labours in due time grows into a magnificent tent of silk, containing various apartments sufficient to defend and shelter them all from the attack of enemies and the inclemency of the seasons. As our caterpillars, like eastern monarchs, are too delicate to adventure their feet upon the rough bark of the tree upon which they feed, they lay a silken carpet over every road and pathway leading to their palace, which extends as far as they have occasion to go for food. To the habitation just described they retreat during heavy rains, and when the sun is too hot:—they likewise pass part of the night in them;—and, indeed, at all times some may usually be found at home. Upon any sudden alarm they retreat to them for safety, and also when they cast their skins:—in the winter they are wholly confined to them, emerging again in the spring: but in May and June they entirely desert them; and, losing all their love for society, live in solitude till they become pupæ, which takes place in about a month. When they desert their nests, the spiders take possession of them; which has given rise to a prevalent though most absurd opinion, that they are the parents of these caterpillars[30].

With other caterpillars the association continues during the whole of the larva state. De Geer mentions one of the saw-flies (Serrifera) of this description which form a common nidus by connecting leaves together with silken threads, each larva moreover spinning a tube of the same material for its own private apartment, in which it glides backwards and forwards upon its back[31]. I have observed similar nidi in this country; the insects that form them belong to the Fabrician genus Lyda.

The most remarkable insects, however, that arrange under this class of imperfect associates, are those that observe a particular order of march. Though they move without beat of drum, they maintain as much regularity in their step as a file of soldiers. It is a most agreeable sight, says one of Nature's most favoured admirers, Bonnet, to see several hundreds of the larvæ of Trichoda Neustria marching after each other, some in straight lines, others in curves of various inflection, resembling, from their fiery colour, a moving cord of gold stretched upon a silken ribband of the purest white; this ribband is the carpeted causeway that leads to their leafy pasture from their nest. Equally amusing is the progress of another moth, the Pityocampa, before noticed; they march together from their common citadel, consisting of pine leaves united and inwoven with the silk which they spin, in a single line: in following each other they describe a multitude of graceful curves of varying figure, thus forming a series of living wreaths, which change their shape every moment:—all move with a uniform pace, no one pressing too forward or loitering behind; when the first stops, all stop, each defiling in exact military order[32].

A still more singular and pleasing spectacle, when their regiments march out to forage, is exhibited by the caterpillars of the Processionary moth Lasiocampa processionea. This moth, which is a native of France, and has not yet been found in this country, inhabits the oak. Each family consists of from 600 to 800 individuals. When young, they have no fixed habitation, but encamp sometimes in one place and sometimes in another, under the shelter of their web: but when they have attained two-thirds of their growth, they weave for themselves a common tent, before described[33]. About sun-set the regiment leaves its quarters; or, to make the metaphor harmonize with the trivial name of the animal, the monks their cœnobium. At their head is a chief, by whose movements their procession is regulated. When he stops, all stop, and proceed when he proceeds; three or four of his immediate followers succeed in the same line, the head of the second touching the tail of the first: then comes an equal series of pairs, next of threes, and so on as far as fifteen or twenty. The whole procession moves regularly on with an even pace, each file treading upon the steps of those that precede it. If the leader, arriving at a particular point, pursues a different direction, all march to that point before they turn. Probably in this they are guided by some scent imparted to the tracks by those that pass over them. Sometimes the order of procession is different; the leader, who moves singly, is followed by two, these are succeeded by three, then come four, and so on. When the leader,—who in nothing differs from the rest, and is probably the caterpillar nearest the entrance to the nest, followed, as I have described,—has proceeded to the distance of about two feet, more or less, he makes a halt; during which those which remain come forth, take their places, the company forms into files, the march is resumed, and all follow as regularly as if they kept time to music. These larvæ may be occasionally found at mid-day out of their nests, packed close one to another without making any movement; so that, although they occupy a space sufficiently ample, it is not easy to discover them. At other times, instead of being simply laid side by side, they are formed into singular masses, in which they are heaped one upon another, and as it were interwoven together. Thus also they are disposed in their nests. Sometimes their families divide into two bands, which never afterwards unite[34].

I have nothing further of importance to communicate to you on imperfect societies: in my next I shall begin the most interesting subject that Entomology offers; a subject, to say the least, including as great a portion both of instruction and amusement as any branch of Natural History affords;—I mean those perfect associations which have for their great object the multiplication of the species, and the education, if such a term may be here employed, of the young. This is too fertile a theme to be confined to a single letter, but must occupy several.

I am, &c.

LETTER XVII.

SOCIETIES OF INSECTS CONTINUED.

PERFECT SOCIETIES. (White Ants and Ants.)

The associations of insects of which my last letter gave you a detail, were of a very imperfect kind, both as to their object and duration: but those which I am now to lay before you exhibit the semblance of a nearer approach, both in their principle and its results, to the societies of man himself. There are two kindred sentiments, that in these last act with most powerful energy—desire and affection.—From the first proceed many wants that cannot be satisfied without the intercourse, aid, and co-operation of others; and by the last we are impelled to seek the good of certain objects, and to delight