starting from the far West, has taken possession of the potato-fields of the continent, and for the extermination of which there is annually spent, by the agricultural communities of the United States, several millions of dollars in labor and in poisons? A few facts like these serve to show that the study of entomology is not a study which deserves to be placed in the category of useless pursuits. Viewed merely from a utilitarian standpoint, this study is one of the most important, far outranking, in its actual value to communities, the study of many branches of zoölogical science which some people affect to regard as of a higher order. The legislature of Pennsylvania acted wisely in passing a law which demands that in every high school established within the State there shall be at least one teacher capable of giving instruction in botany and in entomology. The importance of entomology, while not perceived by the masses as yet, has been recognized by almost all the legislatures of the States; and not only the general government of the United States, but the governments of the individual commonwealths, are at the present time employing a number of carefully trained men, whose business is to ascertain the facts and instruct the people as to the best manner in which to ward off the attacks of the insect swarms, which are respecters neither of size nor beauty in the vegetable world, attacking alike the majestic oak and the lowliest mosses. Genus LYCÆNA, Fabricius (The Blues) "Bright butterflies Fluttered their vans, azure and green and gold." SIR EDWIN ARNOLD. _Butterfly._--Generally small, for the most part blue on the upper side of the wings, white or gray on the under side, variously marked with spots and lines. What has been said in reference to the subdivision of the genus _Thecla_ may be repeated in regard to the genus which we are considering. It has been in recent years subdivided by writers who have given close attention to the matter, and these subdivisions are entirely defensible from a scientific standpoint. Nevertheless, owing to the close resemblance which prevails throughout the group, in this book, which is intended for popular use, the author has deemed it best not to separate the species, as to do so presupposes a minute anatomical knowledge, which the general reader is not likely to possess. _Egg._--The eggs are for the most part flattened, turban-shaped (see p. 4, Fig. 7). _Caterpillar._--Slug-shaped, as in the preceding genera, feeding upon the petals and bracts of flowers, or upon delicate terminal leaves. _Chrysalis._--Closely resembling the chrysalids of the preceding genera. This genus is very widely distributed in the temperate regions of both hemispheres. Many of the species are inhabitants of the cold North or high mountain summits, while others are found in the tropics. (1) =Lycæna fuliginosa=, Edwards, Plate XXX, Fig. 16, ♂, _under side_ (The Sooty Gossamer-wing).