frontal/pretentorial pits (ARTHRO: Insecta) The internal invaginations of the anterior arms of the tentorium.
frontal region (ARTHRO: Crustacea) The anteromedian part of a carapace including the rostrum and the region behind it.
frontal ridge (ARTHRO: Insecta) 1. An anteriorly directed ridge on the dorsal margin of the eye. 2. For mosquitoes, see postfrontal ridge.
frontal sail (MOLL: Gastropoda) In Prosobranchia, an erect transverse fold on the anterior part of the head which may be simple or formed into scallops, tubercles, or projections.
frontal seta 1. (ARTHRO: Diplopoda) One of a pair of setae on either side of the median line of the frontal surface of the head. 2. (ARTHRO: Insecta) One of two setae on the frons of caterpillars.
frontal shield (BRYO: Gymnolaemata) In Cheilostomata, the skeletal structure of the frontal or body wall that supports and protects the retracted organs of an autozooid.
frontal stripe (ARTHRO: Insecta) In Diptera, a membranous or discolored area on the middle front.
frontal suture (ARTHRO: Insecta) 1. One of two sutures arising at the anterior end of the coronal suture which extends ventrad toward the epistomal suture. 2. In Diptera, a suture shaped like an inverted "U", having the base crossing the face above the bases of the antennae, and the arms extending downward on each side of the face; a ptilinal suture.
frontal tentacles (MOLL: Gastropoda) In Opisthobranchia, tentacles just posterior to the mouth; cephalic tentacles.
frontal triangle (ARTHRO: Insecta) In holoptic flies, the triangle between the eyes and the antennae, the apex being above.
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