Length from apex of clypeus to apex of pygidium 17.0–20.0 mm (♂) and 19.0–24.0 mm (♀); width at mid-elytra 10.0–12.0 mm (♂) and 11.0–14.0 mm (♀). Color: Dorsal surface tan to ochre (cream or whitish when alive) with or without weak green reflections, ventral surface castaneous with weak metallic green or red reflections; specimens tend to darken with age. Form (Figs 1–8): Elongate oval, widest at mid-elytra, pygidium exposed beyond apices of elytra; apices rounded with one short spine or tubercle near apex (males) or swelling (females). Head: Disc of frons and clypeus in lateral view flat, clypeus with margins and apex weakly reflexed; length of clypeus to frons (ratio) 0.5–0.6 : 1.0. Frons and clypeus moderately densely punctate, punctures small to moderate in size. Frontoclypeal suture weakly impressed, incomplete at middle. Eye canthus flattened, not weakly cariniform. Interocular width 2.5–3.8 transverse eye diameters. Clypeus rounded, with apex and lateral margin weakly reflexed, lacking bead; frontal view flat with short tawny setae, length (at middle) about 1/10 length of frons, disc moderately densely punctate, lacking setae. Mandible (Fig. 9) broadly rounded externally with 2 interior, acute teeth; molar region broad; mandibular apex always exposed. Labrum (Fig. 11) with apex emarginate medially, surface moderately densely punctate, punctures moderate in size, setose (setae moderately long and thick, tawny). Maxilla (Fig. 10) with 6 teeth; galea not fused, with moderately long setae. Mentum (Fig. 12) subrectangular in shape, broadest at middle, apex emarginated. Antenna with 10 antennomeres and 3-segmented club; club subequal in length to antennomeres 2–7 combined. Pronotum: Widest at base, apical angles acute, basal angles obtuse. Dorsal surface moderately densely punctate; punctures small and moderate in size. Bead complete anteriorly, laterally, and basally; setose basolaterally (setae moderately long, tawny or white). Scutellum: Parabolic, wider than long; base declivous at elytral base; dorsal surface as in pronotum. Wing (Fig. 14): Dense, thick setae present anterior to RA₃₊₄ to apex; ScA with dense, thick setae near fold and with weak precostal pegs from near fold to base; AA₁₊₂ shorter than AA₃₊₄. Elytra: Surface punctate with weakly impressed striae; finely, densely rugose at apex. Punctures sparse to moderately dense, small to moderate in size, lacking setae. Sutural stria indicated by a row of punctures from base of scutellum to apex. Epipleuron from base to metacoxa with shelf and associated setae; beaded. Apex of elytra (Fig. 17) weakly rounded; elytral callus with well-defined tubercle or spine; sutural apex spiniform. Elytral sutural length about 10 times length of scutellum. Propygidium: Hidden beneath elytra. Pygidium: Subtriangular, about twice as wide as long at middle; finely, densely rugopunctate. Margins beaded with sparse, moderately long setae; setae tawny. Apex rounded. Venter (Figs 2–3): Prosternal process elongate-oval, projecting anteroventrally at about 35° with respect to ventral plane; apex produced to level of protrochanter, rounded; surface posteriorly protuberant in basal 1/4, with setaceous punctures; setae long, dense, tawny. Mesometaventral process produced anteriorly to prosternal process; apex acuminate, rounded; ventral surface weakly recurved toward apex in lateral view, lacking setae apically, with moderately dense setae basally (setae moderately dense, moderately long, tawny). Abdominal ventrites 1–4 subequal in length in male and female, ventrite 5 about 1.5–2 times the length of ventrite 4, ventrite 6 subequal in length to ventrite 4 (male) or 1.3 times length of ventrite 4 (female). Abdominal ventrites 1–4 subequal in length in male and female, ventrite 5 about 1.5–2 times the length of ventrite 4, ventrite 6 subequal in length to ventrite 4 (male) or 1.3 times length of ventrite 4 (female). Last ventrite with widest width to median length in males about 5.5:1 and in females about 4.3:1; surface smooth (male) or rugose (female). Last ventrite (male) subequal in length to ventrite 5, quadrate at subapex, subapical corners not produced, surface moderately densely punctate; region from subapex to apex less sclerotized, surface smooth. Last ventrite (female) subequal to ventrite 4, apex trapezoidal, surface rugose. In lateral view, male ventrites flat, female ventrites weakly convex. Legs: Protibia with 3 external teeth subequally separated in apical half; spur present, subapical; inner base lacking protibial notch. Protarsomere 5 of male a little longer than tarsomeres 1–4 and with well-defined ventromedial emargination (Fig. 15). Modified foreclaw of male 1.5–2 times width of unmodified claw, inner subapical tooth present, small. Foreclaws of female simple, internal claw as wide as outer claw. Unguitractor plate laterally flattened, weakly exposed beyond tarsomere 5; apex with 2 short setae. Protarsomere 2 (male) with or without striated region at ventral apex; lacking in female. Mesofemur with acute process projecting posteriorly on posterior margin (male) (Fig. 16). Mesotibia with sides subparallel, apex weakly divergent or parallel; external edge with 2 weak carinae (female), less pronounced in male; inner apex with 2 spurs; apex with 12–15 spinulae. Meso- and metatarsomere 4 apicomedially with 1 outer spinose seta and 1 inner stout spinose seta (male and female). Meso- and metatarsomere 5 with weak, triangular interomedial tooth or swelling. Outer claw of meso- and metatarsal claws slightly longer than inner claw; outer mesotarsal claw twice as wide as inner claw in males, subequal in width in females; metatarsal claws subequal in width; claws simple. Metatibia with sides subparallel, weakly divergent towards apex; external edge with 1–2 weak carinae (slightly more robust in female); inner apex with 2 spurs; inner apex with 14–26 short, stout spinulae. Metacoxal corner (female) weakly produced or square. Spiculum gastrale (Fig. 13): Weakly Y-shaped (arms ~30 degree angle), lacking associated sclerites and setae. Male genitalia (Figs 22–24): Parameres less than twice length of phallobase. Parameres fused dorsoventrally (not laterally), asymmetrical; diagnostic, species specific (Figs 22a, 23a, 24a). Ventral sclerite of phallobase asymmetrical or symmetrical, elongate (produced to apex of phallobase), apex subquadrate; diagnostic, species specific (Figs 22c, 23c, 24c). Female genitalia: Gonocoxites subtriangular to subquadrate with sparse setae; not diagnostic for species.

Figures 1–6. 

Dorsal and lateral habitus of Mesomerodon species. 1–3 M. barclayi sp. n., male holotype, dorsal, ventral, and lateral view 4–5 M. gilletti Soula holotype male specimen and female allotype specimen 6 M. spinipenne Ohaus male non-type specimen

Figures 7–8. 

Live specimens showing cream coloration of Mesomerodon species. 7 M. spinipenne from Manú National Park, Madre de Dios, Peru [image courtesy of Rich C. Hoyer] 8 M. barclayi sp. n. from Payamino Research Station, Orellana, Ecuador [image courtesy of Conrad Gillett].

Figures 9–17. 

Generic characters for Mesomerodon. 9 Left mandible of M. gilletti, dorsal view (broadly rounded externally with 2 interior, acute teeth; molar region broad) 10 Maxilla of M. gilletti, ventral view (with 6 teeth; galea not fused) 11 Labrum, dorsal view, of M. gilletti (apex emarginate medially) 12 Mentum, ventral view, of M. gilletti (subrectangular in shape, broadest at middle, apex emarginated) 13 Spiculum gastrale of M. gilletti 14 Wing of M. spinipenne showing venation and inset showing dense, thick setae associated with ScA and setose region anterior to RA₃₊₄15 Protarsomere 5 of M. barclayi sp. n., male, showing well defined, ventromedial emargination 16 Mesofemur of M. gilletti male, ventral view, showing acute process projecting posteriorly on posterior margin 17 Elytral apex of M. gilletti, lateral view, showing spiniform callus

Biology for species in the genus is not known. Adults likely feed on plant foliage, but no host has been recorded. Because adults are attracted to lights at night, it is likely that feeding occurs at night. Larvae are not described, but likely feed on compost and/or roots.

From the Greek, “mesos” meaning middle or in the middle, “mero” meaning femur, and “odon” meaning tooth. The name refers to the spinose process on the posterior margin of the mesofemur in males, a synapomorphy for species in the genus. The gender is neuter.

(Fig. 18). Three species distributed on western (lowland) Amazonia from Colombia, Ecuador, Peru, and Bolivia. An erroneous record from Brazil (Ohaus 1905) was repeatedly cited by subsequent authors (Blackwelder 1944, Ohaus 1934, 1952, Machatschke 1972, Krajcik 2008, Soula 2008, Moore et al. 2017) (see Mesomerodon spinipenne type material). We record the genus from elevations between 150 to 762 m. A record of the genus occurring at 2800 m (Paucar-Cabrera 2005) is beyond the limits of the genus, and we consider it erroneous. A locality record of M. gilletti from Loja (Ecuador) (Fig. 18 [indicated with question mark]) waits for confirmation through future collecting since a short series of specimens supposedly collected from Loja province (west side of the Andes) seems to be out of the altitudinal and longitudinal reach of the genus. The ranges of two species of Mesomerodon overlap in aseasonal Ecuador in a region known for the highest levels of mammal and plant species diversity (Hoorn et al. 2010). Rutelinae biodiversity in Ecuador is the highest recorded in South America, with 53 genera and 298 species (Paucar-Cabrera 2005). Of these, 92 species of Rutelinae (or 36%) are endemic to the country (Paucar-Cabrera 2005). The distribution of the genus is restricted to low elevations alongside the Andes without extending eastward into the Brazilian Amazon. Mesomerodon exhibits a distributional gap between M. spinipenne and the Ecuadorian species in northern Peru.

Figure 18. 

Distribution of Mesomerodon species in South America. Refer to Suppl. material 1 for associated data.

Within the Andean corridor, the genus level distribution model is congruent with the specimen-based distribution (Fig. 19 vs. Fig. 18). Therefore, the apparent distributional gap between Mesomerodon spinipenne and the Ecuadorian species in northern Peru is unlikely a result of a lack of sampling. The distribution model of the Ecuadorian species (Fig. 20) suggests that either M. barclayi sp. n. or M. gilletti extend into northern Peru. The distribution model for M. spinipenne (Fig. 21) shows a continuous distribution in central and southern Peru with a disconnected population in Bolivia (also corroborated with the specimen-based distribution). Specimen-level data do not corroborate the occurrence of M. spinipenne in western Brazil, northern Colombia, or Venezuela. Collecting may reveal occurrence of the taxon in western Brazil, but we consider it unlikely that the taxon occurs in Colombia or Venezuela because these countries have been well collected.

Figure 19–21. 

Distributional model for Mesomerodon species in South America. 19 all Mesomerodon species 20 M. barclayi sp. n., M. gilletti and unassociated females 21 M. spinipenne. Refer to Appendix 1 for associated data

Species in the genus Mesomerodon are distinguished from other pelidnotine leaf chafers based on the acute, spiniform processes on the apical callus of the elytra in males (Fig. 17; shared with Hoplopelidnota) and an acute process on the posterior margin of the mesofemur in males (Fig. 16; autapomorphic for the genus). The ovate body form, size, and color are similar to some species of Pelidnota (Pelidnota) (e.g., Pelidnota lucida Burmeister, 1844), but the form of the mandible clearly separates the two genera (Mesomerodon species possess a rounded mandibular apex [Fig. 9] whereas Pelidnota species possess a bidentate, reflexed mandibular apex). Additional characters that assist with diagnosis of Mesomerodon include: external edge of protibia with three teeth; pronotum with bead complete anteriorly, laterally and basally; mesoventrite produced beyond mesometaventral suture (Fig. 3); and male genitalia with highly sclerotized ventral sclerite of the phallobase (Figs 22c, 23c, 24c). See Moore et al. (2017) for a key to genera of pelidnotine scarabs.

Figures 22–24. 

Form of the male genitalia (dorsal [a], lateral [b], ventral [c] views) in Mesomerodon species. 22 M. barclayi sp. n. 23 M. gilletti 24 M. spinipenne

Key to Mesomerodon species

Clave para las especies de Mesomerodon

Holotype male and 19 paratypes (10 males, 9 females). Holotype male at ZMHB with label data: a) “Rutelide, Pacayacu, 23.8.37” (handwritten), b) “Mesomerodon spinipenne Ohs., MNHUB Berlin” (typeset), c) male genitalia card mounted, d) our red holotype label. Paratype female at MSPC with label data: a) “Ecuador, Pacayacu, 3.X.37, Dr. Schultze – Rhonhof S.G.” (typeset and handwritten), b) “Pacayacu 3.10.37” (handwritten), c) “loan from Zool.Mus. Berlin” (typeset), d) “Mesomerodon spinipenne Ohs., MNHUB Berlin” (typeset), e) our yellow paratype label. Paratype male at ZMHB with label data: a) ”O.ECUADOR, Sarayacu Feyer” (typeset), b) “Mesomerodon spinipenne, Cotype ♂ Ohs.” (handwritten on red label), c) “kein typus” (handwritten), d) male genitalia card mounted e) our yellow paratype label. Paratype female at ZMHB with label data: a) “O.ECUADOR, Sarayacu Feyer” (typeset), b) “Mesomerodon spinipenne, Cotype ♀ Ohs.” (handwritten on red label), c) “kein Typus” (handwritten), d) our yellow paratype label. Paratype male at ZMHB with label data: a) “O.ECUADOR, Sarayacu Feyer” (typeset), b) “88882” (typeset), c) “♂” (typeset on black bordered label), d) “Mesomerodon spinipenne Ohs., MNHUB Berlin” (typeset), e) male genitalia card mounted, f) our yellow paratype label. Paratype female at ZMHB with label data: a) “Rutelide u. Cyclocephala, Pacayacu 24.9.37” (handwritten), b) “Mesomerodon spinipenne Ohs., MNHUB Berlin” (typeset), c) our yellow paratype label. Paratype female at ZMHB with label data: a) “O. Ecuador, Puyo, A. Schulze” (typeset), b) “Ohaus determ., Mesomerodon spinipenne ♀ Ohs.” (typeset and handwritten), c) our yellow paratype label. Paratype female at ZMHB with label data: a) “O. Ecuador, Puyo, A. Schulze” (typeset), b) “Mesomerodon spinipenne Ohs.” (handwritten), c) “♀” (typeset), d) our yellow paratype label. Paratype male at CCECL with label data: a) ECUADOR (Orellana), Payamino Research Station, 0°29'967"S, 77°17'083"W, 300m Tropical Rainforest, At M.V. light at night, 30.vii–12 viii.2007” (typeset), b) male genitalia card mounted, c) our yellow paratype label. Paratype male at MSPC with label data: a) ECUADOR (Orellana), Payamino Research Station, 0°29'967"S, 77°17'083"W, 300m Tropical Rainforest, At M.V. light at night, 30.vii -12 viii.2007” (typeset), b) “coll. CPDT Gillett, BMNH(E) 2007-65” (typeset), c) “DNA extract No: Meso1, deposited at MSPC” (handwritten), d) male genitalia card mounted, e) “Matthias Seidel Collection 2016”, f) our yellow paratype label. Paratypes (2 males) at BMNH with label data: a) ECUADOR (Orellana), Payamino Research Station, 0°29'967"S, 77°17'083"W, 300m Tropical Rainforest, At M.V. light at night, 30.vii -12 viii.2007” (typeset), b) “coll. CPDT Gillett, BMNH(E) 2007-65” (typeset), c) “DNA extract No: Meso2, deposited at MSPC; no PCR amplification” (handwritten), d) male genitalia card mounted, e) our yellow paratype label. Paratype male at SLCC with label data: a) ”PARAGUAY: Alto Parana, 1.XI.1990” (typeset), b) “Collection S. Le Tirant” (typeset), c) “supposedly mislabeled locality, des. Seidel 2016” (typeset), d) “MESOMERODON SPINIPENNE OHAUS, det. M.E. Jameson 2003” (typeset and handwritten), d) male genitalia card mounted, e) our yellow paratype label. Paratype male at IRSNB with label data: a) ”ECUADOR (Orellana), Payamino Territory, 300m Tropical Rainforest, July 2007” (typeset), b) “DNA extract: Rut105, det. M.Seidel 2016” (typeset and handwritten), c) male genitalia card mounted, d) our yellow paratype label. Paratype male at ZSM with label data: a) ”O.Ecuador, Puyo, A. Schulze, 6.V.35” (typeset and handwritten), b) “Mesomerodon spinipenne Ohs.” (handwritten), c) “Staatssammlung München, 1975, Erwerb Coll. Machatschke”, d) male genitalia card mounted, e) our yellow paratype label. Paratype female at NMPC with label data: a) ”O.Ecuador, Puyo, A. Schulze, 6.V.35” (typeset and handwritten), b) “Ohaus determ., Mesomerodon spinipenne ♀ Ohs.” (typeset and handwritten), c) “Staatssammlung München, 1975, Erwerb Coll. Machatschke”, d) our yellow paratype label. Paratype female at ZSM with label data: a) ”O.Ecuador, Sarayacu Feyer” (typeset), b) “Paratypus, Mesomerodon spinipenne Cotype ♀ Ohs.” (typeset and handwritten), c) “Staatssammlung München, 1975, Erwerb Coll. Machatschke”, d) “NOT a type specimen of Mesomerodon spinipenne, Ohaus, 1905, des. Seidel 2016” (typeset), e) our yellow paratype label. Paratype male at FMNH with label data: a) ”ECUADOR: Pastaza; 300m confluence R. Macuma & R. Morona VII:17:1971, leg. B. Malkin” (typeset), b) “at light” (typeset), c) “on sand river bank” (typeset), d) male genitalia card mounted, f) our yellow paratype label. Paratype female at FMNH with label data: a) ”ECUADOR: Pastaza; 300m confluence R. Macuma & R. Morona VII:17:1971, leg. B. Malkin” (typeset), b) “at light” (typeset), c) “on sand river bank” (typeset), d) “Mesomerodon spp??? DET. A.R.Hardy 1980” (typeset and handwritten), f) our yellow paratype label. Paratype female at FMNH with label data: a) ”ECUADOR: Pastaza; 300m confluence R. Macuma & R. Morona VII:17:1971, leg. B. Malkin” (typeset), b) our yellow paratype label.

(based on 11 males and 9 females). The holotype does not differ significantly from the generic description and suffices for the description of this cryptic species (see “Remarks”). Descriptive details specific to the holotype specimen are indicated. Length from apex of clypeus to apex of pygidium 18–22 mm (♂) (holotype: 19 mm) and 22–25 mm (♀); width at mid-elytra 11–12 mm (♂) (holotype: 11 mm) and 12–15 mm (♀). Color: Cream colored (holotype), tan, or ochre; ventral surface castaneous with weak metallic green reflections. Form: Elytral apices with one short spine (holotype) or swelling (females). Legs: Protarsomere 2 of male ventrally lacking well-defined striae at ventral apex (Fig. 25). Male genitalia (Fig. 22a–c): Parameres with elongate, narrow projection (=stem) and with longitudinal, impressed fissure (Fig. 22a); stem gradually and weakly broadened toward apex, subapex lacking paired, spinose projections; ventral sclerite of phallobase with surface concave, apex quadrate (Fig. 22c); lateral view diagnostic (Fig. 22b).

Males of Mesomerodon barclayi sp. n. are differentiated from other Mesomerodon species by the following combination of characters: Protarsomere 2 ventrally lacking a striated region at the ventral apex (striated in M. spinipenne; apical region lacking striae in M. gilletti [Figs 25–27]) and form of the male genitalia (Fig. 22 versus Fig. 24 in M. spinipenne and Fig. 23 in M. gilletti). Females can only be confidently determined when associated to male specimens from the same collecting event.

Figures 25–27. 

Form of protarsomeres 2 to 4, ventral view, in Mesomerodon species. 25 M. barclayi sp. n., showing protarsomere 2 without stiate region at apex 26 M. gilletti showing protarsomere 2 without striate region at apex 27 M. spinipenne showing protarsomere 2 with striate region apically.

It is our honor to dedicate this species to Max Barclay (Curator, Coleoptera, Department of Entomology), who invited the first and second authors to the 1^st Scarab Symposium at the BMNH in 2014 where cooperation on this work was initiated. Max Barclay has led the way in making biodiversity science more accessible to scientists and citizens alike.

(Fig. 18). Known from western (lowland) Amazonia areas in Ecuador and occurring in apparent sympatry with M. gilletti. Ohaus (1934, 1952) recorded M. spinipenne from Sarayacu, Ecuador. We recovered these specimens in ZMHB and ZSM and identified them as belonging to M. barclayi sp. n.

(Suppl. material 1). 20 specimens from 9 collections.

ECUADOR: Morona-Santiago, Orellana, Pastaza

Based on label data, this species is known to be active in the months of February, August, and November.

Based on label data, adult M. barclayi sp. n. is usually collected at light, thus suggesting activity and feeding at night. Individuals probably occur throughout the year. Immature stages are unknown. Specimens have been recorded at an elevation of 300 m.

As with other cryptic species, the overall body form of M. barclayi sp. n. is similar to other species in the genus. The form of the male genitalia (Fig. 22 versus Figs 23–24) however, is sufficient for identification of M. barclayi sp. n. When developing our species hypotheses, we examined this morphotype in terms of phenotypic, elevational, and seasonal variation within M. spinipenne or M. gilletti, but the consistency in the form of the male genitalia led us to conclude that it is a justified species. Apparent sympatry (in location and phenology) with M. gilletti also led us to carefully examine this species pair. Again, we found that consistency in the male genitalia form was sufficient for diagnosis of both species. Females of M. barclayi sp. n. cannot be identified unless associated with males from the same collecting event.

Holotype male, allotype female, and eight paratypes (four male, four females. Holotype male at CCECL with label data: a) “Tena (E), 9/91, (750m)” (handwritten), b) male genitalia card mounted c) “Holotype, 2007, Mesomerodon gilletti S., Soula” (typeset and handwritten on red label). Allotype female at CCECL with label data: a) “Tena (E), 9/91, (750m)” (handwritten), b) “Allotype, 2007, Mesomerodon gilletti S., Soula” (typeset and handwritten on red label). Paratype male at CCECL with label data: a) “Tena (E), 9/91, (750m)” (handwritten), b) male genitalia card mounted, c) “Paratype, 2007, Mesomerodon gilletti S., Soula” (typeset and handwritten on red label). Paratypes (2 females) at CCECL with label data: a) “Tena (E), 9/91, (750m)” (handwritten), b) “Paratype, 2007, Mesomerodon gilletti S., Soula” (typeset and handwritten on red label). Paratypes (2 males) at CCECL with label data: a) “Misahuali (E.), 5/91” or “Misahuali (Eq.), 5/91” (handwritten), b) male genitalia card mounted, c) “Paratype, 2007, Mesomerodon gilletti S., Soula” (typeset and handwritten on red label). Paratype male at CCECL with label data: a) “EQUATEUR: Prov. NAPO, MISAHUALLI ile ANACONDA, Alt. 350 m.; 17–22.9.1990, Leg. Joss” (typeset), b) male genitalia card mounted, c) “Paratype, 2007, Mesomerodon gilletti S., Soula” (typeset and handwritten on red label). Paratypes (2 females) at CCECL with label data: a) “Misahuali (E.), 5/91” (handwritten), b) “Paratype, 2007, Mesomerodon gilletti S., Soula” (typeset and handwritten on red label).

(based on 50 males and 19 females). Length from apex of clypeus to apex of pygidium 18.0–20.0 mm (♂) and 21.0–24.0 mm (♀); width at mid-elytra 10.0–11.0 mm (♂) and 12.0–14.0 mm (♀). Legs: Protarsomere 2 of male lacking well-defined striae at ventral apex (Fig. 26). Male genitalia (Figs 23): Parameres with elongate, narrow projection (=stem) and with nearly obsolete impressed longitudinal fissure (Fig. 23a); stem broad, not narrowed toward apex, subapex lacking paired, spinose projections; ventral sclerite of phallobase with surface concave, apex quadrate (Fig. 23c); lateral view diagnostic (Fig. 23b).

Mesomerodon gilletti males are differentiated from other Mesomerodon species by the following combination of characters: Protarsomere 2 of male ventrally with striated region poorly defined or lacking at apex (striated in M. spinipenne; lacking in M. barclayi sp. n.; [Figs 25–27]) and parameres, and ventral sclerite of phallobase (Fig. 23 versus Fig. 24 in M. spinipenne and Fig. 22 in M. barclayi sp. n.). Mesomerodon gilletti females can only be confidently determined when associated with male specimens from the same collecting event.

(Fig. 18). Known from western (lowland) Amazonia in Ecuador and Colombia (new country record). The species occurs in apparent sympatry with M. barclayi sp. n. A record of ‘Mesomerodon species 1’ from Napo Province in Paucar-Cabrera (2005) probably represents a record of Mesomerodon gilletti. Records of Mesomerodon from Ecuador (Blackwelder 1944, Ohaus 1918, 1934, 1952, Machatschke 1972, Moore et al. 2017, Paucar-Cabrera 2005) are records for either M. gilletti or M. barclayi sp. n.

(Suppl. material 1). 69 specimens from 12 collections.

COLOMBIA: Putumayo

ECUADOR: Napo, Orellana, Sucumbíos

Based on label data, this species is known to be active in the months of February, May, June, August, September, October, and November.

Based on label data, adult M. gilletti are found associated with lights at night. Immature stages are unknown.

Soula (2008) named this species based on twelve specimens, dedicating the species to Conrad Gillett (then at the BMNH) who provided specimens for Soula’s study. In overall appearance, M. gilletti was not discernable from M. spinipenne except for the “parameres that are different enough to justify the status of the species in its own right” (Soula 2008).

Lectotype male (designated by Soula 2008) and three paralectotypes (1 male, 2 females). Lectotype male at ZMHB with label data: a) “bei Pozuzu, Eckardt S.” and “O. Peru, Chuchurras” (handwritten on verse and obverse), b) “Mesomerodon spinipenne, Type ♂ Ohs.” (handwritten on red label), c) “SYNTYPUS, Mesomerodon spinipenne Ohaus, 1905, labelled by MNHUB 2007” (typeset on red label), d) male genitalia card mounted, e) “Lectotype Mesomerodon spinipenne Oh., 2007 Soula” (typeset and handwritten on red label). Paralectotype female at ZMHB with label data: a) “60.” (handwritten, one egg mounted), b) “BRAZIL R.Purus” (typeset), c) “Mesomerodon spinipenne ♀, Cotype Ohs.” (handwritten on red label), d) “SYNTYPUS, Mesomerodon spinipenne Ohaus, 1905, labelled by MNHUB 2007” (typeset), e) “Paralectotype 2007, Mesomerodon spinipenne Oh. Soula det.” (typeset and handwritten on red label). Paralectotype female at ZMHB with label data: a) “Chuchuras, Amazonas” (handwritten), b) “Mesomerodon spinipenne, Cotype ♀ Ohs.” (handwritten on red label), c) “SYNTYPUS, Mesomerodon spinipenne Ohaus, 1905, labelled by MNHUB 2007” (typeset on red label), d) “Paralectotype 2007, Mesomerodon spinipenne S., Soula det.” (typeset and handwritten on red label). Paralectotype male deposited at BMNH with label data: a) “Chuchurras Peru” (handwritten), b) “Ohaus determ., Mesomerodon spinipenne Ohs.” (typeset and handwritten), c) “Peru 1907•27” (handwritten), d) “Co-type” (typeset on round yellow label), d) “♂” (typeset), e) “Cotypus!” (typeset on red label), f) male genitalia card mounted, g) “Paralectotype, Mesomerodon spinipenne, Ohaus, 1905, M Seidel des. 2016” (typeset on red label).

Ohaus (1905: 321) stated that the type series included at least one male and at least one female (but likely at least two females based on the length/width range that Ohaus provided) from “Peru Chuchuras (Eckhard); Amazonas, Rio Purus.” We found one additional male syntype at the BMNH that fits the measurements provided by Ohaus (1905), and we labeled it as a paralectotype. It is possible that additional paralectotypes may be found in collections.

(based on 52 males and 161 females). Length from apex of clypeus to apex of pygidium 17.0–20.0 mm (♂) and 19.0–24.0 mm (♀); width at mid-elytra 10.0–12.0 mm (♂) and 11.0–14.0 mm (♀). Legs: Protarsomere 2 (♂) with well-defined striae at ventral apex (Fig. 27). Male genitalia (Fig. 24): Parameres with elongate, narrow projection (=stem) and with longitudinal, impressed fissure (Fig. 24a); stem broadened abruptly at apex, subapex with paired, spinose projections (almost appearing broken); ventral sclerite of phallobase with surface concave, apex quadrate (Fig. 24c); lateral view diagnostic (Fig. 24b).

Mesomerodon spinipenne males are differentiated from other Mesomerodon species by the following combination of characters: Protarsomere 2 with well-defined striae at ventral apex (Fig. 27) (lacking striae in M. gilletti and M. barclayi sp. n.; Figs 25–26) and form of the parameres, and form of the ventral sclerite of the phallobase (Fig. 24 versus Fig. 23 in M. gilletti and Fig. 22 in M. barclayi sp. n.). Females can only be confidently determined when associated with male specimens from the same collecting event. Females occurring in Bolivia and Peru are most likely conspecific with M. spinipenne (Figs 6–7).

(Fig. 18). Mesomerodon spinipenne is the most broadly distributed species in the genus, and it occurs from central Peru to central Bolivia in the western (lowland) Amazonia (from 230 to 762 m elevation). The species has been recorded from Brazil, “Rio Purus” (Blackwelder 1944, Ohaus 1905, 1934, 1952, Machatschke 1972, Krajcik 2008, Soula 2008, Moore et al. 2017), but in our view this is an erroneous record. The record is based on a paralectotype female collected at the Rio Purus that rises in the Uyacali Region in Peru and flows into Brazil and which could, therefore, have been collected either in Peru or Brazil. Based on our examination of 213 specimens, we think that this specimen represents a Peruvian locality. Records of the species from Ecuador (Blackwelder 1944, Ohaus 1918, 1934, 1952, Machatschke 1972, Moore et al. 2017, Paucar-Cabrera 2005) are incorrect. These are records for either M. gilletti or M. barclayi sp. n.

(Suppl. material 1). 213 specimens from 18 collections.

BOLIVIA: Cochabamba (Chapare), Huánuco (Blackwelder 1944, Ohaus 1905, 1918, 1934, 1952, Machatschke 1972, Soula 2008, Ratcliffe et al. 2015), Junín (Blackwelder 1944, Ohaus 1905, 1918, 1934, 1952, Machatschke 1972, Soula 2008, Ratcliffe et al. 2015), Pasco (Blackwelder 1944, Ohaus 1905, 1918, 1934, 1952, Machatschke 1972, Soula 2008, Ratcliffe et al. 2015), Santa Cruz (Ichilo, Sara)

PERU: Ayacucho (La Mar), Cusco (Quispicanchi), Huánuco (Leoncio Prado, Puerto Inca), Madre De Dios (Manú, Tambopata), Pasco (Oxapampa), Ucayali (Padre Abad), Santa Cruz (Blackwelder 1944, Ohaus 1918, 1934, 1952, Gutiérrez 1951, Machatschke 1972, Moore et al. 2017).

Based on label data, this species is known to be active in all months except January and February.

Based on label data, adult M. spinipenne are active at night and can be collected at lights. Immature stages are unknown.

Based on body measurements provided by Ohaus (1905), we conclude that he had a minimum of 3 specimens: 1 male (length 18.5mm, width 10.5mm) and 2 females (length 22–23.5mm, width 12.5–13.5mm) from two localities (Chuchuras and Rio Purus). The lectotype specimen at ZMHB was designated by Soula (2008), and it is a male specimen labeled by Ohaus as “type” (“Mesomerodon spinipenne, Type ♂ Ohs.”) and with the locality label “bei Pozuzu, Eckardt S.” and “O. Peru, Chuchurras”. As part of this research, we found and labeled specimens that were invalidly labeled as type specimens and that do not belong to the type series (see “Type Specimens”).

It is possible that the specific epithet, “spinipenne”, refers to the apex of the elytra in the male which possess an apical spine or tubercle. The Latin root “spini” refers to spine or thorn, and the Latin root “penna” refers to wing. This character state is not unique to M. spinipenne; instead, it is a synapomorphy for all species in the genus.