Studies On Cuticular Volatiles Related To Courtship And Hostlocation Of Microplitis Mediator(Hymenoptera:Braconidae)

Microplitis Mediator belongs to Hymenoptera,Braconidae.It's a solitary parasitoid of several Lepidoptera pests,such as Helicoverpaarmigera,Mythimnaseparata and Mamestrabrassicae.With the researches of Chemical communication mechanism in M.Mediator,the semiochemicals have been identified.The semiochemical is playing a vital role in many behaviors like host location,host identification,courtship and copulation.It's also a mean of intraspecific and interspecific identification.Sex pheromones are assumed to play a crucial role in the sexualcommunication and courtship.Recent studies have shown that M.Mediator depends on herbivore-induced plant volatiles for mating location,with the sex pheromone has yet been found.And during the host location process of M.Mediator,the cuticular volatiles act as an inducement.As the host of M.Mediator,M.separata has never been reported to have semiochemicals that act in host location process.The extracts were analyzed through GC-EAD and the active compounds were identified through GC-MS.The behavioral responses of wasps to the GC-EAD active compounds were subsequently tested by EAG and evaluated in Two-choice olfactometer experiment.The results are as follows:1.Behavioral responses of Microplitis Mediator to the extractsThe extract of M.Mediator virgin females can elicit courtship behavior of males.It's shown that there were sex pheromones in the extract of M.Mediator virgin females.The behavioral responses of M.Mediator adults to the extracts of M.separata showed that,the extracts of 1st to 4th instar larvae are significantly attractive to M.Mediator adults,but the extract of 5th instar larvae was not.2.Identification of electrophysiologically active compoundsBy GC-EAD and GC-MS,4 electrophysiologically active components in female body extract were identified as 1-Hydroxy-2-pentanone,n-Octyl acrylate,Heneicosane and 6-Methyloctadecane.10 electrophysiologically active components in Mythimnaseparata larvae body were identified as 2,4-Dimethylheptane,2,5-Dimethylnonane,5-Ethyl-2-methyloctane,Dodecane,1,3-Di-tert-butylbenzene,2,4-Dimethyl-undecane,Hexadecane,Eicosane,1-(+)-Ascorbic acid 2,6-dihexadecanoate and 2,6,10,15-Tetramethylheptadecane.The percentage of every component varies with different instar.3.EAG responses to standard chemicals4 components of female body can elicit EAG responses in both male and female.Males are more active to n-Octyl acrylate than female in high concentration.10 components of M.separata larvae body can elicit EAG responses in both male and female.There was no significant difference between male and female responses in most cases.4.Behavioral responses of Microplitis mediator to standard chemicals and mimetic compoundsn-Octyl acrylate is significantly attractive to male wasps.The mimetic compounds of female body are significantly attractive to both male and female wasps.2,4-Dimethylheptane,2,5-Dimethylnonane,Dodecane,2,4-Dimethyl-undecane,Eicosane and 2,6,10,15-Tetramethylheptadecane are attractive to both male and female wasps.The mimetic compounds of 1st to 4th instar larvae were attractive to both male and female wasps.With the results of EAG responses and the varies of percentage in different instar,2,4-Dimethylheptane,2,5-Dimethylnonane,Hexadecane,2,4-Dimethyl-undecane,Eicosane and 2,6,10,15-Tetramethylheptadecane were identified as pheromone in host location process of M.mediator.