Recent research on the eyes and vision-guided behavior of jumping spiders (Salticidae) is reviewed. Special attention is given to Portia Karsch.

The species in this African, Asian and Australian genus have especially complex predatory strategies. Portia’s preferred prey are other spiders, which are captured through behavioral sequences based on making aggressive-mimicry web signals, problem solving and planning. Recent research has used Portia to study cognitive attributes more often associated with large predatory mammals such as lions and rarely considered in studies on spiders.

In salticids, complex behavior and high-spatial-acuity vision are tightly interrelated. Salticid eyes are unique and complex. How salticid eyes function is reviewed. Size constraints are discussed.

Extensive sampling may be the salticid’s answer to the problem of how to see details of shape and form within the constraints imposed by small size, but speed of perception may be a primary limitation. From many years of studying Portia, our impression is that, although these spiders’ feats of discrimination are impressive, they are often strikingly slow on the uptake. It may be that Portia can see more or less what we can see, but achieves this by means of a slow scanning process. Part of what it means to say an animal ‘sees well’ should perhaps be that it perceives what is out there quickly. On this criterion, Portia may see only poorly.

Another potential limitation is that the small size of Portia’s fovea may limit perception of large objects. Images of small features of animals (eg. a palp, leg or eye of a spider) may be more or less easily sampled by the salticid fovea, whereas sampling critical body parts of larger animals may be exceedingly difficult. When Portia scans with its foveas across smaller objects, such as its usual spider prey, piecing together a ‘picture’ of what it is looking at may be much more feasible than when scanning in a ‘picture’ of a larger animal such as a bird, a frog or a large mantis, all of which are relevant to Portia. Mantises, for instance, readily prey on Portia, yet Portia typically shows no evidence of taking appropriate precautions when coming face to face with these deadly foes. Our impression is that Portia often looks at large mantises and then fails to discern what they are.

When it comes to seeing, it seems that Portia has made efficient use of its limited materials and overcome many, but not all, of the limitations imposed by small size. The same basic principle may apply to cognition. It may be that by making efficient use of limited brain resources (neurons), Portia can achieve considerable cognitive skills, such as problem solving and planning ahead, all the while suffering limitations comparable to those that apply to seeing. For example a big difference between Portia and cats may be the speed at which problems are solved.

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