Flex: to bend: to curve back.
Flexible: pliable; with elastic properties.
Flexile -is: capable of being bent at an angle without breaking: flexible.
Flexuous -ose: almost zig-zag, without acute angles but more acute at angles than undulating: differs from sinuate in being alternately bent and nearly straight.
Flexor: that which bends; applied to muscles.
Flocculus -i: a hairy or bristly appendage on the posterior coxa of some Hymenoptera.
Floccus: a tuft of wool or wool-like hair.
Flosculiferous: species that bear a flosculus.
Flosculus: a small, tubular lunulate anal organ with a central style, in certain Fulgorids.
Fluviatile: inhabiting the margins of running streams.