ROCKY MOUNTAIN LOCUST 373 centuries. The natural history of the Rocky mountain locust is similar to that of all true locusts. The female is furnished at the end of her abdomen with two pairs of horny valves, which open and shut, and which enable her to drill a hole in I I Jlf L, J7 th e ground in which to LIJ '({fJ^ a ^ deposit her eggs. These, ^* c w to the number of from 50 to 100, are voided in a glutinous fluid, which hardens and holds them together, and which, in combination with particles of earth, covers them with a sort of pod. The eggs are de- posited in the invaded country during the lat- ter part of the growing season, and while some few may hatch prematurely the same season, FIG. 5. Anal Characters of Female of Rocky Moun- tain Locust, showing horny valves. FIG. 6. a. Female depositing eggs. b. Egg pod with end broken open. c. i.ggs. d, e. Earth partially removed, showing an egg mass in place and one being placed. /. Place where such a mass has been covered up. the great bulk of them do not hatch till the following spring. The young locust has the general characteristics of the mature insect, and differs principally in lacking wings. After shedding its skin at four different periods, the FIG. 7. a, a. Newly hatched larvae, b. Full-grown larva. C. Pupa. wings are acquired in from six to eight weeks from the time of hatching. It is doubtful whether in their native home the insects show any tendency to migrate except when forced by necessity. They are sluggish in the cooler parts of the day, and fly principally between the hours of 10 A. M. and 4 P. M., and then only when the wind is in the direction they wish to go. Their life is limited by the spring and autumn frosts, and all that hatch in the spring perish at the approach of winter, soon after the eggs are laid. The young " hoppers " in the invaded country often abound to such an extent that they totally destroy all crops. In the spring of 1875, in several of the west- ern counties of Missouri, especially in the mid- dle portion of the state, and in the adjacent part of Kansas, the ground was kept as bare as in midwinter for nearly two months after spring opened, nothing green being left but the leaves on the forest trees, and a small glossy -leaved plant, the amarantm llitum, which they invariably left untouched. "When not too hard pressed for food, they will pass by most species of milkweed (asclepias), as also the wild grass on low prairies. The distress caused by these insects in the part of Missou- ri mentioned, combined with previous short crops from drought and the chinch bug, made public measures of relief necessary; and, al- though the state entomologist insisted that the infliction was temporary and limited to its present area, many persons emigrated, and a day of fasting and prayer was appointed by the governor. These young hoppers travel during the hotter hours of the day in immense schools, not in any particular direction, but in search of food. They walk and hop alter- nately, moving at the rate of about three yards a minute. Toward evening they go to feed- ing, and generally collect afterward on fences or other objects away from the ground, so as to avoid moisture. As they grow older their numbers are continually reduced, not only by the attacks of enemies and by climatic influences, but by devouring one another ; for when they are swarming to so unnatural an extent this cannibalistic propensity is fully de- veloped. Those which acquire wings instinc- tively go toward their native home, or in the direction whence their parents had come the previous year. This exodus begins in Missouri early in June, and reaches its acme about the middle of that month. They generally leave in time to enable the farmers to raise a good crop of corn and of most vegetables. Indeed, the distress and devastation is not unfrequently followed, as in 1875, by great abundance. The incursions generally take place after two or three years of excessive drought, and are likely to be followed by a comparatively wet season. Aside from this somewhat uncertain cause, the total destruction of the vegetation during the first six or eight weeks of spring well nigh ex- terminates many other insect pests, such as the chinch bug ; and the manure left by the locusts, in the very best condition to be appropriated, increases in many cases the fertility of the soil. Not only is there no danger of this plague rav- aging the country E. of the 94th meridian, but there is none of its becoming a permanent evil in any part of the Mississippi valley proper.
