_Destructive Power of Locusts.—Prof. Riley remarks: "No one who has not witnessed the ravaging power of locnsts can fully conceive of or appreciate it. Muscular, gre garious, with powerful jaws and ample digestive and reproductive systems; strong of wing, and assisted by numerous air-sacs that buoy—all these traits conspire to make it the terrible engine of destruction which history shows it to have been under conditions favorable to its excessive multiplication. Insignificant individually, but mighty col lectively, locusts fall upon a country like a plague or a blight. The harvest is at hand; the day breaks with a smiling sun, and all the earth seems glad. Suddenly the sun's face is darkened and clouds obscure the sky: the day closes, and ravenous locust swarms have fallen upon the land. The morrow comes: the fertile land of promise and plenty has become a desolate waste, and the sun shines sadly through an atmosphere alive with myriads of glittering insects. Falling upon a corn-field, they convert in a few hours the green and promising acres into a desolate stretch of bare, spindling stalks and stubs. Their flight may be likened to an immense snow-storm extending from the ground to a height at which our visual organs perceive them only as minute, darting scintillations, leaving the imagination to picture them in indefinite distances beyond. When on the highest peaks of the Snowy range, 14,000 or 15,000 ft. above the sea, Mr. Byers has seen them filling the air as much higher as they could be distinguished with a good field glass. It is a vast cloud of animated specks glittering against the sun. On the horizon they often appear as a dust-tornado, riding upon the wind like an ominous hail-storm, eddying arid whirling about like the wild dead leaves in an autumn storm, and finally sweeping up and past you with a power that is irresistible. They move mainly with the wind, and when there is no wind they whirl about in the air like swarming bees. If a pfv.sing swarm suddenly meets with a change in the atmosphere, such as the approach of a thunder-storm or a gale of wind, they come down precipitately, seeming to fold their wings, and fall by the force of gravity, thousands being killed by the fall, as if upon stone or other hard surface. Col. H. McAllister, of Colorado Springs, Col., in 1875 saw a swaresuddenly come down in that place with a rain • ' The ground was literally covered 2 or 3 in. deep. In rising the next day, by a common impulse they would circle in myriads about you, beating.against everything animate and inanimate, driving into open doors and windows, heaping about your feet and around your buildings, their jaws constantly at work biting and testing all thinos in seeking what they might devour. In the midst of the incessant buzz and noise whicli such a flight produces, in the face of unavoidable destruction everywhere goiug on, one is bewildered and awed at the col lective power of the ravaging host, which calls to mind so forcibly the plagues of Egypt. The noise which their myriad jaws make when engaged in their work of destruction can be realized by any one who has foug,ht a prairie-fire or heard the flames passing before a brisk wind. " The eggs are laid in many kinds of soil, because choice cannot always be made by such ahnost illimitable hosts. Dry meadows, pastures, bare saudy places, and roadsides are overrun with the procreating swarms. The female when about to lay her eggs forces a hole in the ground by means of the tveo pairs of horny valves which open and shut at the tip of her abdomen, and which from their peculiar struc ture are admirably fitted for the purpose. With the valves closed she pushes the tips into the ground, and by a series of muscular efforts and continued opening and shutting of the valves she drills a hole until, in a few minutes, the whole abdomen is buried. The abdomen stretches to its utmost for this purpose, especially at the middle, and the hole is generally a little curved and always more or less oblique. Now with the hind ., legs hoisted straight above the back, and the shanks hugging more or less closely the thighs, she commences ovipositing. When the hole is once -drilled there exudes from - the tip of the body a frothy mucous matter which fills up the bottoin of the hole and bathes the horny valves. This is the sebific fluid which is secreted by the sebific or - eement gland. An egg is laid and deposited in its place by a piece of admirable appa 1 ratus. Then follows a, period of convulsions, during which more mucous material is elaborated until the whole end of the body is bathed in it, when another egg passes down and is placed in position. These alternate processes continue until the full com plement of eggs is in place, the number ranging from 20 to 35. The mucous matter binds all the eggs in a mass, and when the last is laid the mother devotes some time to filling up the somewhat narrowed neck of the burroNv with a compact and cellular mass of the same material, which, though light and easily penetrated, is not easily permeable by water and forms an excellent protection. The examination of one of these egg masses is full of interest. No more perfect arrangement is found in a bee-hive; the eggs are arranged in perfect order, having a beautiful spiral appearance in (me aspect aud showing a quadrangular arrangement in another. The time for drilling the hole and completing the process of making the egg-mass varies with the weather, in the warmest days taking. from 2 to 3 hours, but longer when the mornings and eveuings are cool. The grcnind is often covered by the egg-laying females during the day. It has been thought by some that when the young begin to migrate they are led by kings or queens, and this idea has been formed from seeing a few members of a larger genus of acridium (A. Americana) with them, and also the coral-winged locust.
The Rocky-mountain locust takes about seven weeks from the time of hatching to attain its full size. As the transformations in the orthoptera are incomplete, there is very little difference in the general appearance of the body, except in size, between the young and the adults. The most noticeable difference is the want of wings in the young, as well as the narrower prothorax. The complete development is accomplished through a series of five molts, during the first four of which the wincr-pads become more and more apparent, and during the fifth the insect more rapidly getc's its full wings and ceases growing. The first three of the larval skins are shed on or near the ground, under the grass or other cover, and their dry, cast-off shells are often mistaken for dead locusts. The last two molts are made while the insect fastens itself to some elevated object. Mr. Riley says: " When about to acquire wings the pupa crawls up some post, weed, grass-stalk, or other object, and clutches it securely with the hind-feet, which are drawn up under the body. In doing so the favorite position is with the head down wards, though this is by no means essential. Remaining motionless in this position for several hours, with autennm drawn down over the face and the whole aspect betoken ing helplessness, the thorax, especially between the wing-pads, is noticed to swell. Presently the skin along this swollen portion splits right along the middle of the head and thorax, starting by a transverse, curved suture between the eyes and ending at the base of the abdomen. As soon as the skin is split the soft and white fore-body and head swell and gradually extend more and more by a series of muscular contortions; the new head slowly emerges from the old skin, which, with its empty eyes, is worked back beneath, and the new feelers and legs are being drawn from their casings, and the future wings from their sheaths." This all occupies about 15 minutes, and the newly formed insect now turns round and clambers up the cast-off skin, and there rests while the wings expand and every part of the body. hardens and gains strength. In 10 or 15 minntes from the time of extrication the wings are fully expanded, and hang down like dampened rags. Prom this point on the broad hind-wings begin to fold up like fans beneath the narrower front ones, and in another 10 minutes they have assnmed the normal attitude of rest. Without careful inspection one would be puzzled to know how the now stiff legs had been drawn out of their old cases; but they were exceedingly flexible and capable of bending at every part over thc flexed knoe-joint of the case. The whole operation, from the bursting of the skin to the full development of wings, occupies from one-half to three-quarters of an hour.
The locust has many enemies, or animals that prey upon it. One of the most remarkable is the anthonwia angustifrons, or egg-parasite, the most widespread of all the egg-feeders. In 1876 this parasite destroyed- about one-tenth of all the eggs laid in Missouri, Kansas, and Nebraska; many were seen also in Iowa, Minin•sola, Colorado, and Texas. The larva of this insect is a little less than a quarter of an inch long, and sometimes a dozen or more are found in the same locust-egg-pod, where they suck the juices of the eggs. The winged insect is about the length of the larva, with a spread of wing about twice as great. The larvte of the common flesh-fly also feed upon locust eggs, and many species of ground-beetles also feed upon them, sometimes settling in swarms in fields where locust-eggs have been laid, and often completely devouring them_ They also devour the full-grown locusts. The locust mite yrombidium locustarum, Riley) preys upon the adult locust. In the spring the female of this parasite lays from_ SOO to 400 minute eggs about 2 in. beneath the surface of the ground in the locust-fields. Minute orange-colored mites hatch from these eggs, crawl upon the locusts, and fasten themselves at the base of the wings. The diggcr-wasps (larada semirufa) also catch locusts, sting them, and bury them in their nests for the sustenance of their newly batched young. But the birds are the great natural destroyers of the locusts, and flocks of them have been known to clear a field in a few minutes. See INsEcTivouous BIRDS -Various methods have been devised by the farmers to destroy locusts or prevent their depredations. One method which has been successfully practiced to save a sniall crop is to drag ropes over the surface of the grain, repeating the operation until the insects are driven to other parts. The encouragement of the fly-catching birds is one of the effective measures, and the commission advise the offering of rewards for hawks. This has been done with beneficial results iu Colorado and other states. The destruc tion of the eggs may be accomplished on a great scale by harrowing, plowing, aud irri,gation, the latter method sometimes being much the most economical. Young locusts, before they are winged, may he destroyed by burning the fields when this is feasible. The older locusts are destroyed in various ways by different kinds of appa ratus. Some crush them between rolltrs, some gather them in nets, ban, and other receptacles mounted on wheels and pushed about by hand or driVen by horse-power. One of the most efficient pieces of apparatus is the coal-tar pan, known as "Robbins's. hopperdozer." General
has much in common with other insects, but the proportions vary. A superficial inspection of the locust will show that its body is covered with a hard, articulated shell which protects the internal organs, the articulations having the general fortn of rings, many of which are again subdivided into pieces. There are 17 of these rings or seginents, disposed in three regions, four segments composing the head, three the thorax, and ten the abdomen. The legs consist of five well-marked joiuts, the tarsi or feet having three joints, aud the third joint having two large claws, with a pad between them. The so-called true grasshoppers have tarsi with four joints, and also shrilling organs at the base of the wings, which the locusts have not. The hind-legs, especially the thigh and shank, are very large and well adapted to hoppiug. The sternum is broad and large. The head in the adult locust is chiefly composed of a. single piece called the epicranium, andcarries the compound eyes, the ocelli or simple eye:, and the antennw. 1Vhile there are iu reality four primary segments in the head. of all winged insects, corresponding to the four pairs of appendages in the head, the posterior three segments, after early embryonic life in the locust, cotne to be represented only by their appendages and small portions to which the appendages are attached. The epicranhun represents the antennal segment, and most of the piece represents the tergum, or upper portion of the segment. The antennae, or feelers, are situated in front. of the eyes, and between them is the anterior ocellus, while the two posterior ()cern are situated above the insertion of the antennae. In front of the epicranium is the clypeus, a piece nearly twice as broad as long, and to this is attached a loose flap covering the jaws when they are at rest. This is the upper lip or labrum. There are three pairs or mouth appendages: 1, the true jaws or mandibles, situated on each side of the mouth; 2, the maxillm, divided into three lobes, the inner firmed with spines, the middle unarmed and spatula-shaped; while, 3, the outer lobe is a five-jointed feeler, called the. maxillary palpus. The floor of the mouth is formed by the labium, which is composed of two second maxillte, fused together iu the middle hue. Within the mouth the tongue is placed upon the labium, and is a large, membranous, hollow expansion of the latter organ (Packard). The internal anato y of the locust is really marvelous, although not very complex. The esophagus terminates at the center of the head, where the crop commences, and where there is a slight constriction with oblique folds armed with spine-like teeth. After leaving the head the folds in the crop become longitudinal, upon which the teeth are arranged in rows, each row, composed of groups of from three to six teeth, pointing backward, so as to push the food into the stounich: It is in the crop that the substance known as "molasses" is produced, and which is the partly digested. food, mingled with the secretion of the crop. The true or chyle stomach commences a little behind the insertion of the middle pair of legs. It is paler than the crop, which is. of a flesh color. Between the crop and stomach, externally, there are six remarkable organs, called