Barrier Effect And Repairing Behaviors Of Brochosomal Integuments Of Empoasca Onukii Matsuda

Brochosomes,covering on the Empoasca onukii Matsuda’s integument,are reported to be superhydrophobic.The barrier effect of brochosomal integuments to insecticide droplets was studied in this paper,and then the methods which could damage the brochosomal layer on the body surface of the leafhopper were analyzed.The repairing behaviors of the brochosomal layer were observed and analyzed.The research results are as follows:1.The barrier effect of the brochosomal layer to insecticide droplets on the leafhopper wing surface was analyzed.The dynamic behaviors of insecticide droplets touching the body surface of leafhopper were observed,and the droplets did not roll off automatically on the wing surface covered with brochosomes.72.0% leafhopper adults kept still until the droplets evaporated,and the insecticide droplets will turn into granules or irregular spots after evaporation,and the granules were removed by grooming behaviors of leafhopper in 24 h.The contact angles of the insecticide droplets on the leafhopper wing surface were significantly changed after the removal of brochosomal integuments,which was reduced by 35.4%.The contact micromorphologies between the droplets and the brochosomal integuments were analyzed.The SEM images showed that the contact of the droplets and the brochosomal integuments would cause the brochosome agglomeration,and some brochosomes were integrated with the dried solute.Some drying droplets were turned into spots on the wings with brochosomes detachment.The brochosomal layer covering uniformly on the leafhopper integument will play a barrier effect to the insecticide droplets which touching the surface of the leafhopper.2.The damage effect of adverse environmental conditions and artificial additives to the brochosomal integument of leafhoppers was tested by indicator-spot-method.The results showed that the granules were found on the wing surface of the leafhopper in the treatments of simulated adverse environments,such as natural dust covering,high humidity conditions and rainfall situation,which indicating that the natural conditions would not cause obvious damage to the brochosomal integument.The spot rate of insecticide spraying was only 23.0 ± 5.9%,and the treatment with organosilicon additive Silun 500 mg/L was 54.0 ±7.1%,which indicated that the use of additives could destroy the brochosomal integument effectively.3.The rhythm change of brochosomal secretion of the tea green leafhopper after destruction was analyzed.The interval time between destruction and brochosomal secretion were recorded,which were 22.33± 1.80 h in spraying treatment and 22.71 ± 2.70 h in brushing treatment,which were significantly shorter than the control treatment 30.33 ± 11.67 h.The number of brochosomal secretion times in 5 days was 8.3 ± 1.0 in the spraying treatment and 7.7 ± 1.5 in brushing treatment,which was significantly more than the number of the control treatment,4.6 ± 1.1times.However,the droplets of brochosomal secretion,the anointing rounds and the grooming times in the treated leafhopper groups were not significantly different from the control group.The results showed that the destruction of the brochosomal integument would induce the leafhopper to accelerate brochosome secretion and repairing.4.The organs which related to the brochosomal integument repairing of the tea green leafhopper were analyzed by the organ destruction method.The brochosome field on the leafhopper wing was destroyed by physical measure and the white brochosomal spots were still found in all the treated insects after destruction.While the destruction of hindleg tibial setae by dilute hydrochloric acid,the leafhoppers secreted brochosome droplets as normal,but some insects could not successfully transfer brochosomal droplets to the brochosome fields,and some insects could not squeeze the droplets normally.SEM images showed the top of the hindleg setae became bent after softened by dilute hydrochloric acid,which generate unsuccessful brochosome anointing of the leafhopper.The setae of the leafhopper hindleg tibia play a key role in the repairing behaviors of the brochosomal integument.