Figure 2.

Examples of insect responses to linearly polarized reflections from other substrates. Any shiny, non-metallic surface can produce linearly polarized reflections from unpolarized sunlight, as shown for the example of a flower, where both flowers and leaves can produce this stimulus (symbolized by the double headed arrows) and carry different kinds of information for insects. (1) Blood-sucking horse flies (Tabanidae) are strongly attracted by objects reflecting linearly polarized light (a fact exploited in horse-fly traps). The facts that horses and cattle reflect linearly polarized light is in agreement with these insects using this stimulus to detect their prey. (2) The exocuticle of several species of scarab beetles (Coleoptera) was shown to reflect circularly polarized light, yet it remains unclear whether this stimulus can be perceived by the animals (i.e., rightward- vs. leftward circularly polarized light), since contradicting behavioral studies exist. (3) Bumblebees (Hymenoptera) can be trained to learn different patterns of polarized light, reminiscent of the patterns that could be produced by blooming flowers, suggesting this stimulus may influence their pollenating activity. (4) It is unlikely that female mosquitoes (Nematocera) are attracted by linearly polarized reflections off the body surface of their prey and olfactory stimuli (sweat, CO₂) clearly dominate. Nevertheless, optomotor responses to alternating stripes of orthogonally oriented polarization demonstrate the existence of polarization sensitivity in the ventral half of the retina. (5) Linearly polarized reflections represent an important stimulus for different butterfly species (Lepidoptera): for instance, reflections off the body surface of conspecifics are an important cue for identifying potential mates in an otherwise cluttered, optically rich environment. Furthermore, reflections off leaves bear important information about how well-suited they are as an oviposition site.