Ctenopeuca Bernhauer, 1915

Barroso, Flavia B., Eldredge, K. Taro & Caron, Edilson, 2024, Review of Ctenopeuca Bernhauer, a spiny, pipevine flower-associated rove beetle from South America (Coleoptera, Staphylinidae, Aleocharinae, Oxypodini), Zootaxa 5497 (2), pp. 255-266 : 256-260

Ctenopeuca Bernhauer, 1915

Ctenopeuca Bernhauer, 1915: 299 (original description); Bernhauer & Scheerpeltz, 1926: 766 (list of species); Scheerpeltz, 1933: 1701 (list of species); Blackwelder, 1944: 166 (list of species); Blackwelder, 1952: 114 (nomenclatural notes); Hanley & Ashe, 1998: 184 (mention); Pace, 2008 (mention, key). Pace, 2009 (mention). Asenjo et al., 2019: 183 (mention); Newton 2022 (mention).

(Type species: Ctenopeuca heynei Bernhauer, 1915 (fixed by monotypy).

Diagnosis. Ctenopeuca is a unique genus that may be separated from all other Aleocharinae by the following combination of characters: (1) males dimorphic, major males with elaborate abdominal ornamentation in the form of horns and tubercles ( Figs. 1–6 ); (2) abdominal integument overall smooth and shining ( Figs. 2, 5 , 16 ); (3) pronotum broad and posteriorly broadly arcuate-produced, hypomeron not to just barely visible in lateral view ( Figs. 1, 2, 4, 5 ); (4) mesocoxal cavities contiguous, metasternal process slightly triangularly developed and barely extending between mesocoxae ( Figs. 3, 6 , 15 ); (5) tarsal formula 5-5-5; (6) protibiae adorned with spines (robust socketed setae similar to Aleochara ); (7) labrum roundly produced laterally, appearing medially broadly emarginate ( Figs. 8–9 ); (8) epipharynx with long seta-like cuticular trichae apicolaterally, occasionally visibly past apical labral margin dorsally; (9) mandibles strongly incurved with numerous conspicuous secondary denticulations (teeth) ( Figs. 10–11 ); (10) male tergite VIII emarginate with serrate apical margin, flexor muscle attachment hyperdeveloped ( Figs. 21 , 28 ); (11) male sternite VIII prominently acutely developed medially, flexor muscle attachment hyperdeveloped ( Figs. 22 , 29 ); (12) median lobe without athetine bridge with compressor plate elongate and anteriorly developed ( Figs. 24 , 30 ); (13) apical lobe of median lobe evenly curved paramerally in lateral view ( Figs. 24 , 30 ); (14) copulatory piece with delicate and elongate flagellum, often slightly visible protruding out from internal sac when inverted ( Fig. 30 ); (15) paramere elongate with condylite and paramerite vellums fused and running closely alongside velar phragma ( Fig. 25 ); (16) paramere apical lobe robust, fused to paramerite and velar phragma, and prominently developed anteriorly ( Fig. 25 ).

Redescription (based mainly on C. romani ). Male. Body length, mean 5.57 mm, standard deviation 0.86 mm. Maximum humeral width 1.00 mm. Body elongate; head and pronotum equal in width, elytra somewhat wider than pronotum, and abdomen tapering to apex ( Fig. 2, 5 ). Pronotum and elytra overall dull with minute and dense microsculpture and some dispersed setiferous punctures; Head and abdominal segments slightly glossier, without minute and dense microsculpture. Abdominal setae longer than those of the remaining body. Head as wide as long; frontal suture absent; infraocular carina complete ( Fig. 14 , arrow); neck absent; gular plate broad, with subparallel sides. Antenna long, reaching base of elytra; fine pubescence increasing gradually on antennomeres 5–11 ( Fig. 7 ); scape, pedicel, and antennomeres 3 each longer than wide; antennomere 4 subquadrate; antennomeres 5–10 wider than long, gradually increasing in width towards apex; antennomere 11 longer than wide, length almost equaling three preceding antennomeres combined; coeloconic sensilla present. Labrum transverse ( Fig. 8 ); anterior margin with a protuberance at middle ( Fig. 9 ), each with b-sensilla ( Fig. 9 , bold arrow); a-sensilla long ( Fig. 9 , thin arrow). Mandibles asymmetrical; left with one internal tooth and five dorsal tubercles above it ( Fig. 10 ); right with two internal teeth ( Fig. 11 ). Maxilla with galea and lacinia equal length ( Fig. 12 ); galea two times longer than wide, apical lobe densely ciliate; lacinia narrowing toward the apex, apex strongly curved internally, all internal margin densely ciliate; maxillary palpus with 4 articles, second and third with the same length and 4th about one-third of the length of preceding. Mentum hexagonal, three times wider than long; w-seta long, with the same width of mentum; u-seta short, the same length of mentum. Labium with first palpomere longest ( Fig. 13 ), second and third with the same length; glossa bifurcate, each lobe with long seta. Gular plate moderately broad, with subparallel sides, basal region microsculptured ( Fig. 14 ). Pronotum slightly wider than long; anterior margin truncate; posterior margin broadly curved; hypomera weakly visible in lateral view ( Fig. 1 ). Elytra longer and wider than pronotum; apical margin conspicuously emarginate ( Figs. 2, 5 ). Hind wings developed. Mesoventrite process about half length of mesocoxae, rounded at apex, mesocoxae narrowly separated, mesocoxal cavities margined posteriorly ( Fig. 15 ); metaventrite process shorter than mesoventrite process; isthmus with the same length of mesoventrite process. Tarsal formula 5-5-5. Abdomen gradually narrowing apically, abdominal segment IV the widest; first four visible tergites deeply impressed basally; tergites III, IV and VII at posterior-half with medial spine-like process directed dorsal-posterad (sometimes not developed) ( Figs. 1 , 16 ); sternum III and IV at posterior angles with a pair of spine-like process directed dorsal-posterad (sometimes not developed); tergum IX moderately subdivided at base; tergum VIII with posterior margin emarginate and serrate ( Figs. 21 , 28 ); sternum VIII with posterior margin projected medially ( Figs. 22 , 29 ). Aedeagus elongate; median lobe curved in lateral view ( Fig. 17 ), at the middle of ventral face invaginated with an area not sclerotized ( Fig. 18 ); ostial lamella with densely short spines ( Fig. 19 ); athetine bridge absent; parameres with striated velums ( Fig. 20 ). Female. Similar to male, except by the abdominal segments lacking spines; tergum VIII with posterior margin emarginate (not serrate as male) ( Figs. 26 , 32 ); sternum VIII with posterior margin curved to slightly projected medially ( Figs. 27 , 33 ).

Remarks. Ctenopeuca males exhibit a bimodal distribution for presence/absence of secondary sexual characters. Alpha males exhibit exaggerated abdominal ornamentation, while feminized beta males are indistinguishable from females and sport no abdominal ornamentation. Male dimorphism is often seen in groups where males demonstrate alternative mating strategies, such as fighting (alpha) versus sneaking (beta) males ( Eberhard 1982, Moczek & Emlen 2000, Neff & Svensson 2013, Shuster 1989, Shuster & Wade 1991). Where ecological information is available, all Ctenopeuca are associated with flowers of Aristolochia (Aristolochiacea) , including the two described- (treated here) and several undescribed species. Given Ctenopeuca have been reported from Aristolochia flowers in all known instances, we speculate Ctenopeuca reproduce within Aristolochia flowers where alpha males guard this resource while beta males sneak entry to access mates. Many Aristolochia are notable for their pungent carrion- or dung-like odor that is targeted to attract flies for pollination. We believe adults feed on pollinators within the trumpet-shaped inflorescence, and females lay eggs within the flower where larvae predate and develop. Ctenopeuca, Polycanthode and Hoplandriini represent rare examples of male phenotypic bimodality in Aleocharinae. Whether male phenotype is determined by genotype ( Shuster & Wade 1991), growth environment ( Emlen 1994, Moczek & Emlen 2000), or both is unknown. Therefore, male form ratio and its relationship with frequency dependency and any temporal dynamics are also unknown.

Ctenopeuca presents all diagnostic characters for Oxypodini listed by Seevers (1978), except for tergum IX, which is moderately subdivided at the base (narrowly in other Oxypodini genera). Morphologically Ctenopeuca resembles a Dexiogyia group of Oxypodina (sensu Seevers 1978) because the frontal suture is absent, mesoventrite not carinate, mesoventral process slender and somewhat elongated, pronotum wider and the sternum VIII of male with triangular shaped apex (one difference is the pronotal hypomeron is weakly visible in lateral view in Ctenopeuca ). However, Osswald et al. (2013) dissolved three of four genera originally included in the Dexiogyia group into two subtribes: Microglottina ( Crataraea and Haploglossa ) and Dinardina ( Thiasophila ). Dexiogyia was not included in the study and remains a part of Oxypodina sensu Seevers (1978) . Presently it is not possible to allocate Ctenopeuca to a known subtribe of Oxypodini .

Distribution. South America: Peru and Brazil ( Fig. 34 )

Key to Ctenopeuca species

1. Head and pronotum concolorous, abdominal segments III–IV slightly lighter in color than V–VII ( Fig. 1 ). Antennomere 4 quadrate. Male: posterior margin of abdominal tergum VIII with a prominent tooth on each side of serrate region ( Fig. 21 ). Female: posterior margin of abdominal tergum VIII with a slight tooth on each side of emargination ( Fig. 26 )...... C. heynei

- Head darker than pronotum, abdominal segments III–IV conspicuously lighter in color than V–VII ( Fig. 4 ). Antennomere 4 wider than long ( Fig. 7 ). Male: posterior margin of abdominal tergum VIII without a prominent tooth on each side of serrate region ( Fig. 28 ). Female: posterior margin of abdominal tergum VIII without tooth on each side of emarginate region ( Fig. 32 ).......................................................................................... C. romani

Figures

FIGURE 34. Map of Ctenopeuca distribution. The green spot indicates C. heynei (not exact record), the pink spot indicates C. romani (not exact record), and the red spot indicates C. romani (exact record).

FIGURES 1–6. Habitus of Ctenopeuca. 1–3) Lectotype of C. heynei Bernhauer (FMNH): 1) lateral view (ST3 indicates spine of tergum III, SS3 indicates spine of sternum III, ST4 indicates spine of tergum IV, SS4 indicates spine of sternum IV, ST7 indicates spine of tergum VII), 2) dorsal view, 3) ventral view. 1–3) Lectotype of C. romani Bernhauer (FMNH): 4) lateral view, 5) dorsal view, 6) ventral view. Scale bars 3.0 mm.

FIGURES 7–16. Ctenopeuca romani: 7) Antenna; 8) Labrum, dorsal view; 9) Detail of labrum, dorsal view (bold arrow indicates a-sensilla, thin arrow indicates b-sensilla); 10) Right mandible, dorsal view; 11) Left mandible, dorsal view; 12) Maxilla, dorsal view; 13) Labium, ventral view; 14) Head, ventral view (arrow indicates infraocular carina); 15) Meso- and metaventrite, ventral view; 16) Abdomen, dorsal view (ST3 indicates spine of tergum III, SS3 indicates spine of sternum III, ST4 indicates spine of tergum IV, SS4 indicates spine of sternum IV, ST7 indicates spine of tergum VII).

FIGURES 21–27. Ctenopeuca heynei: 21) Tergum VIII, male, dorsal view; 22) Sternum VIII, male, dorsal view; 23) Median lobe, ventral view; 24) Median lobe, lateral view; 25) Paramere; 26) Tergum VIII, female, dorsal view; 27) Sternum VIII, female, dorsal view.

FIGURES 28–33. Ctenopeuca romani: 28) Tergum VIII, male, dorsal view; 29) Sternum VIII, male, dorsal view; 30) Median lobe, lateral view; 31) Spermatheca; 32) Tergum VIII, female, dorsal view; 33) Sternum VIII, female, dorsal view. Scale bars 0.6mm.

FIGURES 17–20. Ctenopeuca romani: 17) Median lobe, lateral view; 18) Median lobe, ventro-lateral view; 19) Apex of median lobe, lateral view; 20) Paramere, lateral view.