A field study of the phototactic response of Phlebotominae sand flies (Diptera: Psychodidae) to long-wavelength red light in northeast Brazil

Light-emitting diode (LED)-based light trapping has been adopted for monitoring sand flies, vectors of leishmaniasis. Among colors, blue-green wavelengths have been the most efficient light sources, whereas the long-wavelength red light is the least preferred. However, certain preference of some species of sand flies for this wavelength was already reported. Therefore, the objective of this study was to assess the phototactic response of sand flies to different intensities of red light in two areas (forest and peridomicile) of northeast Brazil. Sand flies were collected with LED-baited Silva Suction (SS) traps, being three green-baited SS traps (520 nm) and three red-baited SS traps (650–750 nm), each with different light intensities. A total of 1,935 sand flies were collected in the forest and 903 in the peridomicile. In the forest, Sciopemyia sordellii was the most frequent species (38.24%), followed by Evandromyia lenti (17.31%), Ev. saulensis (15.50%) and Bi. flaviscutellata (8.89%). Green-baited SS traps (31.50 ± 2.83) collected significantly more sand flies than the red-baited SS trap (22.25 ± 2.46). Differently of most species, Sc. sordellii and Bi. flaviscutellata were equally attracted to both wavelengths. In the peridomicile, red-baited (17.75 ± 1.79) and blue-baited (19.88 ± 2.01) traps were equally effective in sampling Lutzomyia longipalpis , the most collected species (96.6%). An intensity-dependent phototactic response to both wavelengths was observed. In general, sand flies respond to the long-wavelength red light in a species-specific manner and the question whether they perceive light in the red region of the spectrum is still open.