Monochromatic UVA at 365 nm (a, c and e) and polychromatic white light (b, d and f) suppress feeding through TRPA1(A). (a and b) Illumination with 365 nm UVA light excites bitter-tasting neurons of i-a bristles at 42.1 mW/cm2, and the response is dependent on TrpA1 (n = 5–8) (a). Polychromatic white light from a Xenon arc lamp stimulates TrpA1-dependent bitter-sensing neurons at 93.4 mW/cm2, which is similar to natural solar intensity (n = 5–9) (b). Neuronal activation by white light requires UV, as it was abolished upon filtering out UV with the thin titanium dioxide-coated glass. * and #p<0.05, *** and ###p<0.001, Student’s t- or Tukey’s test for the first and second illuminations, respectively. (c and d) UVA (c, n = 4–7) or white light illumination (d, n = 4–7) hinders feeding depending on TrpA1(A). UV blocking from white light significantly reduces feeding avoidance (orange bars). * and #p<0.05, ** and ##p<0.01, *** and ###p<0.001, Tukey test for 2.5 and 5 min, respectively. §, §§ and §§§: p<0.05, 0.01 and 0.001, respectively, Student’s t-tests between illuminations with and without the UV filter. (e and f) UV (e, n = 4–8) and white light (f, n = 4–8) intensity dependences of fly (upper) and mosquito (lower) TRPA1 isoforms heterologously expressed in oocytes. UVB at 295 nm (pale purple) produced higher responses than UVA at 365 nm (dark purple) (e). Blocking the UV component of white light significantly reduces the current elicited by white light illumination (f). The half maximal efficacy intensities of UV and white light are given in the text and Supplement file 1. Student’s t-test between illuminations with and without UV filter. * and #, ** and ##, and *** and ###p<0.05, 0.01, and 0.001, respectively (*: +60 and #: −60 mV).