Biology And Ecology Of Thanasimus Lewisi

Thanasimus lewisi, playing a significant role in pressing the outbreak of such pests, adult prey adult bark beetle, and larvae prey larvae bark beetle and longhorns after burrowing into their tunnels. Study on biology and ecology of T. lewisi were conducted. The major research results are showed as follows:1 Life cycleT. lewisi is one generation per year in Mount Tai area. The adult stage lasted from middle April, the high time for adult eclosion are late April to early May. The egg stage lasted from late April to early July, the peak of oviposition is middle and late May. Larvae appeared in early May, matured and hibernated till September.2 Life habit2.1 AdultThe impact of adult Phloeosimus aubei, larvae Tenebrio molitor and artificial diet on the lifespan of adult T. lewisi is not distinct. The female lifespan is positively correlated with the amount of its egg laid. Male-female ratio of eclosion is 1.5:1. Adults of T. lewisi mostly act at daytime, with its motility strongest at 10am~15pm and weak when the sky is overcast. Adults have the internecine habit without sufficient food. The newly eclosion adults laid eggs 2-3 days later after copulation. Eggs are often laid in crevice, with an indefinite number of 4-36 chondrios. In peak period, they can continue to lay eggs for as long as 6 days. Only a few female laid their eggs on the surface when crevices cannot be found. While most of them didn't lay when there is no proper place available.2.2 EggThe difference hatchability of different temperature isn't prominent, with 22℃as maxim. 2.3 LarvaThe newly hatched larvae have the behavior of eating chorions at the second day of hatching. Larvae are inclined to kill each other after second instar. Most of them live separately or 2-3 individuals in the same size live together.3 Effective accumulated temperature of egg stageThe developmental threshold temperature of T. lewisi egg is 15.35±0.56℃, and effective accumulated temperature is 63.35±4.42 d·℃.4 Predation4.1 Predating quantityFemale T. lewisi prey on adult P. aubei and T. piniperda (T. piniperda: 16.8±6.5, P. aubei: 25.8±3.9) more than male (T. piniperda: 7.8±3.6, P. aubei: 23.3±4.6) do. Female and male T. lewisi prey on adult P. aubei (female: 25.8±3.9, male: 23.3±4.6) more than adult T. piniperda (female: 16.8±6.5 , male: 7.8±3.6).4.2 Predation FunctionThe functional response of adult T. lewisi preying on adult T. piniperda belongs to HollingⅡ. The functional response equation is Na = 0. 0635N0 /(1+0.0182N0). When N 0→∞, the daily maximum predation number is 54.7.5 Host selection5.1 Host selection of adult fed on adult P. aubeiThe choice number of female T. lewisi toward adult P. aubei and attacked bark is obviously (P<0.05) higher than clean air, while that of male is unobvious or opposite. The choice number of male and female T. lewisi to frass of P. aubei is obviously (P<0.05) higher than clean air. The choice number of male T. lewisi to attacked bark is significantly (P<0.05) higher than adult P. aubei.5.2 Host selection of adult fed on larva T. molitorThe choice number of male T. lewisi to larva T. molitor is prominently (P<0.05) higher than clean air, while that of female is opposite. The choice number of male T. lewisi to larva T. molitor is distinctly (P<0.05) higher than attacked bark, while that of female is not.5.3 Host selection of adult fed on artificial dietThe choice number of female T. lewisi to artificial diet is prominently (P<0.05) higher than clean air, while that of male is not. The choice number of male and female T. lewisi to artificial diet is not obviously (P<0.05) higher than attacked bark.