SHEEP Nose-Worms, in natural history, a species of fly-worm found in the noses of sheep, goats, and stags, and produced there from the egg of a large two-winged fly.
The frontal sinuses above the nose in sheep and other animals, are the places where these worms live, and attain their full growth. These sinuses are always full of a soft white matter, which furnishes these worms with a proper nourishment, and are sufficiently large for their habitation; and when they have here acquired their destined growth, and come to the condition in which they are fit to undergo their changes for the fly-state, they leave their old habitation, and falling to the earth, bury themselves there; and when these are hatched into flies, the female, when she has been impregnated by the male, knows that the nose of a sheep, or other animal, is the only place to deposit her eggs in order to their coming to good.
Mr Vallisnieri, to whom the world owes so many dis-
coveries in the insect-class, is the first who has given any true account of the origin of these worms. Tho' their true history had been till that time unknown, the creatures themselves were very early discovered, and many ages since were esteemed great medicines in epilepsies.
It is very common to find only one worm in the head of the creature that has them, often two are found, and sometimes three, but very seldom any more than that.
Redi has given a very imperfect figure of this creature, nor is that of Mr Vallisnieri much better. The worm has two brown hooks at the anterior part of its head, placed parallel, or nearly parallel, to one another. It is composed of 11 rings, which together form a conic figure, something flattened, of which the head of the worm is the point. When the worm is young, it is very white; but has two brown spots placed over-against each other, in the hinder part of its body, which are its two posterior stigmata. Each of these spots is parted into two by a concentric circle, which is sensible, as it is whitish, the rest of the spot being brown. It is plainly this very separation which gives passage to the air. When the creature pleases, it shows these; but it can also draw them into a sort of purse in its posterior ring. The anus is just below, and is usually hid by the folds of the skin. The hooks are brown and strong; just above these are two little fleshy horns, and between them is placed the mouth.
This worm, when at its full growth, is considerably large, and becomes brownish, or of a dirty white. Its belly, examined by the microscope, is seen furnished with a number of fine short prickles between the rings: the points of all these are turned backward, and one may even feel these prickles, in drawing the finger along the belly from the hinder part toward the head.
These worms are capable of moving themselves very swiftly; and it is doubtless owing to their motions in the head of the creature, and to the pain that the sensible membranes there must have from being wounded by the hooks and prickles of this animal, that sheep are often seen to grow outrageous, and strike their heads against trees and other hard bodies.
When these worms are taken out of the heads of sheep, if they are put upon the earth, they immediately bury themselves very deeply in it; and if not yet at their full growth, or in a proper state for their changes, they die there: but if it be near the time that they would naturally have quitted their ancient habitation, which may be known by their being changed from their fine white to a brownish colour, then they undergo all their proper changes under a shell made by the hardening of their own skin. This shell is of the same shape with the animal itself, but is of a deep brown.
It takes some time for the creature to undergo its several changes, and that more or less according to the season. Mr Vallisnieri had one produced in the perfect fly-state, after 40 days from the time of its first change. Mr Reaumur found those which formed their shell on the 24th of April, not to produce the fly before the 27th of June.
The creature, when ready to appear in the fly-state, has no great difficulty in the getting out of its case; the swelling and inflating its head, and throwing out its
its bladder, which is the practice of these creatures on this occasion, easily detaches a piece of the shell, originally loose, and gives the fly a sufficient passage.
The fly produced from this worm has all the time of its life a very lazy disposition, and does not like to make any use either of its legs or wings. Its head and corelet together are about as long as its body, which is composed of five rings, streaked on the back; a pale yellow and brown are there disposed in irregular spots: the belly is of the same colour; but they are there more regularly disposed, for the brown here makes three lines, one in the middle, and one on each side, and all the intermediate spaces are yellow. The wings are nearly of the same length with the body, and are a little inclined in their position, so as to lie upon the body; they do not, however, cover it, but a naked space is left between them. The ailerons, or petty wings, which are found under each of the wings, are of a whitish colour, and perfectly cover the balancers, so that they are not to be seen without lifting up these. The upper part of the corelet is full of small black prominences, which, when examined by the microscope, appear as so many corns of gunpowder. Its head is large in proportion to the size of the body, and its reticular eyes are of a deep changeable green. These eyes take up less space in the head than those of most other flies: they leave a considerable space between them; and in that are placed the three smaller or glossy eyes, which are placed in form of a small triangle, and stand so near as to touch one another. The rest of the upper part of the head is yellowish, and, viewed by the microscope, appears cavernous like a sponge, or more; and in the bottom of each of these small cavities is a little black prominence. There are other two hollows in the anterior part of the head, in which the antennæ are placed; these are of the battledoor form, but rather round than flat, and have each a large hair going from them. The under part of the head, which is rounder than the upper, is whitish, and very smooth; it has two sorts of bands directed downward, which are the elongations of the rims of the arches where the antennæ are lodged. The smoothness of the under part of the head makes one see very distinctly these three little tubercles; the upper one brown, the under ones of a pale deadish yellow. The mouth of the fly seems to be placed between these, immediately under the upper tubercle.
The fly will live two months after it is first produced from the shell, but will take no nourishment of any kind; and possibly it may be of the same nature with the butterflies, which never take any food during the whole time of their living in that state.