1. Minute hairs projecting from the integument, they are formed around cellular filaments.

An integument is a natural outer covering or coat: such as, the skin of an animal or the membrane enclosing an organ or the envelope of an ovule.

2. Minute, hair-like structures found on the wings of certain insects; they resemble small covering hairs, but the absence of basal articulation distinguishes them; fixed hairs; aculei; minute non-movable hairs formed from cuticle; may produce an impression of cloudiness or color.