TEST OF A MOSQUITO EGGSHELL ISOLATION METHOD AND SUBSAMPLING PROCEDURE

Production of Aedes vigilax, the common salt-marsh mosquito, can be as sessed by determining eggshell densities found in soil. In this study, 14 field-collected eggshell samples were used to test a subsampling t echnique and compare eggshell counts obtained with a flotation method to those obtained by direct examination of sediment (DES). Relative pr ecision of the subsampling technique was assessed by determining the m inimum number of subsamples required to estimate the true mean and con fidence interval of a sample at a predetermined confidence level. A re gression line was fitted to cube-root transformed eggshell counts obta ined from flotation and DES and found to be significant (P < 0.001, r( 2) = 0.97). The flotation method allowed processing of samples in abou t one-third of the time required by DES, but recovered an average of 4 4% of the eggshells present. Eggshells obtained with the flotation met hod can be used to predict those from DES using the following equation :DES count = [1.386 x (flotation count)(0.33) - 0.01](3).