The distribution of eggs, larvae and plants within crops attacked by wheat bulb fly Leptohylemyia coarctata (Fall.)

Fields at Rothamsted were sampled for several years to assess populations of wheat bulb fly eggs and larvae, and populations of wheat plants and shoots. The results were fitted to the regression equation $\log_{10}(S^2) = \log_{10} a + b \log_{10} m$, where $S^2$ is the variance, $a$ is a sampling factor, $b$ the 'index of aggregation' and $m$ is the mean. Randomly-distributed populations have $b = 1$, aggregated populations have $b > 1$, and populations with a tendency towards regular distribution have $b < 1$. Most of the variates had $b$ slightly greater than one, i.e. the populations were only slightly aggregated, and a square root transformation is appropriate for analysis of data from infested fields.