PHOTOEFFECTS OF VISIBLE AND ULTRAVIOLET RADIATION ON THE TWO-SPOTTED SPIDER MITE, TETRANYCHUS URTICAE

Abstract— The ability of the two-spotted spider mite, Tetranychus urticae Koch, to detect and avoid various wavelengths was examined. The mites were given a choice between two regions: an area on a leaf exposed to light of defined spectral composition or an area protected from certain selected wavelength components. The mites showed little avoidance of visible, UV-A or UV-C wavelengths. In contrast, the animals strongly avoided the UV-B spectral region, indicating that this arthropod can discriminate and respond to the presence of UV-B wavelengths. The adult mites did not appear to be killed by the amount of UV-B they could receive on a sunny summer day in Kentucky (i.e. 20 SU). However, the egg laying capacity of the females was reduced in a linear fashion as dose increased. Thus, avoidance of high UV-B regions on a leaf may contribute to the survival of the species in nature.