Dispersion indices, including (K) the negative binomial distribu­tion, Green's coefficient of dispersion (CO mean crowding (m"), Lioyd's (Patchiness index (m/m*) and variance mean ratio (v/m), were calculat­ed for the populations of two cotton bollworm moths, Pectinophora gos­sypiella and Earias insutana using light traps allover 2 years (January 1997 to December 1998) at five different Governorates, El-Minia, El­Sharkia, Kafr Et-Sheikh, Demeate and El-Kalubia. Comparison showed that: K, C_x and Wm' as well as slopes from regression, all indicated that under the conditions of this test (at densities tested), the popula­tions of the two pests were random. The variance/mean (v/m) ratio fluctuated considerably more than other indices examined, which by comparison, appears less reliable than previously thought.