The phototaxis and photophobia of Callosobruchus maculatus Fabricius and Acanthoscelides obtectus Say to light of different wavelengths and intensities
Callosobruchus maculatus Fabricius and Acanthoscelides obtectus Say(Cleoptera,Bruchidae)are important quarantine insect pests in agriculture in China.However,the phototaxis of both species has not been documented,and it is not clear whether light trap could be used for detecting or controlling them.To address this gap,we examined the phototactic responses of their adults to an array of monochromatic lights and varying light intensities.Furthermore,we observed the distribution patterns of adult C.maculatus and A.obtectus carried in goods under simulated cabin opening scenarios,aiming to determine the feasibility of adopting specific light sources to trap these beetles.The results showed that both C.maculatus and A.obtectus had positive phototaxis to each of the five monochromatic light sources,with the phototaxis rates ranging from 8.9%to 36.6%and 20.5%to 33.3%,respectively.Notably,among the monochromatic lights tested,the green light(520 nm)was most attractant for C.maculates adults,eliciting phototatic rates of 24.4%and 36.6%in female and males,respectively.However,A.obtectus adults prefered blue light(460 nm)among females and red light(620 nm)among males,both achieving phototactic rates exceeding 32%.Both sexes of A.obtectus showed a strong preference to the black light,achieving phototactic rates over 50%across all three tested light intensities,which were significantly higher than those of C.maculatus.Additionally,we discovered that the duration of exposure to light following simulated cargo hold opening had a profound impact on the spatial distribution of adult beetles,with the highest proportion of adults occurring on grain surface or walls of the container within the first hour.In conclusion,C.maculatus and A.obtectus had certain phototactic behaviors towards some light wavelengths,suggesting the potential of exploiting these behaviors in quarantine inspections and pest managements.
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