The meiotic formula of the European spruce beetle, Dendroctonus micans (Kugelann), is 10 AA + Xyp in males and 10 AA + XX in females. This karyotype is different from the morphologically similar Dendroctonus punctatus LeConte (14 AA + Xyp), which is consistent with the taxonomic validity of both species. The chromosome number found in D. micans, added to karyological data from other species of the genus Dendroctonus Erichson, suggest that the karyological diversification within this genus may have occurred in two directions: one toward more southerly latitudes in North America and the other toward Europe and Asia.