New kind of polarotaxis governed by degree of polarization: attraction of tabanid flies to differently polarizing host animals and water surfaces

• Published in: Die Naturwissenschaften Vol. 99; no. 5; pp. 407 - 416
• Main Authors: Egri, Ádám, Blahó, Miklós, Sándor, András, Kriska, György, Gyurkovszky, Mónika, Farkas, Róbert, Horváth, Gábor
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.05.2012
• Subjects: Animals; aquatic insects; Behavior, Animal - physiology; Biomedical and Life Sciences; canopy; Cues; Diptera - physiology; Environment; Female; field experimentation; habitats; Life Sciences; Light; Male; Original Paper; surface water; Tabanidae; Water; Water detection; Degree of polarization; Polarotaxis; Polarization vision; Visual ecology; Direction of polarization; Host choice; Tabanid fly
• ISSN: 0028-1042; 1432-1904
• DOI: 10.1007/s00114-012-0916-2

Aquatic insects find their habitat from a remote distance by means of horizontal polarization of light reflected from the water surface. This kind of positive polarotaxis is governed by the horizontal direction of polarization (E-vector). Tabanid flies also detect water by this kind of polarotaxis. The host choice of blood-sucking female tabanids is partly governed by the linear polarization of light reflected from the host’s coat. Since the coat-reflected light is not always horizontally polarized, host finding by female tabanids may be different from the established horizontal E-vector polarotaxis. To reveal the optical cue of the former polarotaxis, we performed choice experiments in the field with tabanid flies using aerial and ground-based visual targets with different degrees and directions of polarization. We observed a new kind of polarotaxis being governed by the degree of polarization rather than the E-vector direction of reflected light. We show here that female and male tabanids use polarotaxis governed by the horizontal E-vector to find water, while polarotaxis based on the degree of polarization serves host finding by female tabanids. As a practical by-product of our studies, we explain the enigmatic attractiveness of shiny black spheres used in canopy traps to catch tabanids.