Study On Host-Searching Behavior And Hosts Hormone Regulation Of Trichogramma Spp

Some aspects of the chemical communication and physiological accommodation between Trichogramma spp. and Ostrinia furnacalis were studied in the laboratory. First, the external morphology of antennal sensillum of female species of T. ostriniae, T. confusum and T. dendrolimi were observed by scanning electron microscopy(SEM); Next, the behavioural responses of the three Trichogramma species to different extracts of plant volatiles and host volatiles were examined by choice tests using "Y" tube and culture dish; Finally, the juvenile hormone esterase activity and molting hormone titer in 0. furnacalis eggs parasitized in their different development phases by T. ostriniae were measured by RC method and RIA method. The results aresummarized as follows:The external morphology of antennal sensillum were observed and described by SEM for female species of the three kinds of Trichogramma. The numbers and the relative positions of these sensillum were depicted. The special structure on the ventro-lateral margin of falcate sensilla was discovered and its function was confirmed. A single pore at the tip of trichoid sensilla on the apex of the antenna was discovered, which indicated that the trichoid sensilla may perform gustatory function. The differences in the numbers of falcate sensillum , the densities of olfactory pores and shapes of placoid sensillum and the shapes of ampullaceum sensillum among the three species of Trichogramma, were also discussed.The effect of the allelochemicals on T. ostriniae, T. confusum and T. dendrolimi in host searching behaviour was studied, and "Y'-tube olfactometer system and culture utensil method were used. The results demonstrated: The extract of the last abdomen of the female moth, the host-damaged and the healthy stem and leaf of maize were attractive to three trichogramma species. As far as the extract was concerned, the attractive ability were: the last abdomen of Trichogramma> the host-damaged> the stem and the leaf of maize; as far as the allelopathy was concerned, the attractive ability were: T. ostriniae> T. confusum> T. dendrolimi. Compared to the two methods, the olfactometer system was more accurate.The juvenile hormone esterase activity in O. furnacalis eggs parasitized in their different growth phases by T. ostriniae were measured by RC method. The moltinghormone titer in O. furnacalis eggs parasitized in their different development phases by T. ostriniae were measured by RIA method. It was discovered that if parasitization occurred in early stage of host embryonic development (before 72h), T. ostriniae egg would develop, and embryonic development of O. furnacalis would be suppressed. The change pattern of juvenile hormone esterase activity and molting hormone titer of eggs parasitized were according with that of the developing process of T. ostriniae from egg to pupa. If parasitization occurred after 72h, the development of T. ostriniae were suppressed. The result showed that about 72h of the development of O. furnacalis embryo is the key period for T. ostriniae to parasitize successfully.