Three groups of mountain pine beetles,Dendroctonus ponderosaeHopkins, were placed in fresh lodgepole pine,Pinus contortaDouglas var.latifoliaEngelmann, billets and allowed to construct egg galleries. Group I consisted of reemerged females that had previously made egg galleries in the field; group II consisted of new females allowed to mate, then males were removed; and group III consisted of new females with males present throughout gallery construction. Offspring from these rearings were compared by gallery section for brood production, rate of emergence, size, and sex ratio. Reemerged females were as successful in establishing galleries as new females but produced significantly fewer beetles than new females with males present. Offspring of new females emerged at a faster rate than those of reemerged females. Offspring from reemerged females were larger than those of group II females, but not those from group III females. Sex ratios were not significantly different among offspring of the three groups.