free-swimming Swimming about; not sessile.
free-walled colony (BRYO: Stenolaemata) A colony covered loosely by membranous exterior walls that are not attached at oral apertures.
free-wax cell (ARTHRO: Insecta) Cells found in the hemolymph of Aphididae and Coccoidea.
frenate wing coupling (ARTHRO: Insecta) Lepidopterous wing coupling with a well developed frenulum that engages with a catch or retinaculum on the underside of the fore wing, securing the wings together.
frenulum n.; pl. -la [L. dim. frenum, bridle] 1. (ARTHRO: In-
secta) The strong spine or group of bristles on the humeral angle of the hind wing, that projects beneath the fore wing, uniting them in flight; frenum. 2. (CNID) Gelatinous fold supporting the subumbrella of certain jellyfish. 3. (POGON) A v-shaped cuticular thickening held in an epidermal groove that functions as an adhesive device; also called bridle.
frenulum hook (ARTHRO: Insecta) A cuticular clasp (retinacu-lum) that functions in wing coupling.
frenum n.; pl. frenna [L. frenum, bridle] 1. Any fold of skin or tissue supporting an organ. 2. (ARTHRO: Crustacea) Membranous bilateral fold of the carapace of barnacles that holds eggs. 3. (ARTHRO: Insecta) The frenulum.
frilled organ (PLATY: Cestoda) A posterior attachment organ in the order Gyrocotylidea.
fringe n. [L. fimbria, border] 1. To furnish or adorn. 2. Hair, scales or other processes extending beyond the margin, usually of equal length. 3. (MOLL: Bivalvia) Periostracum extending passed the calcareous shell.
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