facet Surface of an ommatidium
facial carinae A pair of carinae (ridges) running between the lateral ocelli and the clypeus.
faculative parthenogenesis Parthenogenesis in which a species reproduces with or without males The offspring are females if the mother is unmated. c.f. obligatory parthenogenesis.
falcate Hooked or curved like a sickle.
fasiculate (Antennæ.) Every joint possessing a distinct pencle, or long hair. (From L. fasciculus, a little bundle.)
fastigium With Orthoptera. Anterior part of vertex of the head projecting forward beyond the eyes. (Latin = a slope, roof.)
fecundity The capacity of producing offspring in great numbers.
felt lines Elongate hairy depressions associated with glands (Hymenoptera)
femur (pl. Femora). The third and usually the stoutest segment of the beetle leg, articulated proximally with trochanter (or if the latter is absent, then the coxa) and distally with the tibia.
filiform antenna Antenna in which most antennomeres are longer than wide and more or less equal in width, and so resemble a filament or thread. The related term setiform has been used for antennae (in fossil beetles) which are narrowed apically, but this condition apparently does not occur in modern forms.
flabellate antenna Antenna in which most antennomeres bear a long, narrow, flattened process.
flagellum (of antenna). That portion of the antenna beyond the pedicel or antennomere 2.
flange A term sometimes used for a broad, projecting or convex margin; here used as a synonym of collar (when referring to the prothorax).
flexion lines, fold lines A distinction used in wing definitions.
fossorial Adapted for digging. [picture]
fossulae spongiosae In Hemiptera, expanded, spongy, setose pads on the fore tibia which assist in holding prey. [picture]
fovea A raised blister-like area of wing membrane. [picture]
frenulum Coupling mechanism of fore and hind wings in moths. [picture]
frons The area between the eyes and just behind the frontoclypeal suture. In Coleoptera it is not or only rarely separated from the vertex posteriorly.
frontal region Usually referring to the area between the anterior portions of the eyes and in front of the eyes, whether there is a frontoclypeal suture or not.
frontoclypeal suture A transverse groove separating the frons and clypeus and forming internally an epistomal ridge. Also called the epistoma.
frontal-orbital bristles Short row of bristles on a fly's head between the frontal bristles and the eye
functional spiracle (of abdomen). Spiracle having a distinct opening and tracheal connection. Non-functional spiracles may be represented by a minute opening or scar and a blocked tracheal remnant. Primitively there are 8 functional abdominal spiracles, but 8 is lost in many taxa (including all Cucujiformia) and 7–8, 6–8 or 4–6 may be lost in some others.
fungivorous Feeding on fungi.
furcula Forked spring of a springtail