INSECT POWDER. 664 INSECTS, FOSSIL. other animals it lias no serious effect; workmen In the pyrclhruinniills sulFer no more incon- venience than millers do from the dust in Hour- mills. The plants are fed to horses and other Etock after the flowers have hecn gathered. In California, where some large farms are devoted wholly to this plant, the industry commenced in 1870, and three years later the small product was sold at .$1U a pound. In 1885 the price had fallen to $0.45 a pound, and has never since risen to unreasonable figures. The seed is sown about half an inch deep in light .soil during autumn or spring, and the young plants trans- planted when a few inches tall to the held. 2 feet by 4 feet apart, given irrigation each month during the dry season, cultivated by horse, and kept free of weeds by hand. A partial crop may be obtained tlie first year after planting, hut the crop of the third year is usually the largest. Generally the plants continue to bear profitably for six years. Tlie flowers are combed from their stems by hand during May and ,Iune, sun- dried, and ground between burr-stones similar to those of old-fashioned flourmillr.. and after bolting packed in air-tight tin cans. Insect powder is usually employed in household use as dust. When flies, mosquitoes, and other insects are numerous and troublesome, it is often heated in closed rooms and the stupefied creatures swept up and destroyed before they recover. It is similarly used in greenhouses. Frequently also it is applied as a solution in water (1 ovince to 2 or 3 gallons) or in alcohol (1 ounce to 4 ounces by weight). The former is applied as mixed: the latter, after daily shaking for a week or more, is filtered and the clear liquid applied with an atomizer. This decoction, if applied to plants, should be diluted somewhat. Pyretlirum is also sometimes mi.xed with kerosene emulsion or other insecticides. See Insecticide. INSECTS, F0S.SIL. Of all animals the insects, with their aerial habits of life, would seem at first thought to be the least liable to entombment and preservation in a fossil state. They are, however, found in great abundance in several localities where the nature of the deposition was particularly favorable to their fossilization. These deposits are nearly all of frcsh-water (lacustrine or marsh) or of estuarine origin, though some few arc purely marine. As a rule the imbedding materials are finely grained shales or limestone concretions in shales, or fossil gums and amber; the amber has furnished by far the most perfect fossil insects known. The shale beds of the Oligocene Tertiary at Florissant, Colo., are also noted for the abundance and j>er- fection of their insect contents. Other noted re- positories of fossil insects are the Carboniferous coal-measure beds of Commentry, France, de- scribed by Brongniart ; the Liassic beds of Scham- belen. Switzerland, of Dobbertin, Germany, and of Gloucestershire. England; and the .Jurassic lithographic limestone of Bavaria. The Ter- tiary localities, from which great numbers of insect remains have been derived, are the Baltic provinces of Germany and Russia, where they occur in amber; the shales of .ix. France, Floris- sant and the White River District of Colorado, and Oening, Radoboj. and Parshberg. The wings seem to be preserved as fossils far more often than other parts of the insect body, and in many formations these are the only parts found. The known fossil insects do not present any great points of dilference from those now living. Those found in the .lcsozoic and Tertiary rocks can be readily jilaeed in modern families; but all Paleozoic insects show a certain general resem- blance, with here and there points of relation- ship to the orders of modem insects. These or- ders did not become fully diircrentiated until Triassic time, although ancestral forms are easily distinguishable among the earlier members of the cla»s. The Paleozoic in.sects have on this ac- count been grouped under the name of i'aheo- dictyoptera, a synthetic group, and have been distributed, according to their resemblances to modern forms, among several orders — the Or- thopteroidca, Ncuroptcroidea, Hemipteroidea, etc., which are directly ancestral to the Post- Paleozoic and modern orders of Orthoptera, Keu- roptera, Hemijitera, etc. The Paleozoic in.sects are of more primitive type, as illustrated chiefly in the wing-structure, than are the Mesozoic in- fects. As a rule their front wings are mem- branous — i.e. they had not yet evolved hardened front wings, such as the elytra and tegmina. that ser»-e as protective coverings for the more deli- cate hind wings of modern insects. Some of the early insects were of gigantic size, compared with their living descendants — Meganeura, an ancestral dragontly found in the Carbnniferous, of Commentry, France, had a body 1(1.5 inches long, and its wings spread over 28.5 inoho. An- other point of interest is that the Paleozoic in- sect fauna was made up almost entirely of cock- roaches. These must have swarmed in the woods and swainps of the Carboniferous and Triassic periods, for their remains are fouml in abundance in the shales and sandstones associated with the coal deposits of those ages. The earliest insects are of very fragmentary nature. The oldest known is supposed to he an ancestor of the bedbugs (Protocimex) found in the Ordovician rocks of Sweden and represented by a single wing. In the Silurian the cockroaches appeared, and they were the predominating types in the Devonian and Carboniferous. The Car- boniferous fauna consists principally of Orthop- tera and Xeuroptera, and of forms intermediate between these two orders, and also of extinct types intermediate between the Orthoptera and the Heiiiiptera. and it is interesting Ijecause of its large numl)er of generalized or synthetic types. In the Triassic the beetles appear suddenly with their characteristic hardened front wings fully developed. This ditrerencc in the character of the front and hind wings is fully marked for the first time in all Triassic insects, and it has be- come more strongly marked since that period. In the Liassic epoch of the .Jurassic period in- sects were abundant, as might lie expected from the general extension of terrestrial conditions during that period. Beetles abound, and as they represent many families still living, they have been used to determine the conditions of life and climate during that period. Leaf and fungus eating beetles and dung-beetles are known. The earliest ants; first well-marked bugs, allies of the squash-bug: the first flies, bees, and perhaps also the earliest moths, are found in this epoch. The Cretaceous insect fauna is small, but that of the succeeding Tertiary, beginning with the Eocene, is almost as well difTerentiatcd as that of the present day. for many of the genera are still members of the living insect fauna. In all
