bodies. By what instinct," he adds, " do these creatures undertake this dangerous flight? Is it not the wise institution of the Creator to destroy a dreadful plague to the country *?" We think that it is more consistent with other instances of extensive destruction among particular species to refer it to the design of Providence to furnish food for carnivorous animals. The day-flies (Ephemerida), for example, are a harmless race, and yet the numbers of them which perish only a few hours after they acquire wings is scarcely inferior to those of the locusts t. Like the locusts, too, they chiefly perish in the water, both affording an abundant banquet for the fishes. There is one circumstance in these migrations, which is remarked by most observers, that appears to corroborate these views; we refer to the direction commonly taken by them being towards the sea, and their pursuing their course with little deviation. The locusts seen by Captains Irby and Mangles, on the southern shore of the Dead Sea, were said to be on their way to Gaza, to which they pass almost annually; those observed in Barbary by Dr. Shaw "marched directly towards the sea §;" and Hasselquist tells us they seldom or never deviate from the direction of their course. These very singular facts are strikingly illustrated by the migrations of a much larger, though it would appear no less destructive animal, the lemming rat (Mus lemmus, LINN.), which inhabits the north of Europe, and lives on vegetable food. The migrations of the lemming take place at uncertain intervals of about ten years, from Lapland towards the southern parts of Sweden, induced, it is supposed, by the foresight of a severe Hasselquist's Voyage, p. 444. See Insect Transformations, pp. 218 and 373. winter, to escape to a more genial climate; though the migration has the effect, like that of the locusts, of f reducing an overgrown population, and at the same of supplying food to many animals who might otherwise have starved. In their journeys, they always endeavour to keep in a direct line; and hence multitudes of them perish in their endeavours to cross lakes and rivers. If they are disturbed or pursued while swimming over a lake, and their phalanx chances to be separated by oars or poles, they will not recede; but keep swimming directly on, and soon get into regular order again. So obstinate, indeed, are they in holding on their direct course, that they have sometimes been known to try to pass over a vessel. This army of rats moves chiefly by night, or early in the morning; and makes such destruction among the herbage, that the surface of the ground over which they have passed appears as if it had been burned. Their numbers have at times induced the people of Norway to believe that they descended from the clouds; and the multitudes that are sometimes found dead on the banks of rivers, or other places, corrupt the whole atmosphere around *. We recollect another remarkable migration of a different species of animal also towards the seacoast, but for a very different purpose, and we mention it here more particularly, because it will lead us back by a natural transition to families of insects influenced by similar motives,-we refer to the landcrab of the West Indies (Ocipoda ruricola, LATREILLE). The usual residence of this species is the inland mountains and woods, where they live in holes dug by themselves. Annually, about the months of April and May, they set forth in a body, often consisting of some millions, for the sea-coast. They always march in a direct line to their place of *Pennant, Arctic Zoology. destination, and are said seldom to turn out of their way, on account of intervening obstacles, and even if they encounter a lofty wall or a house, they will attempt to scale it; but when they meet with a river they follow the course of the stream, as if instinctively aware that it will ultimately lead them to the sea, as was probably the case with the African locusts, mentioned by Jackson. These multitudinous hordes of crabs, however, do not perish in the sea, but go there to spawn; though from this spawn forming a rich banquet for the sea-fish, the providential effect is nearly the same as in the instances of locusts, aphides, lady-birds, and sawflies. Some of the more remarkable migrations of insects are, in the same way, for the purpose of depositing their eggs, or disposing of their supernumerary progeny in suitable localities, in the case, for example, of ants and bees. Kirby and Spence have given the following animated and eloquent account of the migrations of the former. "In the warm days that occur from the end of July to the beginning of September, and sometimes later, the habitations of the various species of ants may be seen to swarm with winged insects, which are the males and females, preparing to quit for ever the scene of their nativity and education. Every thing is in motion-and the silver wings, contrasted with the jet bodies which compose the animated mass, add a degree of splendour to the interesting scene. The bustle increases, till at length the males rise, as it were by one general impulse, into the air, and the females accompany them. The whole swarm alternately rises and falls, with a slow movement, to the height of about ten feet, the males flying obliquely, with a rapid zig-zag motion, and the females, though they follow the general movement of the column, appearing suspended in the air, like bal loons, seemingly with no individual motion, and having their heads turned towards the wind. "Sometimes the swarms of a whole district unite their infinite myriads, and, seen at a distance, produce an effect resembling the flashing of an aurora borealis. Rising with incredible velocity, in distinct columns, they soar above the clouds. Each column looks like a kind of slender net-work, and has a tremulous, undulating motion, which has been observed to be produced by the regular alternate rising and falling just alluded to. The noise emitted by myriads and myriads of these creatures does not exceed the hum of a single wasp. The slightest zephyr disperses them; and if in their progress they chance to be over your head, if you walk slowly on, they will accompany you, and regulate their motions by yours. The females continue sailing majestically in the centre of these numberless males, who are candidates for their favour, each till some fortunate lover darts upon her, and, as the Roman youth did the Sabine virgins, drags his bride from the sportive crowd, and the nuptials are consummated in mid-air; though sometimes the union takes place on the summit of plants, but rarely in the nests*. After this danse de l'amour is celebrated, the males disappear, probably dying, or becoming, with many of the females, the prey of birds or fish t; for since they do not return to the nest, they cannot be destroyed, as some have supposed, like the drone-bees, by the neuters. That many, both males and females, become the prey of fish, I am enabled to assert from my own observation. In the beginning of August, 1812, I was going up the Orford river, in Suffolk, in a row-boat, in the evening, when my attention was caught by an infinite number of winged ants, both males and females, at which the fish were *De Geer, ii. 1104. + Gould, p. 99. everywhere seen darting, floating alive on the surface of the water. While passing the river, these had probably been precipitated into it, either by the wind or by a heavy shower which had just fallen: and M. Huber, after a similar event, observed the earth strewed with females that had lost their wings, all of which could not form colonies. 66 'Captain Haverfield, R. N., gave me an account of an extraordinary appearance of ants observed by him in the Medway, in the autumn of 1814, which is confirmed by the following letter, addressed by the surgeon of the Clorinde, now Dr. Bromley, to Mr. MacLeay: In September, 1814, being on the deck of the hulk to the Clorinde, my attention was drawn to the water by the first-lieutenant (Haverfield) observing there was something black floating down with the tide. On looking with a glass, I discovered they were insects. The boat was sent, and brought a bucket full of them on board; they proved to be a large species of ant, and extended from the upper part of Salt-pan Reach out towards the Great Nore, a distance of five or six miles. The column appeared to be in breadth eight or ten feet, and in height about six inches, which I suppose must have been from their resting one upon another.' These ants were winged-whence this immense column came was not ascertained. From the numbers here agglomerated, one would think that all the ant-hills of Kent and Surrey could scarcely have furnished a sufficient number of males and females to form it. "When Colonel Sir Augustus Frazer, of the horse-artillery, was surveying, on the 6th of October, 1813, the scene of the battle of the Pyrenees, from the summit of the mountain called Pena de Aya, or Les Quartres Couronnes, he and his friends were enveloped. by a swarm of ants, so numerous as en |