(Received January 27, 1992; revised July 6, 1992)
Abstract. The Morisita's model for estimating the habitat preference by the ant lions Genuroides japonicus is generalized by introducing, in addition to the environmental densities a and b, a repulsivity parameter theta. The probability function of the number Ln of individuals choosing fine sand to settle when a total of n ant lions are introduced is examined. A heuristic and the minimum chi-square methods for estimating the parameters a, b and theta are discussed.
Key words and phrases: Eulerian numbers, Gould and Hopper numbers, minimum chi-square estimation, unimodality.