The genus Ips in North America contains several groups of closely related species which are at present poorly defined. Morphological characters alone do not provide an adequate basis for deciding whether some of the forms are specifically distinct or represent mere variations which may occur in the same general locality or even in the same brood. The extent of this variation can be determined only by breeding isolated pairs through successive generations combined with biological studies in the field. The present article describes techniques for rearing successive generations of Ips in the laboratory.