There is some uncertainty as to the particular insect designated by the original Hebrew word appearing in the Scriptures with reference to the fourth plague upon Egypt, the first from which the Israelites in Goshen were spared. (Ex 8:21, 22, 24, 29, 31; Ps 78:45; 105:31) ʽA·rovʹ has been variously rendered “gadfly” (JB, NW, Ro), “beetle” (Yg), “flies” (AS, KJ, RS), “gnats” (AT), and “dog fly” (LXX).
The English designation “gadfly” includes the various kinds of horseflies and botflies. Female horseflies pierce the skin of animals as well as man and then suck their blood. In the larval stage botflies live as parasites in the bodies of animals and man; those that infest humans are found in the tropics. A plague of gadflies would, therefore, have brought great suffering to the Egyptians and their livestock and, in certain cases, even death.