THE entomological publications of the United States Department of Agriculture have for long past been the admiration of European naturalists. Exceptionally valuable, even among that Department's series of excellent memoirs, are two recent papers on Scolytid beetles of the genus Dendroctonus by Dr. A. D. Hopkins, one (Technical Series, No. 17, part i.) being in the main systematic and descriptive, the other (Bulletin No. 83, part i.) dealing for the most part with the bionomics of the beetles and the rôle played by the various species as depredators in North American forests. These papers contain some of the results of seventeen years' original research; probably no such descriptions and figures of the imaginal and larval anatomy of Scolytid beetles as those in the technical memoir have ever been issued before, while in the systematic portion are to be found, not only full structural accounts of the various species, but figures showing the characteristic form of the brood and larval galleries in each case. The accompanying figures, slightly reduced from the original, give some idea of Dr. Hopkins's excellent illustrations.