Why is it worth flying at dusk for aquatic insects? Polarotactic water detection is easiest at low solar elevations

B. Bernáth, József Gál, Gábor Horváth

Research output: Contribution to journalArticle

30 Citations (Scopus)

Abstract

Using 180° field-of-view imaging polarimetry, we measured the reflection-polarization patterns of two artificial surfaces (water-dummies) in the red, green and blue spectral ranges under clear and partly cloudy skies at different solar elevations. The dummies consisted of a horizontal glass pane with a matt black or matt light grey cloth underneath, imitating a dark or bright water body, respectively. Assuming that polarotactic water insects interpret a surface as representing water if the degree of linear polarization of reflected light is higher than a threshold and the deviation of the direction of polarization from the horizontal is lower than a threshold, we calculated the proportion, P, of the artificial surfaces detected polarotactically as water. We found that at sunrise and sunset P is maximal for both water-dummies and their reflection-polarizational characteristics are most similar. From this, we conclude that polarotactic water detection is easiest at low solar elevations, because the risk that a polarotactic insect will be unable to recognize the surface of a dark or bright water body is minimal. This partly explains why many aquatic insect species usually fly en masse at dusk. The daily change in the reflection-polarization pattern of water surfaces is an important visual ecological factor that may contribute to the preference of the twilight period for habitat searching by polarotactic water insects. Air temperature at sunrise is generally low, so dusk is the optimal period for polarotactic aquatic insects to seek new habitats.

Original languageEnglish
Pages (from-to)755-765
Number of pages11
JournalJournal of Experimental Biology
Volume207
Issue number5
DOIs
Publication statusPublished - Feb 2004

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aquatic insects
Insects
flight
insect
Water
polarization
water
Body Water
insects
body water
Ecosystem
surface water
twilight
habitat
field of view
detection
habitats
air temperature
glass
Glass

Keywords

  • 180° field-of-view imaging polarimetry
  • Aquatic habitat recognition
  • Dusk-flying water insects
  • Polarization sensitivity
  • Polarotaxis
  • Reflection polarization

ASJC Scopus subject areas

  • Agricultural and Biological Sciences(all)
  • Agricultural and Biological Sciences (miscellaneous)

Cite this

Why is it worth flying at dusk for aquatic insects? Polarotactic water detection is easiest at low solar elevations. / Bernáth, B.; Gál, József; Horváth, Gábor.

In: Journal of Experimental Biology, Vol. 207, No. 5, 02.2004, p. 755-765.

Research output: Contribution to journalArticle

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