Paulsen, Paulsen, 2013

Paulsen, M. J., 2013, A new genus for the Neotropical species of Aesalus Fabricius, with descriptions of eight new species (Coleoptera: Lucanidae: Aesalinae), Insecta Mundi 2013 (325), pp. 1-25 : 6

Trogellus Paulsen , new genus.

Type species: Trogellus herrmanni Paulsen, here designated.

Description. Coleoptera : Scarabaeoidea: Lucanidae : Aesalinae : Aesalini. Length: 3.7–6.5 mm. Width: 2.2–3.7 mm. Color: Body entirely dark brown, with testaceous to light brown bristles and minute branched scales ( Fig. 7–10 ); surface often obscured by wood debris and residue. Head: Anterior margin of clypeus triangular or rounded. Mentum transversely subrectangular (nominal subgenus) to subquadrate, emarginate anteromedially, often bifoveate on disk. Eye canthus well developed (anterior margin of eye located on dorsal surface of head, per Holloway 1969), varying from short and broad to narrow and elongate. Antenna not geniculate; antennal club composed of 3 antennomeres in both sexes; club weakly asymmetrical, entirely tomentose. Mandibles small in both sexes, not distinctly sexually dimorphic, strongly incurved medially, approximately 1/3 length of head; form, simply falcate, right mandible with 1 strong internal tooth, left mandible with 1 weakly indicated to strong internal tooth; external margin with or without tooth-like process or angulation near middle. Labrum concealed by mandibles dorsally. Pronotum: Form convex, laterally explanate. Surface punctate, some punctures with erect bristles, bristled punctures with anterior tubercles, tubercles often well developed near posterior angles, occasionally indistinct. Elytra: Surface with two kinds of punctures, bristle (acute or blunt) or scale-bearing, with vestiture arising anteriorly in pit (sensu Holloway 1997); bristles erect, forming 8 rows on disc, each bristle with a small tubercle anterior to puncture; scales minute, multi-branched, appearing as brown scurfy covering usually with woody debris adhering, scale pits lacking anterior tubercle. Mesosternum: Mesosternal punctures oval, never lunate. Abdomen: Abdominal segments 1–2 appearing connate; segments 2–5 with deep furrow between segments. Segments 3–5 with scalloped anterior margin. Abdominal punctures predominantly oval with some more elongate punctures laterally (not furrow-like or sublinear), punctures containing setae (not scales). Legs: Anterior tibia dentate with 3–4 distinctly larger teeth, teeth broadly triangular (nominal subgenus; Fig. 11 ) or narrowly acute or peg-like ( Fig. 12 ); teeth decreasing in size proximally; smaller teeth variably present in basal half. Mesotibia with 3–4 strong, external teeth in both sexes. Metatibia strongly, sexually dimorphic, with apex bulbous in females ( Fig. 6 ) and acutely dentate in males ( Fig. 5 ); Males with 0–2 strong external teeth at middle ( Fig. 13–14 ), females with metatibial teeth smaller. Male genitalia: Parameres 1/2 to 1/4 as long as median lobe; median lobe variable, either simply cylindrical (nominal subgenus; Fig. 18–20 ), or with triangular lateral processes ( Fig. 21–23 ), or asymmetrical and shell-shaped ( Fig. 24–30 ).

Diagnosis/Remarks. Trogellus is distinguished from Aesalus by the characters outlined above. The most notable of these are the presence of an ocular canthus and the dorsal vestiture consisting of unicolorous bristles on the elytra with minute, intricately branched scales ( Fig. 7–10 ). It is probable that the branched scales are associated with exudate that adheres wood debris to the elytral surface and results in a scurfy, camouflaging appearance. Members of the nominal subgenus differ in having acute elytral bristles ( Fig. 7 ); distinctly broader, triangular protibial teeth ( Fig. 11 ); a narrowly rectangular mentum without foveae; and simply cylindrical male genitalia.

Etymology. The generic name, gender masculine, is formed to approximate “little Trox ”. The name was chosen based on the close phylogenetic relationship between the Lucanidae and its sister family, Trogidae , which is morphologically most evident in the plesiomorphic aesaline stag beetles.

Figures

Figures 7-10. SEM microscopy of elytral surface and vestiture. 7) Trogellus herrmanni n. sp., acute bristles. 8) T. trogoides, blunt bristles with anterior tubercle, and branched scales. 9) T. trogoides, detail of blunt bristle. 10) T. herrmanni n. sp., detail of branched scales.

Figures 11-14. Leg characters of subgeneric importance. 11) Right protibia of Trogellus herrmanni n. sp. with large triangular teeth (dorsal view). 12) Right protibia of T. trogoides with small peg-like teeth (dorsal view). 13) Left metatibia of T. trogoides showing weak external teeth (ventral view). 14) Left metatibia of T. herrmanni n. sp. showing strong external tooth at middle (ventral view).

Figures 3-6. Trogellus trogoides (Albers). 3) Head, with triangular clypeus, and with arrow indicating ocular canthus. 4) Female habitus. 5) Left metatibia of male showing acute apex (ventral view). 6) Left metatibia of female showing tumid apex (ventral view).

Figures 18–23. Male genitalia of Trogellus species, dorsal view. 18. T. herrmanni n. sp. 19) T. ticiticus n. sp. 20) T. neotropicalis. 21) T. chapinitus n. sp. 22) T. hawksi n. sp. 23) T. trogoides. The male genitalia of T. maesi n. sp. are unknown.

Figures 24–30. Male genitalia of Trogellus subgenus Mayaesalus species, dorsal (Fig. 24–26) and right lateral (Fig. 28–30) views. Outlines of genitalia in dorsal view shown to the right of each. 24, 28) T. narizotus, n. sp. 25, 29) T. catrachitus, n. sp. 26, 30) T. trifinius, n. sp.