Prey size selection and distance estimation in foraging adult dragonflies

Abstract

To determine whether perching dragonflies visually assess the distance to potential prey items, we presented artificial prey, glass beads suspended from fine wires, to perching dragonflies in the field. We videotaped the responses of freely foraging dragonflies (Libellula luctuosa and Sympetrum vicinum-Odonata, suborder Anisoptera) to beads ranging from 0.5 mm to 8 mm in diameter, recording whether or not the dragonflies took off after the beads, and if so, at what distance. Our results indicated that dragonflies were highly selective for bead size. Furthermore, the smaller Sympetrum preferred beads of smaller size and the larger Libellula preferred larger beads. Each species rejected beads as large or larger than their heads, even when the beads subtended the same visual angles as the smaller, attractive beads. Since bead size cannot be determined without reference to distance, we conclude that dragonflies are able to estimate the distance to potential prey items. The range over which they estimate distance is about 1 m for the larger Libellula and 70 cm for the smaller Sympetrum. The mechanism of distance estimation is unknown, but it probably includes both stereopsis and the motion parallax produced by head movements.

The relative roles of vision and chemosensation in mate recognition of Drosophila.

“…Males responded similarly to dummies whether they were perfumed with male D. melanogaster or D. simulans pheromone, perhaps because males of both species produce similar inhibitory compounds. The ability to visually distinguish among dummies and selectively pursue only those that match specific criteria has been extensively studied in other arthropods (Wehner, 1981) including dragonflies (Olberg et al, 2005), blowflies (Boeddeker et al, 2003) and horseshoe crabs (Barlow et al, 1982). Our study suggests that D.…”

Linking biomechanics and ecology through predator–prey interactions: flight performance of dragonflies and their prey

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Local and Large-Range Inhibition in Feature Detection

“…Dragonflies are particularly efficient hunters that detect and plot intercept courses for prey in the frontodorsal visual field (Baird and May, 1997;Olberg et al, 2000Olberg et al, , 2005Olberg et al, , 2007. Dragonflies have been shown behaviorally to be very selective about which targets they pursue, using a variety of selection criteria including target size and distance (with the latter presumably well correlated with apparent speed) (Olberg et al, 2005).…”

“…Dragonflies have been shown behaviorally to be very selective about which targets they pursue, using a variety of selection criteria including target size and distance (with the latter presumably well correlated with apparent speed) (Olberg et al, 2005). Interestingly, many dragonflies will selectively pick off individual targets amid a swarm and may assume foraging locations closer to the prey when they aggregate in a swarm May, 1997, 2003).…”