家蝇对DDT抗性的研究——Ⅰ.家蝇对DDT及666抗性的形成

STUDIES ON HOUSEFLY RESISTANCE TO DDT——Ⅰ. THE DEVELOPMENT OF RESISTANCE TO DDT AND BHC

一、绪论 家蝇对DDT发生有抵抗性的现象,1946年首先在瑞士被人发现;1947年Sacca在意大利作了第一个详细的调查。接着,在世界各国各地都有了这样的报导。在苏联,及在1950年报道了苏联某一小城市中,在当年施用了DDT之后就发生有抵抗DDT的家蝇。及在1951年又做了进一步的家蝇对DDT发生抗性的观察。

The development of resistance to DDT and BHC in common housefly(Musca dome-stica vicina Macq.) was studied in our laboratory in 1952-1956. Housefly larvae werereared on modified NAIDM medium, the method of culturing had been reported else-where (Sun, 1956). They were treated with DDT or BHC and selected for their tole-rance for successive generations. Three kinds of treatments were compared: adultssprayed with DDT-(or BHC-)acetone solution, larvae treated with DDT-(or BHC-) im- pregnated medium, and double treatment. Different concentrations of the insecticideswere used, for DDT--1% and 3% solution, or 80, 300 and 700 ppm in the medium, forBHC--0.01% and 0.03% solution, or 10 ppm in the medium. Insecticide tolerance was tested by bioasscy with Hoskin's horizontal sprayingchamber and topical application method with microsyringe. Five concentrations or fivedosages of the insecticides were used and the corresponding mortality after 24 hoursobtained. Log. concentration or log. dosage was plotted against probit mortality, andLC_(50) or LD_(50) (medium lethal concentration or medium lethal dosage) was calculated.The LC_(05) of DDT for normal fly was 0.8%, using Hoskin's spraying chamber, the cor-responding value for BHC was 0.008%.The LD_(50) of DDT for normal fly was 0.2γ per fly,using topical application method. After selection for 40 generations (first series) and 24 generations (second series)for DDT resistance, the levels of tolerance were 460 times and 51 times of normal flyrespectively. Similarly, the BHC resistance after 30 generations (first series) and 24generations(second series)of selection were 60--80 times and 58--60 times respectively. In the development of DDT resistance, there were a first period during which theresistance increased very gradually and a second period of rapid increase. The secondperiod began about the 20th generation. In the development of BHC resistance, therewas further a third period of fluctuating resistance, but both the first and the secondperiods were shorter than in the case of DDT resistance. The first period covered the1st to the 8th generation, the second period covered the 9th to the 15th generation andthe third, from 16th generation onwards. In the developmeat of DDT and BHC resistance, adult spraying was more effectivethan larval feeding, the double treatment being intermediate in effect. This possiblywas due to the difference in the mode of entry of insecticides and the time for en-zyme adaptation. In all three kinds of treatments, low concentrations of the insectici-des were more effective than the high concentrations, suggesting that selection wasless important than the induction of adaptive changes. Cross tolerance of these resistant flies was examined. DDT-resistant flies were notmuch resistant to BHC, aldrin, dieldrin and toxaphene, but BHC-resistant flies showedmuch higher degree of resistance to aldrin, dieldrin and toxaphene. Moreover, againstthe results of most other workers, they also showed comparatively high tolerance toDDT. Preliminary survey in several cities in North China had also revealed that house-flies had built up in nature resistance to DDT in these three years, and they werevery conspicuously resistant in 1956.