Studies On The Biological Character And Controlling Effects On Aphis Glycines Of Coccinella Quatuordecimpustulata (Linnaeus)

Combining laboratory and field experiments, we studied the biological characteristics,developmental durations, stress resistance of Coccinella quatuordecimpustulata （Linnaeus）, andwe also determined its functional response and controlling effects on Aphis glycines. The resultswere shown as follows:First, The developmental periods, development threshold temperature （DTT）, developmentalrates and effective accumulative temperature （EAT） of C. quatuordecimpustulata were studiedunder the conditions of five constant temperatures in laboratory. The results showed thatdevelopmental periods of C. quatuordecimpustulata became shorter with increasing temperature,and developmental rates got faster in the temperature range from19℃to31℃. Developmentthreshold temperatures of egg, larvae, pupa were11.47,12.15,12.74,15.02,12.96and13.09℃respectively, and their effective accumulative temperatures were39.16,34.06,22.89,21.36,39.93and42.41℃·d degree-day respectively. The Logistic models and developmental periodspredicting equations were made based on the data of development threshold temperature andeffective accumulative temperature.Second, We determined the stress resistance of C. quatuordecimpustulata under lowtemperatures and its hunger tolerance at different temperatures from19℃to31℃. The resultsshowed that cold resistance of adults and the fourth instar larvaes of C. quatuordecimpustulataare stronger than the pupae at5℃. Under the conditions of temperature range from19℃to31℃, the survival days of C. quatuordecimpustulata larvae became longer with thetemperature decreasing.Third, C. quatuordecimpustulata is one of the important predations of aphis, and has evidenteffect on control function of soybean aphis. The functional responses of C.quatuordecimpustulata to soybean aphis were investigated in laboratory. The results showedthat the relationship between the quantity of soybean aphis preyed by ladybirds and the densityof soybean aphis could be represented by a negative accelerative curve. The4th instar larvaehad the highest daily predation capacity, followed by the3rd instar larvae and the adults, the2ndinstar and the1st instar larvae were the lowest. The functional response of C.quatuordecimpustulata to Aphis glycines fitted Holling-Ⅱtype equation and the equations of theadults and1st to4th instar larvae were as follows: Na1=1.1305Nt₁/（1+0.0137Nt₁），Na2= 0.8564Nt₂/（1+0.0491Nt₂），Na3=0.7158Nt₃/（1+0.0142Nt₃）。Na4=0.9983Nt₄/（1+0.0097Nt₄），Na5=1.1309Nt₅/（1+0.0089Nt₅）.Forth, The controlling actions of C. quatuordecimpustulata on soybean aphids were studiedunder laboratory conditions. The results revealed that the controlling effect was100%in tendays when the ratio of adult ladybirds to aphis were1:75. The controlling effect was90%intwelve days when the ratio of adult ladybirds to aphis were1:100. The controlling effect was98%in six days when the ratio of larvae ladybirds to aphis were1:15.Fifth, The controlling effect of C. quatuordecimpustulata on soybean aphis was also studiedunder field conditions. The results showed that the controlling effect was86.7%in fifteen dayswhen the ratio of adult ladybirds to aphis were1:75. C. quatuordecimpustulata had a significantcontrolling effect on soybean aphis when the ratio of adult ladybirds to aphis was lager than1:75. The controlling effect was not significant when the ratio of adult ladybirds to aphis wasless than1:125. With the the young worm age gradually become larger, its activity enhancementis enhanced and predation number become larger，hence the controlling effect is increased. Thecontrolling effect was64.5%in six days when the ratio of larvae ladybirds to aphis were1:10,and it was100%on the8th day. The controlling effect was81.1%in ten days when the ratio oflarvae ladybirds to aphis were1:15, and it was91.5%on the12th day. The controlling effectwas81.3%on the12th day when the ratio of larvae ladybirds to aphis were1:20.