A Study On The Bionomics Of A Tachinid Fly, Nemorilla Maculosa (Meigen)

Nemorilla maculosa Meigen is a tachinid parasitoid(Diptera:Tachinidae)of the beet webworm,Loxostege sticticatis Linne(Lepidoptera:Pyralidae)and other lepidopterous insects.It can effectively control the damages of meadow moth,and can regulate population dynamics of insects in the fields.However,the parasitical behavior and bionomics of N. maculosa have been received little attention so far.In this paper,we studied the biology of tachinid fly,selection to host,effects on fecundity of host densities,and effect on tachinid fly's adult reproduce of complement nutrition.The results may provide important scientific gist for biocontrol of meadow moth.1.The biology of N.maculosaThe basic biology of N.maculosa that contained rules of tachinid fly's emergence, oviposition,mating,and developmental period was study.The results indicated that emergence of N.maculosa focus on daily 8:00～10:00 and 14:00～16:00 times.Emergence durative period were seven days.The male eclosion was earlier to female.New emergence female could immediately mate with male.Mating rate was 90%over when provided for male had emerged one day while female mergence.Generally,durative time of mating was about twenty minutes to thirty minutes.The tachinid fly's individual fecundity varied considerably,it was 134.43 on average individual.Durative period of oviposition was 15.47 days,and lay eggs focused on the 3^rdto 9^thday,it was 67.07%over total.Besides the tachinid fly is single parasitoid in meadow moth.2.The preference of N.maculosa to larval instars of beet webwormThe 3rd,4th,and 5th larvae of beet webworm can be all chosen by N.maculosa,but parasitical percentages were significantly difference.Parasitism in the 5th larvae was highest, the 4th was following,and the 3rd was smallest.Effects of host larval instars on emergence of tachinid fly were significantly difference.The 3rd larva parasitized was void because of no tachinid fly emergence.Little of tachinid fly came out in the 4th larvae was only 8%in sum. Numerous flies emerged from the 5th larvae up to 62.30%.Therefore,above results indicated the 5th larva was most suitable for tachinid fly's rearing.3.The oviposition preference of N.maculosa to positions of the host larvae The choice of N.maculosa to beet webworm larval posts was also specifically.Larval chest was firstly chosen by tachinid fly,head was secondly,and the last was abdomen.This choice was significantly different.Furthermore,lay egg times were different,chest was much more than head and abdomen.It was no effect on tachinid fly's development.4.Effect of the tachinid egg numbers in the host on the pupal weight and survival rate of N.maculosaThe times of tachinid fly(N.maculosa)oviposition on host body was random.One larva could hold several eggs ranging from one to twenty-two of inequality,but only one tachinid fly emerged from host larvae at last.The competition of tachinid fly's maggot existed in host larvae,so the eggs in host might affect tachinid fly's fecundity and development.The results revealed that relation between tachinid fly's pupae weight and host eggs were negative.So the fecundity would be relatively lower if the pupae weight was lighter.Relation between tachinid fly's emergence and host eggs were also negative,and the regress curve was y=-9.956x+47.902,r=-0.947(p＜0.01).5.Effects of host species on the parasitism,survival rate and size of N. maculosaEffects of different species host larvae,Loxostege sticticatis Linne,Spodoptera exigua, Mythimna separata(Walker)on the parasitism,emergence,and individual size of N.maculosa were studied.N.maculosa is one widely parasitoid,it is not only parasitized L.sticticatis,but also parasitized S.exigua and M.separate.In comparison of parasitical percentage,L. sticticatis was significantly different than S.exigua and M.separate.Although the rate of parasitism in L.sticticatis was higher,only one tachinid fly emerged from host.However,it had two or three tachinid flies emerged from M.separate,therefore the percentage of eclosion was no significantly different.Besides that the tachinid fly from M.separate was larger than from L.sticticatis.Their individual was significantly different whichever female or male.6.Effect of host density on parasitism,survival rate,and sex ratio of N. maculosaEffect of host density on parasitism percentage,emergence rate,and gender proportion of N.maculosa was investigated in laboratory.The results indicated relationship between parasitism percentage and host density was negative.That was host density was larger,the parasitic percentage was lower.On the range of 5～20,emergence rate was decreasing with the host density increasing,but in the density of 20～25,the results was opposite.On the other hand,host density had no distinct effect on gender percentage of N.maculosa.In view of the tachind fly offspring reproducing,we should restrict the host density to 10～15 individuals one fly.7.Effect of supplementary nutrition on fecundity and longevity of N.maculosaSugary substance is primary nutrition for tachinid fly adult.It can provide for energy, increase longevity and fecundity,enhance efficiency of foraging host and so on.Consequently, it affected parasitic rate,even offspring's diapauses and survival of tachinid fly.We investigated on the effects of three kinds of sugar solution and pure water on longevity and fecundity of N.maculosa.Results revealed that complement sugar substance had significant effect on tachinid fly longevity and fecundity.The fecundity of N.maculosa feed by honey, glucose and sucrose ranging from 125-139 per female in average,and was not significantly different.The mean fecundity of the tachinid fed by these three types of sugar was significantly greater than that fed by only water.