| The sensitivity of three Musca domestica populations (Org, JS and TA) tofour organophosphrous and two carbamate insecticides were determined byglass vial bioassay method. The results showed that among the threepopulations, the laboratory population Org was most sensitive to all theinsecticides tested except diazion, the TA population was most insensitive.The sensitivity of acetylcholinesterase(AChE) of six populations (Org,JS,TA,TCm,TCt and XWt) to methamidophos and methomyl were also tested,the results indicated that the AChE of Org was also more sensitive to the twoinsecticides than those of other two populations. These results demonstratedthat the sensitivity of Musca domestica to organophosphates and carbamatesdetermined by traditional bioassay method were closely correlated with thesensitivity of their AChE. Therefore, the sensitivity of AChE could beimproved by breeding more sensitive housefly in laboratory. The preparationof susceptible housefly maybe speed up by selecting the parents from Orgpopulation.The susceptible population was selected 4 generations in this study.Comparing to the origin parent housefly, the LC50 values of the offspring tomethamidophos and methomyl decreased, but the confidence limitsoverlapped. The IC50 of methamidophos and methomyl to AChE in theselected strains and original parent houseflies were also conducted. The resultsshowed that the sensitivity of AChE weren,t improved significantly by singlepair selection method, which is consistent to the bioassay results, thatsuggested that the Org population was very sensitive to methamidophos andmethomyl, and it was difficult to get more sensitive offsprings by thetraditional selection of single pair selection method.The sensitivities of AChE in different old housefly were also studied, theresults showed that the sensitivity of AChE to methamidophos and methomylwas most sensitive in the third day after emergence. The IC50 ofmethamidophos and methomyl to the AChE was 3.001±0.031μg/ml and0.319±0.003μg/ml respectively. We also found that the specific activity ofAChE in the head part was higher than those in other parts of the housefly. SoAChE in the head part of 3-days old of housefly was used for pesticidesresidue determination. The inhibition rate of pesticides to AChE were determined under differenttemperature and reaction time. The results showed that the inhibition rate ofmethomyl to AChE was changed evidently with the inhibition time increasedand it began to decrease after inhibition for 30s. While the inhibition rate ofmethamidophos increased all the time. The inhibition rate of methomyldecreased as the temperature going up, but the inhibition rate ofmethamidophos increased at the range of 25℃to 35℃, and reached thehighest at 35℃. Because the rapid and lower limit were required for detectionthe pesticide residue, and the organophosphate were maily used toxicpesticides, so the inhibition time and temperature were defined as 15 min and35℃respectively. The sensitivity and detection limit of BuchE and extracted crude liquid enzyme(AChE)were compared by the rapid detection instrument and terminal method. BuchEwere more sensitive to methamidophos and methomyl than crude liquid enzyme,comparing with the BuchE, the detection limit of crude liquid ( AChE ) tomethamidophos was higher, to Methomyl, which was only 1.06 fold when the rapiddetection instrument was used. The results determined by terminal method showed thatthe detection limit of BuchE to methmidophos was lower than that of extracted crudeliquid(AChE), but to Methomyl which was contrary. After conserved for 130 days at 4℃,The activity of AChE enzymepowdery of Musca domestica was 1.625 ±0.031(OD·mg-1·min-1), 12.9% lowerthan that of former crude liquid enzyme. Compared to that of the first day, the...
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