There are few insects with whose form we are better acquainted than that of the gnat. It is to be found in all latitudes and climates; as prolific in the Polar as in the Equatorial regions. In 1736 they were so numerous, and were seen to rise in such clouds from Salisbury cathedral, that they looked like columns of smoke, and frightened the people, who thought the building was on fire. In 1766, they appeared at Oxford, in the form of a thick black cloud; six columns were observed to ascend the height of fifty or sixty feet. Their bite was attended with alarming inflammation. To some appearances of this kind our great poet, Spenser, alludes, in the following beautiful simile:-- As when a swarm of gnats at eventide, Out of the fennes of Allan doe arise, Their murmurring small trumpets sownden wide, Whiles in the air their clust'ring army flies. That as a cloud doth seem to dim the skies: Ne man nor beast may rest or take repast, For their sharp wounds and noyous injuries, Till the fierce northern wind, with blustering blast, Doth blow them quite away, and in the ocean cast. In Lapland, their numbers have been compared to a flight of snow when the flakes fall thickest, and the minor evil of being nearly suffocated by smoke is endured to get rid of these little pests. Captain Stedman says, that he and his soldiers were so tormented by gnats in America, that they were obliged to dig holes in the ground with their bayonets, and thrust their heads into them for protection and sleep. Humboldt states, that "between the little harbour of Higuerote and the mouth of the Rio-Unare, the wretched inhabitants are accustomed to stretch themselves on the ground, and pass the night buried in the sand three or four inches deep, exposing only the head, which they cover with a handkerchief." After enumerating these and other examples of the achievements of the gnat and musquito tribe, Kirby says, "It is not therefore incredible that Sapor, King of Persia, should have been compelled to raise the siege of Nisibis by a plague of gnats, which attacked his elephants and beasts of burden, and so caused the rout of his army; nor that the inhabitants of various cities should, by an extraordinary multiplication of this plague, have been compelled to desert them; nor that, by their power of doing mischief, like other conquerors who have been the torment of the human race, they should have attained to fame, and have given their name to bays, town, and territories." _Ibid_. _Leaf Caterpillars_.