Portia

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

Distribution

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

Hunting techniques

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 (much like the Pirate spider). Then, when 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.

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.

To make the accurate vision necessary for such complex behavior possible, they employ a two-lens camera eye. With this system, they can see as clearly as a pigeon, but only a minute piece at a time. They are, for example, not able 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.

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. 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.

Species

• Portia africana (Simon, 1886) — West, Central Africa
• Portia albimana (Simon, 1900) — India to Vietnam
• Portia assamensis Wanless, 1978 — India to Malaysia
• Portia crassipalpis (Peckham & Peckham, 1907) — Singapore, Borneo
• Portia fimbriata (Doleschall, 1859) — Nepal, Sri Lanka, Taiwan to Australia
• Portia heteroidea Xie & Yin, 1991 — China
• Portia hoggi Zabka, 1985 — Vietnam
• Portia jianfeng Song & Zhu, 1998 — China
• Portia labiata (Thorell, 1887) — Sri Lanka to Philippines
• Portia orientalis Murphy & Murphy, 1983 — Hong Kong
• Portia quei Zabka, 1985 — China, Vietnam
• Portia schultzi Karsch, 1878 — Central, East, Southern Africa, Madagascar
• Portia songi Tang & Yang, 1997 — China
• Portia strandi Caporiacco, 1941 — Ethiopia
• Portia taiwanica Zhang & Li, 2005 — Taiwan
• Portia wui Peng & Li, 2002 — China
• Portia zhaoi Peng, Li & Chen, 2003 — China

Footnotes

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.

External links

• Description in the Diagnostic Drawing Library
• Guide to Common Singapore Spiders: P. labiata
• Photographs of P. labiata
• Photographs of P. fimbriata
• Photographs of P. schultzi
• Photographs of P. africana
• Photographs of P. quei
• Frontal view of P. fimbriata
• Information about P. fimbriata (with distribution in Australia)
• Prey capture and mating behavior in jumping spiders belonging to the genus Portia

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