Geiserocerus flavifrons sp. nov., here designated.

The name is in honor of the entomologist Michael Geiser, a great coleopterist researcher who largely contributed to the knowledge of world beetles, with a large focus on morphology and taxonomy of soft-bodied families. Michael kindly loaned me several Phengodidae specimens from the BMNH. Singular genitive, masculine.

Antenna with 12 antennomeres, antennomeres IV–XI with two short symmetrical compressed and fusiform branches, slightly longer than respective antennomere, antennomere XII claviform (Fig. 2I); interantennal distance close to 3× antennal socket width (Figs 1C, 2D); labrum fused to frontoclypeus (Figs 1C, 2A); mandibles short, bent almost in a right angle near base, not projected, obliquely crossed over each other, without a notch on external margin to fit other mandible and with extra medial teeth with rhomboid apex (Fig. 2H); maxillary palpi 4-segmented, last segment digitiform (Fig. 2F); labial palpi 3-segmented (Fig. 2G); one gular suture and posterior tentorial pit consisting of a single small fossa (Fig. 1B); elytron around 3× as long as wide, external margin slightly curved and convergent with the other elytron posteriorly, slightly thickened apically (Fig. 4A); wing with radial cell open and transverse, vein r4 interrupted, r3 absent (Fig. 4C); first tarsomere of pro- and mesotarsus with a ventral comb covering the entire tarsomere (Fig. 2J); claws simple, without visible teeth (Fig. 2J); aedeagus with paramere slightly asymmetrical, paramere apex unevenly round, toothed inward, with short and scarce bristles (Fig. 5G–I).

Figure 1. 

Geiserocerus flavifrons gen. nov. et sp. nov., holotype: A. Habitus, dorsal; B. Habitus, lateral; C. Head and pronotum, dorsal. D. Head, lateral.

Figure 2. 

Geiserocerus flavifrons gen. nov. et sp. nov., paratype: A. Head, dorsal; B. Head, ventral; C. Head, lateral; D. Head, frontal; E. Head, posterior; F. Maxilla, ventral; G. Labium, ventral; H. Right mandible, dorsal; I. Antenna, lateral.

Male. Head (Figs 1C, D, 2). Head slightly wider than long, with posterior half of lateral margin sinuous, slightly convergent posteriorly, apical fourth usually covered by pronotum, slightly wider than pronotum (Figs 1C, 2A); antenna 1.5× as long as head width, with 12 antennomeres, antennomeres IV–XI with two short symmetrical compressed and fusiform branches, slightly longer than respective antennomeres, antennomere XII claviform (Fig. 2I); eyes not protruding, coarsely faceted (Fig. 1C, D), frontoclypeus with a subtle declivity between antennae, from interantennal area up to anterior margin of labrum (Fig. 2C), interantennal distance close to 3× antennal socket width (Figs 1C, 2D); labrum fused with frontoclypeus, bilobate by a median emargination on anterior margin (Figs 1C, 2A); mandible short, bent almost in a right angle near base, not projected, obliquely crossed over each other, without a notch on external margin to fit other mandible and with extra medial teeth with rhomboid apex (Fig. 2H); maxilla with palpi 4-segmented, last palpomere digitiform, palpifer distinct, galea distinct, extremely short and free, highly setose, lacinia almost fused with stipe, highly setose, cardo semitriangular, 2× wider than long (Fig. 2F); labium with palpi 3-segmented, short, not covered by mandibles, last palpomere fusiform, ligula absent, prementum quadrate, palpiger absent, mentum and submentum fused in a single piece, which is fused with head (Fig. 2B, G); one gular suture, tentorial pit consisting of a single small fossa (Fig. 2B).

Thorax (Figs 1C, 3). Pronotum quadrate, slightly wider than long, anterior angles dorsally concave, rounded, lateral margins subparallel, posterior margin rounded (Fig. 3A); hypomeron densely setose in anterior half, glabrous in posterior half, transverse in lateral view (2× as long as high), with ventral margin straight up to middle, then oblique until posterior margin of pronotum (Fig. 3D); prosternum 2× as wide as its major length, narrowed parasagittally (Fig. 3B); proendosternite elongated, about as long as distance between the apices of proendosternite arms (Fig. 3C); mesoscutellum fused with mesoscutum, slightly concave in lateral view (Fig. 3D, E); alinotum subquadrate, glabrous, lateral margins subparallel, posterior margin straight, scutum—prescutalplates sclerotized, extending ridges almost to posterior margin (Fig. 3E, F); mesoventrite weakly sclerotized, blunt medially, mesepimeron fused to mesoventrite, mesanepisternum-mesepimeron suture conspicuous (Fig. 3H); metaventrite depressed anteriorly (mesocoxal rests), discrimen distinct by basal half, lateral margins subparallel up to lateral-most part of metacoxa, then convergent posteriorly, posterior margin rounded (Fig. 3H); mesendosternite with two parasagittal thin projections directed upwards (Fig. 3I); metendosternite diamond-shaped, spatulate, 5× as long as wide, median projection acute anteriad, with two small lateral laminae (Fig. 3I); elytron wider in anterior half, slightly convergent posteriorly, subparallel, apex slightly swollen (Fig. 4A); posterior wings with radial cell open and transversal, around 2.5× wider than long, r4 interrupted both in radial cell and RP, r3 absent, RP reaching one third of MP1+2 length, medial field containing five main veins: MP3, MP4, CuA1, CAS and AA4; CuA2 absent, anal lobe well developed, AP3+4 long, J absent (Fig. 4C); legs increasing in length from pro- to metaleg, pro- and mesotarsomere I with a ventral comb covering the entire tarsomere (Fig. 3J); tarsomere I 2× longer than tarsomere II, tarsomeres II–IV decreasing in length, tarsomere IV in all legs of 1/2 length of tarsomere V, claws simple, without any visible teeth (Fig. 3J).

Figure 3. 

Geiserocerus flavifrons gen. nov. et sp. nov., paratype: A. Prothorax, dorsal; B. Prothorax, ventral; C. Prothorax, frontal; D. Prothorax, lateral; E. Meso- and metathorax, dorsal; F. Meso- and metathorax, lateral; G. Metascutum and metascutellum, dorsal; H. Meso- and metathorax, ventral; I. Meso- and metaventrite, dorsal; J. Pro-, meso-, and metaleg, from top to bottom, respectively.

Figure 4. 

Geiserocerus flavifrons gen. nov. et sp. nov., paratype: A. Left elytron, dorsal; Left elytron, lateral; C. Left wing, dorsal.

Figure 5. 

Geiserocerus flavifrons gen. nov. et sp. nov., paratype: A. Abdomen, dorsal; B. Abdomen, ventral; C. Abdominal sternites VII–IX, dorsal; D. Abdominal sternites VII–IX, ventral; E. Abdominal tergites IX and X, dorsal; F. Abdominal sternite IX, ventral; G. Aedeagus, dorsal; H. Aedeagus, ventral; I. Aedeagus, lateral.

Abdomen (Fig. 5). Subparallel, tergites and ventrites extremely transverse, around 3–4× wider than long, slightly increasing in length, tergite VIII as wide as long; tergites with anterior margin deeply emarginate, lateral margins subparallel, posterior margin straight to slightly rounded (Fig. 5A); tergite VII with a fringe of microsetae on posterior margin (Fig. 5C); tergite IX transversal, with a membranous division in middle, anterior margin oblique inward, posterior margin innerly curved; tergite X short, conical, lateral margins subparallel (Fig. 5E); sternites with anterior margin straight, lateral margins subparallel, posterior margin straight to slightly rounded (Fig. 5B), sternite VIII with a membranous, densely setose projection on anterior margin (Fig. 5D), sternite IX elongate, posterior margin slightly emarginate (Fig. 5F); aedeagus trilobed, phallobase attached to median lobe, slightly sclerotized, and shaped as a ribbon-like stripe, median lobe cylindrical, strongly curved at base, rounded apically; flagellum encircled around median lobe at rest; about 2× longer than median lobe length; parameres slightly asymmetrical, narrowing slightly past middle towards apex, which is unevenly round, toothed inward, with short and scarce bristles (Fig. 5G–I).

Length. 4.55 to 5.50 mm.

Female and immature stages. Unknown.

Geiserocerus gen. nov. can be easily separated from most of the genera of Mastinocerinae by the presence of a ventral comb in the pro- and mesotarsomere I. When compared with other genera with the pro- and mesotarsomere I ventral combs, it can be separated from all of them, with the exception of Pseudomastinocerus Wittmer, 1963, by the medial teeth on mandible. It can be differentiated from Pseudomastinocerus by the small eyes, covering around half of head in lateral view (eyes large, covering almost the entire head in lateral view in Pseudomastinocerus), separated by more than 2× the eye width in ventral view (separated by less than an eye width in ventral view in Pseudomastinocerus), antennomere XII claviform (cylindrical in Pseudomastinocerus) and paramere slightly asymmetrical (paramere symmetrical in Pseudomastinocerus).

A combination of the Latin adjective flavus, “yellow”, and feminine noun frons, “forehead”, in reference to the yellowish coloration present on the anterior region of the head of the specimens of this species. Name in apposition.

Los Volcanes refugee, Amboro National Park, Santa Cruz, Bolívia.

Body overall brown to dark brown, with light brown antennae and yellow to yellowish brown head dorsally and ventrally (anterior region to almost the entire head, varying between specimens), prosternum, mesosternum, legs and aedeagus (Fig. 1A, B). Eyes occupying almost 1/6 of head width in dorsal view (Figs 1C, 2A); in lateral view, posterior margin vertical, straight (Figs 1D, 2C). Antennomere IV 1.5× as long as III, crescent until VIII, IX subequal to VIII and X–XI slightly decrescent, XII subequal to XI (Fig. 2I). Pronotum slightly wider than long, anterior margin rounded, posterior margin slightly curved (Figs 1C, 3A). Elytron around 3× as long as wide (Fig. 4A).

Male. Measurements (n = 6): Total length: 4.55–5.50 mm (aver. 4.90 mm, 5.50 mm in holotype). Head length: 0.59–0.66 mm (aver. 0.61 mm, 0.57 mm in holotype). Head width: 0.84–0.90 mm (aver. 0.88 mm, 0.89 mm in holotype). Pronotum length: 0.69–0.76 mm (aver. 0.73 mm, 0.74 in holotype). Pronotum maximum width: 0.74–0.83 (aver. 0.81 mm, 0.82 in holotype). Elytron length: 1.56–1.62 mm (aver. 1.58 mm, 1.56 mm in holotype). Elytron maximum width: 0.48–0.51 mm (aver. 0.50 mm, 0.48 in holotype).

Morphology: Head slightly wider than long, integument glossy, smooth, coarsely punctate, eyes small, feebly protruding, occupying around 1/6 of the width in dorsal view (Figs 1C, 2A) post-ocular area subequal to eye length in lateral view, posterior margin straight, straight (Figs 1D, 2C); antennomere IV 1.5× as long as III, crescent until VIII, IX subequal to VIII and X–XI slightly decrescent, XII subequal to XI (Fig. 2J); maxilla with last palpomere as long as the three preceding ones combined (Fig. 2F); labium with last palpomere 1.5× as long as the two preceding ones (Fig. 2G). Pronotum slightly wider than long, integument glossy, smooth, coarsely punctured, anterior margin rounded, lateral margins dorsally subparallels, slightly convergent anteriorly, posterior margin slightly curved (Figs 1C, 3A). Elytron heavily setigerous punctate, around 3× as long as wide (Fig. 4A). Posterior wings with venation as in the genus description (Fig. 4C). Tergite IX transversal, 2× as wide as long in the middle line; tergite X 2× as long as wide (Fig. 5E); Sternite VIII with posterior margin slightly marginated (Fig. 5D); sternite IX almost 2× as long as wide when including membranous area, posterior margin distinctly emarginate (Fig. 5F). Aedeagus with phallobase sclerotized, transverse and shaped as a ribbon-like stripe, medially separated; median lobe cylindrical, strongly curved at base, rounded and not constricted apically, flagellum encircled around median lobe at rest; about 2× as long as median lobe length, with serration in the apical half; paramere parallels, slightly asymmetrical, narrowing slightly past the middle towards the apex, which is truncate, toothed innard, with short and scarce bristles (Fig. 5G–I).

Coloration. Body overall brown to dark brown, with light brown antennae, brown to yellowish brown head dorsally and ventrally (anterior region to almost the entire head, varying between specimens – yellowish brown in the anterior half, medially yellowish brown and laterally brown in the posterior half of the holotype), yellowish light brown prosternum, mesosternum, legs and aedeagus (Fig. 1A, B).

Immatures and females. Unknown.

Geiserocerus flavifrons sp. nov. is only known to occur in the Parque Nacional Amboró, Santa Cruz, Bolívia (Fig. 6). The National park is a region where four major biomes come into contact: the humid vegetation from Amazonia, the seasonal subtropical lowland vegetation from the Chaco, the subtropical highland vegetation from the Andes and the seasonal vegetation of the Chiquitanía (Ibisch et al. 2003). The specific site of the sampling, Los Volcones refugee, has a heterogeneous phytophysiognomy, being composed of elements belonging to seasonal forests as well as to humid tropical forests (Linares-Palomino et al. 2008).

Figure 6. 

Distribution of Geiserocerus flavifrons gen. nov. et sp. nov. Type locality marked in pink.

All specimens were collected between November and December, by the end of the spring and beginning of the summer in the southern hemisphere. Species of this genus were never seen alive, so there is no data regarding their habits.

Holotype: BOLIVIA. Santa Cruz. BOLIVIA: Santa Cruz/ Amboro National Park/ Los Volcanes, c. 1000m/ S18°06’ W63°36’/ 20/xi-12/xii/2004\\ Flight Intercept Trap/ Mendel, H. &/ Barclay, M. V. L./ BMNH(E)2004-280\\ Geiserocerus/ flavifrons/ HOLOTYPE/ det. Roza, A.S. (1 male) (BMNH). Paratypes: Santa Cruz. BOLIVIA: Same data as holotype except last label: Geiserocerus/ flavifrons/ PARATYPE/ det. Roza, A.S. (2 males) (BMNH), (1 male) (DZRJ); Santa Cruz/ Amboro National Park/ Los Volcanes, c. 1000m/ S18°06’ W63°36’/ 20/xi-12/xii/2004\\ Flight Intercept Trap/ Mendel, H. &/ Barclay, M. V. L./ iBMNH(E)2004-280\\ Eurymastinocerus sp./ Quintino, H. Y. S. det 2017\\ Geiserocerus/ flavifrons/ PARATYPE/ det. Roza, A.S. and a (1 male) (BMNH); Santa Cruz/ Amboro National Park/ Los Volcanes, c. 1000m/ S18°06’ W63°36’/ 20/xi-12/xii/2004\\ Flight Intercept Trap/ Mendel, H. &/ Barclay, M. V. L./ BMNH(E)2004-280\\ Phengodidae/ det E. Jiménez-Sánchez 2006\\ Geiserocerus/ flavifrons/ PARATYPE/ det. Roza, A.S. and a (1 male) (BMNH).