ture of the hammock, consolidated and made the interior covering of this delicate creature. As the worms themselves were of a colour inclining to a dark brown, this superficial tincture seems to have been entirely purged off into the shell. For

After the worms had continued in this state during the whole month of June, whether they gnawed their way through the ends of their shells and hammocks, or that exit was prepared for them by some corrosive matter oozing from their mouths, I know not, but they came out almost all in the space of one morning, the most beautiful fly or moth my eyes ever beheld. Its shape was extremely elegant; its head, upper wings, body, legs, and antennæ, were of the purest white, and glittered as if they were clothed with some shining kind of substance. I rubbed some of this off, and upon viewing it in a microscope, found it looked like small cones of polished silver, or down cut into bits extremely small and pointed. The upper wings were regularly studded with black spots, and extended themselves somewhat farther than its tail. The under wings, which were a little shorter, were of a duskish colour, and prettily fringed at the extremities. This lovely work of nature seemed, after its resurrection, to have no dependence on material food. The cornel had recovered a new set of leaves by the time the fly appeared, but it never touched them; and those that came out in my room, lived as long there as the rest, which enjoyed the open air, and the tree on which they were bred. If they did feed, it must have been on some other adventurer of the air, too minute to be visible. Those that were confined in my room, discharged a small drop of brown liquor, in which I suppose their eggs were contained; but as they were not deposited in a proper receptacle or matrix, they did not produce worms the next season. As the cornel-tree is the peculiar habitation of the worm and fly, and supplies the former with food in its leaves, so it is certainly the only nurse of the egg. It is likely the eggs were discharged into the little apertures about the buds, where they might most conveniently be nourished, by the return of that genial juice or spirit, with which the cornel is by nature fitted to cherish and raise them into life. The flies seemed to be of the most delicate

nature in respect to heat and cold. The former they could bear with difficulty, the latter not at all. Scarce any of them survived the 1st of August. They loved rest, and did not care to flutter much about. While they were yet in their chrysalis state, I brought great lumps of them to my room, and those which happened to be bruised in pulling them from the trees, produced flies distorted, either in the wings, or other parts; but this distortion generally wore. off in a little time, and the pretty creature recovered its natural elegance of shape.

The place where these cornel trees stand, is surrounded by steep hills, and sheltered beside with a very thick plantation. This was certainly no inconsiderable help to the prodigious increase of this puny and delicate creature. I verily believe, both an unusual warmth of air, and a deep shade were equally necessary to it, for I observed that those cornels that stood more exposed to the cool air and sun, abounded less with worms than the rest.

In the beginning of May, 1738, the worms began again, in prodigious numbers, to work; and having covered some trees, they were stopped, and most of them destroyed by the foul weather that followed.

In 1739 they appeared in small numbers, and much shrunk in their size; they wrought only sufficient covering for themselves.

They appeared again last year, but it was plain the great frost had destroyed most of their eggs, and checked the growth of those that escaped, for there were very few of them to be seen, and twelve of them were scarcely as large as one in May, 1737.

It may be asked, how these creatures came to be bred on these trees, and what occasioned the prodigious increase of them at that time? I can only offer conjectures by way of solution to these queries. I hope however they will not seem improbable; but rather help to clear up these difficulties, and at the same time carry our eyes a little farther into nature, than merely what concerns this species of insects.

There is not an animal, nor a vegetable, that may not be considered as a little world, in respect to the habitation and nourishment it affords to certain insects peculiar to

itself. The scheme of life begins in vegetation, and whereever on the earth, or in the water, nature is able to produce vegetables, she always obliges them to pay for their elemental nourishment to certain insects, animals, or fishes, which she billets on them. These again are forced to refund to others, and to diet, and lodge, each of them, a set of living creatures, assigned them by the universal scheme of things.

This traffic in life, this just community in nature, which suffers nothing to subsist merely for itself, is found not only every where on the face of the earth, but also in all lakes, pools, rivers, and in the ocean. By microscopes we discover a prodigious variety of little creatures in the water, all feeding either on the floating vegetables, which that element in a state of stagnation produces, or on one another. As to the sea in particular, we know only what happens about the shores where we see vegetables of various kinds, on which a like variety of insects are bred and nourished. These, with a prodigions number of others bred in the mud, become the prey of the smaller kind of fishes, and they again of the greater. That this scheme of nature, found every where else, dives also into the depths of the ocean, may appear probable both from the wise frugality of nature, which hath a useful end in every thing, and besides, rejoices in filling the world with life and motion; and from the wonderful kinds of fishes (some of them partaking of a human shape) which are now and then washed up by violent storms from the deeper waters, or happen to pursue their prey from the low-lands of the ocean, to the higher grounds at the shores.

Franciscus Redi, in his curious and learned treatise concerning the generation of insects, hath not only refuted the foolish notion of equivocal generation, but also hath shewn us, that each animal and vegetable hath its own peculiar insects to maintain; and Eleazar Albin, in his collection of various caterpillars, and the butterflies into which they are changed, hath given us a beautiful demonstration, from above a hundred instances, that each species hath its own proper plant, to which it is by nature necessarily adapted, and on which only it can feed, and live any time.

The cornel now is the plant, on which alone this species

of caterpillars, of which we have been speaking, can be propagated and fed. As is the case throughout the whole vegetable world, in regard to the respective insect of every plant; the specific qualities with which the juices of this tree are impregnated, fit it for the support of this, and perhaps no other worm. The chymists tell us, that in the essential oil consists the peculiar and distinguishing qualities of a plant. If so it is, then it follows, that the insect of each plant is furnished with such organs either of manducation, or digestion, as enable it to extract better than the nicest chymist, the essential oil of its own plant, in which consists that nutritive specialty by which it is fitted to become its peculiar food.

As to the question, how this plant came to receive the eggs of this fly, it may be answered that it received them just as all other plants come by the eggs of their own flies. Before such trees are removed from the neighbourhood of those from whence they sprung, they receive sufficient colonies from those already peopled, and so carry off a stock, which they extend again to their suckers; and it is probable that no single plant is destitute of its own insect; because the flies of every plant have continual access to their own plants, and no doubt are prompted either by the sight or smell, or some other quality, of their native vegetable, which is congenial to them, to propagate their kind upon them. And as this act is probably attended with some degree of pleasure, it keeps them continually busy in the work of impregnating the proper plant.

So much may suffice to shew how this tree came to be peopled by this kind of insect.

I will now assign such conjectural reasons as have occurred to me for the extraordinary increase of this insect in 1737.

The succession of seven or eight mild winters, which preceded May, 1737, might, by preserving their eggs, give occasion to the surprising increase of these worms at that time. And as they are one of the earliest kinds, the prodigious warm May of that year, so hatched their eggs for them, that they all came to perfection. Whereas the more common worms and flies that do not make their appearance, till later in the season, meeting with the sharp easterly

winds that blow during the months of July and August, were in a good measure destroyed; otherwise it is possible they too might have had an extraordinary increase that

summer.

However I own this reason hath its objections, and doth not fully satisfy me. There is scarcely a year that is not remarkable for an extraordinary production of some one kind of insects and flies, when no colourable account can be assigned for it, from the known temperament of the year. Insects, as well as fevers, are epidemical, and probably depend, like them, upon a certain unknown constitution of the air. Nay, who knows, but all epidemic disorders are nothing else but prodigious flights of invisible flies, of which, each sort, according as the constitution of the year favours it, takes its turn to multiply from equally little worms, bred in putrid carcasses, especially after great battles; and being raised from thence into the air, are wafted, not only from one body to another, but also into distant countries. Sydenham, and if I forget not, others have observed that the season immediately preceding that in which the plague raged, abounded unusually with all sorts of flies; which shews at least, that the constitution of the air doth at those times greatly favour the production of those creatures. Besides, as the usual preservatives against infection, such as vinegar, tobacco, rue, wormwood, &c. are endued with very acrid and pungent particles, perhaps they defend us from the contagion no otherwise, than by stinging and killing the invisible flies, before they can lay their eggs.

Be this however as it will, it is certain, there is such a constitution as we have been speaking of, in respect both to distempers and insects. But whence this proceeds, whether from the sun alone, or from the joint influence of other planets, or the transudations of mineral vapours, or fermentation in the soil of the earth; and farther, whether this sort of climacterick in the seasons, be stational or casual, I leave the naturalist to judge. I only insist that such a temperies or crasis there is, which, running through all nature, doth at certain times, give more than ordinary energy to the prolific powers of such animals or plants, as are of nature congruous to such crasis.