page_title: Portia (spider)
section_title: Vision
hierarchical_section_title: Portia (spider) / Vision
caption_attribution_description: English: Diagram of the visual fields of the spider as viewed from above. The function of the small posterior medial eyes (PME) is not known. Čeština: Vizuální schéma skákavkovitých pavouků
context_page_description: Portia is a genus of jumping spider that feeds on other spiders. They are remarkable for their intelligent hunting behaviour, which suggests that they are capable of learning and problem solving, traits normally attributed to much larger animals.
context_section_description: Portia species have complex eyes that support exceptional spatial acuity. They have 8 eyes. Three pairs of eyes positioned along the sides of the cephalothorax (called the secondary eyes) have a combined field-of-view of almost 360° and serve primarily as movement detectors. A pair of forward-facing anterior median eyes (called the principal eyes) are adapted for colour vision and high spatial acuity.
  The main eyes focus accurately on an object at distances from approximately 2 centimetres (0.79 in) to infinity, and in practice can see up to about 75 centimetres (30 in). Like all jumping spiders, Portias can take in only a small visual field at one time, as the most acute part of a main eye can see all of a circle up to 12 millimetres (¹⁄₂ in) wide at 20 centimetres (8 in) away, or up to 18 millimetres (³⁄₄ in) wide at 30 centimetres (12 in) away. Jumping spiders' main eyes can see from red to ultraviolet.
  The inter-receptor angles of Portia's eyes may be as small as 2.4 minutes of arc, which is only six times worse than in humans, and is six times better than in the most acute insect eye. It is also clearer in daylight than a cat's vision.
  P. africana relies on visual features of general morphology and colour (or relative brightness) when identifying prey types. P. schultzi′s hunting is stimulated only by vision, and prey close by but hidden causes no response. P. fimbriata use visual cues to distinguish members of the same species from other salticids.
  Cross and Jackson (2014) suggest that P. africana is capable of mentally rotating visual objects held in its working memory.
  However, a Portia takes a relatively long time to see objects, possibly because getting a good image out of such small eyes is a complex process and requires a lot of scanning. This makes a Portia vulnerable to much larger predators such as birds, frogs and mantises, which a Portia often cannot identify because of the predator's size.
caption: Diagram of the visual fields of the spider as viewed from above
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