Spatial distribution is one of the most characteristic properties of insect populations ; in most cases it allows us to define them (Legay and Debouzie, 1985). Spatial distributions of insect populations are not fixed but dynamic. Thus variations in space and in time of the pattern of individuals occur not only at the scale of the species, but also at the population one. For example, differences between the dynamics of two populations of the butterfly Euphydryas editha may be as great as those between E. editha and E. chalcedona (Ehrlich et al., 1975).