Museum of Natural History.

[edit] External links

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