Studies On Factors Influencing The Growth And Development In Diachasmimorpha Longicaudata (Ashmead)

Diachasmimorpha longicaudata (Ashmead) was a major larval parasitoid of Bactrocera dorsails(Hendel). A series of observation and experimentation on the basic biology and ecology charactors of D. longicaudata were carried out in order to offer valuable consult for mass rearing and releasing in controlling B. dorsails.D. longicaudata operated as a parasite of B. dorsail larvae at various instars. Selective experiments indicated that D. longicaudata preferred to parasitize 2,3-instar-old B. dorsail larvae when 1～3-instar-old B. dorsail larvae were all existed, and the parasitism rates were separately 83.6% and 75.5%; The parasitism rate on 1-instar-old larvae was significantly lower than 2,3-instar-old, the selective coefficient was merely 0.14; Compared with the lethality rate in the 1～3-instar-old B. dorsail larvae, D. longicaudata made more lethal affects to 1-instar-old larvae than 2,3-instar-old B. dorsail larvae.A male parasitoid could successfully mate with average of 11.2 female parasitoids. D. longicaudata could lay eggs longest for 14 days continuously. The day had much to do with the productivity of female D. longicaudata:one 3～10-day-old female D. longicaudata could produce 9.6～16.4 eggs averagely, the productivity rates increased slowly, the highest productivity was 16.4 eggs in the sixth day. Then the productivity rates decreased slowly, the productivity was merely 3.5～8.0 after the 11 days. The mortality rate of female D. longicaudata arrived at 60% in the fifteenth day, and the survived female D. longicaudata could not lay eggs any more.In the same temperature, the longer pupa stored, the lower the eclosion was. The highest eclosion rate of the pupa was at 22℃when the time of storing pupae was the same. It could be deduced from the experimental results, the lower the temperature was, the lower the eclosion rate of pupae was. The longer the cold treatment was, the lower the emergence rate of pupae was. However, the eclosion rate of pupae decreased when the storing temperature was higher than the optimal temperature (the highest eclosion rate emerged at 22℃in this experiment ).Eclosion time of D. longicaudata on storing pupae at 13℃delayed distinctly, its duration reduced with the rise in temperature. At the same temperature, the longer the storage, expansus and body length showed a downward trend . When stored at the same time, the expansus and the body length both increased as the temperature increased (the expansus and body length both showed the largest at 22℃), they slight decreased at 25℃. With the increased density of hosts, the percentage of not parasitized hosts increased from 36.73% to 84.53%; the percentage of superparasitization decreased from 30.61% to 0.00%. Host density (x) correlated with the percentage of superparasitization(y), which came up to mathematical equation y = -0.1304 x + 11.238, R~2 = 0.7655. Superparasitization prolonged the eclosion period from ovum to eclosion, and the increased numbers of parasitism (x) correlated with prolonged eclosion period of development (y), which came up to mathematical equation y = 1.719 x + 9.327, R~2 = 0.9849. The productivity of the female parasitoids produced by superparasitization was much lower than parasitized only once. With the increased numbers of parasitism, the productivity decreased. The numbers of parasitism (x) correlated with the productivity (y), which came up to mathematical equation y = - 9.23 x + 127.47, R~2 = 0.8393.The longevity of♀adult parasitoids were shorter than♂adult parasitoids, it reflected that the stress resistence of♀adult parasitoids was inferior to♂adult parasitoids to a certain extent.Inbreeding(1)could produce progeny with certainly female sex ratio, but it was much lower than the female quantity which was produced by adult parasitoids having distant relationship; Inbreeding(2)could produce progeny with lower female sex ratio, it indicated that inbreeding might be a important factor causing the progeny sex ratio decreased; the progeny sex rate of bisexual hybridition was 197.63%, The sex ratio of progeny produced by parthenogensis parasitoids mating female adult parasitoids was 32.14% only;the progeny of parthenogenesis was male toally.The female sex ratio decreased with increasing wasp density, B. dorsail larvae were exposed to 10 parasitoids produced grogency with smallest female sex ratio 11.04%,whereas the greatest female sex ratio 60.80% was obstained for those exposed to 1 parasitoid.D. longicaudata operated as a parasite of B. dorsail larval at various instars. The female sex ratio of progeny increased as the instar of the host increased. The female sex ratio of D. longicaudata emerging from parasitized 3-instar-old hosts was the 63.55%, and the female sex ratio from 1-instar-old hosts was 21.35%. Supplying varied foods affected the female sex ratio of progeny.The female sex ratio decreased with increasing parasited numbers. In the time, the progeny amount decreased.