Reproduction Biology Of Male Adults Of The Hawthorn Spider Mite,Tetranychus Viennensis (Acari:Tetranychidae)

The hawthorn spider mite,Tetranychus viennensis Zacher(Acari : Tetranychidae),mainly damages apple,peach,pear,cherry,hawthorn,plum and other deciduous fruit trees in northern China.This pest suck juices from leaves and the young sprout at any stages and attract the concern of most economic entomologists.This research investigated the reproductive behavior of the mite under laboratory conditions,aims to improve our understanding the population dynamic mechanism and sexual ratio regulation so that we can predict and control the insects.The main results are listed as following:(1)Bionomic of male adults of T.viennensisThe mites are haplodiploid and the females are engaged in facultative parthenogenesis,so we study males from parthenogenesis and gamogenesis.The results showed that the developmental stage between males from parthenogenesis and gamogenesis were not significant,including egg stage,larval stage,stage of nymph,stage of adult and all quiescent stages.Their emergence time was both focused on 14:00-22:00.Searching rate and time for quiescent deutonymph females by parthenogenesis male was 35.29%,261.7 s and gamogenesis male was 47.5%,302.36 s.There was no significance in the searching rate and time.In the mating competition experiments,there was no significant difference.These two males have no significant difference in various aspects so we use the parthenogenesis males in the following study because of their easily acquired.(2)Mating strategy of male adults of T.viennensisPre-copulatory mate guarding: In experimental population,male mites mainly guarded the second and the third level female,guarding rate for the second level is 12.94% and the third level is 16.61%.Males prefer guarding the third level female nymphs than the second level female nymphs and males prefer mating directly than guarding the nymphs.Copulatory mate guarding: Females accept the second mating but 63.6% of the mating duration is less than 50 s.In the meanwhile,female adults who accept twice mating have no significant difference with females who accept once mating in oviposition and sex ratio of offspring.Post-copulatory mate guarding: Upon emergence of adults,males continued to mate with females until the end of their life.The copulation duration of the first mating of males was the longest and became significantly shorter in following mating.The least copulation duration of a male to inseminate a female was 50 s,much shorter than in nature.The behavior that male adults did not leave after fertilizing called post-copulatory mate guarding.In a word,male adults engaged in pre-and post-copulatory to ensure paternity.(3)Searching and mating abilities of male adultsFactors of females,probably chemical substances released by female and the female bodies could not affect searching rate of males.While,when the crawling traces was decreased,searching rate of males reduced significantly and the searching time was on the rise.So we deduce trails of females mainly affect the searching behavior of male adults.The newly emerged male adults copulated and inseminated 26-37 females,and contributed to 688-989 daughters over their lifetime,depending on the sex ratio.The age(in days)of male adult significantly affected their mating capability.The daily number of mating of male adults significantly decreased when they were 5 days-old whereas had no obvious change when they were within 3 daysold.However,the male adults were still able to inseminate several females per day when they were over 7 days-old.The mating history of male adults imposed significant effects on their mating capability.The daily number of mating of male adults significantly decreased when they historically mated more than 20 times,but male adults could maintain the capability to inseminate females sufficiently even they had inseminated 30 females.(4)Mating choice and mating competition of male adultsThe results showed that,male could not distinguish mating status of females.Males can distinguish the age of females that they prefer 5 d females rather than newly emerged females.In the mating competition of different age males,competitive increased from 1 d to 3 d but it remained unchanged from 3d to 7d.The competition between males who had experienced copulation and males who never experienced copulation had no significant difference.This syudy clarified there is no difference between the parthenogenesis and gamogenesis males.So we research the reproduction biology of the hawthorn spider mite by parthenogenesis males.In general,male adults are engaged in pre-copulatory and post-copulatory guarding to improve success ratio of reproduction.In addition,male adults have an extraordinary reproduction potential to copulate inseminate and fertilize female adults.The results of the study provided important evidence for the further study of reproduction and the impact of male adults in population dynamic.