Acanthoderes bialbomaculata Zajciw (1964) : 159

Silva Júnior, José O., Haseyama, Kirstern L. F. & Souza, Diego de S., 2021, Phylogenetic approach redefines Plistonax (Coleoptera, Cerambycidae, Lamiinae) with new combinations and a new genus of flat-faced long-horned beetles, Organisms Diversity & Evolution (New York, N. Y.) 21 (2), pp. 491-520 : 510-511

Acanthoderes bialbomaculata Zajciw (1964): 159 , fig. 1; Julio et al. (2000): 30 (type).

Acanthoderes (Psapharochrus) bialbomaculatus Monné (1994) : 58 (cat); Galileo and Martins (1999): 92 (distr.); Martínez (2000): 93 (distr.).

Psapharochrus bialbomaculatus Monné (2005): 200 (cat); Wappes et al. (2006): 33 (distr.); Morvan and Morati (2006): 38 (distr.); Monné et al. (2012a): 32 (distr.); Morvan and Roguet (2013): 17 (distr.).

Plistonax bialbomaculatus Tavakilian and Néouze (2013): 49 (comb. nov.); Monné and Monné (2016): 56 (type); Morvan and Roguet (2014): 19; García et al. (2019): 367 (distr.); Monné (2021) (cat).

Type locality: holotype (male) – Peru, Junín, Satipo ( MNRJ) ( Fig. 10f ) .

Diagnosis. Antennomere III–VI with two dark-brown stains ( Fig. 10f ). Pronotum with lateral tubercle elongated, subacute (Figs. 4b, 10f). Elytral punctures without internal semierect setae ( Fig. 10f ).

Distribution. Peru [Junín] (Fig. S4c).

Remarks. Originally described by Zajciw (1964) as Acanthoderes bialbomaculata , based on a single specimen from Peru, this species was transferred to Psapharochrus (currently Aegomorphus ) by Monné (1994) and then to Plistonax by Tavakilian and Néouze (2013). One of the features used to justify the combination in Plistonax was the presence of the internal semierect seta in the elytral punctures, but after analyzing the original description and the photograph of the holotype ( Fig. 10f ), it has become clear that this seta is absent in this species. P. bialbomaculatus has a pattern of pubescence very similar to P. ariasi , mainly on the antenna and elytra. Historically, the elytral pattern of pubescence is an important feature for identification in Lamiinae , which has led to disarray in the determination of this species in collections. After revising the historical records of the species, and after comparing with the photo and description of the holotype, we were able to ascertain that most records are in fact P. ariasi . The specimens recorded for Colombia ( Galileo and Martins 1999; García et al. 2019) were identified as P. ariasi , a species recently recorded from this country by Taboada-Verona and Botero (2019). The specimen from Bolivia recorded by Wappes et al. (2006) has clear morphological differences from P. bialbomaculatus , but it was not possible to associate its identity with any other species, and for this reason, this record was not considered here. Lastly, it was not possible to access the photograph of the specimen recorded from French Guiana by Morvan and Morati (2006), and hence, we decided not to consider this record as valid for P. bialbomaculatus . Therefore, we determine that P. bialbomaculatus is known only from the type locality in Peru. It was not possible to investigate the type material, which was lost in a fire that destroyed many specimens housed in the Museu Nacional (MNRJ) in 2018. However, there is a photographic register of the holotype digitally available in Monné et al. (2021).

Plistonax difficilis ( Melzer, 1934) , comb. nov. (Fig. 13h, i, j, k, l, m, n)

Idiomerus difficilis Melzer (1934): 98 , fig. 13; Zikán and Wygodzinsky (1948): 54 (type); Buck (1959): 604 (distr.); Bachmann and Di Iorio (2002): 66 (type).

Acanthoderes (Psapharochrus) minuta Fuchs (1958): 57 ; Viana (1972): 375 (distr.).

Psapharochrus minutus Monné (2005): 209 (cat); Wappes et al. (2006): 33 (distr.).

Melzerus difficilis Monné (2005): 179 (cat, comb. nov.); Monné and Monné (2006): 40 , fig. 4 (distr., syn); Wappes et al. (2006): 32 (distr.); Demez and Touroult (2011): 104 (distr.); Monné et al. (2017b): 49 (type); Barros et al. (2019): 187 (distr.); Monné (2021) (cat).

Type locality: holotype (male) – Brazil, São Paulo, Amparo ( MZSP) .

Diagnosis. Pronotum with median tubercles very elevated ( Fig. 2d ), with a third median tubercle at central region (Fig. 13h, j); median-longitudinal ridge absent. Femora with one yellow stain on inner surface of globose region (only males) (Fig. 13i).

Redescription. Male (♂) (Figs. 13h–i). General surface covered with decumbent light-brown setae, merged with yellowish and grayish setae. Legs with sparse white setae. Head. Large punctures. Gena of subequal length to lower ocular lobe. Frons and around of ocular lobes with white and yellow setae. Vertex with one pair of little distinct tubercles.

Antenna. Pedicel about 1/3 length of scape; antennomere III about 1.3 length of scape; antennomere IV subequal in length to scape; following antennomeres decreasing gradually in length. Antennomeres V–XI each with one dark-brown stain subapical, intercalated by yellowish stains. Inner surface with distinct erect setae on antennomeres I–V. Antenna reaching elytral apex at antennomere VIII. Prothorax. Pronotum with short lateral tubercle, covered by yellowish setae. Prosternal process with lateral margin straight. Mesothorax. Scutellum mostly covered by dark-brown setae, with a median-longitudinal yellowish band. Mesoventral process width smaller than diameter of mesocoxa; one pair of distinct antero-lateral tubercles, slightly elevated. Elytra. Median-basal crest starting from base, reaching about half of elytron, curved and with small ridges on anterior region. A mid-basal white stain, and transversal black stains anteriorly, both locat- ed between crests and elytral suture; one pair of black stains on post-median region; one pair of curved black stains, near elytral slope; slope area with yellowish stain; other small black or white stains sparse; margin with yellowish stain. Internal semierect seta in punctures white, small and thick, strongly expanded towards apex, with deep and sparse sulci (Fig. 13n). Elytral apex rounded. Legs. Femora with yellowish, white, and brown setae. Tibiae slightly expanded towards apex, with two dark-brown stains, intercalated by yellowish stains. Tarsomerus I covered with white setae, tarsomeres II–V with white and brown setae. Abdomen. Entirely covered with yellowish setae, sparser at median region. Male terminalia ( Fig. 14g, h, i, j, k, l ). Tegmen ( Fig. 14g ). Ringed part convex, with inner margin weakly sclerotized anteriorly; remaining surface membranous; apex rounded, with median reentrance. Paramere with weak, uniform sclerotization, narrowed towards apex; basal region expanded laterally, with row of short setae; apex entirely covered by long setae; remaining surface with short and sparse setae. Endophallus ( Fig. 14h–i ). Median lobe slightly curved at anterior region (lateral view), with dorsal lobe indistinguishable; ventral lobe weakly sclerotized at median region, stronger at apex and antero-lateral region; apex slightly narrowed, with median deep invagination. Median strut membranous, smooth, with apex rounded. Internal sac with one pair of sclerotized structures anteriorly; one small sclerotized and bifurcated structure posteriorly. Ventral arc ( Fig. 14j ). Membranous, with stem slightly curved at apex, slightly wider at base of stem. Tergites ( Fig. 14k–l ). Tergites VII and VIII wider than longer, both covered with short setae posteriorly, entirely sclerotized, with base and apex rounded. Tergite VIII with membranous apophysis.

Female (♀) (Fig. 13j–k). Differs from male in the following: antenna reaching elytral apex at antennomere IX; femora without yellow stain on inner surface.

Variation. Transversal black stains on anterior region of elytra may be absent; the pattern of elytral stains may vary considerably; yellowish stain on elytral slope may be whitish.

Measurements (mm). Total length (6.6–8.7); elytral length (4.7–6); pronotum length (1.3–1.9); umeral width (2.9–3.6); pronotum width (2.3–3.1).

Distribution. Argentina [Formosa, Tucumán], Bolivia [Beni, Santa Cruz], Brazil [Amazonas n.rec., Goiás, Mato Grosso, Minas Gerais, Paraíba n.rec., Paraná, Rio Grande do Sul, Rondônia, São Paulo], Paraguay [Itapúa], Peru [Junín, Ucayali] (Fig. S4d).

Remarks. In the original description, Melzer (1934) described a new genus for his species ( Idiomerus difficilis ). He commented on the semierect seta in the elytral punctures, noticing the similarity with P. albolinitus . However, he stated that the protarsus of Plistonax has fringes of setae, a feature that was absent in his new genus. The protarsal fringes of setae occur in the males of most genera in Acanthoderini , sometimes more evident in some than in others, but they are definitely present in P. difficilis (Fig. 13i). This species is distinctly small- er than other Plistonax , with clear diagnostic characteristics. The new records indicate that the species may have a broader distribution. Although previously known from a wide geographical range in South America (from Peru to southern Brazil), there are new records from latitudes nearest from the equatorian line, and areas historically less explored, as northeast Brazil. Since it was the only species of Melzerus , this genus is now a synonym of Plistonax .

Figures

Fig. 10 Holotypes of some species of Plistonax: a Plistonax multipunctatus Thomson, 1864 (=P. albolinitus). b Plistonax albituberculatus Silva Júnior & Souza, 2019. c Acanthoderes albolinitus Bates, 1861 (=P. albolinitus). d Plistonax antonkozlovi Santos-Silva, Nascimento & Silva Júnior, 2020. e Acanthoderes ariasi Chemsak & Hovore, 2002 (=P. ariasi comb. nov.). f Acanthoderes bialbomaculata Zajciw, 1964 (=P. bialbomaculatus). g P. senecauxi

Fig. 2 Character photographs: a 2:0 frons with small punctures (anterior view, Aegomorphus jaspideus). b 2:1 frons with large punctures (anterior view, A. travassosi). c 21:0 mesoventral process with antero-lateral tuber- cles slightly elevated (lateral view, Plistonax albolinitus). d 21:1 mesoventral process with antero-lateral tubercles very ele- vated (lateral view, Acanthoderes (Acanthoderes) daviesii). e 4:1 male’s antennomeres VI–XI with tubercles in the inner surface and 11:1 male’s antennomeres IX–XI with black setae in the inner sur- face (lateral view, male of P. albolinitus). f 6:1 antennomere III with darker stain near apex, 7:1 antennomere III with darker stain near base, 8:1 antennomere IV with darker stain near base, 9:0 antennomeres IV–XI with darker stain near apex in subapical posi- tion, and 10:1 antennomeres III– VII with erect setae in the inner surface (dorsal view, P. rafaeli). g 9:1 antennomeres IV–XI with darker stain near apex in apical position (dorsal view, P. insolitus). White dashed lines highlight the character states 2:0 and 2:1; blue arrows highlight the character states 6:1, 7:1, 8:1, 9:0, and 9:1; red arrows highlight the character state 10:1. Scale bars: 1 mm

Fig. 14 Male terminalia: Plistonax ariasi (a–f): a tegmen (ventral view); b endophallus (ventral view); c endophallus (lateral view); d ventral arc (ventral view); e tergite VII (dorsal view); f tergite VIII (dorsal view). P. difficilis (g–l): g tegmen (ventral view); h endophallus (ventral view); i endophallus (lateral view); j ventral arc (ventral view); k tergite VII (dorsal view); l tergite VIII (dorsal view). Points and gray shapes represent sclerotized structures. Scale bars: 0.5 mm