Unguis: one of the claws at the end of the tarsus: also applied to a short process on the 6th antennal joint in some Aphids.
Ungula: a hoof, claw or talon.
Ungulate: shaped like a hoof.
Uni-: one, a combining form.
Unicolorous: of one color throughout.
Unidentate: with one tooth only.
Uniplicate: with a single fold or line of folding.
Unique: one only: unlike any other.
Unisexual: of one sex only: applied to Aphids and Cynipids where only parthenogenic females are known.
Upper austral zone: is divided into an eastern humid or Carolinian area, and a western arid or upper Sonoran area, which pass insensibly into each other near the 100th meridian: see Carolinian and upper Sonoran.