Pselaphacus dentatus Germar, 1824

Pselaphacus dentatus Germar, 1824

Figs 8–12 View FIGURE 8 View FIGURE 9 View FIGURE 10 View FIGURE 11 View FIGURE 12 .

Pselaphacus dentatus Germar 1824: 615 ( Triplax View in CoL ). Type locality: “Brasilia”; type deposited at ZMHU [according to Alvarenga, 1994]. Lacordaire 1842: 87 ( Pselaphacus ) [brief redescription, distribution]; Crotch 1876: 421 [distribution]; Gemminger & Harold 1876: 3688 [distribution]; Kuhnt 1909: 59 [distribution]; 1911: 39 [distribution]; Blackwelder, 1945: 464 [distribution]; Guérin 1948: 19 [catalog]; Skelley 1998b: 12 [catalog]. Known geographic distribution: South and Southwest Regions of Brazil.

Adult diagnosis. Body elongated, elliptical, glabrous and shiny. Head, pronotum and appendages dark brown to black. Elytra reddish orange with black patches; starting from the scutellar shield, each elytron has a slightly elongated patch projecting divergently, a spot on the humeral region, a thin pigmented band that runs the meso-elytral suture and the outer elytral margin and a transverse fascia, not reaching the lateral elytral margins, with three emarginations on the anterior and posterior margins; elongated apical spot. Each elytron has nine longitudinal striae of coarse punctures in the orange area; surface between striae with fine dense punctation. Head of penile flagellum bifurcated, forming U-shaped emargination (shallow, compared to the emargination present in P. signatus ) anterior edges truncated and slightly divergent ( Figs 8–9 View FIGURE 8 View FIGURE 9 ).

Adult redescription. Measurement with n = 5, unless otherwise specified. TL 10.00–11.85 (10.24 ± 0.79). Body elongated, elliptical, TL/EW 1.78–2.08 (1.91 ± 0.11); GD/EW 0.45–0.59 (0.56 ± 0.06) glabrous, and shiny. Head, pronotum, and appendages black to dark brown, elytra reddish orange with black spots. Venter between black and dark brown in fully pigmented individuals. Head prognathous, glabrous, punctation dense and fine at the frons, however, coarser and sparser ventrally and in the vertex; frontoclypeal suture incomplete. Clypeus deeply emarginate, with an angled outline in males ( Fig. 10a View FIGURE 10 ) or rounded in females ( Fig. 10b View FIGURE 10 ). Antennae brown, setose; club with comparatively shorter and denser vestiture. Proportions between length to each antennomere and that of the 2nd respectively from 1 st to 11 th (right antenna; n = 1) as follows: 1.36, 1.00, 1.92, 0.88, 0.92, 0.92, 0.88, 0.92, 1.20, 1.08, 1.40. FL 1.62–2.15 (1.69 ± 0.21), CL 1.00–1.15 (1.12 ± 0.06). Eyes glabrous, coarsely facetted GW 0.69–0.92 (0.77 ± 0.09). Mouthparts ( Figs 8d–h View FIGURE 8 ) mobile labrum, well sclerotized anteriorly, distal margin covered by long setae. Mandibles slightly asymmetrical, robust and with few setae; right mandible with three teeth, the most proximal less developed, the central more prominent, left mandible has two teeth and a deep groove between them; prostheca membranous and pubescent, setose anteriorly; costate mola, inner edge longer in the right mandible; galea subtriangular with setose extension towards the sagittal plane; lacinia narrower and longer in relation to the galea, with apical margin, setose; basal maxillary palpomere approximately twice the length of the two adjacent ones combined, apical palpomere subtriangular, with patch of setae at the apex; labial palpi with dilated apical palpomere, strongly sclerotized and covered by scattered setae; mentum with subpentagonal elevate plate. Thorax with subtrapezoidal pronotum, black, glabrous, with fine and dense punctation; punctures separated by about three puncture-widths. Anterior pronotal edge with two shallow emarginations just behind eyes; lateral pronotal borders convergent anteriorly, lateral carina complete; posterior edge expanded medially. Scutellar shield subpentagonal, glabrous, punctation fine; BW 0.58–0.77 (0.69 ± 0.07). Elytra EL 7.77–9.15 (7.92 ± 0.66); glabrous, reddish orange with black spots; color pattern and punctation as in diagnosis. Hind wings posterior wing venation pattern as described above for P. signatus . Prosternum convex, cup-shaped, with a slight median emargination on the prosternal process; glabrous; oval procoxal cavities, externally closed. Mesoventrite convex, glabrous, deep grooves surrounding mesocoxal cavities. Metaventrite convex; with faint punctations and setae; discrimen usually shorter than that of P. signatus , extending for about two thirds of the metaventrite; metacoxal lines present. Metendosternite well-developed ( Fig. 9g View FIGURE 9 ), rigid, translucent yellow, convex metendosternal stalk; central sclerotization of the anterior process, approximately 0.25x the length of the central sclerotization of the metendosternal stalk; metendosternal lamina ear shaped. Legs procoxa oval, mesocoxa subglobular, and metacoxa transverse; elongated femora, especially the metafemur, glabrous, without spines and with tiny, barely visible setae on their distal margin; tibiae elongated, subtriangular, apically setose; pro-, meso-, and metatibia have two spurs at the apex of inner margin; tarsi densely pubescent. Abdominal ventrites with shallow punctation; punctures separated by an approximate distance of 1–2 diameters; fine and sparse setae visible on the five ventrites; setae and punctures absent or less evident in the articulation regions between the ventrites; coxal lines on first ventrite conspicuous; length of the ventrites from first to fifth (on the median longitudinal line, n = 1): 1.51; 0.91; 0.83; 0.82; 1.02. Male terminalia ( Fig. 9c–f View FIGURE 9 ) with elongated penis, slightly curved; internal sac with a well-developed flagellum, with a bifurcated head, forming a shallow U-shaped emargination, with anteriorly truncated and slightly divergent edges; tegmen apical portion strongly sclerotized, conical, distally pubescent. Female terminalia ( Fig. 9a– b View FIGURE 9 ) with cylindrical gonostyli, well-sclerotized, with pubescent apex; gonocoxites slightly more sclerotized apically; spermatheca hazelnut-shaped, strongly sclerotized capsule; bursa copulatrix membranous; tergite and sternite VIII well-sclerotized, with pubescent posterior edges; well-developed spiculum ventrale. A membranous tube, about 1 mm long when fully extended, connects segment VIII to the posterior structures of the terminalia.

Last instar larvae. ( Fig. 11a–b, e–j View FIGURE 11 ) Measurements (n = 1): TL 14.23; PW 2.77; CAP 1.08. Slightly fusiform. Tegument cream-colored; head capsule and tarsal claws light brown, mandibles dark brown; dorsum covered by transverse light orange plates, bordered by a light brown outline, with barely visible setiferous tubercles; plates interrupted at medial line. Head ( Fig. 11e–g View FIGURE 11 ) hypognathous; strongly sclerotized cephalic capsule with short projections covering most of it, epicranial suture V-shaped; coronal suture absent; stemmata posterior to the antennal insertion, four latero-dorsally and one latero-ventrally. Antennae with 3-antennomeres, first transverse; second elongated with a small membranous sensory cone; third short and cylindrical with short distal bristles. Fronto-clypeal suture complete; clypeus anterior margin with subtriangular emargination, less sclerotized than frons. Mouthparts protracted; labrum transverse, with median emargination anteriorly; mandibles movable, symmetrical, 3-toothed apex, with the median tooth being more prominent; mola and prostheca membranous with microdenticles; mala bilobed with thick setae; stipes elongated; cardo transverse; maxillary palpi with 3-palpomeres, third palpomere longer and narrower; labial palpi with 2-palpomeres, first wider than second; mentum and gula subtrapezoidal, membranous. Thorax with prothorax slightly narrower and longer than meso- or metathorax in dorsal view; meso- and metathorax plates like those from prothorax but wider; a pair of large annular-biforous spiracles ( Fig. 11i–j View FIGURE 11 ) located laterally between pro- and mesothorax. Legs subcylindrical, with fine and short setae; coxa wide; trochanter subpentagonal; femur wider and longer than tibia; tarsunguli with well-sclerotized claws. Abdomen with 10 segments, with 9 visible from the top; a pair of annular-biforous spiracles on the sides of each segment from first to eighth. The ninth segment is smaller, depressed, with a dorsal region containing a light orange plate with a thick dark brown outline and a pair of dark urogomphi ( Fig. 11h View FIGURE 11 ), with small setiferous tubercles. Tenth segment tubular and ventral, bilobed at the apex.

Pupae. ( Fig. 11b View FIGURE 11 ) Measurements (n = 1): TL 12.46; PW 3.92. Adectic and exarate. Whitish, many setae of varying sizes; sharp projections along each side of the meso-dorsal line from the thorax to the penultimate abdominal segment. Long and thin setae present along the dorsolateral angles. Head hypognathous, not visible in dorsal view. Pronotum subtrapezoidal, about as long as the other thoracic segments combined. Abdomen gradually narrows towards the apex.

Life Cycle. From the numerous collection activities conducted, immature individuals of P. dentatus were found on only one occasion. Four last instar larvae were found on the abaxial surface of a F. brasiliensis basidiome, along with one adult. The larvae and the adult were brought to the laboratory. One of the larvae was sacrificed in boiling water and preserved in 70% alcohol for later analysis. The remaining larvae were transferred to a rearing container prepared as described in the methodology. The larvae were fed with F. brasiliensis basidiomes until, approximately three days later, they ceased feeding and burrowed into the shallow soil layer at the bottom of the terrarium, like P. signatus . Pupation occurred after approximately sixteen days, and the adults emerged about thirty days later. The adults initially exhibited lethargic behavior, which decreased as the pigmentation process advanced. The adult was dissected for sex determination, and it was found to be a female.

Remarks

Pselaphacus dentatus type specimen was not located by us, but Alvarenga (1994) mentioned it is deposited in the Natural History Museum of Berlin. Despite this, P. dentatus is well-represented in several collections (ISCPM, personal observation) . In the present study, we included images ( Fig. 12e–f View FIGURE 12 ) of five specimens deposited in the Brême historical collection (MRSN).

Specimens examined. Adults. 1 specimen (CELC) “CELC005549 \ BR: MG, Viçosa "Mata da Biologia"; 26.x.2016 Pecci-Maddalena, I.S.C. & Orsetti, A leg.”; 1 (CELC) “CELC005564 \ BR: MG, Viçosa, Mata da Biologia; 30.x.2020; G.L.N. Martins leg.”; 1 (CELC) “CELC005569 \ BRASIL: MG, Viçosa Mata da Biologia 21.ii.2015; FIT leg. S. Aloquio, A. Orsetti & M. Bento ”; 1 (CELC) “CELC005571 \ BR: MG, Viçosa, Mata da Biologia; 21.iii.2021; G.L.N. Martins leg.”; 1 (CELC) “CELC005705 \ BR: MG, Viçosa, Mata da Biologia; 30.ix.2020; G.L.N. Martins leg.”; 1 (CELC) “CELC005706 \ BR: MG, Viçosa, Mata da Biologia; 30.x.2020; G.L.N. Martins leg.”; 1 (CELC) “CELC005707 \ BR: MG, Viçosa, Mata da Biologia; 30.x.2020; G.L.N. Martins leg.”; 1 (CELC) “CELC005570 \ Brasil: MG, Viçosa " Mato do Paraíso: Trilha Principal " 15.xii.2014 Pecci-Maddalena, ISC. leg.”; 1 (CERPE) “ BRASIL, RJ, Nova Friburgo, Conquista, 850m - XII.2004 E. & P. Grossi Leg. ”; 1 (CERPE) “ BRASIL, RJ, Nova Friburgo, Sítio Caturama 1100 m - 01 - 31.I.2005 E. J. Grossi Leg. ”. Immatures. 1 specimen (CELC) “CELC005722 \ 1 pupa - Pselaphacus dentatus . Larvas de último instar coletada "aos cuidados de fêmea adulta" em 30.x.2020 -> Mata da Biologia BRA, MG, Viçosa Pupa emergiu 19.xi.2020 Martins, GLN leg. Os adultos provenientes desta criação emergiram 02.xii.2020 [handwritten]”; 1 (CELC) “CELC005723 \ 1 Larva Pselaphacus dentatus BRA, MG, Viçosa Mata da Bio. 30.x.2020 Martins, G. [handwritten]”.

Comparative notes regarding Pselaphacus larvae. Although quite similar, the larvae of Pselaphacus species described so far show some distinguishable differences. Between P. signatus and P. dentatus , the most easily recognized differences are in the color of the cephalic capsule, which is darker in P. signatus . Additionally, P. dentatus has a very well-developed semilunar fleck anterior to the thoracic spiracle, poorly developed in P. signatus (see Figs 7 View FIGURE 7 and 11 View FIGURE 11 ). As noted by Casari et al. (2024), P. procerus Kuhnt, 1910 has a distal tooth at the urogomphi apex, a structure not present in the other known larvae of the genus. Being one of the largest species in the genus, the larvae of P. nigropunctatus Percheron, 1835 , can be easily distinguished by size; reaching approximately 30 mm as described by Costa et al. (1988), it is about twice the length of the others.