Spectral discriminative ability of larvae of Trogoderma granarium Everts

The photic reaction of larvae of Trogoderma granarium at different spectral ranges indicates a maximum in orange light (λ=600 mμ+) and in blue light (λ max.=440 mμ). The lowest percentage of larvae was caught at violet (λ max.=370 mμ) and green (λ max.=525 mμ). Bilateral illumination with adjacent spectral ranges showed that discrimination between short wavelengths is stronger than between long ones. When given the choice between light and dark, the insects invariably showed a photonegative reaction, which was strongest in blue light (λ max.=440 mμ) and less pronounced in orange and red light. Experiments carried out on responses to orange and blue in different intensity ratios showed that at equal light intensities the photic reaction to orange light exceeds by more than a ratio of 8 : 1 the reaction to blue light. The positive reaction to orange is inversed at orange light intensities above 200 times as high as the intensity of blue light, and the larvae are attracted to blue. Thus, each wavelength range has a specific brightness for the larvae which also depends on its light intensity.