In 1891 C. J. Maynard published a _Manual of North American Butterflies_ with ten colored plates; the plates are very poor indeed, and the text not much better. In 1893 Dr. Samuel Hubbard Scudder, the author of the three great volumes on the New England species, brought out a little book called _The Life of a Butterfly_. It is a brief and popular account of the life-history of _Anosia plexippus_, the Monarch or Milkweed butterfly, which is common everywhere. Dr. Scudder’s _Brief Guide to the Commoner Butterflies of the Northern United States and Canada_ also appeared in 1893--a very useful little book. In 1898 Dr. W. J. Holland, Director of the Carnegie Museum at Pittsburgh, published his famous _Butterfly Book_, in which he described more than five hundred species, accompanying each description with a sketch of the life-history and habits in all cases where these details were known. The magnificent colored photograph plates are quite equal for all practical purposes to the hand-colored drawings of Edwards and Scudder, and enable the veriest tyro to classify any of the commoner butterflies simply by comparing them with the pictures. Besides the detailed description of each species there is a great deal of miscellaneous information of interest to the general reader. Because of the new process of reproducing photographs in colors the book sold very cheaply--never more than four or five dollars--and has done more to arouse a popular interest in butterflies than all other works together. Many of the elementary books since 1898 are indebted to Holland’s book, and the present booklet is no exception. In 1905 William Greenwood Wright of San Francisco, published a book called _West Coast Butterflies_. This work is illustrated with colored plates nearly as good as Holland’s, and is indispensable to those interested in California species. George B. Longstaff’s _Butterfly-Hunting in Many Lands_ appeared in 1912. The book itself is of no great interest to North Americans, as Longstaff spent only two weeks here, and came no farther south than Montreal. Still, his chapter of _Bionomic Notes_ deals with butterflies in general and is well worth reading. The best part of the book, however, is the appendix, which contains E. A. Elliott’s translations of Fritz Müller’s famous papers on scent-producing organs in butterflies. The most important of these had never been published except in some obscure Portuguese journals, practically inaccessible to the American student. In 1916, encouraged by the success of his _Butterfly Book_, Dr. Holland prepared a pocket manual called the _Butterfly Guide_, with colored figures representing some two hundred and fifty species. In 1917 there appeared Clarence M. Weed’s _Butterflies Worth Knowing_, with thirty-two plates in color. This is one of the best of the smaller popular books, and contains a great deal of valuable modern material, but is not to be compared with Holland’s work.