GAD-BEE, or Gad fly, in natural history, the common name for a winged insect, called also the dun fly or ox fly; a creature very troublesome to cows, horses, &c. This creature examined by the microscope hath some peculiarities worthy of observation. It has, like the gnat, a long proboscis, with a sharp dart or two darts sheathed within it; the use of these darts is to penetrate the flesh of animals for the sucking their blood, whereas the proboscis can only serve to suck the dews from flowers, &c.
The eggs of this fly are laid in the waters, and there produce a very remarkable sort of maggot. It is a brown one of a long flattened figure, with a pencil of down-hairs at its tail, which it spreads into a circular form on the surface of the water, while its head is sunk down in search of food. When the creature would descend towards the bottom, these hairs are made to approach one another in an oval form; and in this state they inclose a bubble of air, by means of which it is able to rise again; and if this bubble by any accident escapes, the creature immediately squeezes out of its own body another to supply its place. The fruit of this maggot hath three divisions; whence are thrust out three little pointed bodies like serpents tongues. These maggots are very common on the surface of ditch-water; and the motion of their intestines is very singular and observable.