in the centre of the cell, and in the interior of this it continues to work for five days. If the cells containing the spinning silk-worms are placed regularly on the line, in the order in which they begin to spin, then there will occur no difficulty in taking them off in the succession in which they stand, as the first in order on the line will be the first requiring to be wound off. After a silk-worm has been ten days in the cell, its cocoon of yellow silk will be compact and complete; this must be taken out of the cell and the exterior or waste silk stripped off, until a single thread runs by itself; an operation which will be much assisted by allowing the cocoon to float on warm water. When so much of the silk has been wound off, that the remainder appears of a thinner, paler and inferior quality, the thread should be broken, the remaining portion of the cocoon being weak, gummy, and of little value; this should be taken out of the water and laid aside, to prevent its getting entangled with the others.

Within the cocoon is the chrysalis, from which the future moth is produced; these may be thrown on a tray containing bran, which will absorb the moisture that would otherwise remain on them after their long soaking. When silk-worms are reared for profit, there is a far greater number of chrysalides than are wanted; these may be given to fowls, which are exceedingly fond of them, and to which they afford a wholesome and nutritious diet. In a fortnight or three weeks after the winding of the silk, some of the chrysalides will be found cracking and opening, and the perfect moths will then appear: these are small sluggish creatures, of a pale buff colour, seldom leaving the tray, mat or paper on which they are placed, and where the females lay their eggs.

As regards the hatching of the eggs, it is important to know that this may be retarded as long as the owner pleases, by subjection to a low temperature; and it will be well for

those who purpose keeping silk-worms for the sake of profit, to defer the hatching of the eggs until the mulberry-trees are sufficiently forward to ensure a constant supply of food. The usual time for the hatching of silk-worms' eggs in this country is about the 12th of May, but a fortnight later is much better; for at that time the mulberry-trees have not generally put forth their leaves, and great difficulty continually occurs in procuring food: for, as far as we have yet learned, no other food than mulberry-leaves affords to silkworms wholesome nutriment; lettuce, dog-wood and blackcurrant leaves have been often tried, but without success.

It may be remarked that in winding off the silk, when the single threads of half a dozen cocoons are found, they may be guided with one hand on a small reel constructed for the purpose, which may be turned with the other hand, the cocoons at the same time floating on a basin of warm water.

a, Eggs of the breeze-fly of the horse. b, the same magnified. c, larva or bot. d, chrysalis. e, perfect insect. f, position of the female in the act of oviposition.

CHAPTER III.

HISTORY OF BREEZE-FLIES.*

THE name of gad-fly has been repeatedly given to the insects whose history is detailed in this chapter, but that term more properly belongs to those blood-sucking flies which cause such pain and misery to our horses, in places abounding in wood, especially in warm cloudy weather and before thunder showers. The present insects when in the larva state are termed "bots" in horses, "maggots" in sheep, and "wornils" or "warbles" in cows and oxen; and these three represent three divisions of the family, differing essentially in their history. The perfect insect produced from each kind of larva is properly termed a breeze-fly.

* Authority :—An Essay on the Bots of Horses and other animals, by Bracy Clark, F.L.S.

The opinions respecting the breeze-fly of the horse, or bot as it is usually termed, as to the benefit or injury derived from it, are very opposite; some observers go so far as to assert that the larvæ occasionally completely perforate the stomach of the horse, causing disease, pain, and even death; others regard them as perfectly innocuous; and one author, whose careful and laborious investigations entitle his opinions to the greatest respect, believes the effect of bots to be salutiferous rather than otherwise: this author is Mr. Bracy Clark, and from his masterly essay the following particulars are extracted.

The female fly in approaching the horse for the purpose of oviposition, carries her body nearly upright in the air, the protruded ovipositor being curved inwards and upwards. Suspending herself for a few seconds before the part of the horse on which she intends to deposit the egg, she suddenly darts upon it, and leaves the egg adhering to the hair: she hardly appears to settle, but merely touches the hair with the egg held out on the extreme point of the ovipositor (see fig. ƒ), the egg adhering by means of a glutinous liquor with which it is covered. She then leaves the horse at a small distance, prepares a second egg, and, poising herself before the part, deposits it in the same way the liquor dries, and the egg becomes firmly glued to the hair. This is repeated till four or five hundred eggs are sometimes placed on one horse. The skin of the horse is usually thrown into a tremulous motion on the touch of the insect, which merely arises from the very great irritability of the skin and cutaneous muscles at this season of the year, occasioned by the heat and continual teazing of the flies, till at length these muscles appear to act involuntarily on the slightest touch of any body whatever.

The fly does not deposit her eggs at random on the horse's body, but selects those parts which are most likely

to be nibbled by the horse: the inside of the knee is frequently chosen, but all naturalists must have remarked how commonly the eggs of the bot are deposited on that part of a horse's shoulder which he can never reach with his mouth, and thus, to a casual observer, it would seem that they must perish, and fail in the object for which their parent designed them. Now there is a provision of nature which exactly counteracts this difficulty. When horses are together in a pasture, and one of them feels an irritation on any part of the neck or shoulder which he cannot reach with his mouth, he will nibble another horse in the corresponding part of his neck or shoul

der, and the horse so nibbled will immediately perform the kind office required, and begin nibbling away in the part indicated. The horses, when they become used to this fly, and find it does them no injury by sucking their blood, hardly regard it, and do not appear at all aware of its object.

When the eggs have remained on the hairs four or five days they become mature, after which time the slightest application of warmth and moisture is sufficient to bring forth in an instant the latent larva. At this time, if the lips or tongue of the horse touch the egg, its operculum is thrown open and the young larva liberated: this readily adheres to the moist surface of the tongue, and is from thence conveyed with the food to the stomach. It is worthy of remark, that it is probable the greater part of the eggs deposited by this fly are taken up in consequence of the irritation of other flies, as the Tabani and Stomoxides, which, by perpetually settling on the skin, occasion a horse to nibble himself in those parts, and thus receive the larvæ on the tongue and lips whence they are introduced into the stomach. The egg is glued on the hair with the broad end