Most animals must integrate input from different sensory organs. For example, females might choose mates based on multimodal signals, such as vibratory and visual cues (Hebets and Uetz 1999). Other animals have several sense organs within the same modality. For instance, many insects have both compound eyes, which discern image detail, and ocelli, which are sensitive only to light and dark (reviewed in Cronin et al. 2014). Spiders are particularly interesting because most species have eight eyes of two different types. Most well studied are the jumping spiders (Family Salticidae) are characterized by their powerful visual acuity, which is used for many complex behaviors such as predation and courtship. They have four pairs of eyes, which consist of a single cornea and retina, of two morphological types: the principal and the secondary eyes (Figure 1). The corneas of jumping spiders are integrated in their exoskeletons and do not move. The tiny, boomerang shaped retinas of the principal eyes have the best resolution but are restricted by a narrow field of view. In order to examine a visual scene, jumping spiders use a set of six muscles to move the retinas, which are situated at the back of long tubes within the cephalothorax (Land, 1969; Figure 2). This scanning can increase the angle of view from approximately 10°to 58°(Land, 1969).
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