none An analytical method for the description of intrinsic variability in insect development rates for incorporation in phenology models is presented. Two sets of experimental data are used as examples. The method is easy to apply, can describe data accurately, produces highly realistic simulations of insect development, and is amenable to the simulation of age-dependent mortality, feeding, and reproduction. The method was developed for univoltine insects with discrete generations, but it can also be applied to multivoltine species with overlapping generations. A modification of the method to handle small samples is also discussed and applied to data. Techniques; Ecological techniques; Life cycle and development Insecta; Choristoneura fumiferana (Tortricidae ); Neodiprion sertifer (Diprionidae ); Apanteles fumiferanae (Braconidae ); Ecological modelling; Phenology simulation, development rate variation use; Life cycle; Phenology simulation from developmental rate variation data; Development; Rate variability, description & use in phenology simulation