Egg and nauplii development of co-existing populations of Calanus glacialis and C. finmarchicus from Disko Bay, western Greenland, were measured in the laboratory with and without addition of food. Egg hatching rate was measured at 5 temperatures from 0-10 °C and the fit to a Belěhrádek equation was highly significant (r2> 0.99). There was little difference between hatching and development rates of the two species; however, the egg hatching rate at low temperatures was faster than predicted from measurements made in other areas. Also nauplii development times at 0 °C were similar, with C. glacialis and C. finmarchicus reaching nauplii stage six after 44 and 48 days, respectively. The laboratory reared nauplii could be separated accurately to species by stage and length alone. However separation by size was not possible for the in situ community of nauplii where the influence of food and temperature made the size distribution more variable.