A Model Relating Numbers of Dispersing Insects to Distance and Time

A simple model is proposed relating numbers of dispersing insects (Y) to distance (x) from a release point and time (t). The model, in the form log Y = a-b $\surd$ x-ht+cx log t, fits several sets of data from cabbage root fly and Drosophila. A model with bx instead of b$\surd$ x appears to fit some data for tsetse flies and mosquitoes. Replacing b $\surd$ x or bx by bx$^q$ might lead to greater generality but would make the model more difficult both to fit and to interpret. For another set of experiments with cabbage root fly with variable trap spacing (s) a modification of the model to log Y = a - ht + p $\log$ s fits data from traps at release points with different trap spacings. In biological terms, the results suggest that, although dispersing insects tend to move away from each other, this is partly countered by a considerable random element in this movement.