BOT, BOTFLY (cf. Gael. Lotus, belly-worm). Names common to several dipterous insects of the family (Estrid:c, which are parasitic in their early stages upon or within. certain domestic and wild animals.
The llottsE-Bor, or hot-fly of the horse (Gas trophilus equi, Fab.). is a creature well known to stockmen and veterinary surgeons. The adult ily is about three-quarters of an inch in length; the body is very hairy and brown in color. The female has an extensile abdomen. She poises herself in flight near a horse, then darts sud denly toward the animal, gluing an egg to a hair almost instantly. then retreating for a yard or two until another egg is ready to be deposited.
In this way hundreds of eggs may be deposited upon a horse in a short time. The larva•, or maggots, soon form within the eggs, but these do not hatch unless the horse licks itself, in which case the eggs are carried to the alimentary canal, hatch almost immediately, and the larva. enter the stomach, where they attach themselves to its wall and remain until fully grown. The inner stomach-wall of a horse is frequently cov ered with large patches of these larva: densely crowded together. This attachment to the walls of the stomach probably causes an irritation which interferes with the normal action of the glands, or reduces the glandular surface; the grubs also probably extract some nutriment from the walls of the stomach. There can be little doubt that the presence of these grubs is in jurious to the horse, although some stock-raisers consider this injury insignificant. When fully grown the lame loose their hold and pass through the pyloric orifice of the stomach and down through the intestines, occasionally at taching themselves to the intestinal wall or to the wall of the rectum, causing irritation which is sometimes severe. They are finally voided with the excrement, transformed to pup(enearthe surface of the ground, and eventually the adult flies appear. There seems to be but one genera tion annually. horses kept in stables are little troubled it' they are well groomed. In pastures or on ranges, however, unless the stock is washed every two or three weeks, hots are apt to be present. Turpentine. used with care, is consid ered a remedy for those which succeed in es tablishing themselves in the stomach.
The Ox-Ilo.r. ox-warble, ox-wormal, or heel-fly, as it is termed in the West (sometimes simply 'the grub'), belongs to a different genus of (Es tridw and has quite different habits. The Ameri
can species is Hypoderma lineata, and the European species is Hypoderma boric, L. The 'grubs' of this species are found in lumps or pockets in the skin of cattle and it was formerly supposed that the fly laid its eggs upon the hairs and that the larva- worked their way through the skin, forming cysts in which they remained through the entire larval life, but it has recently been discovered that the life of the species is more complicated. The flies appear early in the spring and attach their eggs to the hairs, particularly of the legs, Of cattle, and especially the part just above the hoof, whence comes the name 'heel-fly.' The eggs, or the quickly hatching larva', are carried into the mouth of the animal when it licks its legs, and the larva penetrates the walls of the (esophagus by 1111'011S of its strong spines. After penetrating the (esophagus it casts its skin and becomes nearly smooth, and for several months works through the connective tissue between the skin and the flesh, penetrating gradually down the neck and ultimately reaching a point beneath the skin in the region of the back. in the mean time, all traces of inflammation have disappeared from the (esophagus. When the final position is reached the grub molts again, becomes more .spiny, and bores a hole through the skin through which it gets air for breathing. Its presence causes much irritation, and it feeds upon the pus and hloody serum which collect. Several in dividuals usually join together in one of these punctures or sores. When fully grown it forces its way through the skin, drops to the ground, where it transforms to a pupa, and the follow ing spring the adult fly emerges. The adult looks much like the common honey-bee. It is about half an inch long, black in color, and is clothed with reddish-brown hairs. An oily ap plication to the wound will kill the grubs, and some simple antiseptie, like carbolic acid, causes a rapid healing. When the insects are common, however, cattle become emaeiated and their skins are spoiled for commercial purposes by the per forations. The money lost in the United States through the work of this insect is very great.