Taxonomic and nomenclatorial revision of the Neotropical genus Phaeoxantha Chaudoir (Coleoptera: Cicindelidae) Author Moravec, Jiří 0000-0001-5294-6410 Mendel University in Brno, Faculty of Forestry and Wood Technology, Department of Forest Ecology, Zemědělská 3, CZ- 613 00 Brno, Czech Republic. jirmor @ quick. cz; https: // orcid. org / 0000 - 0001 - 5294 - 6410 jirmor@quick.cz Author Dheurle, Charles 0000-0001-5294-6410 Mendel University in Brno, Faculty of Forestry and Wood Technology, Department of Forest Ecology, Zemědělská 3, CZ- 613 00 Brno, Czech Republic. jirmor @ quick. cz; https: // orcid. org / 0000 - 0001 - 5294 - 6410 & 5 place Jenson, F- 52200 Langres, France. charles. dheurle @ wanadoo. fr; https: // orcid. org / 0000 - 0002 - 2580 - 6962 Corresponding author & Mendel University in Brno, Faculty of Forestry and Wood Technology, Department of Forest Ecology, Zemědělská 3, CZ- 613 00 Brno, Czech Republic. jirmor @ quick. cz; https: // orcid. org / 0000 - 0001 - 5294 - 6410 jirmor@quick.cz text Zootaxa 2023 2023-12-14 5386 1 1 83 https://www.mapress.com/zt/article/download/zootaxa.5386.1.1/52481 journal article 10.11646/zootaxa.5386.1.1 1175-5334 10376586 9A5C0CC4-3D86-45BD-97FC-694A4E31A8B5 Phaeoxantha ( Phaeoxantha ) bifasciata ( Brullé, 1837 ) stat restit. ( Figs 161–258 ) Megacephala bifasciata Brullé, 1837: 1 , Pl. 1, fig, 1—published in order to rectify the concept of the name Megacephala aequinoctialis sensu Dejean (1825: 14) , which was based on misidentification and is in fact a subsequent usage of the name Cicindela aequinoctialis Linnaeus, 1763: 395 – which is in fact Pheropsophus aequinoctialis ( Linnaeus, 1763 ) ( Brachinini , Carabidae ). See “Remarks” below. Megacephala aequinoctialis sensu Dejean (1825: 14) . Non Cicindela aequinoctialis Linnaeus, 1763: 395 , nec Linnaeus: 1767: 658 (as “ equinoctialis ”), nec Fabricius 1775: 226 , which is Pheropsophus aequinoctialis ( Linnaeus, 1763 ) . Phaeoxantha aequinoctialis : Chaudoir 1850: 7 (as a synonym of Phaeoxantha bifasciata ( Brullé, 1837 ) . Phaeoxantha bifasciata : Lacordaire 1842: 22 ; 1843: 202 . Tetracha bifasciata : Lacordaire 1843: 102 . Phoeoxantha (sic!) aequinoctialis : Lucas 1859: 26 (with M. bifasciata as a junior synonym and wrong spelling of the genus-group name). Phaeoxantha aequinoctialis bifasciata : Chaudoir 1865: 41 . Tetracha bifasciata : Thomson 1857: 46 . Tetracha Aequinoxialis [sic!]: Thomson 1857: 46 . (as a synonym of T. bifasciata ). Tetracha bifasciata var. obscura Dokhtouroff, 1882: 68 , pl. 8, fig, 6 – synonymy by Horn (1910) . Phaeoxantha aequinoctialis : Chaudoir 1865: 41 . Phaeoxantha aequinoctialis : Fleutiaux 1894: 26 , 27 (see “Remarks” below). Phaeoxantha bifasciata : Fleutiaux 1894: 26 , 27. Tetracha (Phaeoxantha) aequinoctialis : Horn 1903: 332 . Megacephala ( Phaeoxantha ) aequinoctialis aequinoctialis : Horn 1910: 137 . Megacephala ( Phaeoxantha ) aequinoctialis bifasciata : Horn 1910: 137 Phaeoxantha aequinoctialis : Cassola & Pearson 2001: 11 . Phaeoxantha aequinoctialis aequinoctialis : Zerm & Adis (2001a) :142 . Phaeoxantha aequinoctialis bifasciata : Zerm & Adis (2001a) :142 . Unavailable names . “ Megacephala quinoctialis [sic!] Fabr. [sic!] Var. Frontalis . Audouin [sic!], Bolivia ”: Dejean 1836: 2 – a confused name in litt. Non Cicindela frontalis Audouin & Brullé, 1839 which is Calyptoglossa frontalis (Audouin & Brullé, 1839) . Tetracha Ephippium : Thomson 1857: 46 , partim – “collection name” in litt. , as a synonym of T. bifasciata , but due to the Argentinean occurrence at least partly confused with P. cruciata by Thomson (1857) . Phaeoxantha puberula : Chaudoir: 1865: 42 “( vix var. praec. )” – nomen nudum, in litt. Type locality . Bolivia : Moxos , banks of Rio Mamore and Rio Piray . Type material. Lectotype (designated here) of Megacephala bifasciata Brullé , ♂ in MNHN , labelled: “Muséum Paris / Bolivie / (Mojos) / D’Orbigny 1834” [light ochre, printed] // “78-2 [illegible] / 34” [tarnished, circular, handwritten] // “ Type ” [red, printed]. Note to the lectotype designation . The lectotype is designated here to assure stability of this taxon, particularly due to its common confusions. Other material examined . Specimens with densely setose elytra as in the type of Megacephala bifasciata . 1 ♂ in CCJM : “Nariño, Colombia / Amazonica / 10.XI.1995 , Mráček lgt.”. 2 ♂♂ , 2 ♀♀ in CDCL : “Lecourt G. Coll. / VIII.1995 / Carimagua, 310 m / Colombie ”. 4 ♂♂ , 2 ♀♀ in CDCL : “ Peru / Iquitos, Loreto / Rio Amazonas / Coll. Dheurle” // “ V.2010 / Patrick Demez leg ”. 1 ♀ in JBCB : “ Peru / Parq. Nat. Manu / VI-VIII.1997 Peprný lgt.”. 1 ♂ in JWCW : “ Peru , Iquitos / Amazonas, 100m / 5.X.1975 leg. Post, Bauer, Lobin” // “ Megacephala aequinoctialis Dej. / Dr. K. Mandl det. 1976”. 1 ♀ in JWCW : with same label data, but with: “ Megacephala aequinoctialis bifasciata Dr. K. Mandl det. 1976” [sic!]. 1 ♀ in JWCW : “SO Peru , 16.VIII.1975 / Iberia , 250m / 69°35´/11°21´/ leg. Bauer, Lobin, Post”. 1 ♂ , 1 ♀ in CDCL : “Pucallpa, Pérou / VI.1992 , Dheurle C”. 2 ♂♂ , 3 ♀♀ in CDCL : “ Amazones ” // “ Tetracha / bifasciata/Amazone”. 1 ♂ , 2 ♀♀ in COSJ : “ Peru – Pasco / Puerto Palcazu env. / 21.XI.2001 / O. Šafránek lgt.” 11 ♂♂ , 5 ♀♀ [elytra prevailingly black] in MKPC : “ Peru , Loreto / Pevas, Rio Amazonas / 1-30.VIII.2011 , J.J. Ramirez leg.”. 2 ♂♂ in MKPC : “ Peru / Madre de Dios / Tambopata River / P. River Lodge / 8-XI. I.1995 , M. KlÍcha lgt.”. 1 ♀ in JWCW : “Braziliam Rio Solimões / Ilha da Paciência, 40km / upstr. mouth of Rio Negro / M. Zerm leg. 26.XI.1998 M. Zerm leg.” // “ Phaeoxantha a. aequinoctialis Dejean, 1825 / det. J. Wiesner, 2000 ”. 1 ♂ , 1 ♀ in JWCW : “ Bolivia , Cochabamba / Rio Cesarsama / Carrasco, 18.XII.2002 / leg. J. Ledezma & al.” // “ Phaeoxantha aequinoctialis bifasciata / ( Brullé, 1837 ) det. J. Wiesner, 2003”. 1 ♂ in CCJM [almost entirely black, as in “var.” obscura ”]: “ Brazil , Amazonas / 5 km N. of Tefe, Praia de Coati / dark sand on Solimoes bank, 6.X.1993 / M. Hrabovsky lgt.”. Specimens with sparser setosity. 1 ♀ in JWCW : “ Venezuela / Buena Vista ” // “ Megacephala aequinoctialis bifasciata Brullé / det. J. Wiesner , 1979” 1 ♀ in JWCW : “ Venezuela / Buena Vista ” // “ Megacephala aequinoctialis aequinoctialis Dej.Dr. K. Mandl det. 1976” . 3 ♂♂ , 3 ♀♀ in JWCW : “ Venezuela Orinoco Delta / Tucupita – Manamo / 10.IV.1990 , leg. A. Kierst ” // “ Megacephala aequinoctialis bifasciata Brullé / det. J. Wiesner , 1990” . 2 ♂♂ , 1 ♀ in CJVB : “ Venezuela / ter. Amazonia / Orinoco Island / 1.-10.IV.1996 Šebela lgt.” . 1 ♂ in CCJM , 1 ♀ in JBCB : “ Venezuela / Orinoco San Fernando / IV.1996 leg Šebela” . 1 ♂ in MKPC : “ Venezuela / Edo. Bolivar / Caicara de Orinoco / 29.II.1987 , Milan KřÍž lget” . 1 ♀ in CCJM : “ Bolivia Rio Seco / Sta. Cruz ”. 2 ♂♂ , 3 ♀♀ in COSJ , 1 ♂ in CCJM : “ Bolivia – Chuquisaca dept. / 50 km N of Villamontes / Machareti env., 21.I.2020 / 20°50´03´´S , 63°18´51´´W , 640 m / O. Šafránek et M. Amaya lgt.” . 3 ♂♂ , 2 ♀♀ in COSJ , 1 ♂ in CCJM : “ Bolivia , Santa Cruz depart./ 18 km NE of Cabezas , Rio Seco / 18°39´43´´S , 63°14´26´´W , 495 m / 24.I.2016 , O. Šafránek lgt.” . 3 ♂♂ , 2 ♀♀ in CJVB : ibid, except for “ Zd. Mráček lgt.” . 1 ♂ , 1 ♀ in COSJ : “ Bolivia , Santa Cruz depart./ cca 3 km SW from Buena Vista / 17°29´02´´S , 63°40´54´´W , / 332 m , 18.-20.I.2018 / O. Šafránek et M. Amaya lgt.” . FIGURES 161–164. Phaeoxantha ( P .) bifasciata (Brullé) , Moxos, Bolivia, ♂, 18.5 mm, LT (MNHN). 161—habitus, 18.5 mm; 162—labrum; 163—lateral view; 164—labels. Bars = 1 mm. Image credit Luboš Purchart. Specimens with sparse or dense but mostly short setae. 3 ♀♀ in MHCP: “ Brasil / R. Preto da I Eva / 20.-25.XI.1994 / Hrdý M. lgt.” . 2 ♂♂ , 4 ♀♀ in CCJM , 2 ♂♂ , 1 ♀ in CJVB : “ Brazil , Amazonas / L. bank of Rio Negro / 8 km N. of Manaus / on white sand beach / 4.X.1989 M. Hrabovsky ” . 1 ♂ , 1 ♀ in CCJM with same label data except for: “ 6.X.1989 ” . 2 ♂♂ , 2 ♀♀ in CCJM , 4 ♀♀ in CJVB : “ Brasilia – Amazonia / Manaus – Rio Negro / 20.IX-14.X.1989 / M + P. Hrabovský leg” . 1 ♂ in CCJM : “ Brazil , Mandioka Is. Rio Negro / 26.II.1993 , M. Hrabovsky leg.” . 1 ♂ in CCJM , 1 ♀ in CJVB : “ Brasilia , Pará – Santarem / Rio Tapajos / 30.IX.1989 M. Hrabovský leg.” . 1 ♀ in CJVB : “ Brasilia , Pará – Santarem / stony port bank / 1.X.1989 M. Hrabovský leg.” . 1 ♂ , 1 ♀ in CDCL : “ Obidos , Para / Brésil . Mai. 86 / Dheurle. Coll” . 1 ♂ , 1 ♀ : in CDCL : “ Brésil / Sao Paulo / d’ Olivençia” . 2 ♂♂ , 2 ♀♀ in MHCP: “ Brasil / R. Preto da I Eva / 20.-25.XI.1994 / Hrdý M. lgt.”. Evidently mislabelled specimen : 1 ♂ in JWCW : “ Argentina / Corientes ” [see “ Distribution and ecology” below] . FIGURES 165–168. Phaeoxantha ( P .) bifasciata (Brullé) , ♂ from Nariño, Colombia (CCJM). 165—habitus, 17.5 mm; 166— pronotum; 167—aedeagus; 168—labrum. Bars = 1 mm. FIGURES 169–172. Phaeoxantha ( P .) bifasciata (Brullé) , ♂ from Nariño, Colombia (CCJM), elytron and its surface details. Bars = 1 mm. Differential diagnosis and variability . Phaeoxantha ( P .) bifasciata is the largest species of the nominotypical subgenus, adults are 15–18 (–19) mm long, outer elytral margins more or less distinctly attenuated towards apices, particularly notably in males, less distinctly in females. The mandibles ( Figs 173 , 203 , 222 , 236–237 ) are similar to all preceding species, except for the presence of fourth tooth (in each mandible), which is in the nominotypical subgenus shared only with P . ( P .) cruciata . The labrum is also of the same transverse shape with rounded lateral margins. The elytral shape and generally finer umbilicate punctation on the anteromedian area (within black areas) differentiate P . ( P .) bifasciata from P . ( P .) cruciata , although the roughness of the sculpture is rather variable, as also is the elytral setal vesture, particularly in different populations of P . ( P .) bifasciata , as also obvious from the illustrations presented here. During our revision of many specimens from different countries and places, we have found the following three “patterns” among P. bifasciata populations. Adults from Peru and Colombia but also partly from Brazil and Bolivia (“pattern 1” – Figs 161–201 ) possess mostly the same or similar characters as the lectotype of P. bifasciata (despite the fact that the type comes from Moxos, Bolivia ). Their elytral setosity is mostly very dense, sometimes passing also on the pronotum and head parts. Sometimes the dense setosity is in correlation with finer umbilicate elytral sculpture (within black areas), and these Peruvian and Colombian specimens also have elongated apical portion of their aedeagi. However, both these characters are somewhat variable and aedeagi with shorter apical portions occur in syntopic males. Adult specimens from Manaus / Rio Negro and Sao Paulo d’Olivença (“pattern 2” – Figs 235–249 ) also possess dense setosity on their elytra, but the setae are variably sparser or also shorter (barely visible on light elytral areas), yet present throughout the elytral surface and outer margins; their elytral surface sculpture (on black areas) is mostly coarser, and brown to black areas are mostly yet variably reduced, in some adults even more extended than in Fig. 244 . Their aedeagi are mostly with shorter apical portion. FIGURES 173–179. Phaeoxantha ( P .) bifasciata (Brullé) , from Peru. 173—head, ♂, Rio Palcazu (COSJ); 174—labrum, ♂, ibid.; 175–176—aedeagus: 175—Rio Palcazu (COSJ); 176—Iquitos (JWCW); 177–179—elytron and details of its surface, Iquitos (JWCW). Bars = 1 mm. FIGURES 180–186. Phaeoxantha ( P .) bifasciata (Brullé) , from Iquitos, Peru (JWCW). 180—pronotum, ♂; 181—ditto, detail of sculpture; 182–186—elytron: 182—♂; 183—ditto, detail of surface; 184—elytra, ♀; 185–186—ditto, surface details. Bars = 1 mm. FIGURES 187–189. Phaeoxantha ( P .) bifasciata (Brullé) , ♀, ST of syn. “var.” obscura (Dokhtouroff), “Amazon” (SDEI). 187—habitus, 18.5 mm; 188—labels; 189—labrum. Bars = 1 mm. Image credit Kevin Weissing. FIGURES 190–201. Phaeoxantha ( P .) bifasciata (Brullé) .190–196, 198–201—elytra: 190—♀, Brazil, Teffe (CCJM); 191– 192—ditto, details of surface; 193—♀, Brazil, Rio Solimoes (JWCW); 194–196—Bolivia, Rio Cesarsama (JWCW): 194—♀; 195—♂; 196—ditto, surface detail; 197—♂, aedeagus; 198–201—historical specimens ex Chaudoir (MNHN): 198—♀, as P. bifasciata ; 199—ditto, surface detail; 200—♀, as “ P. aequinoctialis ”; 201—ditto, surface detail. Bars = 1 mm. FIGURES 202–211. Phaeoxantha ( P .) bifasciata (Brullé) , from Cabezas, Bolivia (COSJ). 202—habitus, ♂, 15.3 mm; 203— mandibles, ♂; 204–205—labrum: 204—♂; 205—♀; 206—maxillae, ♂; 207–211—elytra: 207–208—♂♂; 209—♀; 210 ♂; 211—ditto, surface detail. Bars = 1 mm. FIGURES 212–220. Phaeoxantha ( P .) bifasciata (Brullé) , Bolivia. 212—pronotum, ♂, Cabezas (COSJ); 213—ditto, surface detail; 214–218—elytra: 214—♂, Mchareti (COSJ); 215—ditto, surface detail; 216—♀, Buena Vista (JWCW); 217–218—dit- to, surface detail. 219–220—male aedeagus: 219—Mchareti (COSJ); 220—Cabezaz (COSJ); Bars = 1 mm. FIGURES 221–226. Phaeoxantha ( P .) bifasciata (Brullé) , from Orinoco, Venezuela. 221—habitus, ♂, 18 mm, San Fernando (CCJM); 222—mandibles, ♂, Tucupita (JWCW); 223–224—labrum: 223—♂, San Fernando (CCJM); 224—♀, Tucupita (JWCW); 225—pronotum, ♂, San Fernando (CCJM); 226—ditto, surface detail. Bars = 1 mm. FIGURES 227–234. Phaeoxantha ( P .) bifasciata (Brullé) , from Orinoco, Venezuela. 227–232—elytra: 227—♂, San Fernando (CCJM); 228–229—ditto, surface detail; 230—♂, Tucupita (JWCW); 231—ditto, surface detail; 232—♀, ibid.; 233–234—aedeagus: 233—ibid.; 234—San Fernando, CCJM. Bars = 1 mm. FIGURES 235–240. Phaeoxantha ( P .) bifasciata (Brullé) , from Manaus—Rio Negro, Brazil (CCJM). 235—habitus, ♂, 14.5 mm; 236—head; 237—mandibles, ♂; 238–240—male labrum. Bars = 1 mm. FIGURES 241–249. Phaeoxantha ( P .) bifasciata (Brullé) , from Manaus—Rio Negro, Brazil (CCJM). 241—habitus, ♀, 18.5 mm; 242–249—male elytra and surface details. Bars = 1 mm. FIGURES 250–258. Phaeoxantha ( P .) bifasciata (Brullé) , from Manaus—Rio Negro, Brazil (CCJM). 250–252—male pronotum (251—surface detail); 253–255—aedeagus; 256–257—internal sac; 258—dorsal aspect. Bars = 1 mm. Third of the forms (“pattern 3” – Figs 203–232 ) is represented by populations from Orinoco, Venezuela and two disjunct Bolivian localities. Their elytra are mostly sparsely setose, in some adults the setae are confined to umbilicate punctures which are coarser (the same as in “pattern 2”); nonetheless, some specimens have denser setosity yet mostly not as dense as in “pattern 1”, but some Venezuelan syntopic adults have the setosity as dense as in the lectotype . Posterior and anterior pronotal lobe has mostly a mosaic-like surface. Their aedeagi are with elongated apex. However, further examination has revealed that these characters are variable throughout the countries and the large Amazon Basin, including the mostly pale coloured specimens from Brazilian area of Manaus, as well as from Bolivia (though the elytral surface is mostly consistent in individual populations), and that also the shape of the aedeagus apex varies (for instance in the examined syntopic specimens from Iquitos, Peru ). The expansion of the black elytral spots is also variable, specimens from white sands are lighter with reduced brownish-black spots, while those from dark sand have their spots larger, sometimes they are prevailingly or almost entirely black, as in the type of “var”. obscura ( Dokhtouroff, 1882 ) ( Fig. 187 ) and in the male (CCJM) listed above from Brazilian Teffe. In addition, also some of the syntopic adults from Orinoco, Venezuela , possess variable elytral coloration and surfaces (some of them have their elytra densely setose and finely and densely umbilicate-sculptured, similar to the elytral surface in the lectotype ). Moreover, and this is very important (see “Remarks” below), two examined females from the Dejean-Chaudoir collection, one standing in MNHN as “ P. aequinoctialis ”, the second as P. bifasciata , exhibit transiting characters, including their elytral setosity which is only somewhat sparser in the former than in the latter ( Figs 198–201 ). Consequently, despite some differences in individual populations, we cannot reliably determine distinguishing characters due to the existing variability, and finding a representative specimen of Megacephala aequinoctialis sensu Dejean (1825) is evidently barely possible. As a result, we believe that there is only one, highly variable species, which is P . ( P .) bifasciata (see “Remarks” below). Distribution and ecology . According to the protologue by Brullé (1837) , the type locality of Megacephala bifasciata is Bolivia , Moxos (written “Mojos” on the label – Fig. 164 ), situated, on the banks of Rio Mamore, which is one of the largest Amazon tributaries. The type locality means very probably Llanos de Moxos (also spelled as “Llanos de Mojos”) in the district of Beni . Brullé (1837) described the ecology as (freely translated from French): “ It occurs there in August to October, staying (adults) during the day at the bottom of the holes on the banks of the rivers of Mamore and Piray, and do not come out until the onset of night, when they run with extreme speed in search of their food ”. It is interesting that Brullé mentioned also Rio Piray, which is situated in the Bolivian province of Santa Cruz (distant from Moxos); nevertheless, the two rivers are partly connected through the basin formed by streams of Rio Mamore, Rio Grande and Rio Yapacani, yet in a long distance before it reaches the city of Santa Cruz de la Sierra (see the map Fig. 328 ). The above-listed Bolivian records are from larger sandy beaches in areas between foothills of the Southern Andean Yungas and Gran Chaco (Rio Seco, Camiri, Machareti – O. Šafránek pers. com.). Both historical and recently caught adult specimens come from various localities throughout the large Amazon Basin (see the above-listed label data and under the figures Figs 161–258 ). The above-listed old male specimen ( JWCW ), clearly conspecific with the lectotype of P. ( P .) bifasciata , but bearing a graphite-pencil-handwritten label: “ Argentina / Corientes ” (collector and date missing), was evidently mislabelled . The biology of this species (under “P. a. aequinoctialis ” ), its life cycles of adults and larvae observed in the Central Amazonian floodplains in the region of Manaus, were published by Zerm & Adis (2001a , b, c). It is obviously a flightless beetle, lacking flight muscles as observed by Zerm & Adis (2002) . It is noteworthy to mention that in the key to larvae by Arndt et al. (2002) the authors described some different characters (particularly differences in number of setae) between the larvae of Phaeoxantha a. aequinoctialis and P. a bifasciata (identified as such by the cited authors). Nevertheless, the authors mentioned that the number of setae was variable and the larval species and its instar was often possible to determine only by combining the number of setae on galeomere with pronotal width; it seems that the identification of larval species might be difficult. Moreover, larvae of these two taxa were collected in the same area of Manaus (although not exactly in the same places). Therefore, further studies are necessary for confirmation of the larval differences. Remarks . As already mentioned in “Introduction”, Megacephala bifasciata was published by Brullé (1837) in order to rectify the dubious concept of Megacephala aequinoctialis sensu auctorum (primarily sensu Dejean 1825 , 1833 , 1836 ). The taxon has been hitherto commonly yet incorrectly treated as Phaeoxantha aequinoctialis aequinoctialis ( Dejean, 1825 ) . There is no doubt that Dejean (1825) was referring to a Megacephala species , but he did not at any point assert or provide anything that could be interpreted as a valid description of a new and independent taxon under Article 12 of ICZN (1999) . Instead, he explicitly referred to Linnaeus (1763) and to a quite identical redescription by Fabricius (1775) , because he erroneously believed that his Megacephala was conspecific with the Cicindela by Linnaeus (1763) . The use of the name by Dejean must be therefore interpreted as a misidentification and subsequent usage of the name Cicindela aequinoctialis Linnaeus, 1763 , which is in fact a bombardier beetle (tribe Brachinini , Carabidae ), presently known as Pheropsophus aequinoctialis ( Linnaeus, 1763 ) . The same misinterpretation was maintained by Dejean (1833 , 1836 ) and for instance also by Laporte de Castelnau (1834) . Apart from that we were not able to distinguish reliably any other taxon within populations of P . ( P .) bifasciata , including a specimen that could possibly represent a neotype of Megacephala aequinoctialis sensu Dejean and sensu auctorum , one more reason for which we are unable to preserve the name aequinoctialis in Megacephalini , is the very inconsistent concept of “ P. aequinoctialis ” used by individual authors. Most of them simplified the taxonomy and quite uncritically treated P. bifasciata as a subspecies of “ P. aequinoctialis ” which they incorrectly attributed to Dejean. For instance, Fleutiaux (1894) separated these two taxa in a key to Phaeoxantha species and described their distinguishing characters. His concept of P. bifasciata (despite the fact that he did not mention any setosity) partly corresponds to the lectotype of P. bifasciata . However, the characters mentioned by Fleutiaux for “ P. aequinoctialis ”, e.g., paler elytra with smaller brownish spots, “ lesser extent than the yellow part ” are in great contradiction to Dejean (1825) , who characterized the elytra with obviously very large, dark brown confluent spots connected along the suture and forming a “ large kidney-shaped spot ” . This all corresponds to our concept of only one, variable species, treated here as P. ( P .) bifasciata ( Brullé, 1837 ) , which was validly published, supported by a good illustration and by the preserved type specimen in MNHN, examined and designated as the lectotype here ( Figs 161–164 ). Moreover, as the name bifasciata has also been in common use to the present day, the name aequinoctialis cannot be considered a nomen protectum under Article 23.9.3 ( ICZN 1999 ). We suppose that due to the wide distribution of the populations, possibly tending towards allopatric speciation under continuous evolutionary forces, also a molecular study might be very difficult. Any partial DNA tests, when only incomplete material gained from only individual samples is sequenced, may result in inconsistent and misleading results (as in several published cases) even if latest methods are used, particularly from samples obtained from a GenBank with unreliable identification due to the variability and particularly different concepts by authors who identified the taxa. Subgenus Euphaeoxantha subgen. nov. Type species . Megacephala testudinea Klug, 1834 (see “Note” below). Differential diagnosis . The five species of this new subgenus are immediately distinguished from the nominotypical subgenus by their much larger, robust and brownish to dark brown, 20–27 mm long and 7.80–12 mm wide body (females narrower than males), abnormally shaped male mandibles with particularly aberrant right mandible ( Figs 8–9 ) and consistently very different shape of 6–8-setose labrum with deep excision on either side, forming large lateral teeth and with distinctly prolonged, 4-dentate anteromedian lobe ( Figs 10–12 ). Outer pronotal margins distinctly constricted towards posterior lobe which is markedly narrower than anterior one. Note to the type designation . Phaeoxantha ( Euphaeoxantha ) subgen. nov. partly corresponds to the unnamed subgenus (with type species Megacephala testudinea ) indicated in a subgeneric division of Phaeoxantha by Westwood (1853: 218) where Westwood clearly designated Phaeoxantha bifasciata as the type species of Ammosia , which is thus clearly a junior synonym of Phaeoxantha , while he simultaneously designated P. testudinea as the type species for a not yet described, unnamed subgenus (named Euphaeoxantha subgen nov. here). Similarly, Chaudoir (1865: 42) treated Megacephala testudinea and M. klugii clearly separated from Phaeoxantha , as he listed them in order after the genus Metriocheila Thomson, 1857 , thus isolated from all the species treated here in the nominotypical subgenus. Distribution and biology. Species of the newly proposed subgenus occur in areas of the large Amazon Basin, but mainly in the Rio de la Plate Basin (see under each species below), partly in the same areas and similar biotopes as the species of the nominotypical subgenus, such as sandy beaches of seasonal rivers, marshlands and other similar biotopes. Results of life cycles of adults and larvae of P . ( E .) klugii and P . ( E .) lindemannae occurring in open areas of Central Amazonian floodplains in the region of Manaus, including larval development (also reared in the laboratory), were presented by Zerm & Adis (2001a , b, c) and Zerm et al. (2001). Key to species of Phaeoxantha ( Euphaeoxantha ) Universal characters. Body large, male mandibles abnormally shaped, particularly right mandible distinctly aberrant-shaped ( Figs 8–9 ) 1 Elytra uniformly pale brownish coloured or somewhat darkened, lacking any black maculae.................................................................................................. P . ( E .) lindemannae ( Mandl, 1964 ) – Elytra generally darker and either with black anteapical (mostly lacrymoidal) macula or variably black diffusing area on posterior part of elytral disc along sutures...................................................................... 2 2 Elytra in males more or less distinctly but always notably dilated posteriad at anteapical angles....................... 3 – Elytra of almost uniform oval-shape in both sexes (widest in male but never distinctly dilated posteriad at anteapical angles). First three protarsomeres in males only slightly dilated (unique character within the genus). Male mandibles with terminal teeth notably short, wide and abruptly pointed; third tooth in female right mandible acute and notably longer than second tooth........................................................................... P . ( E .) bucephala (W. Horn, 1909) 3 Elytra with diffusing black area on posterior part of elytral disc along sutures, diffusing towards anteapical angles (lacking sharply-circumscribed black anteapical macula), rarely elytra prevailingly blackened. Third tooth in right mandible in males flattened (fin-like shaped), while long and acute in females. Aedeagus apex distinctly hooked dorsad (unique shape within the genus)..................................................................... P . ( E .) testudinea ( Klug, 1834 ) – Elytra with black, clearly delineated (mostly lacrymoidal) anteapical macula which is often prolonged posteromesad towards sutures by thinner appendix............................................................................. 4 4 Male elytra appearing rather elongate, yet moderately or distinctly dilated posteriad. Right mandible in male with second tooth small but well-developed and clearly separated from the terminal tooth and distant from third tooth; female mandibles with sharpened apices of teeth, generally with second and third teeth approximately of the same size................................................................................................... P . ( E .) klugii ( Chaudoir, 1850 ) – Male elytra appearing shorter, as usually more distinctly dilated posteriad and with small anteapical impression. Right mandible in male with second tooth small and mostly tightly appressed to terminal tooth and more markedly distant from the third tooth; right mandible in females usually with second tooth smaller than third tooth.............. P . ( E .) wimmeri ( Mandl, 1958 )