Basilar membrane: a thin membrane separating the cones and rods from the optic tract.
Basilar space: Odonata; that area at base of wings, between media and cubitus.
Basi-proboscis: basal third of the flexed proboscis of muscid flies.
Batesian mimicry: see mimicry.
Bathmis: see pterostigma.
Bave: the fluid silk as it is spun by caterpillars.
Beak: any notable prolongation of the front of the head: the snout in Rhynchophora: specifically, the jointed structure covering the lancets in the hemipterous mouth.
Bearded: fringed with hair: see barbated.
Belly: venter; under side of abdomen.
Belonoid: needle-like.