When censused using a grid of 1 km2 quadrats all populations yielded a variance:mean ratio of 1.0, though each population showed a different pattern of aggregation and none corresponded to a Poisson distribution. The variance:mean ratio is useless as a measure of departure from randomness, though it is widely recommended as such. The ratio is also uninterpretable as a measure of aggregation except for its coincidental relationship to indices such as the Morisita index of aggregation I(M). IM can be defined in terms of the probability of 2 randomly selected individuals being found in the same quadrat or sampling unit. It can be generalized to yield a family of indices, IMr, relating to the probablity of r randomly selected individuals being found in the same sampling unit. Presentation of a plot of IMr versus r may often be preferable to condensation of all information on aggregation into a single value, such as IM. Comment is offered on the need to consider a range of spatial scales, on the corresponding definitional and scale aspects of plotless sampling, and on the fruitlessness of attempting to view spatial patterns themselves as consisting of only 2 distinct aspects, such as intensity and grain. -from Author
