Orientation by jumping spiders of the genus Phidippus (Araneae: Salticidae) during the pursuit of prey

Abstract

1. Jumping spiders of the genus Phidippus tend to occupy waiting positions on plants during the day. From such reconnaissance positions, the spiders often utilize an indirect route of access (detour) to attain a position from which sighted prey (the primary objective of pursuit) can be captured. 2. Selection of an appropriate route of access is based upon movement toward a visually determined secondary objective (part of a plant) which may provide access to the prey position (Fig. 2, Table 1). 3. During pursuit, the spider retains a memory of the relative position of the prey at all times. This memory of prey position is frequently expressed in the form of a reorientation turn to face the expected position of the prey (Fig. 1). Each reorientation can be considered to initiate a new segment of the pursuit. 4. Phidippus employ the immediate direction (or route) of pursuit as a reference direction, for the determination of prey position (Figs. 3 and 4). The spider compensates for its own movement in determining the direction of the prey from a new position (Fig. 5). 5. The spider retains a memory of the prey direction with reference to gravity (Fig. 6); this memory of the inclination of prey direction can take precedence over conflicting information based upon the use of the route as a reference direction (Figs. 7 and 8). 6. Visual cues provided by both the background and the immediate plant configuration can be used by the spider to determine a (radial) direction in the plane perpendicular to the route of pursuit (Fig. 9, Table 2). 7. The jumping spider must employ at least two independent reference systems (route direction, gravity, visual cues) in concert to determine the position of the prey in space (Fig. 10 and Table 3, Fig. 11). 8. Apart from the context of predatory pursuit, the indirect pursuit of visually determined objectives is a general feature of the movement of salticid spiders upon vegetation.