Effects Of Environmental Factors On Melanic,Pupal Weight,Food Unilization Of The Mythimna Separata(Walker)

The variation of body color of insects is the result of adapting to the natural environment.The complex and variable ecological environment can not only change the body color of insects,but also affect their physiological function.Essential differences exist in the aspects of the adaptive ability to environment,reproduction and feeding.As an agricultural pest,the melanism can occur due to the change of density in the larvage stage.Therefore,the physiological function of Mythimna separata(Walker)and its population characteristics can be explored by changing population density.In order to clarify the effect of environmental factors on the melanism of Mythimna separata(Walker),this paper aimed to select the Mythimna separata(Walker)as the research object,and use the 3 horizontal orthogonal test method in which three factors were selected,including the temperature,humidity,and volume(feeding space).The Temperature was set as 25 ?,21 ?,17 ?,respectively;the humidity was 75% RH,60% RH,45% RH,respectively;and the volume was ?8 × 12 cm3,?8 × 8 cm3,?8× 4 cm3,respectively.The breeding density was 10 per bottle.Five replicates were involved in each test.The larvae used in the experiment were by given birth by a pair of male and female insect mites by mating.The eggs were hatched into larvae within 48 hours and were moved into bottles.The body color of larva changed at each age,and which tended to stabe at the age of six.In the 2nd day in age six,the body color of larva was took pictures of and measured,and did analysis by using the Image Pro Plus software.The results showed that body color of larva change significantly under different feeding environment(P <0.05).The melanism values of Mythimna separata(Walker)larva increased along with the increase of humidity and volume.While decreased along with the increase of temperature.The melanism value was maximum with the temperature 17 ?,the humidity of 75%,and the volume of ?8 × 12cm3.That meant the feeding density was the maximum for the larva.Weighed the pupas that were pupated by larva within 48 hours,then did analysis by SPSS 17.0.The results showed that the variation of temperature and volume had significant effect on the pupal weight(P<0.05),but the varitation of humidity had insignificant(P>0.05).The weight of pupa increased together with the increase of temperature and breeding space.However,it decreased together with the increase of humidity.The pupal weight of larvae was the maximum under the condition of temperature 25 ?,humidity 45% RH and volume of ?8 × 12cm3.In order to understand the relationship between the digestibility and the rough gr owth rate and the environmental factors,the larvae feeding rate,fecal excretion and b ody weight were measured under different environmental conditions.The change of la rvae body weight,the approximate digestibility and rough growth rate,During the firs t and fourth days of the growth and development at 5 instars,it indicated that feed inta ke and fecal excretion did not show significant effect on the first day(P>0.05).The ch ange of temperature and volume had significant effect on the total food intake of 5 an d 6 larvae(P <0.05).The change of humidity had no significant effect on total food in take(P >0.05).There was no significant difference in fecal excretion between 5 and 6larvae and temperature,humidity and feeding space(P> 0.05).