Nealcidion chloroxanthon, Vlasak & Nascimento & Santos-Silva, 2025

Nealcidion chloroxanthon sp. nov.

( Figs 1–10 View FIGURES 1–5 View FIGURES 6–10 )

Description. Holotype male ( Figs 1–5 View FIGURES 1–5 ). Head capsule dark brown; ventral mouthparts reddish brown, except palpomeres blackish with the apex of maxillary palpomeres IV and labial palpomeres III reddish brown; anteclypeus mostly brown posteriorly, with area close to labrum dark brown; labrum dark brown on posterior 3/4, brown on anterior quarter; mandibles dark reddish brown on basal2/3,blackish on apical third; scape irregularly greenish yellow on basal third and mostly dark brown on remaining dorsal surface, greenish yellow laterally, gradually darker from middle and becoming reddish brown close to apex, and mostly orangish brown on ventral surface; pedicel mostly dark brown; antennomere III dark brown on apex, irregularly, mostly dark brown dorsally, and irregularly orangish brown on remaining surface, this area slightly darker near dark-brown apex; antennomere IV mostly dull yellowish brown, except dark-brown apex; antennomeres V–X light reddish brown except dark-brown apex. Prothorax dark brown. Ventral surface of meso- and metathorax black except dark-brown central area of mesoventrite and base of mesoventral process and orangish-brown area close to metacoxal cavities. Scutellum dark brown. Elytra dark brown basally, gradually dark green on remaining surface, this area more brownish green depending on light intensity and lighter posteriorly. Pro- and mesocoxae orange with irregular dark areas; metacoxae dark brown laterally, orange on remaining surface. Trochanters orangish. Femora orangish basally, irregularly, both orangish and greenish on remaining peduncle, light green on femoral clubs. Basal 2/3 of tibiae mostly light green, apical third of protibiae both dark brown and dark orangish brown, apical third of mesotibiae dark brown on dorsal sulcus, dark orangish brown on remaining surface except blackish dorsal apex and dark-brown ventral apex, and apical third of metatibiae brown dorsally, dark brown on apex of ventral surface, and orangish brown on remaining surface. Protarsi dark brown basally, gradually blackish toward apex; meso- and metatarsomeres I orange except dark brown apical third; meso- and metatarsomeres II–III dark brown and IV–V and claws black. Abdominal ventrites dark brown laterally, black centrally.

Head. Frons, vertex, antennal tubercles, genae, and area behind eyes with dense greenish-yellow pubescence, except glabrous median groove, this area diamond-shaped between antennal tubercles and upper eye lobes, and apex of genae, pubescence slightly sparser on antennal tubercles and slightly darker on superior region of frons; frons with one long, erect brown seta close to eyes; frons, vertex, antennal tubercles, and area behind eyes abundantly, finely, shallowly punctate. Wide central area of postclypeus with dense greenish-yellow pubescence close to frons, almost glabrous centrally, and with moderately abundant yellowish-white setae directed forward close to anteclypeus; with a few long, erect brown setae interspersed posteriorly. Sides of postclypeus glabrous. Labrum with moderately sparse yellowish-white pubescence posteriorly, long, erect setae directed forward about middle, setae yellowish white centrally, yellowish brown laterally, and glabrous on anterior region, except fringe of yellowish-brown setae on anterior margin. Gulamentum glabrous, except yellowish-white pubescence on intermaxillary process. Maximum diameter of upper eye lobes slightly shorter than basal diameter of scape; distance between upper eye lobes 0.36 times distance between outer margins of eyes; in frontal view, distance between lower eye lobes 0.64 times distance between outer margins of eyes. Antennae 1.9 times elytral length, reaching elytral apex at basal third of antennomere VII. Scape with moderately abundant yellowish pubescence not obscuring integument, except dark-brown pubescence not obscuring integument on dark dorsal area. Pedicel with yellowish-white pubescence not obscuring integument on part of basal half and dark-brown pubescence not obscuring integument on remaining surface; with a few moderately long, erect dark-brown setae ventrally. Antennomere III mostly with dark-brown pubescence not obscuring integument dorsally and on apical dark area and yellowish pubescence not obscuring integument on remaining surface; with moderately long, erect, thick dark-brown setae interspersed ventrally and short dark-brown setae directed backward apically on dorsal and lateral surfaces. Antennomeres IV–XI with abundant yellowish pubescence not obscuring integument on light integumental area, pubescence appearing to be darker depending on light intensity and source, and abundant dark-brown pubescence not obscuring integument on dark integumental area; IV with a few short, erect, thick dark-brown setae interspersed ventrally, distinctly more abundant apically; VI–VII with a few short, erect, thick setae on ventral apex; IV–VII with short, thick dark-brown setae directed backward on apex of dorsal and lateral surfaces; apex of XI with short, bristly yellowish-white setae. Antennal formula (ratio) based on antennomere III: scape = 0.92; pedicel = 0.12; IV = 0.76; V = 0.53; VI = 0.46; VII = 0.43; VIII = 0.39; IX = 0.37; X = 0.35; XI = 0.35.

Thorax. Prothorax wider than long; anterior constriction well marked; sides divergent from anterior constriction to lateral tubercle, convergent from lateral tubercle to posterior sixth, then parallel-sided toward posterolateral angle; lateral tubercles large, subconical. Pronotum densely, minutely punctate, except smooth area close to anterior margin and posterior sulcus, and transverse row with coarse punctures near posterior margin, punctures not follow toward sides of prothorax; posterior sulcus well marked laterally, almost absent centrally; widely, longitudinally depressed centrally; with dense, wide, longitudinal greenish-yellow pubescent band centrally, from anterior to posterior margins, abundant greenish-yellow pubescence laterally, pubescence denser close to lateral tubercles of prothorax and lighter than on central pubescent band, and abundant brownish-yellow pubescence not obscuring integument on remaining surface, except glabrous anterior constriction and posterior sulcus; with a few long, erect dark-brown setae on sides of posterior third. Sides of prothorax with abundant greenish-yellow pubescence, denser on some areas, except glabrous anterior and posterior sulcus. Prosternum with dense greenish-yellow pubescence laterally and abundant greenish-yellow pubescence centrally partially obscuring integument, except glabrous anterior sulcus, narrow white pubescent area close to sides of procoxal cavities, and glabrous remaining area close to procoxal cavities. Prosternal process with abundant greenish-yellow pubescence partially obscuring integument, except glabrous sides and narrow transverse white pubescent area on apex; narrowest area 0.38 times procoxal width. Mesoventrite with abundant white pubescence not obscuring integument, except dense greenish-yellow pubescence close to superior region of mesanepisterna. Mesanepisterna and mesepimera with dense greenish-yellow pubescence. Mesoventral process with somewhat abundant whitish pubescence laterally, abundant whitish pubescence centrally, with greenish-yellow pubescence interspersed anteriorly, and sparse, both whitish and greenish-yellow pubescence on remaining surface; sides convergent from base to near apex, then slightly widened; narrowest area 0.44 times mesocoxal width. Metanepisterna with abundant whitish pubescence not obscuring integument on anterior third and dense greenish-yellow pubescence on remaining surface. Metaventrite with dense greenish-yellow pubescence laterally, except white pubescence close to mesocoxal cavities, whitish pubescence denser toward metanepisterna, and abundant, both whitish and greenish-yellow pubescence close to metacoxal cavities; remaining surface with abundant whitish pubescence not obscuring integument, with greenish-white pubescence interspersed on some areas, except very sparse whitish pubescence on large posterocentral region, absent on metathoracic discrimen and posterior area close to abdominal process. Scutellum glabrous anterocentrally, dense greenish-yellow pubescence on remaining surface, with whitish pubescence interspersed on sides of basal area. Elytra. Abundantly, coarsely punctate on anterior sixth, punctures gradually sparser, finer from anterior sixth to posterior fifth, absent on posterior fifth; centrobasal crest large, elevated, rounded and without erect setae dorsally; with well-marked, longitudinal carina from centrobasal crest to posterolateral angle, carina arched inward on its anterior quarter and slightly obliquely inclined toward posterolateral angle on its posterior seventh; area between dorsal carina and suture depressed; with abundant greenish-yellow pubescence, partially obscuring integument on some areas, dense around centrobasal crest, except: four irregular, large dark-green pubescence areas, from epipleural margin to dorsal surface, pubescence lighter on posterior area, only the third reaching suture; dashed, slightly oblique white pubescent band on basal half of dorsal surface; dashed white pubescent band on epipleural margin, this area partially greenish-yellow anteriorly; dashed white pubescent band along suture, except area close to scutellum with white pubescent band interspersed among greenish-yellow pubescence; somewhat small, irregular white pubescent spots on posterior half; area between white pubescent maculae on dashed bands with somewhat abundant dark-green pubescence not obscuring integument. Sides of basal area with minute, erect, thick dark-brown setae ( Fig. 5 View FIGURES 1–5 ). Apex obliquely concave, making outer angle acutely triangularly elongated and sutural angle slightly projected. Legs. Coxae with abundant yellow pubescence not obscuring integument, pubescence more greenish yellow depending on light intensity, except abundant white pubescence not obscuring integument on part of area close to margins. Trochanters with moderately abundant white pubescence not obscuring integument. Femora with abundant greenish-yellow pubescence not obscuring integument, except profemoral peduncle with moderately abundant white pubescence not obscuring integument, and base of dorsal surface and entire ventral surface of meso- and metafemoral peduncles with abundant white pubescence not obscuring integument. Tibiae with abundant greenish-yellow pubescence partially obscuring integument, except; base of ventral surface glabrous; dorsal apex of protibiae glabrous; protibiae with short, erect dark-brown setae ventrally about middle; protibiae with dense, bristly yellowish-brown pubescence ventrally on apical half; pubescence sparse on posterior third of meso- and metatibiae; posterior third of meso- and metatibiae with short, erect, thick dark-brown setae, setae denser on mesotibiae; area close to apex of ventral surface of meso- and metatibiae with dense, bristly yellowish-brown pubescence; and posterior third of ventral surface of metatibiae with somewhat sparse, short, erect dark-brown setae. Protibiae arched, widened inward apically. Dorsal surface of tarsomeres I with abundant light greenish-yellow pubescence not obscuring integument, pubescence lighter on meso- and metatarsi; pro- and mesotarsomeres II–III with somewhat abundant greenish-yellow pubescence not obscuring integument; metatarsomeres II–III with abundant greenish-yellow pubescence laterally and sparser, somewhat greenish pubescence centrally; pro- and mesotarsomeres IV–V with somewhat abundant dark-brown pubescence not obscuring integument; metatarsomeres IV–V with abundant both light greenish-yellow and whitish pubescence on basal half, and somewhat abundant dark-brown pubescence not obscuring integument on posterior half; tarsomeres with a few long, erect dark-brown setae except on IV; metatarsomere I 1.25 times longer than II–III together.

Abdomen. Ventrites with dense greenish-yellow pubescence laterally and sparse whitish pubescence centrally; apex of ventrite 5 widely concave, making the outer angles spiniform.

Female ( Figs 7, 9, 10 View FIGURES 6–10 ). Similar to male, differing mainly by femoral clubs stouter; additionally, antennae slightly shorter, reaching elytral apex at basal third of antennomere VIII.

Dimensions (mm) (holotype male/ paratype males/ paratype females). Total length, 8.80/7.95–8.50/6.70–9.00; prothoracic length, 1.50/1.35–1.50/1.05–1.50; anterior prothoracic width, 1.55/1.55–1.60/1.30–1.70; posterior prothoracic width, 1.85/1.75–1.80/1.50–1.95; maximum prothoracic width, 2.40/2.20–2.35/1.85–2.35; humeral width, 3.15/2.95–3.05/2.35–3.35; elytral length, 6.45/5.90–6.30/4.85–6.75.

Type material. Holotype male from ECUADOR, Napo: 2100m, Cosanga, 25 Nov 2022, J. Vlasak leg. ( MZSP) . Paratypes — ECUADOR, Napo: 1 male 1500m, Pacto Sumaco, 5–7 Sep 2024, J. Vlasak leg. ( JVCO) ; 1 male, 3 females 3400m, Papallacta, 1 Sep 2024, J. Vlasak leg. ( JVCO) .

Etymology. The specific epithet “chloroxanthon ”, from Greek “χλωρός” (chloros)-pale green, and “ξανθός” (xanthos)-yellow, refers to the overall greenish-yellow color of this beetle.

Remarks. We believe that Nealcidion is not a natural group because it brings together species with very different features ( Bates 1863; Monné 1977). However, as these differences are mixed among species, it is not possible, at the moment, to know which of them could actually represent generic and not specific differences. Monné (2009) described Tropidocoleus to include T. bicarinatus Monné, 2009 and commented (translated): “ Tropidocoleus gen. nov. belongs to the group of genera with elytra without erect setae, with centrobasal crest, without lateral [humeral] carinae, and with dorsal carinae. This group includes Cobelura Erichson, 1847 and the Group I ( Bates 1863: 105) of Nealcidion Monné, 1977 , with dorsal carinae on elytra, from the centrobasal crest to the outer apical angle of elytra.” Additionally, Monné (2009) commented that in Tropidocoleus , Cobelura , and the Group I of Nealcidion the sides of the prothorax are either rounded or with a poorly developed swelling, and have one dorsal carina on each elytron. However, there are species in Nealcidion with humeral carinae well marked, at least keel-shaped on part of the elytra (e.g. N. kayi Nascimento, Santos-Silva & McClarin, 2020 ; N. trivittatum ( Bates, 1863) ; and N. apunctatum Vlasak & Santos-Silva, 2024 ). Furthermore, there are species in Nealcidion with two or more dorsal carinae (e.g. N. griseum (Aurivillius, 1900) ; N. eulophum (Bates, 1881) ; and the shape of the sides of the prothorax is variable, uniformly rounded from base to near apex, with rounded central protuberance, or somewhat distinctly projected and subconical. Monné (2009) also defined Tropidocoleus as having narrow upper eye lobes, with the distance between them about five times the diameter of one lobe, and the lower eye lobes about as long as the genae. Although the length of the lower eye lobes in Nealcidion is often much longer than the genae, there are species with the lower eye lobes as long, shorter, or distinctly shorter than the genae. Finally, Monné (2009) affirmed that the centrobasal crest of the elytra in Tropidocoleus is prominent and without erect setae [apically]. However, the centrobasal crest in the species of Nealcidion is extremely variable, from slightly elevated to distinctly elevated, from short to moderately long, and with or without erect setae on top. Therefore, the differences pointed out separating Tropidocoleus from Nealcidion are problematic. We are pointing out the problems regarding Tropidocoleus here because the new species presents some features that allow it to be included in this genus, especially the shape of the lateral tubercles of the prothorax.

Nealcidion chloroxanthon is similar to N. obliquum Vlasak & Santos-Silva, 2022 (see photographs on Bezark (2025) and Vlasak & Santos-Silva (2022)), but differs especially as follows: general pubescence mostly greenish-yellow; pronotum with wide, longitudinal greenish-yellow pubescence centrally and without longitudinal dark pubescent bands on sides of central region; and different pubescent pattern. In N. obliquum , the general pubescence is not greenish-yellow, central area of pronotum longitudinally glabrous centrally, with moderately narrow, longitudinal light pubescent band on sides of glabrous area, and large, longitudinal dark pubescent area close to central area, and different pubescent pattern.