Numerical Behavior of a Gypsy Moth Population System

The numerical behavior of a gypsy moth population system observed in eastern New England between 1911 and 1931 is described. Rates of change in egg mass density from years ( n ) to ( n + 1) were related to rates of change in density from years ( n - 1) to ( n ) and to an index of the density level of the overall population system, termed "zone density." When zone density was high, individual populations tended to increase to and maintain high density levels. When zone density was low, individual populations tended to achieve and maintain low densities. Numerically unstable populations between years ( n - 1) to ( n ) tended to remain numerically unstable from years ( n ) to ( n + 1). Forest Sci. 19:162-167.