Phototactic Behavior of Henosepilachna Vigintioctomaculata Motschulsky (Coleoptera: Coccinellidae)

The potato ladybird beetle, Henosepilachna vigintioctomaculata Motschulsky, is a common phytophagous pest of many crops worldwide. At present, there are few published studies available on environmentally friendly management of this pest, compared with those on the use of chemical pesticides. The few studies that are available have suggested that the phototactic response of this beetle could be exploited in its management. We studied the phototactic behavior of H. vigintioctomaculata in response to 17 wavelengths of monochromatic lights and 10 illumination intensities of three of these wavelengths. The beetles showed a positively phototactic response to most wavelengths from 340 to 689 nm, except for the blue wavelength (492 nm). In addition, the beetles exhibited varying levels of sensitivity to illumination intensities from 10 to 190 lux under ultraviolet (UV) (340 nm), red (649 nm), green (510 nm), and white light. The general overall pattern of phototactic response rate, from short to long wavelengths, was a U-shaped curve. Thus, the beetles were most sensitive to UV light and red light. The response of the beetles to illumination intensity was correlated with light wavelength; therefore, the phototactic response rate (PRR) to UV light was always higher compared with the PRRs to other light. Our results highlight the positive phototactic behavior of H. vigintioctomaculata to different light wavelengths and illumination intensities. Such behavior could be exploited for noninvasive management using colored lights to control this important agricultural pest.