Mean development rate of eggs of the Colorado potato beetle,Leptinotarsa decemlineata(Say), at 10 constant temperatures over the range 15 to 33°C is fit with a bounded sigmoid curve. The distribution of development rates is modeled using a temperature-dependent normalizing function and a sigmoid curve fit to cumulative development. When eggs are alternated between 25 and 35°C for limited durations, development rates vary from those predicted using constant-temperature results. This is explained as a product of selective mortality and time lags in shifts between rate-controlling mechanisms. Mean development rate of larvae at 10 constant temperatures over the range 15 to 33°C is fit with a simple sigmoid curve, and distributed development of larvae is described in a manner similar to that used to describe the distribution of egg development rates. Total feeding of the 4 larval instars over the range 15 to 33°C is described as a constant (instars 1 and 2) or a 2nd-order polynomial (instars 3 and 4). Mean development rate of pupae at 11 constant temperatures over the range 10 to 31°C is fit with a simple sigmoid curve.