The Visual Structure And Behavior Mechanism Of Phototaxis Of Megalurothrips Usitatus Bagnall

Bean flower thrips,Megalurothrips usitatus Bagall,is one of the economically important insect pests of leguminous crops in china,many leguminous crops are widely distributed throughout tropical and subtropical areas,including Guangxi,Guangdong,Hainan,Taiwan,and other provinces.Thrips damage is caused by direct feeding,ovipositing and transmitting plant tospoviruses.Thrips is very difficult to control due to its biological characteristics such as a high reproductive rate,low sensitivity to number of commercially available insecticides,ovipositing in plant tissues,and pupating in the soil.At present,M.usitatus mainly rely on chemical control,and the production excessive use of pesticides and the residual excess lead to the "poison cowpea" event frequency.Therefore,the aim of this study is to provide a scientific basis for the development of light and efficient light and efficient monitoring and control technology based on light color,which is based on the research on the phototaxis behavior of ordinary thrips and its compound eye structure.The main results are as follows:The external morphology of the compound eye of M.usitatus were observed by using a scanning electron microscopy(SEM).Results showed that the compound eye was locted on both sides of the haed,the compound eyes both of male and female were a quarter of the ellip soid and slightly outward convex.Male and female eyes have approximately 65 and 74 ommatidia.The ommatidium in the central region were in regular hexagon and lined closely,while those in the rim were not close.There were some sense hair between the ommaitia of compound eye of male and female.Transmission electron microscopy(TEM)observations showed the the thickness of cornea was 4.0 ?m,while the outer and inner radius of curvature was 4.52 ?m and 6.05 ?m.Repectively,the cornea was muli deck,and in longitudinal sections the laminations appear strongly curved.Below the cornea of each ommatidium was crystalline composed of four cone cell.The study revealed that M.usitatus possesses an opposition eye,and have the following feature: O mmatidial units consist of the diptric apparatus(made up of the cornea and crystalline)and the photoreceptor(composed of small omentum,rhabdom and basement mermbrance).Furthermore,more ommatidium contained a pair of primary pigment cells as well as some secondary pigment cell.The study used ten color sticky traps in laboratory and field to study the color preference of M.usitatus.The results showed that: adult had the highest trend rates to bule and followed by light blue and purple.Then,The study used the RGB mode,combined converting RGB values to virtual wavelengths and spectral reflectance to study the most preferred colors of M.usitatus.The laboratory tests screened six virtual wavelength blue between 440 nm-490 nm,and we found that the attractiveness of color with 470 nm virtual wavelength significantly higher than the other.The color taxis of M.usitatus was experimented with five-colored LED,blue(461±5 nm),green(519±5 nm),yellow(570±5 nm),red(650±5 nm),white and black(CK),the results showed that: Adult had the highest trend rates to bule(461±5 nm)and the lowest trend rates to black when exposed to light.In addition,the phototactic rations of M.usitatus adults are affected by age,mating status had a significant effet on the phototaxis of both males and females,phototaxis in males was significantly inhibited by mating but mated females showed stronger phototaxis than virgin females.To clarify the daily rhythm of M.usitatus population,blue sticky traps were used for trapping and monitoring.The daily activity rhythm of the M.usitatus population showed a regular regularty,the daily active peak was 8:00-10:00,10:00-12:00 followed and they were inactive at night.All M.usitatus behaviors were observed by pair(male and female)rearing individually in the laboratory.The results showed that the major behaviors were resting,accounting for 65.85 %,while mating was minimum,accounting for 0.09%.There are significant differences in diurnal time of various behaviors.The peak of foraging was recorded at 8:30-9:30,the peak of moving was recorded at 10:00-11:00,and the peak of resting were 3:00-4:00 and 22:00-23:00.Analysis found that the happen percentages of various behavious had significant different time period of all day.The happen percetages of resting at night higher than those at day,but foraging,moving and mating at day wre higher than those at night.