Streblopus Van Lansberge, 1874

Cupello, Mario, Ribeiro-Costa, Cibele S. & Vaz-De, Fernando Z., 2020, Systematics of the enigmatic South American Streblopus Van Lansberge, 1874 dung beetles and their transatlantic origin: a case study on the role of dispersal events in the biogeographical history of the Scarabaeinae (Coleoptera: Scarabaeidae), European Journal of Taxonomy 603, pp. 1-85 : 8-17

Genus Streblopus Van Lansberge, 1874

Colonychus Harold, 1868: 10 .

Streblopus Van Lansberge, 1874a: 9–10 .

Streblopoides Balthasar, 1938: 215–216 .

Colonychus ‒ Van Lansberge 1874a: 10 (as possible synonym of Streblopus ). — Kolbe 1905: 552; 1907: 27. — Gillet 1911: 42 (as synonym of Streblopus ). — Lucas 1920: 197 (as synonym of Streblopus ). — Paulian1939:26 (as synonym of Streblopus ).— Blackwelder 1944:203 (as synonym of Streblopus ).— Pereira & Martínez 1956: 99 (as a supposed preoccupied synonym of Streblopus ). — Halffter 1961: 226, 229 (as synonym of Streblopus ). — Vulcano & Pereira 1964: 580 (as a supposed nomen nudum referring to Streblopus ). — Halffter & Martínez 1966: 152 (as a supposed nomen nudum referring to Streblopus ). — Krajcik 2006: 163 (as synonym of Streblopus ). — Chamorro et al. 2019: 234 (as a supposed nomen nudum referring to Streblopus ). — Cupello & Vaz-de-Mello 2019: 168–171 (as synonym of Streblopus ).

Streblopus – Van Lansberge1874b:187 ,189.— Karsch1887:1.— Ritsema1888:209.— Gillet1911:42.— Lucas 1920:617.— Olsoufieff 1935:34.— Paulian1938: 234; 1939: 26. — Balthasar 1941:345; 1951: 330. — Blackwelder 1944: 203. — Pereira & Martínez 1956: 94, 99, 182. — Halffter 1961: 229–230, 253; 1974: 257; 2003: 22. — Vulcano & Pereira 1964: 580; 1967: 548–549. — Halffter & Matthews 1966: 260. — Halffter & Martínez 1966: 103, 152–163, figs 13–21; 1967: 79; 1968: 210; 1977: 34, 43. — Matthews 1971: 49. — Martínez & Halffter 1972: 33. — Halffter & Edmonds 1982: 201. — Hanski & Cambefort 1991: 472. — Vaz-de-Mello 2000: 195. — Medina & Scholtz 2005: 154. — Krajcik 2006: 163; 2012: 249. – Scholtz et al. 2009: 566. — Carvajal-López et al. 2011: 122, 316. — Vaz-de-Mello et al. 2011: 6, 11, 18, 25, 33, 40, 45. — Carvajal-López 2012: 195. — Chamorro et al. 2018: 98; 2019: 10, 234. — Cupello & Vaz-de-Mello 2019: 168–171.

Streblopoides – Balthasar 1941: 346 ; 1951: 331. — Blackwelder 1944: 203. — Pereira & Martínez 1956: 99. — Halffter 1961: 229; 1974: 257 (as synonym of Streblopus ). — Vulcano & Pereira 1964: 580. — Halffter & Matthews 1966: 260. — Halffter & Martínez 1966: 103, 153–154, 158 (as synonym of Streblopus ); 1967: 79 (as synonym of Streblopus ); 1977: 34, 43 (as synonym of Streblopus ). — Krajcik 2006: 163 (as of dubious validity). — Chamorro et al. 2019: 234 (as synonym of Streblopus ). — Cupello & Vaz-de-Mello 2019: 168–169 (as synonym of Streblopus ).

Type species

Colonychus: Never fixed (see discussion below). – Streblopus : Streblopus opatroides Van Lansberge, 1874 , by original monotypy ( Van Lansberge 1874a: 9–10). – Streblopoides : Streblopoides punctatus Balthasar, 1938 , by original monotypy ( Balthasar 1938: 215–216).

Etymology

Colonychus: Dubious. Possibly from the Latin prefix ‘ col- ’, meaning ‘with’, and the Greek word ‘ onychus ’, meaning ‘claw’ ( Brown 1956). Masculine. – Streblopus: Dubious. Possibly derived from the Greek word ‘ Streblos ’ for ‘twisted, crooked, wrinkled’ ( Brown 1956). Masculine. – Streblopoides: Derived from Streblopus in reference to the close relationship between Balthasar’s new genus and Van Lansberge’s.

Differential diagnosis

Streblopus is possibly the most readily differentiable genus of the New World dung beetle fauna. As all identification keys that included Streblopus have noted( Paulian 1938; Pereira& Martínez1956; Vulcano& Pereira 1967; Halffter & Martínez 1977; Vaz-de-Mello et al. 2011), the posteromedian dentiform process of the pronotum of both species is unique among the Scarabaeinae ( Figs 1 A–C, 3A, C–D, 12A–B) and can be confidently used to separate the genus from the other groups in the subfamily. The general aspect of the body, which is very elongate, flattened and shows neither cephalic nor pronotal horns, also adds to the peculiar appearance of the genus ( Figs 1 A–C, 3A, C–D), as well as the shape of its labial palpi, whose basal palpomere is unusually expanded ( Fig. 11D ). Indeed, Streblopus is so distinctive that it is difficult to point out any genera with which it could be confused. From the Deltochilini , apart from the characters listed above, Streblopus differs by its mesotibiae being abruptly expanded at the apex in males ( Fig. 18A, C ); from Deltochilum , in particular, a genus that was once said to be similar to Streblopus ( Van Lansberge 1874a; Balthasar 1938) and with which it shares a wide pseudepipleura, Streblopus is different, among many other features, by the absence of tubercles at the apex of the elytra. Its slender metatibiae ( Fig. 20 A–D), in turn, will separate Streblopus from Dichotomiini and Coprini , while the presence of tarsal claws (among many other characters) differentiates the genus from the Eucraniini and the absence of three pairs of sharp clypeal teeth will separate it from Scarabaeini . Finally, Streblopus is different from the Eurysternini in not having a visible scutellum, its mesocoxae are obliquely positioned ( Fig. 13 C–F) and the labial palpi are 3-articulated ( Fig. 11D ), whereas Eurysternus , the only genus of its tribe, has a visible scutellum, parallel mesocoxae and 2-articulated labial palpi (see Génier 2009 for more details). Although certainly far from being exclusive to Streblopus , the labrum having the anterior margin deeply emarginated ( Fig. 8 A–D), the protarsi being absent in both sexes ( Figs 15 A–H, 16C), the metacoxae having a lateral spur covering the epipleura ( Fig. 19A ), the hind wing having a deep notch at the area of the anal fold ( Fig. 21F ), the asymmetrical parameres ( Fig. 23 A–H) and the reduced sclerites of the internal sac ( Figs 24 A–F, 25A–E) are also remarkable features of this genus.

Redescription

HEAD. Transverse, with apex ranging from clearly emarginated (males of S. opatroides ) to truncate (females of S. punctatus ); emargination, when present, flanked by two small teeth; remainder of outer edge simply rounded, with no accessory teeth or notch between clypeus and paraocular areas (ʻgenaeʼ) ( Fig. 5 A–D). Suture between clypeus and paraocular areas present and well-marked, with a tenuous tumescence (more evident in males) on clypeus adjacent to suture ( Fig. 5 A–D); fronto-clypeal suture vestigial, present very shortly and only at laterals adjacent to eyes ( Fig. 5 A–D). Eyes with dorsal surface wide, largest width as wide as one-fifth to one-fourth of interocular space; with a short ( S. punctatus ) or pronounced ( S. opatroides ) canthus ( Fig. 5 E–F). Entire dorsal surface of head covered by small umbilicate punctation, progressively denser from apex of clypeus towards frons and paraocular area; dorsal surface almost entirely flat, without any traces of horns, tubercles or elevations; a very tenuous depression present only behind apical emargination of clypeus and in paraocular areas in front of eyes. Clypeal process transverse, with apex either rounded ( Fig. 16A ) or acuminate ( Fig. 16B ). Antennae 8- or 9-articulated (funicle with 3 or 4 articles) ( Fig. 7 A–B). Labrum with lateral projections well developed and with anterior labral margin deeply U-emarginated; epipharynx with well-developed median brush and well-delimited lateral files ( Fig. 8 A–D). Mandibles ( Fig. 9 A–C), maxillae ( Fig. 10 A–C) and labium ( Fig. 11 A–C) typical of dung beetles, without any notable variation, except for shape of 3-articulated labial palpi, with basal palpomere largely expanded and almost twice as long as second and third palpomeres combined ( Fig. 11D ).

THORAX. Pronotum transverse, convex, with no elevations, grooves or depressions ( Fig. 12 A–B); lateral foveae tiny, but clearly impressed; posterior foveae absent; lateral and anterior edges marginate, anterior margin with a membranous area covering base of frons; lateral edges sinuous in both dorsal and lateral views;postero-lateral angles strongly projecting in an acuminate(or slightly rounded) projection; posterior edge highly sinuous, with a strong flange projecting backwards at centre covering base of elytral suture; surface of pronotum covered by umbilicate punctation, varying in density between species. Hypomeron with anterior region covered by small umbilicate punctures similar to and bearing setae slightly longer than those of head and pronotum, and posterior region with punctures with setae much longer than on rest of tegument ( Fig. 13A ); hypomeral carina completely absent; anterior region of hypomeron not excavated, posterior region declivous ( Fig. 13A ). Prosternum, mesoventrite, mesanepisterna and metanepisterna entirely covered by umbilicate punctation, varying in density between species ( Fig. 13 B–F); tegument between punctures smooth or with a very diffuse rivulose microsculpture. Mesoventrite wide, with a broad transverse groove at centre ( Fig. 13B ). Meso-metaventral suture arched ( Fig. 13B ). Metaventrite covered by umbilicate punctation, denser towards anterior lobe and sides; centre almost devoid of any punctation; posterior region clearly depressed, varying in degree between sexes ( Fig. 13 C–F).

LEGS. With a highly marked sexual dimorphism and intrasexual allometric variation.All femora and tibiae with ventral surface covered by umbilicate punctation ( Figs 14 A–B, 17A–F, 18A–D, 19B–E, 20A–D). Protarsi lacking in both sexes. Protibiae with three acute teeth on apical half of exterior edge; basal half marked by a row of smaller denticles ( Fig. 15 A–H). Mesocoxae obliquely orientated to one another, with surface covered by umbilicate punctation, ranging in density between species ( Fig. 13 C–F). Meso- and metafemora linear and lacking both anterior and posterior margins ( Figs 17 A–F, 19B–E). Mesotibiae slender, but abruptly expanded near apex ( Fig. 18 A–D). Mesotarsi long and slender, at least as long as mesotibiae; basal and apical mesotarsomeres subequal in length and as long as mesotarsomeres II–IV combined. Metacoxae with external spur covering epipleura ( Fig. 19A , red arrow). Metatrochanters with a sexually-dimorphic brush of long setae at posterior edge ( Fig. 19 B–E). Metatibiae slender, longer than metafemora ( Fig. 20 A–D). Metatarsi long, at least as long as half-length of metatibiae; metatarsomeres I–IV more or less equivalent in length (tarsomeres slightly shorter towards apex); metatarsomere V very long, almost as long as combined length of metatarsomeres II–IV. Meso- and metatarsal claws curved, well developed.

ELYTRA. With a broad pseudepipleura delimited by a short carina adjacent to stria VII; epipleura very narrow ( Fig. 21A ). With nine fine and well-delimited striae, seven on disc and two on pseudepipleura; striae interrupted by umbilicate punctures along their entire length. Striae I and IX, II and VIII, and III and IV or V connected to one another at apex of elytra; stria VIII absent at base of pseudepipleura. Elytral tegument with umbilicate punctation and with well-delimited alveolar microsculpture between umbilicate punctures. Elytral umbilicate punctures of subequal width or with variable width. Scutellary impression absent; scutellum not visible from above, entirely covered by base of elytra.

ABDOMEN. With six ventrites covered by umbilicate punctation. Ventrites I–IV with punctation more clearly marked at their anterior half; ventrite V evenly punctate; ventrite VI evenly punctate at sides and smooth or with punctures very sparse at centre. Abdomen very short at centre, with length subequal to separation between meso- and metacoxae. Ventrite VI as long as ventrites III–V combined. Pygidium very short and deflected towards venter, surface covered by umbilicate punctures; completely marginate, with basal margin slightly raised ( Fig. 22C ); prepygidium grooved at centre, surface lacking umbilicate punctation ( Fig. 22C ).

TERMINALIA. Aedeagus: Parameres largely asymmetrical, right paramere with clear apical projection ( Fig. 23 A–H); in dorsal view, with lateral edges straight or curved; in lateral view, ventral region straight or inclined towards apex, with either well-delimited or tenuous pair of ventral keels. Internal sac with only three sclerites: axial, subaxial and superior right peripheral sclerites ( Figs 24 A–F, 25A–E); superior right peripheral sclerite with well-delimited superior ring and broad, long inferior lobe (ʻcableʼ) with triangular area more sclerotized near edge ( Figs 24E , 25E ); axial and subapical sclerites only loosely connected, easily separable. With well-developed raspule covered by tiny scales ( Figs 24 A–C, 25A–C). – Genital segment: With well-developed medial sclerotized plate and lateral sclerotized plates ( Fig. 26 A–B). – Spermatheca: C-shaped, both externally and internally smooth, with or without pair of apical hooks ( Fig. 27 A–C).

SEXUAL DIMORPHISM. Male: Metaventrite strongly excavated posteriorly; concavity marked anteriorly by strong spur ( Fig. 13C, E ). Profemora robust, strongly enlarged at centre ( Fig.14A,C ); with anterior margin raised at centre into one or two strong spurs ( Fig. 14A, C ); trochantofemoral articulation with raised edge forming a short spine or not. Protibiae robust, curved inwards and downwards, with ventral carina interrupted by a longitudinal row of strong teeth; when fully closed, protibiae completely cover anterior edge of profemora; protibial spur present or not ( Figs 15A, C, E, G , 16C ); apical region of protibiae truncate and expanded inwards into long spur, with two transverse rows of setae (one covering anterior edge of apical lateral teeth, the other covering long spur) ( Fig. 16C ). Mesotibiae with internal angle of apical edge strongly projecting ( Fig. 18A, C ). Metatrochanter with wide brush of long setae, covering almost entire posterior edge ( Fig. 19B, D ). Metatibiae with apical edge strongly projecting inwards ( Figs 19E , 20C, E ); metatibial spur very short, rudimentary, much shorter than basal metatarsomere ( Fig. 20E ). Abdomen, in lateral view, contracted, concave ( Fig. 22A ). – Female: Metaventrite only shallowly excavated posteriorly, without indentation marking anterior margin of concavity ( Fig. 13D, F ). Profemora more linear, anterior margin simple, not raised ( Fig. 14B, D ); trochantofemoral articulation not developed into spur. Protibiae gracile, only slightly bent inward, not bent downwards ( Fig. 15B, D, F, H ); internal angle of apex projected into short spur ( Fig. 15B, D, F, H ); ventral carina simple, not interrupted by row of teeth; at apex, ventral carina marked by tuft of long setae. Mesotibiae with apical expansion, a result of a slight expansion of both internal and external edges, not only internal one ( Fig. 18B, D ). Metatrochanter with thin brush of long setae on posterior edge ( Fig. 19C, E ). Metatibiae with apex not expanded inwards, but with sharp spine at internal angle ( Fig. 20D, F ); metatibial spur well developed, very long, longer than basal metatarsomere ( Fig. 20F ). Abdomen, in lateral view, flat ( Fig. 22B ).

Distribution

As discussed in detail below, the distribution of Streblopus is clearly relict. While one species, S. punctatus , is known from some few sub-Andean localities in eastern Amazonia in Peru and Ecuador, the other, S. opatroides , is known from a larger number of places, but which cover a more limited range in the Atlantic Forest along the Brazilian states of Bahia and Espírito Santo. The genus, therefore, is present in – and limited to – the two major tropical forest ecosystems of South America east of the Andes, and its two species are separated by more than 2000 km of open and drier landscapes composing the Cerrado, in the central area of the South American Dry Diagonal ( Fig. 4 ).

Ecology

Almost nothing is known about the biology of Streblopus . The specimens gathered over the past years at CEMT and CMNC were mostly collected using pitfall traps baited with human faeces; no specimens are known to have been collected using other types of bait (except literature records for pig dung) or traps. Judging from its morphology, especially the shape of its metatibiae, which are slender and long in both species, we assume the genus should be a roller (something Halffter & Martínez (1966: 157) had already hypothesized) and possibly belongs to the functional Pattern IV of Halffter & Edmonds’ classification of dung beetle nesting behaviour ( Halffter & Edmonds 1982). Also based on the morphology, the genus is almost certainly nocturnal, as indicated by the large size of the dorsal surface of its eyes ( Raine et al. 2019; Tocco et al. 2019) and the dark dorsal colouration, without any or with only few traces of metallic sheen ( Hernández 2002; Feer & Pincebourde 2005).

Remarks

As discussed in the Introduction, the first name by which the genus was referred to in the literature was Colonychus by Harold (1868). Although it was only six years later that Van Lansberge (1874) established the name Streblopus , almost all authors except Kolbe (1905, 1907) have been using Van Lansberge’s name instead of Colonychus , mostly treating the latter as either a nomen nudum ( Vulcano & Pereira 1964; Halffter & Martínez 1966) or an available preoccupied name ( Pereira & Martínez 1956). However, since Harold (1868) did not intend to establish a new nominal genus nor included a nominal species in it, one is led to ask whether Colonychus is available or not and, if so, whether it is indeed a synonym of Streblopus . If both questions have a positive answer, then the validity of Streblopus would be threatened in favour of Colonychus , something that would disturb a nomenclatural stability that has reigned for almost 150 years.

As for the availability of Colonychus, Harold (1868: 10) cited the name in his discussion on the affinities of some Old World genera of Scarabaeinae with the New World genus Canthon , the group he was revising in that paper. There, Harold mentioned that a specimen bearing Klug’s then-unpublished name Colonychus in the Berlin museum could be a link between the African “Epirhinen” and Canthon , and discussed the characteristics that differentiate the two genera, stating the following:

“In between these [‘Epirhinen’] and Canthon , there may be, however, placed a yet undescribed genus, which was indicated as Colonychus by Klug at the Berlin museum, and which is characterized by absent protarsi, elytra surpassing the abdomen, very slightly laterally compressed metatarsi and angularly inwards-dilated apices of the tibiae”; in the original German: “ Zwischen diesen [‘Epirhinen’] und Canthon dürfte aber eine noch unbeschriebene, im Berliner Museum von Klug als Colonychus verzeichnete brasilianische Gattung sich einreihen, die durch fehlende Vordertarsen, den Hinterleib überragende Flügeldecken, seitlich nur sehr wenig flachgedrückte Hinterfüsse und am Ende nach innen hackig erweiterte Schienen ausgezeichnet ist ” ( Harold 1868: 10).

Therefore, although Harold clearly did not intend to formally describe the new genus Colonychus (even attributing its authorship to the German entomologist Johann Christoph Friedrich Klug (1775–1856) and not citing the genus in his catalogue of the world Scarabaeinae the following year, Harold 1869), he expressly presented characters that both describe the genus and differentiate it from related groups. In doing so, Harold (1868) complied with all the availability criteria established by the Articles 10, 11 and 12 of the ICZN Code and, therefore, made Colonychus an available name ( ICZN 1999). It is particularly important to stress here that the fact that Harold did not assign any nominal species to Colonychus does not interfere with our conclusion, since neither the inclusion of a nominal species nor the fixation of a type species are necessary conditions for a nominal genus published before 1931 to be available under the provisions of the current Code. The fact that Article 69.3 recognizes the possibility of a genus being established without any included species and introduces the concept of “subsequent monotypy” confirms this interpretation.

But while certainly available, is Colonychus a synonym of Streblopus as sustained by all authors who have cited the former name since the 19 th century? Since no type species has ever been fixed for Colonychus , it is impossible to answer this question objectively, but several facts indicate that this is indeed the case. Firstly, although rather schematic, Harold’s description of Colonychus is consistent with the morphology of Streblopus , as is the geographical origin cited ( Brazil). More importantly, Van Lansberge (1874a) himself recognized the possibility of Colonychus being a synonym of Streblopus in the original publication of the latter name (he cited “ Colonychus Klug in litt. ” followed by a question mark after the description of his new genus), and this synonymy has been accepted by all authors ever since ( Gillet 1911; Lucas 1920; Paulian 1939; Blackwelder 1944; Pereira & Martínez 1956; Vulcano & Pereira 1964; Halffter & Martínez 1966; Krajcik 2006).

In June 2016, the first author visited the ZMHB and looked without success for the Klug specimen cited by Harold (1868); in fact, no specimens of Streblopus were found either there or in any other German collection surveyed by us. Halffter & Martínez (1966), however, having studied the Harold collection housed in the MNHN, found a male S. opatroides labelled “ Colonychus / ex Musaeo E. Harold, ex Collection Oberthur” [sic]. This specimen was re-examined by the first author at the MNHN in September 2019 and we can confirm its species identity and the label information provided by Halffter & Martínez (1966), transcribing the latter as follows (italics indicate handwritten data, slashes separate lines): 1. “ Colónyčhus ”, 2. “Ex-Musaeo / E. Harold”, 3. “Museum Paris / ex Coll. / R.Oberthur”, 4. “ Streblopus / opatroides / Lansberge / det. G. Halffter ‘66 ”. If not the Klug specimen cited by Harold (1868) and not found by MC in the ZMHB (and it does not seem to be, since the handwriting of the Colonychus label is not similar to Klug’s), at least this male’s identity as a member of Colonychus was not doubted by Harold. Indeed, it is possible that Harold himself was the author of this specimen’s Colonychus label and that he based the identification on a comparison with the Klug specimen in Berlin. If correct, this indicates that Colonychus does refer to the same genus taxon as Streblopus and that both names are, therefore, subjective synonyms. It is important to note that Paulian (1939), who also studied material at the MNHN, did not mention the “ Colonychus specimen” examined by Halffter & Martínez (1966) and found by us there, probably because Harold’s collection only went to the MNHN in 1952, when the René Oberthür collection was incorporated into that museum ( Horn et al. 1990b).

Being available and a senior synonym of Streblopus, Colonychus has nomenclatural priority over the former nominal genus and would have to be used as the valid name for the genus taxon that includes S. opatroides and S. punctatus . A final allegation against the use of Colonychus comes from Pereira & Martínez (1956), who argued the name is preoccupied, but who did not state what senior homonym would that be. After searching both in the Nomenclator Zoologicus ( Anonymous 2004) and on Google, we were unable to find any Colonychus other than Harold’s. It seems, therefore, that Pereira & Martínez’s (1956) characterization of Colonychus as a junior homonym is incorrect.

In sum, Colonychus Harold, 1868 is an available name, a senior subjective synonym of Streblopus Van Lansberge, 1874 and, not being preoccupied, would have to be used as the valid name for the genus following the Principle of Priority. We are of the opinion, however, that using Colonychus as valid after a period of 150 years of an almost unanimous use of Streblopus as the valid name of the genus, and relegating the latter to invalidity, would not serve the Code’s goal of nomenclatural stability and, therefore, should not be put in practice. In our opinion, reversal of priority, as established in the Code’s Article 23.9, is the best way to preserve stability in this case. While complying with the conditions of Article 23.9.1.2, unfortunately this case does not comply with Article 23.9.1.1, since Kolbe (1905, 1907) cited Colonychus in passing as a valid genus in two rather brief discussions about the generic composition of Canthonini . Consequently, we are not free to use Articles 23.9.1 and 23.9.2 to consider Colonychus a nomen oblitum and, in this way, definitely preserve Streblopus as valid. We have decided, therefore, to invoke Articles 23.9.3 and 82.1.3 and referred this case to the International Commission on Zoological Nomenclature and asked for the conservation of Streblopus by suppressing Colonychus for the purposes of the Principle of Priority ( Cupello & Vaz-de-Mello 2019). Until the Commission rules on this case, the use of the junior synonym, Streblopus , should be maintained according to Article 23.9.3.

Identification key to the species of Streblopus Van Lansberge, 1874

1. Clypeus of males strongly emarginated at apex, emargination flanked by two tiny, but evident teeth ( Fig. 5A ); females with only tenuous emargination and teeth ( Fig. 5B ). Eye canthus long, reaching centre of eyes in lateral view ( Fig. 5D ). Clypeal process rounded at apex ( Fig. 6A ). Antennae 9-articulated ( Fig. 7A ). Pronotum entirely covered by dense umbilicate punctation ( Fig. 12A ). Metaventrite of males with broad concavity on posterior region ( Fig. 13C ). Protibiae of females with lateral teeth equally distant from one another and pointed more or less laterally ( Fig. 15B, F ). Protibial spur present only in females; spur straight and apically bifurcated ( Fig. 15B, F ). Mesofemora of males with brush of setae at basal half of posterior edge ( Fig. 17A ). Mesotibiae of males with short apical expansion ( Fig. 18A ); mesotibiae of females with apical edge deeply emarginated ( Fig. 18B ). Metafemora of males with long spur at posterior edge ( Fig. 19B ); both sexes glabrous on posterior edge (except for tuft of setae on surface of male posterior spur). Metatibiae of males with a longitudinal row of sharp teeth at base ( Fig. 20A ); females without such teeth ( Fig. 20B ). Elytra covered by dense umbilicate punctation and with distal calluses only slightly projected ( Fig. 21D ); epipleural carina entirely interrupted by umbilicate punctures ( Fig. 21B ) (Atlantic Forest in the Brazilian states of Bahia and Espírito Santo) ......... Streblopus opatroides Van Lansberge, 1874

– Clypeus of males only tenuously emarginated at apex and flanked by two fairly tenuous teeth ( Fig. 5C ); females with apex of clypeus straight or only tenuously emarginated, teeth absent or only tenuously marked ( Fig. 5D ). Eye canthus short, not reaching centre of eyes in lateral view ( Fig. 5E ). Clypeal process triangular, acuminate at apex ( Fig. 6B ). Antennae 8-articulated ( Fig. 7B ). Pronotum with centre only sparsely covered by tiny umbilicate punctures ( Fig. 12B ); umbilicate punctures progressively denser towards sides. Metaventrite of males with a narrower concavity on posterior region ( Fig. 13E ). Protibiae of females with two most distal teeth closer to one another than to proximal teeth; all teeth pointed distinctly forwards ( Fig. 15D, H ); protibial spur present in both sexes; female spur curved apically, not bifurcated ( Fig. 15D, H ). Mesofemora of males with posterior edge entirely glabrous or with a few sparse setae ( Fig. 17C, E ). Mesotibiae of males with long apical expansion ( Fig. 18C ); metatibiae of females with rounded apical edge ( Fig. 18D ). Metafemora of males with a short spur near metatrochanter; both sexes with posterior edge with long setae, which form a welldefined brush in males ( Fig. 19 D–E). Metatibiae of both sexes without lateral teeth ( Fig. 20 C–D). Elytra covered by sparse umbilicate punctation and with distal calluses strongly projecting ( Fig. 21E ); epipleural carina smooth or with only some sparse and tiny punctures ( Fig. 21C ) (Sub-Andean areas in the Peruvian and Ecuadorian Amazon Forest) ......... Streblopus punctatus ( Balthasar, 1938)

Figures

Fig. 1. Streblopus opatroides van Lansberge, 1874. A‒B. Ordinary specimens, dorsal view. A. ♂. B. ♀. C‒D. Lectotype, ♂. C. Dorsal view. D. Attached labels.

Fig. 11. Labium of Streblopus opatroides van Lansberge, 1874 (left palpus removed). A. Ventral view (aboral surface). B. Dorsal view (oral surface). C. Lateral view. D. Removed left palpus. Note the unusual shape of the palpus, with the basal palpomere remarkably enlarged. Abbreviations: gl = glossa; glf = glossal flap; lbpl = labial palp; lshpx = lateral hypopharyngeal sclerite; mt = mentum; pmts = premental sclerite; shp = suspensorium of hypopharynx; vapmts = ventral angles of premental sclerites.

Fig. 18. Mesotibiae. A‒B. Streblopus opatroides van Lansberge, 1874. A. ♂. B. ♀. C‒D. S. punctatus (Balthasar, 1938). C. ♂. D. ♀. Observe that females of S. opatroides differ from those of S. punctatus by having a deep emargination at the apical edge of the mesotibiae (red arrow shows emargination).

Fig. 20. Posterior legs. A‒D. Metatibiae. A‒B. Streblopus opatroides van Lansberge, 1874. A. ♂. B. ♀. C‒D. S. punctatus (Balthasar, 1938). C. ♂. D. ♀. Note the strong sexual dimorphism and the many differences between the species. E‒F. Metatarsi and apex of metatibia of S. opatroides. E. ♂. F. ♀. Observe how much shorter the male metatibial spur is in comparison to that of the female.

Fig. 13. Venter. A‒B. Streblopus opatroides van Lansberge, 1874. A. Hypomeron. B. Mesoventrite and anterior region of metaventrite. C‒F. Metaventrite and abdomen. C‒D. S. opatroides. C. ♂. D. ♀. E‒F. S. punctatus (Balthasar, 1938). E. ♂. F. ♀. Note in particular the distinction between the species and sexes in the shape of the concavity of the posterior region of the metaventrite.

Fig. 8. Labrum. A‒B. Streblopus opatroides van Lansberge, 1874. A. Aboral surface (dorsal view). B. Oral surface (ventral view; epipharynx). C‒D. S. punctatus (Balthasar, 1938). C. Aboral surface. D. Oral surface. Note the many differences between the two species, particularly the much denser and shorter setation of the median area in S. punctatus, the much longer median brush of S. opatroides and the dissimilarities in the shape of the anterior epypharingeal margin. The black arrow shows the anterior margin of the labrum, while the red arrow indicates the anterolateral region. Abbreviations: afr = apical fringe of labrum; ampr = antero-median process of labral suspensorium; lf = lateral files; mbr = medial brush of labrum; pmpr = postero-median process of labral suspensorium; ppm = proplegmatium; ssma = socketed setae of median area; topr = tormal process of labral suspensorium.

Fig. 15. Protibiae. A‒D. Dorsal view. A‒B. Streblopus opatroides van Lansberge, 1874. A. ♂. B. ♀. C‒D. S. punctatus (Balthasar, 1938). C. ♂. D. ♀. E‒H. Ventral view. E‒F. S. opatroides. E. ♂. F. ♀. G‒H. S. punctatus. G. ♂. H. ♀. Notice the many differences between the species and sexes, in particular the presence of a protibial spur in males of S. punctatus (and its absence in S. opatroides) and the different shapes of the spurs and of the lateral teeth in females of the two species.

Fig. 19. Posterior legs. A. Metacoxa of Streblopus opatroides van Lansberge, 1874. Arrow shows the lateral spur present in both sexes of both species. Note also that the spur covers the epipleura and possibly maintains the elytra pressed against the body, thus avoiding loss of water or the entry of sediment beneath the elytra in a similar way to that hypothesized for the metanepisternal tab of the Phanaeini and other tunneller groups (Edmonds 1972; Cupello & Vaz-de-Mello 2016). B‒E. Metafemora and metatrochanters. B‒C. S. opatroides. B. ♂. C. ♀. D‒E. S. punctatus (Balthasar, 1938). D. ♂. E. ♀. Note the strong sexual dimorphism and the many differences between the species.

Fig. 21. Wings. A‒E. Elytra. A. Lateral view of elytra of Streblopus opatroides van Lansberge, 1874. Note the very wide pseudepiplera and narrow epipleura. B‒C. Pseudepipleural carina (indicated by red arrows). B. S. opatroides. C. S. punctatus (Balthasar, 1938). Observe that the pseudepipleural carina in B is completely interrupted by umbilicate punctures, whereas the pseudepipleural carina in C is almost completely smooth, with very tiny and isolated punctures. D‒E. Lateral view of apex of elytra. D. S. opatroides. E. S. punctatus. Note how the distal calluses (shown by blue arrows) of S. punctatus are much more strongly projecting than those of S. opatroides. F. Right hind wing of Streblopus opatroides. Red arrow shows the notch of the anal fold. Abbreviations: AA = anal anterior; AP = anal posterior; Cu = cubitus; J = jugal; MP = media posterior; MPa = accessory MP; r4 = cross-vein r4 (cross-vein connecting veins RA3+4 and RP2); RA = radius anterior; RP = radius posterior; ScA = subcosta anterior.

Fig. 23. Genital capsule. A‒D. Streblopus opatroides van Lansberge, 1874. A. Dorsal view. B‒C. Lateral view from slightly different angles (red arrow shows the ventral surface and its keel). D. Ventral view. E‒H. S. punctatus. (Balthasar, 1938). E. Dorsal view. F‒G. Lateral view from slightly different angles (red arrow indicates ventral surface). H. Ventral view. Observe the differences in the shape of the parameres, in particular how the apical hook is much more prominent in S. punctatus.

Fig. 24. Internal sac of Streblopus opatroides van Lansberge, 1874. A‒C. Different views of the undissected internal sac and sclerites in resting position. D. Superior right peripheral sclerite. Arrow indicates a triangular area of a more sclerotized tegument that is probably homologous to a similar triangular area on the SRP of S. punctatus (Balthasar, 1938). E‒F. Apical and subapical sclerites. E. Resting position. F. Sclerites after separation. Abbreviations: A = axial sclerite; Rp = raspule; SA = subaxial sclerite; SRP = superior right peripheral sclerite; T = temones.

Fig. 5. Head. A‒D. Dorsal view. A‒B. Streblopus opatroides van Lansberge, 1874. A. ♂. B. ♀. C‒D. S. punctatus (Balthasar, 1938). C. ♂. D. ♀. Note how the emargination of the apex of the clypeus varies between the species and sexes, being greater in males of S. opatroides than in males of S. punctatus and females of both sexes. E‒F. Lateral view. E. S. opatroides. F. S. punctatus. Red arrow indicates the canthus. Observe that the canthus is much longer in S. opatroides than in S. punctatus.

Fig. 16. Protibiae. A‒B. Lateral view. A. Streblopus opatroides van Lansberge, 1874. B. S. punctatus (Balthasar, 1938). Note the how the protibia of S. opatroides is much more curved than that of S. punctatus. C. Frontal view of the protibia of S. punctatus. Note the presence of a protibial spur.

Fig. 7. Antennae. A. Streblopus opatroides van Lansberge, 1874. B. S. punctatus (Balthasar, 1938). Note the differences between the two species concerning the colour of the apical flagellomeres and the number and shape of the articles. In S. punctatus, the suppression of arthrogenesis between ancestral articles III and IV has resulted in a reduction of the total number of antennomeres from 9 to 8.

Fig. 9. Mandibles of Streblopus opatroides van Lansberge, 1874. A‒B. Ventral view. A. Left mandible. B. Right mandible. C. Lateral view of right mandible. Abbreviations: apmm = apodemes of mandibular muscles; cmb = comb of incisor lobe of mandible; conj = conjunctivus of mandible; inlb = incisor lobe of mandible; mac = mandibular acetabulum; molb = molar lobe of mandible.

Fig. 10. Maxillae of Streblopus opatroides van Lansberge, 1874. A. Dorsal view with extended lacinia. B. Dorsal view. C. Ventral view. Abbreviations: car = cardo; darsgal = dorsal articular sclerite of galea; gal = galea; lac = lacinia; mxpl = maxillary palpus; prcar = articular process of cardo; ss1–4 = stipal sclerite 1–4; varsgal = ventral articular sclerite of galea.

Fig. 12. Pronotum. A. Streblopus opatroides van Lansberge, 1874. B. S. punctatus (Balthasar, 1938). Note the differences in the umbilicate punctation and colour between the species.

Fig. 14. Profemora. A‒B. Streblopus opatroides van Lansberge, 1874. A. ♂. B. ♀. C‒D. S. punctatus (Balthasar, 1938). C. ♂. D. ♀. Note the differences between the species and sexes in relation to the overall shape of the profemora and the presence of spurs on the anterior edge in males.

Fig. 17. Mesofemora. A‒B. Streblopus opatroides van Lansberge, 1874. A. ♂. B. ♀. Note the sexual dimorphism in the presence of a long row of setae on the posterior edge of the male mesofemur. C‒F. S. punctatus (Balthasar, 1938). C. ♂. D. ♀. E‒F. Detail of posterior region of metafemora. E. ♂. F. ♀. Note the strong alveolar microsculpture present near the posterior edge in males and the high concentration of umbilicate punctures in the same region in females.

Fig. 22. Abdomen of Streblopus opatroides van Lansberge, 1874. A‒B. Lateral view. A. ♂. B. ♀. Note that the female abdomen has a straighter surface than that of the male, which is concave (red arrow shows this concavity). C. Pygidium and prepygidium.

Fig. 25. Internal sac of Streblopus punctatus (Balthasar, 1938). A‒B. General aspect before dissection. C. Raspule. D. Apical and subapical sclerites. E. Superior right peripheral sclerite. Arrow indicates a triangular area of a more sclerotized tegument that is probably homologous to a similar triangular area on the SRP of S. opatroides van Lansberge, 1874. Abbreviations: A = axial sclerite; Rp = raspule; SA = subaxial sclerite; SRP = superior right peripheral sclerite; T = temones.

Fig. 26. Genital segment. A. Streblopus opatroides van Lansberge, 1874. B. S. punctatus (Balthasar, 1938). Note that the medial sclerotized plate is larger and more sclerotized in S. punctatus than in S. opatroides; other differences refer to their lateral arches (indicated by blue arrows), which are concave in S. opatroides and more or less straight in S. punctatus, and the posterior arms of the MSP (indicated by red arrows), which are well developed and separated by a deep ʻU-shapeʼ in S. punctatus and only slightly indicated in S. opatroides. Abbreviations: LSP = lateral sclerotized plate; MSP = medial sclerotized plate.

Fig. 27. Female genitalia. A‒C. Spermatheca. A. Streblopus opatroides van Lansberge, 1874. B‒C. S. punctatus (Balthasar, 1938) (slightly different views). Observe that the spermatheca of the latter species is more slender and has a unique pair of apical hooks (red arrow). D. General view of the entire female genitalia of S. punctatus.

Fig. 4. Distribution of Streblopus van Lansberge, 1874. Note how the two species are widely separated by the vast South American Dry Diagonal stretching between Amazonia and the Atlantic Forest. During several different times over the Neogene, forest corridors connected the two biomes and the populations of Streblopus could move from one to the other. When the forest retreated, the distribution of the genus became relict.

Fig. 6. Head. A‒B. Clypeal process. A. Streblopus opatroides van Lansberge, 1874. B. S. punctatus (Balthasar, 1938). C. Ventral view of head, S. opatroides.