Nothing is more aggravating than to be compelled, soon after completing a monographic work, to make changes in the nomenclature and synonymy; yet this is the purpose of this paper concerning the genus Acronycta, which was monographed by Dr. H. G. Dyar and myself in Proc. U. S. Nat. Mus., XXI., pp. 1–194, 1898.

It was explained in the introduction to this paper that, because of its interesting early stages, the late Dr. C. V. Riley had been, for years, accumulating material for a thorough study of Acronycta; therefore I had made no effort to become closely familiar with the species. Some time before, Dr. A. G. Butler, of the British Museum, attracted in the same way by the larval difference, had divided the species among several genera, referred to several families; allowing superficial and secondary characters to mislead him, as be has since admitted. In 1886, while arranging the Grote material, Dr. Butler made comparisons with other types in the Museum, the results of which were published in 1887 in “Entomologica Americana.”