| Hymenopterous insects involve numerous species, and many of them are advantageous to plants. Scelionidae parasitoids specialy parasitize in or on Lepidopterous or Heteropterous pests and are better biological control agents. Some hymenopteraous parasitoids were utilized successfully in China. Trissolcus japonicus Ashmead is attributed to Hymenoptera, Apocrita, Proctotrupoidea, Scelionidae, Trissolcus. It extensively spreads in many districts of our country and is solitary endoparasitoid that specificly parasitize in or on forest or orchard pests. In other countries, some reports on T. japonicus only are discovered in taxonomy, but not in biology, ethology and reproduction utilization. In China, the description on pentatomid egg parasitoids has been discovered in morphology and other observations, however no study on T. japonicus has been discovered to date. Therefore, the studies in the paper started from parasitic investigation in field and then described the morphological charactistics, parasitic behaviors, reproductive system, developmental temperatures, developmental periods, and superparasitism as well.In host rearing and field investigation, the bug occurs two generations in Beijing in a year and both are partial generations. Overwintering adults partially foraged in March but slightly damaged to plants. They intensively damaged to plants from the end of April to the middle of May. The nymph has five instars. Two instars nymph starts to forage. Different instars have different developmental periods. The second generation hosts peaked from July to August and adults overwintered in the middle of September and remained eggs in the body to lay them next spring. T. japonicus followed host eggs , but a few of parasitoids had been lower in parasitization .The parasitization rate in the second generation host eggs had been up to 80%.Female parasitoid has knee-formed antennae, 11 segments, terminal 5 segments black, the other brownish yellow. Male Antenna is club, 12 segments, well brownish yellow. Thorax very strongly convex dorsally; mesoscutum with distinct notauli and with roughened micro-sculptures becoming weaker toward scutellum; metathorax has dorsellum with reticulate carina; abdominal carinate and excavated basally, first and second tergum combine.Host selection involves habitat location, host location, host palpation, oviposition, marking host, recovery palpation. They associate with physical and chemical kairomones, and ovipositize in an egg within 2min. Female competition resulted in one parasitizing; male competition resulted in one mating; larval competition resulted in one hatching.Reproductive system:Ovaries have 40~60 eggs. Hatched and mated parasitoids parasitized in hosts immediately. Ovarioles are panoisttic. Receptaculum seminis andDufour's gland associated with median oviduct. No poison gland had been discovered.The most suitable temperatures are between 24 and 33℃ and both sexes developed successfully from egg to adult emergence at constant temperatures ranging from 18 to 33℃.Males developed faster than females did. The low and high constant temperatures used in this study reduced to some extent the percentage of successful emergence of adult parasitoids. This paper also studied on the embryonic development of T.japonicus eggs, and drew the pattern of specific cleavage. The first instar larvae have temporary accessory organs, meaty setae. The second instar larva, hymenopteriform, no foot, transparent, saccate. The prepupae, pupae, developmental periods in each duration had been studied, too. The marker, parasitoid-egg ratio and parasitic species play a major part in superparasitism . With the increase of parasitoids on the determined egg mass, the number of superparasitism significantly increased ,as did no marker on the egg shell. Conspecific parasitoids have the abilities to discriminate the marker, heteroparasitoids do not. On the other hand, superparasitism resulted in extending developmental time , shortening adult longevity and decreasing female sex r...
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