ABSTRACT
Head, including eyes, slightly narrower than pronotum in Phengodini (Figs. 1-2), as wide as or slightly wider than pronotum in Mastinocerini (Figs. 3-6); prognathous; surface glabrous in Zarhipis LeConte and Stenophrixothrix Wittmer, finely rugose in Paraptorthodius Schaeffer, Phengodes Illiger, and Distremocephalus, and coarsely rugose in Cenophengus LeConte. Vertex with transverse groove behind antennal insertions in Phengodes; flat, with triangular depression in Zarhipis; flat to slightly convex in Stenophrixothrix and Cenophengus; slightly to broadly depressed in Distremocephalus and Paraptorthodius. Frons flat, with median, longitudinal depression, slightly declivitous in Phengodes; flat, narrowed, slightly declivitous in Stenophrixothrix, Distremocephalus, and Cenophengus; sharply angled ventrally in Zarhipis and Paraptorthodius. Antenna with 12 antennomeres, antennomere I large, cylindrical to globose, antennomeres II-III short, transverse to submoniliform, antennomeres IV-XI elongate, 2-3 times as long as wide, cylindrical, bi-pectinate; pectines 5-6 times as long as antennomere in Phengodini, 2-4 times as long as antennomere in Stenophrixothrix, Distremocephalus, and Cenophengus, and 1.5 times as long as antennomere in Paraptorthodius; pectines cylindrical, densely covered with long setae in Phengodini, Stenophrixothrix, and Distremocephalus, pectines flattened, densely covered with short setae in Cenophengus and Paraptorthodius; antennomere XII greatly elongate, 4-6 times as long as wide. Antennal insertions widely separated (i.e., greater than length of antennomere I) in
Phengodini; moderately separated (i.e., separated by length of antennomere I) in Paraptorthodius; and narrowly separated (i.e., separated by less than length of antennomere I) in Stenophrixothrix, Distremocephalus, and Cenophengus. Antennal insertions exposed, except in Phengodes where they are covered by a prominent frontal ridge, and Cenophengus where they are covered by a small ridge. Labrum bilobed, distinct in Phengodini, small in Mastinocerini. Mandibles slender, sharply curved, apices acute; prominent in Phengodini, smaller in most Mastinocerini, reduced in Cenophengus. Maxillary palpi four-segmented, long, filiform; in Phengodini, maxillary palpomere I short, II very elongate, nearly as long as III + IV combined, III elongate and cylindrical, IV only moderately expanded at apex, nearly as long as or slightly longer than mandible; in Mastinocerini, maxillary palpomeres IIII short, IV distinctly broadly expanded at apex, longer than II+III combined, distinctly longer than mandible. Labial palp three-segmented, filiform, two-thirds length of maxillary palp in Phengodini; short, less than half length of maxillary palp in Mastinocerini. Gular area large, broad, convex, well developed between and behind eyes in Phengodini; moderate sized, flat, only moderately developed between eyes in Mastinocerini, except in Stenophrixothrix where it is narrowed, barely visible between eyes. In Phengodini, posterior tentorial pits combined, forming a single, deep pit immediately posterior to labium. In Mastinocerini, posterior tentorial pits separated, appearing as two small pits immediately posterior to labium, except in Stenophrixothrix where they are difficult to see. Eyes very large, strongly convex, circular to oval in outline, lateral in position on head, widely separated dorsally, widely to moderately separated ventrally, except in Stenophrixothrix where they nearly meet ventrally.
