Researches On The Characteristics Of Arthropod Community Structure And Predatism Of Dominant Natural Enemies In Different Ecotype Summer Cornfields

This paper studied the characters of insects community structure,the temporal pattern and the Predation pattern of main natural enemies on pests of summer cornfield.The main contents and conclusions are as follow:1.The corn fields insects in Taian have abundant community species and different community have obvious differences.119 species of corn fields including 67 species of pests and 52 species of natural enemies were obtained through investigation of three kind of different ecotype cornfield and set up a record of arthropod.The characteristic of community structure and the relative abundance of each group were analyzed using some indices.2.The dominant species of different ecotype cornfields arthropod community were certained according to dominance index , they are Rhopalosiphum maidis (Fitch) ,Tetranychus truncates,Ostrinia furnacalis (Guenee) ,Helicoverpa armigera (Hubner) ,and so on.It was found that Aphididae of Phytophagous group dominated in number. Propylaea japonica (Thunberg),Scolothrips takahashii Priesner , Misumenops tricuspidatus (Fabricius) ,Sirthenea flavipes (Stal.)of natural enemies group dominated in number.There exists differences in the community species composition in different ecotype cornfields.3.The similarity of different ecotype cornfields were analyzed by the following indexes including species richness,ecological dominance, community diversity and evenness. It was found from the study:the species richness(53),species diversity index(1.5667)and evenness(0.3147)of pure cornfield were lowest in three different ecotype cornfields,but the ecological dominance(0.8319)was the highest,it showed that the community structure was not reasonable,and pests in such cornfields tend to breakout,it should be controlled strongly;ecological dominance of insects community in corn-vegetable and corn-fruit fields are lower than that in pure cornfield.The species richness,species diversity index and evenness are all higher than pure cornfields natural enemies number is relatively more which make a reasonable community structure.4.The temporal characters of the different ecotype cornfields were researched using the characteristics of community structure and the characters of different time series,it was found that the species richness of cornfield varied very much in different time series.The species richness become more and more after July 15th and reached the largest number 61 at August 13th after that the species richness become smaller and at September 29th reached the lowest number.5 . The predation functional response of Propylaea japonica (Thunberg),Chrysopa sinica Tjeder,Misumenops tricuspidatus (Fabricius) on main cornfield pests were studied.It was found that the functional response were all belong to Holling-â…¡model,and got the mathematical model using which to account the daily predation number.