Sensilla types. Representative scanning electron micrographs showing sensilla types found on An. gambiae s.s. and An. quadriannulatus female antennae. External sensilla morphologies are indistinguishable in these species. (A) Sharp trichoid (hair) sensilla showing their smooth surfaces, socket-less bases, and tapered ends. (B) Base of a sensilla chaetica (bristle) with large socket. (C) Blunt trichoid (hair) sensillum. (D) Grooved peg (basiconic) sensillum. (E) Large coeloconic (pitted peg) sensillum with large cuticular opening and longitudinally grooved peg set deep within. (F) Small coeloconic (pitted peg) sensillum with small opening and peg not visible. (G) Tip of the 13th flagellomere showing small coeloconic sensilla at the distal end (inset arrowheads) and along the surface (arrow), as well as a single small chaetica (bristle). This sensilla arrangement is typical of both An. gambiae s.s. and An. quadriannulatus antennae. (H) Sensillum ampullaceum surrounded by microtrichia on the ventral surface of the first flagellomere.