用浸叶法测定了采自我国不同地区（泰安、莱阳、南京、北京和安阳）的棉蚜品系Ⅰ、Ⅱ、Ⅲ、Ⅳ、Ⅴ对久效磷、甲胺磷、抗蚜威和灭多威等杀虫剂的抗性水平，各棉蚜品系对杀虫剂的抗性依次为Ⅴ>Ⅳ>Ⅲ，Ⅱ>Ⅰ。进一步研究表明，Ⅴ和Ⅳ品系棉蚜乙酰胆碱酯酶对杀虫剂的敏感性显著下降，Ⅱ品系次之，Ⅲ和Ⅰ品系接近于敏感品系。Ⅴ和Ⅳ品系乙酰胆碱酯酶的Km值显著下降，表明酶发生了质的变化。不同棉蚜抗性品系的酯酶（全酯酶和羧酸酯酶）活性均显著升高，其中Ⅲ品系的酯酶活力为Ⅱ品系的2倍。Ⅴ品系羧酸酯酶Km值达2460.4μmol/L，而Ⅳ品系仅为84.4μmol/L，该两个品系羧酸酯酶发生了质的变化。研究结果表明，不同抗性程度的棉蚜品系均存在代谢抗性和靶标抗性。低抗水平的棉蚜品系，以代谢抗性为主，靶标抗性为辅；中抗水平的棉蚜品系，抑或由于解毒代谢酶的活性显著增强，也可能由于靶标的敏感性显著下降；而高抗水平的棉蚜品系，依赖于代谢抗性和靶标抗性的联合作用。

gossypii Glover. The procedure involved filtration on a sephadex G-25 column, separation with sephadex G-200 and procainamide offinity column. AChE from both susceptible and resistant strains were purified to a single band as resolved on denaturing polyacrylamide gel electrophoresis (SDS-PAGE). The specific activity increased by 35, 100- and 33, 680-fold with a yield of 30.3 and 29.8%, respectively. The molecular mass of the purified AChE was about 63, 500 Dalton as etermined by SDS-PAGE. However, three bands resolved on PAGE gel electrophoresis, leading to the inference that native AChE exists in three forms. The optimum conditions for measuring the activity of purified AChE with kinetic method were 0.02M phosphate buffer, pH7.2, 0.02mM 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB), AND 25℃. Investigation also revealed that crude extract and purified AChE had different kinetic characteristics and inhibiroty properties. They responded differently to varied DTNB, ATChI, and phosphate buffer ion concentrations, as well as pH, temperature, and inhibitors. The purified AChE was more sensitive to eserine, methamidophos, and pirimicarb. Especially for resistant aphids, the sensitivity of purified AChE to methamidophos and pirimicarb was enhanced 6.43 and 11.73 times, respectively. We infer that one or more factors in the crude extract from the resistance stain have more influence on AChE sensitivity. Further study is needed to investigate the basis of these observations.

Observation of the oviposition behavior of cotton bollworm demonstrated the existence of substances that can act as oviposition deterrents. The scales, abdomens and tarsi of the moths, the most likely carrier, were extracted for the substances. An acetone extract exhibiting an oviposition deterrent effect was analyzed using gas chromatography and combined gas chromatography-massspectroscopy. Three components, 4-methyl-4-hydroxyl-pentanone-2, hexadecanoic acid and (Z)-9-octadecenoic acid, were identified, being present in the ratio 1:2:2. Experiments with synthetic mixtures indicated that a mixture of equal amounts of the two organic acids exhibited similar repellent and deterrent activity to a synthetic mixture of all three components. It is concluded that the natural oviposition-deterring pheromone is a mixture of hexadecanoic acid and (Z)-9-octadecenoic acid.

A field population of brown planthoppers (Nilaparvata lugens St

ated by the PHYLIP program package inferred that AChE2 of A. gossypii is a more ancestral form of AChE. Homology modeling of structures using Torpedo californica (2ACE_) and Drosophila melanogaster (1Q09:A) native acetylcholinesterase structure as main template indicated that the two AChEs of Aphis gossypii might have different three-dimensional structures. Alternative splicing of Ace1 near the 5’-end resulting in two proteins differing by the presence or absence of a fragment of four amino acids is also reported.