Spatial distribution pattern of water chestnut beetle (Galerucella birmanica Jacoby)

Two regression models and nine indices of aggregation［K、C、C_A、I、I_δ、M^*、M^*/x、L^*、L^*/(1+x)］were used to test the spatial distribution patterns of population of Galerucella birmanica Jacoby in the water chestnut fields. The results indicate that the distribution patterns belong to an aggregated distribution and incline to an even distribution at a low density. The beetles occur in the loose colonies. The regression relation between the size of individual group (L^*) and the average density (x) is L^*=17.7117+1.5701x. The testing result of using the model, x=k_c(P^-1/kc₀-1),to analyze the correlation between the rate of insect-free plants and average intensity shows that this model is practical to estimate the average intensity of insects in fields. The reason for the aggregation has been analyzed with Blackith's λ. The result shows that their aggregation seems to be due to both the biological characters of population of beetles and the growth of water chestnut.