The blue gum chalcid, Leptocybe invasa Fisher & La Salle (Hymenoptera: Eulophidae), is a recently described pest of eucalyptus, which was origined from Australia but first recorded in the Middle East and Mediterranean countries in 2000. The adults of this pest is small black wasp with parthenogenesic or bisexual reprodunction and strict proovigenesis, it lays eggs in the bark of shoots, petioles or the midribs of leaves of Eucalyptus plants, inducing severe injury such as bump-like galls and thereby damages the leaf midribs, petioles and stems. The damage of L. invasa is more severe on seedlings and young trees than that on old trees, which has drew attention not only to the increasing damage on the infested trees but also to the potential economic damage of Eucalyptus forests in more than 25 countries including China. The first record of L. invasa in China was in Dongxing county, Guangxi Province in 2007, subsequently found in Guangdong, Hainan and Fujian, and now it has been classified as a quarantine pest in many provinces of China including Guangxi, Guangdong, Fujian, Hainan, Sichuan and Jiangxi. Eucalyptus trees are the backbone of afforested areas due to their roles in economic development and environmental maintenance such as major source of timber, firewood and shelterbelts of drifting sands and typhoon, thus how to control the damage of L. invasa is an emergency issue to be solved for Eucalyptus plantation. However, so far very little is known about the biology of this pest.
In present study, the morphology of different instars, the fertility, fecundity, female proportion, adult longevity of F1-F4 generation as well as the daily oviposition and daily survival of the L. invasa in Guangzhou were investigated under lab conditions of (26±1)℃, RH 60%-85%, photoperiod (L:D)14:10. The continuous life table of L. invasa were determined based on the parameters mentioned above in 2010-2011. Results showed that, there are four generations of L. invasa in Guangzhou and its overwintering stages include old larvae and pupae from the middle of November to end of March next year. Among four generations of L. invasa in one year, the fertility per female in the second generation was significantly lower than those of other three generations (125.13 vs 176.43, 162.83, 167.20), but there was no significant differences among the fertilities of first, third and forth generation, similar as to the fecundity of L. invasa in four generations (10.94 vs 16.70, 17.33, 14.16). The female proportion of L. invasa ranged from 0.9332 to 0.9476, which showed a female bias in its reproduction. Feeding with 40% honey solution can markedly prolonged the longevity of L. invasa adults comparing with those in water trials. The longest and shortest longevities of female were found in F1 and F4 generations (8.15 vs 3.81), while those were found in F4/F3 and F2 generations for male L. invasa (6.68 vs 3.40). The net reproductive rate (R₀), mean generation time (T), finite rate of increase (λ) and intrinsic rate of increase (r_m) waved distinctly among different generations, whereas the largest r_m was recorded in the 3rd generation, which revealed that the population increase and damage of L. invasa is the fastest or most severe in the 3^rd generation, occurring in July to September in Guangzhou area. The ecological mechanisms of life table diversity among L. invasa different generations were also discussed.