The ectoparasitoid beetle, Dastarcus helophoroides (Fairmaire) (Coleoptera: Bothrideridae), has been widely used as a biological control agent for many cerambycid beetles in China, Korea, and Japan. However, much less is known about its phototactic behavior to visual stimuli. In this paper, the phototactic behavioral response of D. helophoroides to 27 monochromatic lights and to nine illumination intensities of the most attractive light was evaluated using light-emitting diodes (LEDs) as light sources. The results showed that in dual choice between darkness and individual LED light, D. helophoroides adults exhibited a positively phototactic response to all wavelengths ranging from 300 to 860 nm. The near-infrared light (NIR, ranging from 700 to 760 nm) elicited stronger phototactic behavioral response, showing a preference for NIR wavelengths light. In paired choice among four preferred NIR lights, D. helophoroides adults displayed a significantly more favorable response to NIR light at 700 nm. Furthermore, the beetles expressed varying levels of sensitivity to illumination intensities from 1 to 600 lux under NIR light at 700 nm. The phototactic response was strongest at 7 lux and a statistically significant downward trend was found with increasing or decreasing the illumination intensities. These findings clearly demonstrate that D. helophoroides is a positively phototactic insect and its phototactic behavior is significantly influenced by light wavelength and illumination intensity, among which NIR light with peak wavelength at 700 nm and an intensity at 7 lux are most suitable in attracting D. helophoroides adults.
Keywords: Dastarcus helophoroides (Fairmaire); illumination intensity; light wavelength; phototactic response rate; phototaxis.
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