ther; but it may be proper to make an observation or two on the eggs themselves, applicable generally to all insect eggs, which are exposed to the storms of winter. The glutinous matter by which the eggs are united, when protruded from the insect, and which is so necessary for preserving them in a mass, and for fixing them to the spot, is found, contrary to the nature of many similar substances, to be insoluble in water, and therefore incapable of being affected by the copious rains to which they are destined to be exposed. But this is not so remarkable as another fact, which has been proved by some severe tests, and which shows how admirably the constitution of these eggs is adapted to the season of winter. Both Spallanzani and Hunter made experiments to ascertain the degree of cold which the eggs of insects were capable of enduring without injury; and we subjoin the statement of the latter:-"I have exposed eggs to a more rigorous trial than the winter of 1709.* Those of several insects, and, among others, the silk-worm, moth, and elm-butterfly, were inclosed in a glass vessel, and buried five hours in a mixture of ice and sal gum (rock salt). The thermometer fell 6° below In the middle of the following spring, however, caterpillars came from all the eggs, and at the same time as from those which had suffered no cold. In the following year I submitted them to an experiment still more hazardous. A mixture of ice and sal gum, with the fuming spirit of nitre (nitrate of ammonia), reduced the thermometer 22° below zero,—that is, 23° lower than the cold of 1709. They were not injured, as I had evident proof, by their being hatched."

zero.

It is, indeed, a singular and unaccountable fact, that the eggs of these insects are incapable of being frozen even by the intense cold now mentioned. Spallanzani discovered this, by crushing some of them with the nail, when he found that their contents remained fluid; and

* The year 1709 is celebrated for its rigour, and its fatal effects on plants and animals. Farenheit's thermometer fell to one degree below zero, and yet the insects were as numerous in spring as ever.

he justly infers, that the included embryos remain equally unfrozen. The final cause of this is easily understood; but the chemical property which resists so severe a trial, has not been ascertained.

The modes by which instinct has taught insects to preserve their eggs during winter, are very various. One of these I have already detailed; but, before leaving the subject, there is another which, on account of its singularity, I cannot deny myself the pleasure of mentioning; I allude to the cochineal insects (coccida), so called from one of the species furnishing the well-known valuable dye-stuff. These little insects contrive to render their dead bodies useful to their future progeny, by protecting their eggs from the severity of the weather. They die in the act of incubation. Their eggs are deposited under their bodies, which become glued to the spot, and thus serve as a covering. In this state the dead insects appear on the bark of trees, like small warts, of various forms. The mother is seldom larger than a pepper-corn, yet the number of eggs which she lays amounts to several thousands. Some of them secrete a sort of white silky gum, very like gossamer, as the first bed of their eggs. Some naturalists have supposed this substance to be of the nature of the spider's web; but the author of "Insect Transformations" says, he has ascertained it to be "precisely similar to the gluten which envelopes the eggs of most insects."

SIXTH WEEK-WEDNESDAY.

HYBERNATION OF INSECTS.-VARIOUS STATES.

TURNING from the consideration of insect eggs, let us look to some of the other means which the Creator has employed for preserving these minute animals during the rigorous season of the year. Some assume the chrysalis

form, in which state they require no food, and can endure a greater degree of cold than in their more perfect condition, though they are much inferior, in this respect, to the eggs already mentioned. We shall take an example of this method of hybernation from the butterfly family, which is remarkable for the variety of modes by which the Author of Nature has provided for the safety of the different species. The history of the large white butterfly, which we select, is not perhaps so peculiar, among the insect tribes, as it is remarkable. It undergoes a double round of transformations in the course of the year, and its instincts are wonderfully adapted to the state of the season in each. From the chrysalis state, these insects assume that of caterpillars, about the last days of April, or the beginning of the following month. They first appear on wing in the middle of May, and, about the end of the same month, lay their eggs in clusters on the under side of cabbage-leaves. In a few days after, the caterpillars come forth, and continue to feed together till the end of June, when they are at their full growth. They then wander about in search of convenient places to fix themselves, where, after their change, the chrysalis may be sheltered. When such are found, they each fasten their tail by a web, and carry a strong thread of the same round their body, near the head; and, thus firmly secured, hang a few hours, when the chrysalis becomes perfectly formed, and divested of the caterpillar's skin. In fourteen days after this, the fly is on the wing.* Such is the history of their first series of transformations. But a long period of genial weather still remains, and a new succession of changes takes place. The butterfly lays its eggs, which are again converted into caterpillars, and about the end of September, these caterpillars become chrysalides, in which state they are prepared to pass the winter. Now, however, as if acquainted with the change which nature is about to undergo, they do not seek for protection beneath the fading vegetation which formed

* Goldsmith's Animated Nature, Note by Captain Brown, vol. iv. p. 297. VOL. I. K

their previous retreat, but may be found hanging under the copings of garden walls, under pales, and in other places, where they can have a tolerable shelter from the inclemency of the weather, and yet be in the neighbourhood of their food, when they throw off this state of inactivity on the revival of nature in spring.

An instance of the hybernation of insects, in the caterpillar state, may be found in another branch of this family, that of the Marsh Fritillary. These small butterflies, the colour of which is a brownish orange, variegated with orange and black, are found in the caterpillar state, in the month of September. As the season advances, they spin for themselves a fine web, in which they congregate, and under covert of which they pass the winter. During this time, they are so nearly reduced to a torpid state, as to require no food; nor do they venture out of their covering, till invited by the warmth of spring. They have not yet come to their full size, and their growth is suspended during winter. If we pursue their history a little farther, we find that, about the end of April, they are in full maturity, and, suspending themselves by the tail, change into chrysalides. "Their mode of suspension," says Captain Brown, " is a singular instance of the extraordinary power of instinct. They first draw two or three small blades of grass across toward the top, and fasten them together by means of their silk, then hang themselves beneath the centre of these, each having his own little canopy. By this means, they are not only hidden from the sight of birds, but defended, in a great measure, from the damage they might otherwise sustain from windy and boisterous weather."

In speaking of the hybernation of caterpillars, we must not forget to mention a beneficent provision by which many species are defended from the cold; we allude to the hair which at that season covers their bodies. The younger Huber found some larvæ of the smaller species of ants, which spend the winter heaped up in the lowermost floor of their dwelling; and he remarks, that "those

"Goldsmith's Animated Nature," Note, p. 298.

which are to pass the winter in this state, are covered with hair, which is not the case in summer, affording another proof of that Providence with which, naturalists are struck at every step." Now, the very same thing occurs among various tribes of caterpillars, though it is by no means the case with all insects that pass the winter in this form. Even those which envelope themselves in silken shrouds, have generally this additional protection, of which the caterpillars of the brown tail moth and mallow butterfly are instances. Some are thickly clothed with hair, a remarkable example of which occurs in the caterpillar of the drinker moth, whose very feet are covered with fine shaggy down. This insect does not become torpid in winter; and, as it feeds on grass, it can always find plenty of food. "When a fine sunny day chances to break in upon the gloom of winter, this pretty insect may be often seen stretched at its full length on a low twig, or the withered stem of a nettle, basking in the sunshine with apparent delight."

Some insects survive the winter in their perfect state, but these are comparatively few. Several species of the genus Vanessa, are of this number; but it is observed by Mr Rennie, that this can only be positively affirmed of the female. It is certain, however, that, even in this state, insects will bear an almost incredible degree of cold with impunity. We extract two instances recorded in the publication of Mr Rennie, on Insect Transformations, already alluded to.† "In Newfoundland, Captain Buchan saw a lake, which, in the evening, was entirely still and frozen over; but, as soon as the sun had dissolved the ice in the morning, it was all in a bustle of animation, in consequence, as was discovered, of myriads of flies let loose, while many still remained infixed and frozen round." A still stronger instance is mentioned by Ellis, in which " large black mass, like coal or peat upon the hearth, dissolved, when thrown upon the fire, into a cloud of mosquitoes (Culicidae)."

* Insect Transformations, p. 193.

† Ib. p. 406.

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