alternative definition added over 9 years ago by Istvan Miko

A pair of longitudinal ridges on the head, located dorsally behind the clypeus and between the antennal sockets. They are very variable in length and strength of development, frequently being short and simple (Fig. 523; fc) but sometimes extending back to the occipital margin of the head (Fig 525; fc). In some groups the frontal carinae are vestigial or absent, but elsewhere they may be strongly developed or form the dorsal margins of extensive antennal scrobes (Fig. 526; fc, scb). Commonly the frontal carinae anteriorly are expanded into projecting lobate extensions, the frontal lobes (Figs. 524-526; ff), which partially or entirely cover and conceal the antennal sockets. Frontal lobes may be the only expression of the frontal carinae in some groups. Sometimes the portion of the torulus closest to the cephalic midline is raised and expanded into a small, laterally projecting lobe, which may extend beyond the lateral margin of the frontal carina or lobe.

alternative definition added over 9 years ago by Istvan Miko

A pair of longitudinal ridges on the frons, behind the clypeus and between or often partly covering the antennal fossae. Their length is variable: they may be absent or vestigial to very long, extending back to the posterior cephalic margin. They are often expanded anteriorly to form the frontal lobes. In some ant taxa, they may be the dorsal margin of the antennal scrobes.