From June to October, and particularly in August, gadflies or breeze-flies (OEstridae), seek to lay their eggs on convenient parts of horses during the hottest hours of the day. The female flies of the kind that is most common in England, lay their light orange-coloured eggs, which are about the 1/20th of an inch in diameter, chiefly on the breast, front of the fore-arms, and those parts of the shoulders and sides that are in reach of the horse's tongue. They adhere to the hairs by means of a sticky substance which the fly ejects along with them. The eggs on becoming hatched in about three weeks (Joly), produce small worms, which irritate the skin by their movements, and thus prompt the horse to lick them off and take them into his mouth, with the result that they gain access to various parts of the alimentary canal, to the walls of which they attach themselves, and are then called dots. During the months bot flies are laying, grooms should be careful to examine their horses after the animals come in, and pick off and destroy all the eggs which they can find.

We may temporarily protect a horse from the attacks of flies by lightly sponging him over with a mixture of I part paraffin oil to 10 parts of milk, well shaken up. A better emulsion can be made with similar proportions of this oil and water, and adding a little gum tragacanth. Gobbels-Copette (Nos Animaux Domestiques) states that in Canada a mixture of paraffin oil prepared as follows, is used with much success for spraying animals twice a week, in order to protect them from flies : Dissolve 2 oz. of yellow soap in a pint of boiling water; add a quart of paraffin; briskly stir up the mixture until it forms a creamy emulsion; and use for spraying purposes, I part of the mixture to 9 parts of water. The Count St. Marsault (Journal d' Agriculture pratique) recommends an ointment (to be applied to the body by means of a rag) made by boiling for five minutes a large handful of laurel leaves in two pounds of lard. A decoction of walnut leaves is said to have a good effect for the purpose in question.

In many hot countries, flies annoy horses so much that special precautions have to be taken against their entrance into stables, which they as a rule invade only during the hot hours of the day. They may be kept out by placing a net across the stable door and windows - which we may suppose are left open for purposes of coolness - provided that light is not let through from the other side. Flies appear to experience no fear in passing through the meshes of a net which is held up to the light. Failing a net, screens of various kinds can be used. Dirt in a stable has a great attraction for flies. The smoke of burning dried cow-dung or burning dried horse-dung is often employed in India for driving flies away from horses. The use of peat moss appears to have a good effect in preventing flies from entering stables. I do not know whether this effect is due to the smell of this litter, or to its dark colour.