In the Philosophical Transactions for the year 1767, is an account of uncommonly numerous swarms of gnats which made their appearance at Oxford, during the months of July, August, and September of the preceding year. So many myriads sometimes occupied the same part of the atmosphere in contiguous bodies, that they resembled a very black cloud, greatly darkened the air, and almost totally interrupted the solar rays. The repeated bites of these malignant insects were so severe, that the legs, arms, heads, and other parts of many persons were swelled to an enormous size. The colour of the parts was red and fiery, perfectly similar to that of some of the most alarming inflammations. Some of these gnats had their bodies greatly distended by the uncommon quantities of blood which they had imbibed.
In short, there is no species of insects more troublesome to mankind than the gnat; others give more pain with their stings, but it is only when they are attacked, or by accident, that we are stung by them; but the gnats thirst for our blood, and follow us in whole companies to attack us. In marshy places of this country the limbs of the inhabitants are kept swelled during the whole season. In warmer climates, particularly the West Indies, they are, under the denomination of musquetoes, still more formidable.
Hooke, in his Micrographia, pleads in justification of these terrible little insects, that they do not wound the skin and suck the blood out of enmity or revenge, but through mere necessity, and to satisfy their hunger:--it may be so; and on this account we cannot annex the criminality to them which appertains to such of the highest rank in the scale of the animal creation, who, though not urged by the same powerful motive, pursue a somewhat similar conduct; but those who have experienced their assaults, will scarcely admit this plea as a sufficient apology, or feel themselves amicably disposed towards them; as, from whatever cause their attacks may proceed, the effect is so very unpleasant, as almost to justify the sufferers in addressing them in the language of the frogs in the fable to the boys, “Consider, I beseech ye, that though this may be sport to you, it is death to us,” and ejaculating a wish, that they might be enabled to gratify their rapacious appetites by some other means. EDIT.