title: New kind of polarotaxis governed by degree of polarization: attraction of tabanid flies to differently polarizing host animals and water surfaces.
abstract: 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.
authors.affiliation: Environmental Optics Laboratory, Department of Biological Physics, Physical Institute, Eötvös University, Pázmány sétány 1, 1117, Budapest, Hungary.
authors.forename: Ádám
authors.initials: Á
authors.lastname: Egri
authors.forename: Miklós
authors.initials: M
authors.lastname: Blahó
authors.forename: András
authors.initials: A
authors.lastname: Sándor
authors.forename: György
authors.initials: G
authors.lastname: Kriska
authors.forename: Mónika
authors.initials: M
authors.lastname: Gyurkovszky
authors.forename: Róbert
authors.initials: R
authors.lastname: Farkas
authors.forename: Gábor
authors.initials: G
authors.lastname: Horváth
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000502:physiology*; D003463:Cues; D004175:Diptera / Q000502:physiology*; D005260:Female; D008027:Light; D008297:Male; D014867:Water
chemical_list: D014867:Water