Studies On Biology And Host Selection Of Scleroderma Guani Xiao Et Wu

Scleroderma guani Xiao et Wu is a parasitoid of many borers, especially larvae and pupae of long-horned beetles. Host choice and oviposition behavior was studied. The main results were as follows:1 Lab reproduction and conservation of hostsLab hatching rate of eggs of Semanotus bifasciatus is 80% above. The average survival rate of larvae living in cypress trunk was 56.9%. Death rate of Larvae of Xylotrechus chinensis and Apriona germari living in mulberry trunks was less than that of by other methods.2 Oviposition behavior The oviposition behavior of S. guani on S. bifasciatus larva includes: aggregating, host examinating, host stinging, host clearing, host feeding, walking, oviposition and resting. The duration of oviposition was 4～5 days. The percent of eggs on the first and second oviposition day was 80% of total. Eggs distuibuted on the intersegmental membrane on both sides of X,chinensis and the number of eggs on both sides was significantly different from that on other place. The distributing of eggs on T. molitor was random.3 Parasitism rates of S. guani on different insects The paralysis rate and parasitism rate of S. guani on different insect were different. Female wasp only paralysed Bombyx mori and Leucania separata. Eggs on Apis cerana pupae do not hatch. On S. bifasciatus larvae, parasitism rate was highest and on T. molitor larvae, lowest. Parasitism rate to larvae was higher than that of to pupae. 4 Effect of different factors on parasitism Different factors, including different treatments of hosts, host weight, ratio of parasites to hosts, parasitism experience, affected parasitism. On hosts treated with mixed solution of chloroform and alcohol(1:10) for 2 hours, parasitism rate and fecundity per female were higher than those on control hosts, but period of pre-oviposition prolongs and sex ratio decreases. As weight of hosts increases, period of pre-oviposition prolongs; fecundity per female and sex ratio increases and development period varied little. As ratio of parasites to hosts increases, fecundity per female increased; sex ratio of offspring wasp decreased and development period varied little. Experienced parasites expend significantly less time before oviposition and laid more eggs than inexperienced parasites.5 Biological characters of S. guani on different hosts On different hosts, period of pre-oviposition, egg period, larva period and pupa period were different. On T. molitor pupae and X. chinensis pupae, egg period was longest and shortest, respectively. On A. germari larvae and T. molitor pupae, larval period was longest and shortest, respectively. On Acantholyda posticalis larvae and X. chinensis pupae, pupa period were longest and shortest, respectively. On hosts with appropriate size, fecundity per female and eclosion rate and sex ratio of bethylid on long-horned beetle larvae and pupae were higher than that on other hosts. fecundity per female and eclosion rate and sex ratio on S. bifasciatus was highest. Sex ratio varied evidently on different hosts and was lowest on T. molitor pupae.6 Release bethylid to control S. bifasciatus in forestIn the forest of Mountain Tai, the parasites were released on trees bored by long-horned beetle larvae in the middle ten days of June. When ratio of hosts to parasites was 1:6～10 and 1:12～20, parasitism rates was higher. After releasing parasites continuously for two years in Longshan park, Feicheng City, number of injured trees decreased.