title: Unexpected attraction of polarotactic water-leaving insects to matt black car surfaces: mattness of paintwork cannot eliminate the polarized light pollution of black cars.
abstract: The horizontally polarizing surface parts of shiny black cars (the reflection-polarization characteristics of which are similar to those of water surfaces) attract water-leaving polarotactic insects. Thus, shiny black cars are typical sources of polarized light pollution endangering water-leaving insects. A new fashion fad is to make car-bodies matt black or grey. Since rough (matt) surfaces depolarize the reflected light, one of the ways of reducing polarized light pollution is to make matt the concerned surface. Consequently, matt black/grey cars may not induce polarized light pollution, which would be an advantageous feature for environmental protection. To test this idea, we performed field experiments with horizontal shiny and matt black car-body surfaces laid on the ground. Using imaging polarimetry, in multiple-choice field experiments we investigated the attractiveness of these test surfaces to various water-leaving polarotactic insects and obtained the following results: (i) The attractiveness of black car-bodies to polarotactic insects depends in complex manner on the surface roughness (shiny, matt) and species (mayflies, dolichopodids, tabanids). (ii) Non-expectedly, the matt dark grey car finish is much more attractive to mayflies (being endangered and protected in many countries) than matt black finish. (iii) The polarized light pollution of shiny black cars usually cannot be reduced with the use of matt painting. On the basis of these, our two novel findings are that (a) matt car-paints are highly polarization reflecting, and (b) these matt paints are not suitable to repel polarotactic insects. Hence, the recent technology used to make matt the car-bodies cannot eliminate or even can enhance the attractiveness of black/grey cars to water-leaving insects. Thus, changing shiny black car painting to matt one is a disadvantageous fashion fad concerning the reduction of polarized light pollution of black vehicles.
authors: Environmental Optics Laboratory, Department of Biological Physics, Physical Institute, Eötvös University, Budapest, Hungary.
authors: Miklos
authors: M
authors: Blaho
authors: Environmental Optics Laboratory, Department of Biological Physics, Physical Institute, Eötvös University, Budapest, Hungary.
authors: Tamas
authors: T
authors: Herczeg
authors: Group for Methodology in Biology Teaching, Biological Institute, Eötvös University, Budapest, Hungary; Danube Research Institute, Centre for Ecological Research, Hungarian Academy of Sciences, Budapest, Hungary.
authors: Gyorgy
authors: G
authors: Kriska
authors: Environmental Optics Laboratory, Department of Biological Physics, Physical Institute, Eötvös University, Budapest, Hungary.
authors: Adam
authors: A
authors: Egri
authors: Environmental Optics Laboratory, Department of Biological Physics, Physical Institute, Eötvös University, Budapest, Hungary.
authors: Denes
authors: D
authors: Szaz
authors: Environmental Optics Laboratory, Department of Biological Physics, Physical Institute, Eötvös University, Budapest, Hungary.
authors: Alexandra
authors: A
authors: Farkas
authors: Danube Research Institute, Centre for Ecological Research, Hungarian Academy of Sciences, Budapest, Hungary.
authors: Nikolett
authors: N
authors: Tarjanyi
authors: Environmental Optics Laboratory, Department of Biological Physics, Physical Institute, Eötvös University, Budapest, Hungary; Group for Methodology in Biology Teaching, Biological Institute, Eötvös University, Budapest, Hungary.
authors: Laszlo
authors: L
authors: Czinke
authors: Environmental Optics Laboratory, Department of Biological Physics, Physical Institute, Eötvös University, Budapest, Hungary.
authors: Andras
authors: A
authors: Barta
authors: Environmental Optics Laboratory, Department of Biological Physics, Physical Institute, Eötvös University, Budapest, Hungary.
authors: Gabor
authors: G
authors: Horvath
mesh_terms: D000818:Animals; D001522:Behavior, Animal; D007313:Insecta; D008027:Light