Mosquito eye design: conical rhabdoms are matched to wide aperture lenses

Night–active mosquitoes have photopigment–containing rhabdoms that take the form of a wide hollow cone, with the distal apex at the focus of the ommatidial lens. It is shown geometrically, and with the aid of a gelatin model, that such a structure can trap light over an angle of up to 60°, roughly equal to the width of the cone of light provided by the lens. This gives a gain in light–gathering power of up to nine times that of the more usual cylinder–shaped rhabdom with an acceptance angle of less than 25°.