Preliminary Study on Growth and Feeding Amount of Ascotis selenaria Larva

It is necessary to research defoliator development and the feeding law in order to estimate the developmental stage of defoliator in the field,forecast the extent of their damage and establish the prevention strategy scientifically.Ascotis selenaria is a kind of important defoliator pests of soybean.Up to now,there is no consistent conclusion on its feeding amount and instars.In this experiment,the development and feeding amount of Ascotis selenaria were observed systematically using the method of single larvae fed by detached leaves.The results showed that Ascotis selenaria larvae undergo 6 instars at temperature of 27℃-28℃ and the average developmental duration of larva was 19.05 days.The instar from 1to 6 instar was 3.07,2.00,1.86,2.24,3.33,6.38 d,respectively.Head width and body length were both increasing with the instars,the growth equation as follows:head width y1=0.178e0.489x(R2=0.997);body length,y2=1.671e0.519x(R2=0.994).Total feeding amount of Ascotis selenaria larva was 7 218.88 mm2 and about 2 669.50 mg.The relationship between developmental duration and feeding amount is:leaf area,y1=6.387e1.202x(R2=0.976);leaf weight,y2=0.467e1.319x(R2=0.949).The 4th-6th-instar larva's feeding amount account for more than 98% of the whole larva duration.