【Abstract】 Objective To investigate the resistance of Culex tritaeniorhynchus to insecticides used frequently in high incidence areas of Japanese encephalitis in Shaanxi province. Methods The density of mosquitoes was calculated by labor hour method. Larva death rate of five insecticides and LC50 of eight insecticides were determined by distinguishing dosage method and median lethal dose method respectively. Results The average density of Cx.tritaeniorhynchus in breeding farm was 194.91/man· hour. The mortality of mosquitoes in Nanzheng, Hanyin, Hanbin and Pingli county was 1.84％-13.65％ and 10.86％-31.25％ after treatment by DDVP and deltamethrin for 24 h. Maximum LC50 of the same insecticide in different areas was1.27-8.00 times of the minimum. Conclusion Cx.tritaeniorhynchus developed different resistance to tested insecticides in four investigation sites, except that it was susceptible to cypermethrin in Hanbin, Nanzheng county and to DDT in Pingli, Nanzheng county. Cx.tritaeniorhynchus populations had developed high resistance to DDVP and deltamethrin, moderate resistance to permethrin. Rotational or mixed use of insecticides with different action mechanisms should be adopted to postpone the development of insecticide resistance.

【Abstract】 Objective To test the control efficacy of different chemicals to Culex pipiens pallens. Methods The methods of laboratory efficacy test for aerosol and simulated field efficacy test were used in this study. Results KT₅₀ values of seven aerosols to Cx.pipiens pallens was 1.30-4.40 min, and the mortality rate was about 95.0%-100% after treatment for 24 h. The knockdown rate and the mortality rate were all within 93.0%-100% after treatment in the simulated field for 1h and 24 h. The control efficacy of seven chenmicals accorded with the national standards, but there was still more significant difference among them. Conclusion The control efficacy of 0.05% tetramethrin·cypermethrin was the best, which had the characteristics of fast knockdown, high mortality and low cost.

Objective To provide scientific data for deratization by comparing the control effect of coumatetraly,brodifacoum and sodium diphacinone in the laboratory and the field.Methods Selective feeding method in single cage was used to determine the palatability of the poison baits and the control effect in the laboratory.A hennery in dingbian county and two sanitariums in the suburbs of xi'an were selected as test fields and the powder trace method was used to determine the rodent density.Results The feeding indexes to coumatetraly,brodifacoum and sodium diphacinone were 0.61,0.24 and 0.51 respectively,which reached A,B and A grade respectively.The corrected mortality in the laboratory was 100%,reaching A grade.And that in the field were 91.34%,80.94% and 88.39% respectively,which also reached A,B and B grade respectively.Conclusion Three anticoagulants had good palatability and good control effect in the laboratory.Especially,the control effect of coumatetraly was the best among three anticoagulants.

Objective To grasp the ecological feature of nocturnal rodents in plague epidemic areas, Shaanxi province. Methods The nocturnal rodents were captured in different habitat every month. The parasitic fleas were collected, dissected and observed, as well as do plague bacillus culture and serum detection. Results 192 nocturnal rodents of 8 species were captured. Of which, the Cricetulus barabensis was the dominant specie. The quantity of nocturnal rodents was higher in spring and summer than in autumn and winter. The Cr.barabensis inhabits adult woods and the Meriones meridianus inhabits dikes and semifixed dunes. 188 parasitic fleas, which belonged to 8 species of 8 genera of 4 families, were collected from the nocturnal rodents. The Neopsylla bidentatiformis and Xenopsylla conformis conformis were dominant species. The reproduction peak of nocturnal rodents was in summer. The dominant nocturnal rodents could be infected by the plague bacillus. Conclusion The ecological feature of nocturnal rodents in plague epidemic areas, Shaanxi province is different from that in other areas. It is important for the efficient prevention and control of plague to monitor systematically rodent density and detect serum.

Objective To separate automatically the imagoes and larvae of Blattela germanica.Methods Put the Blattela germanica's imagoes and larvae which attach to the zigzag slips into one side of the vat of separate apparatus,together with the slips,and in another side the vat,put food and water to make a temptation.Results On the fourth day the separative rate of germanica's imagoes and larvae was above 50%,above 90% on the sixth day.Conclusion Depending on temptation of food and water,the separate apparatus can separate the Blattela germanica's imagoes and larvae automatically,and the ages of acquired larvae are uniform on the whole.