_Speed attained by Insects._--Many instances might be quoted of the marvellous powers of flight possessed by insects as a class. The male of the silkworm-moth (_Attacus Paphia_) is stated to travel more than 100 miles a day;[87] and an anonymous writer in Nicholson’s Journal[88] calculates that the common house-fly (_Musca domestica_), in ordinary flight, makes 600 strokes per second, and advances twenty-five feet, but that the rate of speed, if the insect be alarmed, may be increased six or seven fold, so that under certain circumstances it can outstrip the fleetest racehorse. Every one when riding on a warm summer day must have been struck with the cloud of flies which buzz about his horse’s ears even when the animal is urged to its fastest paces; and it is no uncommon thing to see a bee or a wasp endeavouring to get in at the window of a railway car in full motion. If a small insect like a fly can outstrip a racehorse, an insect as large as a horse would travel very much faster than a cannon-ball. Leeuwenhoek relates a most exciting chase which he once beheld in a menagerie about 100 feet long between a swallow and a dragon-fly (_Mordella_). The insect flew with incredible speed, and wheeled with such address, that the swallow, notwithstanding its utmost efforts, completely failed to overtake and capture it.[89] [87] Linn. Trans. vii. p. 40. [88] Vol. iii. p. 36. [89] “The hobby falcon, which abounds in Bulgaria during the summer months, hawks _large dragonflies_, which it seizes with the foot and devours whilst in the air. It also kills swifts, larks, turtle-doves, and bee-birds, although more rarely.”--Falconry in the British Isles, by Francis Henry Salvin and William Brodrick. Lond. 1855.