Bionomics And Diapause Induction Of A Parasitoid Wasp, Agrypon Flexorius Thunberg, Of A Meadow Moth, Loxostege Sticticalis Linnaeus

The meadow moth, Loxostege sticticalis L.(Lepidoptera: Pyralidae) was one of the major pests infarmland and grassland. The meadow moth was one of migratory pests that had a wide distribution ofhost and had devastated damages on various plants. The meadow moth had caused four outbreaks since1949and led to great damages and great economic losses on agriculture. Agrypon flexorius Thunberg(Ichneumonidae) was one of a dominant parasitoid of the sugar-beet webworm. In order to use Agryponflexorius T. to protect aganist the meadow moth, this paper systemically investigated the biologycharacristics, diapause induction and cold storage of Agrypon flexorius T.. The results were as follows:1. The basic biology characteristics of Agrypon flexorius T.The author gave an account of studies on the preliminary bionomics of Agrypon flexorius Thunberg(Ichneumonidae), a dominant parasitoid of the sugar-beet webworm, Loxostege sticticalis L.. At present,there were less relevant reports and literatures on the bionomics of Agrypon flexorius T.. We conducteda sets of experiments in field and laboratory, and the results showed, at23℃，the developmentalduration from egg to adult lasts30-37days. The parasitical percent of A. flexorius on L. sticticalis infield comprised only3.04per cent. The natural average sex ratio (female/male) was approximately3.97:1. The females and males paired readily when24hours after emergence, the mating time generallylasted10min and reached the maximum when the sex ratio was1:1. The mated female began tooviposit when one day old after mating and the oviposition period was relatively short,1min-2min.The eggs were laid in the head and thorax of host. For the most part, adults adopted bisexualreproduction, except in the absence of males, that parthenogenesis was arrhenotokous. In the case ofunmated females, the longevity of females that were given different nutrition totally reached the highestpoint at16℃. At22℃，females lived for17.6d when given cane sugar. In the case that female had laideggs on host,20%hydromel was the most suitable nutrition for reproduction. The percentage parasitismof L. sticticalis by A. flexorius reached the highest when given4th instars host, its averages comprised40.23per cent.2. Functional response of Agrypon flexorius T. to Loxostege sticticalis L.The results showed that the functional response was belong to Holling type II, the fitted equationwas Na=0.7575No／(1+0.7575×0.0694No)；The number of parasitize increased with an increasedensity of Loxostege sticticalis L., but the searching efficiency decreased with the increase of Agryponflexorius T. and Loxostege sticticalis L. density；The daily maximum numbers of parasitize was14.41.The models provided scientific basis for the control of Agrypon flexorius T. to Loxostege sticticalis L.3. The Selectivity of Agrypon flexorius Thunberg to different hostCompared with blank contrast group, females of Agrypon flexorius were attracted to the volatilesfrom its larva and frass, and other females were not. When each two of different larva or frass werecombined, the attraction of Agrypon flexorius to different larva or frass were incoherence, providingdifferent larva, Agrypon flexorius only laid eggs on Loxostege sticticalis L..4. Diapause induction and cold storage of diapause cocoons in Agrypon flexorius Thunberg Chilling temperature and short-day photoperiod were the main factors of diapause induction, andtemperature was the major factor that governing the induction of larva diapause in Agrypon flexoriusThunberg, photoperiod alone partly stimulate A. flexorius to enter diapause. No diapause was induced at26℃at any photoperiod examined, while the day length less than12h was beneficial to diapause at23℃. The egg and1instars were the most sensitive stage for diapause induction. The diapause cocoonsinduced at17℃and8h of light should not be conserved for more than3months at4℃.