Cephalcia masuttii sp. n. is described from the SE Alps of Europe, based on morphological, biological, and genetic studies. The larvae feed gregariously on Picea abies. The species has been recorded also from Central Siberia and NE China, where the larvae feed on Picea obovata and Picea koraiensis, respectively. Indications exist that it may be more widely distributed in Europe and northern Asia. The strict gregariousness of larvae of this species is peculiar among spruce feeders of Cephalcia. Morphologically the adults are most similar to Cephalcia alashanica, with which they are compared. An allozyme analysis showed that the populations from Europe and China are quite similar and clearly different from the other species living on spruce. The karyotype of C. masuttii (n = 25) is also described.