Why do red and dark-coloured cars lure aquatic insects? The attraction of water insects to car paintwork explained by reflection–polarization signals

Abstract

We reveal here the visual ecological reasons for the phenomenon that aquatic insects often land on red, black and dark-coloured cars. Monitoring the numbers of aquatic beetles and bugs attracted to shiny black, white, red and yellow horizontal plastic sheets, we found that red and black reflectors are equally highly attractive to water insects, while yellow and white reflectors are unattractive. The reflection-polarization patterns of black, white, red and yellow cars were measured in the red, green and blue parts of the spectrum. In the blue and green, the degree of linear polarization p of light reflected from red and black cars is high and the direction of polarization of light reflected from red and black car roofs, bonnets and boots is nearly horizontal. Thus, the horizontal surfaces of red and black cars are highly attractive to red-blind polarotactic water insects. The p of light reflected from the horizontal surfaces of yellow and white cars is low and its direction of polarization is usually not horizontal. Consequently, yellow and white cars are unattractive to polarotactic water insects. The visual deception of aquatic insects by cars can be explained solely by the reflection-polarizational characteristics of the car paintwork.

Phototaxis and polarotaxis hand in hand: night dispersal flight of aquatic insects distracted synergistically by light intensity and reflection polarization

“…The same is true also for the aquatic insect species studied earlier (Csabai et al 2006(Csabai et al , 2012Kriska et al 2006;Csabai 2009, 2013) and also in the present work at the same marsh-land site. Thus, in the case of the PP treatment the relevant optical variable of the plastic sheet was only the horizontal polarization, rather than the higher intensity of reflected light.…”

“…These beetles are good flyers and possess strong positive phototaxis (Scapini et al 1993). Since on the basis of Supplementary Table S1 in our PO treatment they were captured only in a negligible number (N PO = 39, which is only 0.95 % of N total = 4087), while in the PH treatment we captured N PH = 3018 (73.84 %) individuals from this taxon, it seems to be exclusively phototactic, as also concluded by earlier investigators (Csabai et al 2006(Csabai et al , 2012Boda and Csabai 2013). However, in the PP treatment we captured only N PP = 1029 (25.18 %) Heterocerus (Supplementary Table S1), in spite of the presence of intense unpolarized direct light (emitted by the lamp used) presenting a bright phototactic stimulus.…”

“…Boda and Csabai 2009;Yee et al 2009) and abiotic (e.g. Weigelhofer et al 1992) interacting factors resulting in well-defined seasonal and diel dispersal patterns of aquatic insects (Csabai et al 2006(Csabai et al , 2012Boda and Csabai 2013). The regular dispersal flight of aquatic insects can be seriously distracted by various man-made objects Horváth et al 2007;Málnás et al 2011).…”

“…asphalt roads, oil lakes, black plastic sheets used in agriculture, shiny dark-coloured cars, solar panels and collectors) -mimicking the reflection-polarization characteristics of water surfaces -may confuse flying, water-seeking polarotactic water insects. These man-made polarizing reflecting surfaces cause daylong polarized light pollution, that has disastrous consequences for polarotactic insects (Horváth and Zeil 1996;Kriska et al 2006;Bernáth et al 2001;Horváth et al 2009Horváth et al , 2010a.…”

Insights from chironomid oviposition is useful to visual pest control

“…Since misidentification of appropriate oviposition sites is common (e.g. Horváth & Zeil, 1996;Kriska et al 2006;Horváth et al, 2009), polarized reflecting egg-traps should be highly effective in controlling species with a similar life-style to that of C. transvaalensis.…”