AbstractThe spectral sensitivity of the compound eye in a moth (Manduca sexta) was tested electrophysiologically by extracellular recordings in the wavelength region 310 to 650 nm, a) during dark‐adaptation, and b) during exposure to violet (408 nm) and red (680 nm) light. Sensitivity maxima were found at 370 to 390 nm, 450 to 470 nm, and 530 to 550 nm. During exposure to violet light a larger decrease in sensitivity was found for the maxima at 370 to 390 nm and 450 to 470 nm compared to that at 530 to 550 nm. During exposure to red light a larger decrease in sensitivity was found for the latter maximum. The results are interpreted as evidence for at least two photoreceptor types with different spectral sensitivity maxima. Intracellular recordings from single photoreceptors showed maxima in the same wavelength regions as those found extracellularly. The spectral sensitivities obtained were approximately similar. The homogeneity of the intracellular recordings is suggested to be due to interreceptor couplin