of London. In many parishes subscriptions were opened, and the poor people employed to cut off and collect the webs at one shilling per bushel, which were burnt under the inspection of the parish officers. At the first onset fourscore bushels were collected in one day in the parish of Clapham. Some writers went so far as to assert that they were a usual presage of the plague, others that they would destroy all kinds of vegetables, and thus starve the cattle in the fields. Prayers were even offered up in some churches, on account of their great number, which was considered by some sufficient to render the air pestilential. This idea is founded on the grossest ignorance, and carries with it its own refutation; the health of the public was by no means affected by them, either immediately or remotely.

The pest which caused these ravages and fright, is the caterpillar of the brown-tailed moth, the young caterpillars of which are hatched early in autumn. As soon as they quit the egg they set about spinning a web, and having formed a small one, they proceed to feed on the foliage, by eating the upper surface and fleshy part of the leaf, and leaving the under side and ribs. It is curious to observe with what regularity they marshal themselves for this purpose. Thus they proceed daily, spinning and enlarging their web, to which they retreat every night and in bad weather, and extending their depredations. In the course of a few weeks their operations begin to be visible on the trees; their web as yet is not so conspicuous, as those leaves which are stripped of their green part assume a dead appearance. Now is the time to destroy them, while their nest is small, and their ravages just visible, by collecting the twigs and branches on which they lie hid in their web, and then burning them, merely to prevent their returning again to the trees and shrubs. If this operation is performed early it will save the autumnal

verdure of the foliage. Should the web, however, be left till winter, it will have acquired a stronger and tougher texture, so as to bear pulling off, which should be preferred to pruning in certain cases, especially where it regards the fruit-trees. In short, no other remedy will avail. When benumbing winter arrives, they confine themselves entirely to their silken habitation; they then not only secure the general web on all sides as strongly as they can, to exclude impertinent intruders, but each individual spins a thin case for itself. Here they rest in a state of torpid security till the genial warmth of the spring animates them afresh, and informs them that the all-bountiful Author of Nature has provided food convenient for them. Thus apprized, they issue forth in the daytime and in fine weather, as before; but having acquired stronger powers, and the foliage they have now to encounter being more tender, they become less scrupulous in their feeding, and devour the whole of it. A disposition to associate continues with them till they have changed their last skins, when they usually separate, each endeavouring to provide in the best manner for itself. At this period many are attacked by the ichneumon-fly. Some, however, continue together, when each spins a separate web, in which it changes to a chrysalis ; this usually takes place about the beginning of June. It remains about three weeks in a state of perfect quietude, when it changes in July to the moth, which is perfectly white, except that at the end of the abdomen is a tuft of brown down, with which the female covers her eggs after they are laid.

The most probable causes of their appearance are, the peculiarity of the weather, and the plenty or scarcity of the enemies of the insect. As to the former, warm and dry weather is universally allowed to promote the generation of insects; violent winds, heavy and long-continued rains, or extreme

cold, are, on the contrary, supposed to check and destroy them. It is, however, wonderful to observe with what address they secure themselves from the effects of the two former. Such as feed on boughs, on such occasions, creep from them to the large branches or body of the tree, where they rest unshaken; and those which reside in webs are so secured as to suffer little injury from any of those causes. It appears that the only mischief these caterpillars are capable of occasioning is to rob particular trees and shrubs of their foliage and blossoms it remains to consider how far the trees and shrubs will be injured by such a loss, and how far it may be injurious to their owners. It has been found, by repeated observation, that those trees and shrubs which have been entirely stripped have not been killed thereby, but as soon as the caterpillars have removed to change to chrysalis, they have put forth fresh foliage: the only loss, therefore, the owner sustains from their depredations on those trees which are not cultivated for the sake of the fruit, is some check to their growth, and a temporary deprivation of the beauties of spring and autumn. But the gardeners sustain more serious injuries by these insects, as they destroy the blossoms in the bud as well as the fruit.

CHAPTER XX.

THE NATURAL HISTORY OF THE FLEA.

Its supposed Manner of Appearance-Its eggs-Rösel's Opinion with respect to the Young-Defrance's Opinion-The Manner of preparing Food for the young Larva-Description of its Pupa and Cocoon-Perfect Insect, its Habits.

EWLIN, in his book of Travels in Turkey, has recorded a singular tradition of the history of the flea and its confraternity, as preserved among a sect of Kurds, who dwelt in his time at the foot of Mount Sindshar. "When Noah's ark," says the legend, "sprung a leak by striking against a rock in the vicinity of Mount Sindshar, and Noah despaired altogether of safety, the serpent promised to help him out of his mishap if he would engage to feed him upon human flesh after the deluge had subsided. Noah pledged himself to do so; and the serpent, coiling himself up, drove his body into the fracture and stopped the leak. When the pluvious element was appeased, and all were making their way out of the ark, the serpent insisted upon the fulfilment of the pledge he had received; but Noah, by Gabriel's advice, committed the pledge to the flames, and scattering its ashes in the air, there arose out of them fleas, flies, lice, bugs, and all such sorts of vermin as prey upon human blood, and after this fashion was Noah's pledge redeemed." Setting aside all the marvellous contained in this legend, it is not difficult to trace in it the germes of that vulgar error which attributes the production of various small but noxious species of insects to the existence of what is termed “a blight,” an error founded upon the most untenable ideas of natural history,

but which is, nevertheless, so deeply rooted, that it requires "line upon line, and precept upon precept," to dislodge it from the minds even of well-educated, persons.

Descending, however, from fiction to plain matter of fact, we propose in this chapter to detail the natural history and series of transformations which the insect first mentioned undergoes previous to appearing in its perfect state, and which, although our readers may probably have no idea of their existence, are not less remarkable than those of the butterfly or the beetle.

It appears that Aristotle was the first author who was acquainted with any of these changes, since he noticed not only that the flea has distinct sexes, but that it produced σkwans woɛideis; from not, however, tracing the insect through its different states, he fancied this progeny was completely sui generis and imperfect, and that the perfect insect was generated spontaneously in the earth, just as at the present day plant-lice, turnip-flies, &c., are supposed to be generated spontaneously in the air. Indeed, as Mr. Mac Leay observes, it is always either at the egg or pupa state that Aristotle, and, we may add, many other naturalists, have lost sight of the metamorphosis, and, in the absence of experiment, have had recourse to fancy. Hence, the name given to this insect by the Romans, Pulex, is stated by Isidorus to have been derived from pulvis,* dust, quasi pulveris filius. So likewise Mouffet tells us, that the flea is produced from the dust, especially when moistened with urine, the smallest ones springing from putrid matter; and Scaliger relates that they are produced from the moistened humours among the hairs of dogs.

The Dutch naturalist Leeuwenhoeck was, how

* Our English name Flea, and the German Flock, are evidently deduced from the quick mctions of this insect.