Studies On The Activity Of Red Imported Fire Ant Solenopsis Invicta Buren Workers

The red imported fire ant,Solenopsis invicta Buren(Hymenoptera:Formicidae, Myrmicinae,Solenopsis),is a dangerous pest and recently intruded into China,and S. invicta has more strong competition than other fauna in infested area.The paper deals with effects of the mound size and structure of red imported fire ant(RIFA), environment,temperature,humidity,interfered degree and pesticides ect.on the activity laws of RIFA workers.The aim of this study is to offer scientific gists to effectively control RIFA.1 The study method of RIFA workers' activityThe study method of RIFA activity was conducted by ruler-marker method (scale:100cm)in the outer conditions of natural changing temperature.The results showed that the orientations of ruler-mark insert into mound can be randomly selected,and the various indexes of RIFA workers' activity were observed and noted in randomly sides of ruler.To note and reflect the RIFA activity,photoes of RIFA workers of climbing up the rule in every other 15s within 180s had been took.The center depth of mound inserted by ruler was 6cm.Moreover,the accumulation of workers,most reached height,average reached height and RIFA workers to renew placid time were introduced advance and the proportion coefficients were 0.4,0.1, 0.3,0.2 respectively,and the highest limit values of various indexes were 800,120cm, 40cm,50s respectively.As a result,a formula was set up as follow:Standard value=observe value of various indexes/highest limit value of various indexesActivity index=standard value of accumulation of workers×0.4+standard value of most reached height×0.1+standard value of average reached height×0.3+standard value of renewed placid time×0.22 The effects of mound size and the structure of colonization on workers' activityThe RIFA activity was studied by ruler-marker in different environments and the results showed that most of indexes of workers' activity in two environments were relative to mound volume and many models between them had been set up.1)Green belt areaMost reached height-mound volume y=10.6041nx-32.901(R²=0.5962, p=0.01) Average reached height-mound volume y=2.17431nx-7.1736(R²=0.6582, p=0.01)Renewed placid time-mound volume y=16.6471nx+19.666(R²=0.5546, p=0.01)The accumulation of workers-mound volume y=129.621nx-716.36(R²= 0.6126,p=0.01)1)Wasteland areaMost reached height-mound volume y=4.361nx-57.53(R²=0.6742,p=0.01)The accumulation of workers-mound volume y=84.361nx-216.73(R²= 0.6352,p=0.01)The activity indexes increased when the mound volume became bigger,and the trends of workers number on ruler-marker accord with room model Y=ae^bx.The worker activity indexes increased accord with the gradually enhanced workers number of activitive mound and offsprings' number.3 The study on the relationship between RIFA workers' activity with temperature and humidityThe worker activity in sunshine,cloudy and rain and the effects of temperature, humidity on RIFA workers' activity had been studied.The results show that workers' activity was more active in sunshine and cloudy weather and relatively weak in rain. When the temperature(T＜24℃)lower in morning,the workers' activity of all mounds was fallower,index of workers' activity was lower,but strengthen gradually with the temperature rose and reached at a most strengthen degree when in 9:30～11:30.Then workers' activity fallower gradually and the index of workers' activity dropper gradually with the temperature rose,and the index value of workers' activity was least when temperature reach at 37℃(13:30).After that,workers' activity became strengthen again when temperature declined.The relationships between RIFA workers' activity and relative humidity of air,relative humidity of soil (6cm)and relative humidity of mound center(6cm)were not significant.4 The effect of interference on workers' activityThe effect of interference on workers' activity was important.The survey of RIFA workers' activity was conducted by continuing interference on different mounds and the results were suggested that the workers' activity presented a downtrend and the relationship between the index of workers' activity in all mounds and interference time was accord with conic model:Y=ax²+bx+c. 5 The effect of treat with pesticide on workers' activityAll kinds of pesticides were used to manage active mounds to determine the variational conditions of RIFA workers' activity after treated with pesticids to find out the controlling effect,and the results showed that workers' activity weaken after treated with 0.1%Fipronil 1d,while workers' activity weaken significantly only in treated with the other four pesticides,4.5%cypermethrin,0.02%Spinosad,0.30% fenoxycarb and 1%sulfluramid after 3d.And workers' activity weaked gradually along with the prolongation of controlling time after active mounds treated with last three pesticides.The relation equation between index of workers' activity(Y)and treating time(X)had been set up.4.5%cypermethrin:y=0.0041x²-0.0469x+0.2607(R²=0.9496,p=0.05)0.1%Fipronil:y=0.0001x⁴-0.0028x³+0.0234x²-0.0712x+0.2602(R²= 0.9998,p=0.05)0.02%Spinosad:y=0.0024x²-0.0456x+0.2390(R²=0.9921,p=0.05)0.30%fenoxycarb:y=0.0026x²-0.0464x+0.2588(R²=0.9933,p=0.05)1%sulfluramid:y=0.0012x²-0.0321x+0.2251(R²=0.9925,p=0.05)To use 0.02%Spinosad deal with mound,the suited dose was 15～25g.6 The study on the seasonal changing laws of RIFA workers' activityThe RIFA workers' activity had been mensurated in two environments through one year.The results suggested that workers' activity had reached in a most strongthen degree in March and April,but it became the most weakly in January,and went up at a peak in Agust and September.