Studies On Phototaxis Of Chinese Wolfberry Aphid(Aphis Gossypii)

? Objective?Chinese wolfberry is one of the important economic plants in the north of China.It is easy to have insect infestation because of its flourish foliage,and the aphids(Aphis gossypii)have always the largest number of them.At present,the main means of controlling aphids are using chemical drugs,which may lead to environmental pollution and threaten food safety.The methods used in the physical control of the aphids are sticky coloured card and insecticidal lamp,which are well-adapted for most insects but poor targeting to specific one.Therefore,it may trap the beneficial insects and cause the destruction of agricultural ecological balance.The study on the phototaxis of different insects can find the sensitive spectral range of pests and their natural enemy insects,and the results could be used for developing new technology.The structures of compound eyes were studied by scanning electron microscope,phototaxis of Chinese wolfberry aphid(Aphis gossypii)was studied using some of ethology methods and the range of Sensitive spectrum could be found.The results of the paper may supply some data support for the development of more efficient and reasonable prevention and control measures.?Methods?1.The structure of the Chinese wolfberry aphids' compound eyes were studied by scanning electron microscope.Photos were taken and ImageJ1.46 was used to measure the size of compound eyes and ommatidia,and analysis the interommatidial angles.SPSS24.0 was used to analyze the compound eye parameters under different light conditions.2.Monochromatic lights were obtained by using different filters with the central wavelength of 420 nm,450nm,510 nm,550nm,575 nm,583nm and 650 nm,and slide rheostat was used for keeping the same light intensities under different wavelength.The phototaxis of Chinese wolfberry aphid(Aphis gossypii)in different developing stages was tested and the data was collected and analyzed by SPSS24.0.3.Different light intensities,including 200 Lux,350Lux,500 Lux,650Lux and 800 Lux,were obtained using slide rheostat.The phototaxis displacement and response rate of Chinese wolfberry aphid(Aphis gossypii)in different developing stages was tested under the different light intensities.The data was collected and analyzed by SPSS24.0.?Results?1.The compound eyes are oval in shape and located on the lateral sides of the head.Each compound eye consist of about 128 ommatidia.Ommatidia in the central area of compound eyes are smooth and with regular shape,and ommatidia in the edge area are irregular and have smooth surface too.Ommatidia are not closely aligned,but with obvious gap between each other.The interommatidial angle is about 30°.There was no significant difference between experimental groups and the control groups in the compound eye parameters(P=0.7).2.Significant phototaxis was showed by Chinese wolfberry aphid(Aphis gossypii)in different developing stages,which were tested in the same light intensity.All the aphids show the highest response rate under white light.3.The phototaxis displacements under monochromatic light of different wavelengths in visible light wave length in first and second instars are 575nm> 450nm> 550nm> 510nm> 420nm> 583nm> 650 nm,and those phototaxis displacements in third and fouth instars are 575nm> 450nm> 550nm> 510nm> 420nm> 583nm> 650 nm,The phototaxis displacements under monochromatic light of different wavelengths in visible light wave length in wingless adults are 575nm> 450nm> 550nm> 510nm> 420nm> 583nm> 650 nm.Sensitive spectral ranges of aphids in different developing stage are 450-575 nm.4.In light intensity behavior tests,the age of 1-2 instar,3-4 instar and wingless aphids showed similar behavior regularities,that is the stimulus of 200 lux light producing minimum phototaxis rate,and the stimulus of 800 lux light producing maximum phototaxis rate.The aphid's response rates to monochromatic lights increased with the increase of light intensities.First and second instars have the lowest phototaxis displacements and response rates,the phototaxis displacements and response rates of third and fouth instars were almost the same with those of wingless adults.5.There was no significant correlation between phototaxis displacement and response rate in this research.?Conclusion?1.The compound eyes of Chinese wolfberry aphid(Aphis gossypii)were not well developed.Ommatidia were arranged dispersedly and with large interommatidial angles.There was no sensilla and other derived structures.All the characters were matched the characteristics of compound eyes in diurnal insects.2.The most sensitive wavelength of Chinese wolfberry aphid in this research is 575 nm,andthe most sensitive light intensity is 800 Lux.The response rate of aphid to the condition mentioned above may reach more than 80%.