The number of known living species is be tween 100,000 and 200,000, and over 10,000 spe cies are known to inhabit the United States. About 1,000 fossil species are known.
Coleoptera have been the favorites of ento mologists. They have been studied when in their perfect state more than any other insects, but owing to the difficulty of finding their larvae and carrying them through the successive stages of growth, the early stages of compara tively few species are known. The metamor phoses are complete, and in this respect the beetles are much in advance of the orders of net-veined insects in which the transformations are incomplete. Many beetles, as the species of Cetonia, etc., visit flowers to collect and eat the pollen, and in doing so bring about the fertilization of those flowers.
Classification.— The systematic arrange ment of the Coleoptera is in an unsettled state. The tiger and ground beetles are generally con sidered to be the (highest* Coleoptera, but in reality they appeared to be allied to what were the more primitive and generalized types, while what are by some authors regarded as the tlowestp beetles, that is, the weevils, are the most specialized or most highly modified. As all our classifications begin with the more primitive or earliest forms, and end with the most specialized, we should begin with the Carabida or ground beetles, as being the near est representatives of what are supposed to be the earliest beetles. We would, therefore, adopt provisionally Sharp's primary divisions of Coleoptera, with some important changes. His first division of series comprises the lamel licorns (May beetle, etc.), and his second the Adelphaga or ground beetles. This order should be reversed.
Series 1. Adelphaga (Carabida of some au thors). Antenna long, slender, filiform; tarsi five-jointed; maxilla highly developed, three lobed, the outer palpus shaped. (Ground and tiger beetles).
Series 2. Lamellicornia. Antenna short, the terminal joints leaf-like; tarsi five-jointed.
Series 3. Polymorpha. Antenna either club like or serrated, variable in shape, as are the number of joints of the tarsus. (Buprestida, spring-beetles, etc., including many families).
Series 4. Heteromera. Front and middle tarsi five-jointed, hind tarsi four-jointed; other characters very variable. Tenebrionida, Can tharida, or blister-beetles (Qv.), etc.
Series 5. Phytophaga. Tarsi four-jointed but with a small additional joint at the base of the fourth joint; sole usually densely pubescent.
(Boring or longicorn beetles; Cerambycidee, leaf-beetle, potato beetle).
Series 6. Rhyncophora. (Weevils). Head prolonged in front to form a beak; palpi much reduced; tarsi four-jointed, but with an ad ditional minute joint at the end of the fourth. The term Isomera was applied by Le Conte and Horn to a combination of series 1, 2, 3 and 5.
Phylogeny.-- The Coleoptera are supposed by Braver and also Packard to have descended from some type allied to a Campodea-like an cestor. The larva of the ground beetles are allied by their long legs and biting mouth-parts to the common Campodea-like progenitor; they appear to have undergone the least modification from the shape of the primitive coleopterous larva; the footless grubs of boring beetles, longicorns and weevils, being secondary forms. Thus the Coratida and next after them the rose-beetles (Staphylinida) have been regarded as the nearest to the earliest type of beetles.
Fossil
The earliest known re mains of Coleoptera are five specimens from the carboniferous strata of Silesia, of which four are wing covers and one is a pronotum; these have been referred by Karsch to the families Carabida or Tenebrionida. In the lower Jurassic, however, comparatively well preserved remains of six families (Carabidee, Dytiscida, Elaterida, Scarabeeida, Ceramoycida and Chrysomelida) have been detected, showing that, early in the Mesozoic era, nearly all the principal types of beetles had appeared; whence we naturally suppose that their an cestors evolved during the Carboniferous period, though their remains have not yet been discovered. During the Tertiary age beetles became more abundant, and a greater number of species belonging to existing genera ha-/e been found. The Oligocene fresh-water de posits of Aix and Provence, of Florissant, Colo., contain many kinds of beetles, as also do the Miocene amber of the Baltic coast in Prussia and the lignite of Bohemia, as well as the fresh-water marls of Germany, Utah and Wyoming. Of the weevils 350 Tertiary species have been described, their hard bodies account ing for their preservation. •
writings of Say, Har ris and others; especially Le Conte and Horn;
of America north of Mexico,'