Study On The Diapause Characteristics Of Helicoverpa Assulta

Diapause is a strategy of insects to adapt adverse environment that the insect development is rest. Some kinds of external environment will induce insects’diapause, such as temperature, light, food and so on. In this study, the effects of temperatures on the diapause in Helicoverpa assulta were evaluated and to illustrate the ecological adaptation in the physiological level. The main results were as followed:1.The induction, maintenance, termination of winter diapause of Helicoverpa assulta:The winter diapause rate were92.22%、91.86%、59.55%, respectively, for third, fourth, sixth, under20℃with L8:D16;74.09%、60.13%、0.46%、0, respectively, for third, fourth, sixth and prepupa stage, under22℃with L8:D16; and74.52%、25.15%、0、0, for third, fourth, sixth and prepupa stage, under24℃with L8:D16, showing significant difference in diapause induction in each stage. The diapause development period ranged from170-495days under20℃, nearly85.5%pupae lasted more than240days. When winter diapausing pupae were at4℃for30days,60days and90days, the result showed that the diapause development were nearly same and it was best to keep30days that the survival rate was the highest.2. The winter diapause physiological characteristics of Helicoverpa assulta:In the12days after pupation, the total loss of weight of winter diapausing pupae was significantly lower than that of non-diapausing pupae, respectively were:2.91mg,10.41mg; The lipid content of winter diapausing pupae and non-diapausing pupae were:48.77、36.99mg/individual, The glycogen content were:4.67、2.80mg/individual. Both lipid and glycogen of diapausing pupae were significantly higher than those of the non-diapausing pupae. The results indicate that with winter diapause Helicoverpa assulta can accumulate a great deal of energy substances and decrease metoblism to survive cold winter.3. The induction, maintenance, termination of summer diapause of Helicoverpa assulta:The summer diapause rate were:1.75%、4.10%、8.59%、0.92%for third, fourth, sixth and prepupa stage, respectively, under33℃with L16:D8.25.96%、25.71%、22.76%、 11.31%, for four stages under35℃withL16:D8. Moreover, diapausing rate of male was significantly higher than that of female.33℃is the critical temperature and the diapause development period is13.43days. Summer-diapausing pupae spent about3days to terminate which was significantly longer than developmental pupae reared at27℃.4. The summer diapause physiological characteristics of Helicoverpa assulta:Both the curves of weight loss and the curves of respiratory of diapausing pupae were significantly lower than those of the non-diapausing pupae. The lipid content were:48.52、40.34mg/individual. The glycogen content were:5.95、2.30mg/individua. Both the content of lipid and glycogen of diapausing pupae were higher than those of non-diapausing pupae significantly. These results also indicate that diapause can accumulate energy substances and reduce metoblism to survive adverse environment.5. Ecological adaptive of summer diapause:We discussed the feather malformation and reproduction under high temperature and found that the feather malformation rate under35℃was56.68%, that was significantly higher than17.24%under27℃. Both the egg number of female moth and egg fertilization rate which feathered under high temperature were lower than those under normal environment. The high temperature is not conducive to eclosion and reduces the fecundity of adult moth. Studies have shown that Helicoverpa assulta can escape from effects of high temperature and improve the fitness.