| Megastigmus sp. belongs to Megastigmus Dalman, Megastigminae, Torymidae, Hymenoptera. It is a main pest insect which larvae damage endosperm in seeds of cypress trees and the damage seeds cannot germinating. Larval and pupal development occurs entirely with in a single seed. Therefore,the development of seed trading carries the risk of introduction of this seed chalcids with seed lots. In order to provide a theory foundation for preventing against the seed chalcid, systematical research has been carried out for the first time on the geographical distribution, damage percent, biological characteristics, the relationship between the damage and the environment and spatial distribution of the laval of Megastigmus sp. in this paper. Whats more, the volatile substance from conifers cones and branch were analyzed and studied.The investigation from 2005 to 2007 indicated that Megastigmus sp. only damaged seeds of Sabina recurva var. coxii and it mostly distributes Qujing and Kunming in Yunnan province. 1.3~34.4 percent of the Sabina recurva var. coxii cones were damaged by Megastigmus sp.The life history and biological characteristics of every stage of Megastigmus sp. were observed both in the field and in the lab. Megastigmus sp. has one generation per year in Qujing area of Yunnan Province, over winters as larvae, and pupates in April. The adult emergence time is in middle June, and its eclosin peak period is in late June, and the adults oviposit their eggs in current year young cones. The larvae hatch in middle June, growing in the cones until April of second year and pupates again. The peak emergence time of the day is at 6:00~9:00 and 12:00~15:00. The adult sex ratio of female to male is 0.9:1, the average longevity of female adults is 7.1d, and the average longevity of male adults is 5.2d. The phototaxis experiment indicated that the adult have strong taxis to ultraviolet light, therefore, measures may be taken to lures and kills Megastigmus sp. in the adult emergence peak period.The investigation of the cones in different growth periods matching with the survey of damage of Megastigmus sp. at the same time indicated that the damage of Megastigmus sp. is synchro with the growth of cone. The cypress trees at low altitude stands were damaged more serious than that at high altitude stands. Basic regulation is, the cypress trees in the middle-aged stands and the edge of stand were damaged more serious than that in mature stands and young stands and pure stands by Megastigmus sp. The cypress trees in sunny side of the hill were damged more serious than that in shady side of the hill, the cypress cones in lower part of the crown were damged more serious than that in higher part of the crown, the cypress cones in south and west side of the crown were damged more serious than that in east and northern side of the crown.By investigating 5 sampling plots in the cypress forest in Qujing and Kunming, regression analysis and several aggregation indices were used to determine the larvae spatial distribution pattern. The equations of succession sampling are set up based on the regression models and the theoretical sampling number of forest survey is analyzed and calculated. The results show that the spatial distribution pattern of the larva belongs to the aggregation, Iwao regression model indicated that the larvae individual attract each other. In addition,the aggregation average method by Blackith was applied to analyze the aggregation reasons of the larva, the spatial distribution pattern of the larva was positively related to its biological characteristics and environment. Results of multiple regression analysis, indicated that east of crown lower part unify west of crown upside was the best sampling spot. Take fits the equation of optimal sampling which the effect good Taylor model determined as d(n)= 30n±31.083 n (n means sampling number).XAD2 adsorption and GC-MS were used to analyze and determine the volatile materials from the healthy cones and branch of Sabina recurva var. coxii, and Abies georgei var. smithii and Pinus armandii. The result indicated that the volatile from cones and branch of Sabina recurva var. coxii were similar, but the volatile from cones of Sabina recurva var. coxii, Abies georgei var.smithii, Pinus armandii. were different.5 volatile substance were identified from cones of Sabina recurva var. coxii, all are monoterpenes, sabinene and limonene are mainly volatile substance from cones of Sabina recurva var. coxii(both account for 92.72%). 14 volatile substance were identified from cones of Abies georgei var. smithii, monoterpenes account for 97%, phenol type account for 0.95%, alcohol type account for 1.99%,β-phellandrene,ɑ-pinene,β-pinene and laurene are mainly volatile substance from cones of Abies georgei var. smithii (this 4 kinds account for 87.62%). 7 volatile substance were identified from cones of Pinus armandii, all are monoterpenes,ɑ-pinene, limonene,β-myrcene andβ-pinene are mainly volatile substance from cones of Pinus armandii (this 4 kinds account for 97.84%).According to three kind of cone volatile substance test result, through contrastive analysis, the extrapolation is thatɑ-thujene may have attractive function in the host choice process of Megastigmus sp. In addition,ɑ-thujene, sabinene and limonene allocated proportion may have the attractive function too. On the contrary,β-pinene may have deterant function in host localization process of Megastigmus sp. The role and function of different volatile substances or their combined forms to deterant the damage by Megastigmus sp. remains to be studied.
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