Streblopus opatroides 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 : 18-38

Streblopus opatroides Van Lansberge, 1874

Figs 1–2 , 4 , 5 A–B, E, 6A, C, 7A, 8A–B, 9–11, 12A, 13A–D, 14A–B, 15A–B, E–F, 16A, 17A–B, 18A–B, 19A–C, 20A–B, E–F, 21A–B, D, F, 22, 23A–D, 24, 26A, 27A, 28

Streblopus opatroides Van Lansberge 1874a: 10 .

Streblopus opatroides ‒ Ritsema 1888: 209 . — Gillet 1911: 42. — Lucas 1920: 617. — Paulian 1939: 26–27. — Balthasar 1941: 345; 1951: 331. — Blackwelder 1944: 203. — Pereira & Martínez 1956: 99. — Vulcano & Pereira 1964: 580; 1967: 549. — Halffter & Martínez 1966: 153–162, 165, figs 13–17. — Vaz-de-Mello 2000: 195. — Krajcik 2006: 163; 2012: 249. — Molano-Rendón & MedinaUribe 2010: 692. — Vaz-de-Mello et al. 2011: 66, fig. 161. — Carvajal-López 2012: 195. — Medina et al. 2013: 461, 463, 473, fig. 65. — Audino et al., 2014: supplementary data 3. — Ratcliffe et al. 2015: 196. — Tarasov & Génier 2015: 55, 64, 76, figs 4–7, 9, 30d–f, 35p, 44c. — Chamorro et al. 2019: 234. — Cupello & Vaz-de-Mello 2019: 168–171.

Material examined

Lectotype (here designated)

BRAZIL • ♂; Bahia; “ LECTOTYPE ♂ / Streblopus / opatroides / van Lansb. / des. F.Z.Vaz-de-Mello, 20 14 ” [FZVM’s handwriting], “ Streblopus / opatroides / Lansberge / det. G. Halffter ‘66 ” [Gonzalo Halffter’s handwriting], “ Streblopus / opatroides / Bahia Lansb ” [Van Lansberge’s handwriting], “Museum Paris / ex Coll. / R. Oberthur ”, “Ex-Musaeo / E. Harold ”, “TYPE”; genital capsule extracted and glued to a paper card, ex Edgar von Harold and R. Oberthür collections ( Fig. 1 C–D); MNHN.

Paralectotypes

BRAZIL • ♀; “ Streblopus / opatroides / Lansb / Brésil ” [Van Lansberge’s handwriting], “ cf. Col.Hefte / XII, 1874, p. 10 ” [unknown handwriting], “ Colonychus / Har.” [unknown handwriting], “ type / (etiq. de l’auteur ” [unknown handwriting], “ J.J. Gillet det., vend.: / Streblopus / opatroides Lansb. / R.M.H.N. Belg. 10.640” [unknown handwriting], “Ex-Typis”, “ PARALECTOTYPE ♀ / Streblopus opatroi- / des Van Lansberge / labelled by Cupello, 2019 ” [MC’s handwriting]; ex J.J. Gillet collection; RBINS • Remaining paralectotypes unknown.

Other material (40 ♂♂, 24 ♀♀)

BRAZIL – Bahia • 1 ♂; MZSP • 6 ♂♂ (1 with genitalia dissected); Potiraguá (“ Itambé ”), Fazenda Independência ; 15°42′39″ S, 39°34′08″ W; 245 m a.s.l.; 5 Feb. 2009; J.G. Mota-Souza leg.; pitfall baited with human faeces; CEMT • 5 ♂♂; Maraú, Área de Proteção Ambiental (APA) da Baía de Camamu; 14°09′38.3″ S, 39°00′23.3″ W; 27 Nov. 2014; C.M.Q. Costa et al. leg.; pitfall baited with human faeces; CEMT • 1 ♂, 1 ♀ (left antenna, mouthparts and genitalia dissected); Porto Seguro ; 15 Jul. 1990; E. and P. Grossi leg.; ex Everardo and Paschoal Grossi collection; CEMT • 1 ♂; Porto Seguro ; Jul. 1993; E. Grossi leg.; CEMT • 2 ♂♂, 1 ♀ (genitalia dissected); Porto Seguro, Reserva Particular do Patrimônio Ambiental (RPPN) Estação Veracel (“RPPN / Esta 500 Vera Cel ”); Dec. 2004; J. Louzada leg.; ex W.D. Edmonds collection; TAMU • 2 ♀♀ (1 with genitalia and right wing dissected); Porto Seguro, RPPN Estação Veracel ; 16°23′17″ S, 39°10′24″ W; 95 m a.s.l.; 12 May 2012; L.D. Audino leg.; CEMT • 2 ♂♂, 4 ♀♀; Porto Seguro, RPPN Estação Veracel ; 16°19′08″ S, 39°06′45″ W; 80 m a.s.l.; 15 May 2012; L.D. Audino leg.; CEMT • 3 ♂♂, 5 ♀♀ (1 with genitalia dissected); Porto Seguro, RPPN Estação Veracel ; 16°22′33″ S, 39°08′54″ W; 95 m a.s.l.; 18 May 2012; L.D. Audino leg.; CEMT • 1 ♂; Porto Seguro, RPPN Estação Veracel ; 16°23′16″ S, 39°10′01″ W; 65 m a.s.l.; 3 Jun. 2012; L.D. Audino leg.; CEMT • 1 ♂; Porto Seguro, RPPN Estação Veracel ; 16°23′16″ S, 39°10′01″ W; 65 m a.s.l.; 3 Jun. 2012; L.D. Audino leg.; TAMU • 1 ♀; Santa Teresinha, Serra da Jiboia ; 12°51′11.3″ S, 39°28′32″ W; 800 m a.s.l.; 8 Jun. 2007; Rafael and Xavier Francisco leg.; hand collection; ex Everardo and Paschoal Grossi collection; CEMT • 9 ♂♂ (1 with left antenna, mouthparts, both posterior wings and genitalia dissected, 2 with genitalia dissected); Uruçuca, Parque Estadual da Serra do Conduru ; 14°29′42.6″ S, 39°08′17.2″ W; 27 Sep. 2014; C.M.O. Costa et al. leg.; pitfall baited with human faeces; CEMT • 1 ♀; Uruçuca, Parque Estadual da Serra do Conduru ; 14°29′42.6″ S, 39°08′17.2″ W; 27 Sep. 2014; C.M.O. Costa et al. leg.; pitfall baited with human faeces; DZUP • 1 ♂; Valença, Cachoeira do Candengo ; 3 Mar. 1987; Johann Becker (“ J.B. ”) leg.; MNRJ . – Espírito Santo • 1 ♀; Descourtilz leg.; ex Fry collection; BMNH • 1 ♂ (genitalia dissected); Linhares ; Oct. 2004; P.C. Grossi leg.; ex Everardo and Paschoal Grossi collection; CEMT • 1 ♂ (genitalia dissected); Linhares, Fazenda Lagoa do Macuco ; 19°03′50″ S, 39°58′43″ W; 10 m a.s.l.; 27 Jan. 2000; F. Génier and S. Ide leg.; pitfall baited with dung; CEMT • 1 ♀; Linhares, Reserva Natural Vale (“ResNatVal”); 19°04′33″ S, 39°52′39″ W; 7 Apr. 2016; F. Cassar leg.; pitfall with human faeces; CEMT • 1 ♀; Linhares, Reserva Natural Vale (“ResNatVal”); 19°06′18″ S, 39°57′52″ W; 25 Jul. 2016; F. Cassar leg.; pitfall with human faeces; CEMT • 1 ♂, 1 ♀; Linhares, Reserva Natural Vale (“ResNatVal”); 19°06′21″ S, 39°56′44″ W; 25 Jul. 2016; F. Cassar leg.; pitfall with human faeces; CEMT • 1 ♀; Linhares, Reserva Natural Vale (“ResNatVal”); 19°08′06″ S, 39°53′20″ W; 25 Jul 2016; F. Cassar leg.; pitfall with human faeces; CEMT . – Rio Grande do Norte • 1 ♂; Natal; dubious record; ex Boucomont and Van Lansberge collections; MNHN .

UNKNOWN LOCALITY • 1 ♀; MNHN • 1 ♂ (possibly identified by Harold as Colonychus ); ex Edgar von Harold and R. Oberthür collections; MNHN • 1 ♂; ex E. Candèze collection; RBINS.

Erroneous record

COLOMBIA • 1 ♂; Tolima, Honda; ex Balthasar collection; NMPC .

Not studied (label information provided by François Génier (CMNC); 8 ♂♂, 15 ♀♀)

BRAZIL – Espírito Santo • 3 ♂♂, 9 ♀♀; Linhares, Fazenda Lagoa do Macuco ; 19°03′50″ S, 39°58′43″ W; 10 m a.s.l.; 25 Jan. 2000; F. Génier and S. Ide leg.; in Bruce Gill, Trond Larsen and Claudia Medina personal collections; CMNC • 4 ♂♂, 5 ♀♀; same collection data as for preceding but 27 Jan. 2000; in Philippe Moretto personal collection; CMNC • 1 ♂, 1 ♀; same collection data as for preceding but 28 Jan. 2000; in Bruce Gill personal collection; CMNC .

Etymology

As noted by Max Barclay (pers. comm. to MC, Sep. 2019), the specific name ʻ opatroides ʼ is a clear reference to the overall morphological similarity, particularly of the shape of the pronotum, of this species to the widespread Opatrum Fabricius, 1775 tenebrionids. Such a similarity is, of course, completely analogous. According to Gemminger (1870), Opatrum (or Hopatrum ) comes from the Greek word meaning ʻsame fatherʼ (or eodem patre, in Gemminger’s Latin translation of the name).

Redescription

MEASUREMENTS. Males (27 spec.): TL: AV 14.05, MX 17.25, MN 10.5. EW: AV 9.29, MX 11.68, MN 8.0. PW: AV 8.22, MX 10.69, MN 6.9. – Females (22 spec.): TL: AV 14.32, MX 15.9, MN 12.0. EW: AV 9.39, MX 10.56, MN 8.64. PW: AV 8.49, MX 9.92, MN 7.28.

COLOURATION. Antennal club with yellowish tegument and pubescence. Dorsal and especially ventral colouration variable, presumably geographically: mostly populations with dorsum mostly light to dark brown, with reddish and olivaceous silky reflections throughout tegument, but particularly at outer limits of head and pronotum, at base and outer limits of elytra and throughout pygidium; venter, including surface of legs, completely covered by strong reddish sheen; populations in southeast Bahia with dorsum and venter completely devoid of, or with very discreet, silky sheen, almost completely dark brown, sometimes venter almost entirely black.

HEAD. Canthus long, digitiform ( Fig. 5E ). Clypeal process a short transverse carina, rounded at apex ( Fig. 6A ). Antennae with 9 articles; first article of funicle evidently shorter than rest of funicle combined ( Fig. 7A ). Labrum with anterolateral projections well projected and with external margin softly rounded; anterior labral margin broad, anterolateral projections widely separated; epipharynx with long medial brush and median area not so densely covered by long, thin setae, which leave a broad, glabrous central area ( Fig. 8 C–D).

THORAX. Pronotum with entire surface covered by dense umbilicate punctation; punctation denser from centre towards sides and anterolateral angles, but punctures never confluent ( Fig. 12A ); umbilicate punctures covering even margins; tegument between punctures with diffuse microsculpture. Prosternum, mesoventrite, mesanepisterna, metanepisterna and metaventrite entirely covered by dense umbilicate punctation and diffuse microsculpture between punctures ( Fig. 13 B–D); umbilicate punctation less dense towards anterior and posterior region of metaventrite.

LEGS. Trochantofemoral articulation sexually dimorphic (see below). Mesocoxae with most of surface covered by umbilicate punctation, except anterior half with wide areas of smooth tegument. Mesofemora with or without brush of setae on posterior edge depending on sex (see below) ( Fig. 17 A–B); ventral surface covered by dense umbilicate punctation, denser near posterior edge; tegument between umbilicate punctures with diffuse microsculpture, except near posterior edge, which is sexually dimorphic (see below). Metafemora with posterior edge glabrous and without crenulation in both sexes (except brush of setae at male metafemoral spur); ventral surface with umbilicate punctation evenly distributed across most of surface, punctation denser near posterior edge ( Fig. 19 B–C). Metatibiae with ventral surface without umbilicate punctures or with umbilicate punctures limited to apical region ( Fig. 20 A–B).

WINGS. Elytra with striae fine, but always clearly impressed, never discontinuous; tegument covered by umbilicate punctation and well-delimited alveolar microsculpture between umbilicate punctures; alveoli sometimes ill-delimited and microsculpture more diffuse; lateral carina (pseudepipleural carina) completely interrupted by row of umbilicate punctures ( Fig. 21B ); apices of elytra not strongly deflected; distal calluses only slightly projected ( Fig. 21D ). Hing wing with a deep notch at area of anal fold; venation as in Fig. 21F.

TERMINALIA. Aedeagus: Right paramere with discreet, though still clearly discernible, apical projection ( Fig. 23 A–D); parameres, in dorsal view, with external edges curved ( Fig. 23A ); in lateral view, ventral region with well-projected keel and clear inclination towards apex ( Fig. 23 B–C). Internal sac with welldelimited and sclerotized sclerites: axial and subaxial sclerite similar in shape, both simply curved, falciform, axial sclerite shorter than subaxial ( Fig. 24 E–F). – Genital segment: Medial sclerotized plate (MSP) not so sclerotized, lateral arches concave; posterior arms of MSP only slightly indicated and with no clear emargination between them ( Fig. 26B ). – Spermatheca: Broad, in particular basal branch, without pair of apical hooks ( Fig. 27A ).

SEXUAL DIMORPHISM. Male: Clypeus evidently emarginated at apex, with two tiny, but evident teeth flanking emargination ( Fig. 5A ). Metaventrite with deep and wide excavation on posterior region, marked anteriorly by strong spur ( Fig. 13C ). Profemora with anterior margin raised at centre into two strong spurs ( Fig. 14A ); trochantofemoral articulation with raised edge forming short spine. Protibiae as described above for genus; protibial spur absent ( Fig. 15A, E ). Mesofemora with basal half of posterior edge covered by brush of long setae (may be absent in very worn specimens) ( Fig. 17A ); area covered by brush of setae crenulated; near posterior edge, umbilicate punctures surrounded by dense alveolar microsculpture. Mesotibiae with internal edge with two longitudinal rows of long, dense setae ( Fig. 18A ). Metafemora with long spur on posterior edge, spur wavy and with brush of long setae at its external face ( Fig. 19B ). Metatibiae with row of sharp teeth at base on internal edge ( Fig. 20A ). – Female: Clypeus only slightly emarginated at apex, with rudimentary teeth flanking emargination ( Fig. 5B ). Metaventrite with shallower, narrower excavation on posterior region, with no anterior spur ( Fig. 13D ). Profemora more linear, anterior margin simple, not raised ( Fig. 14B ); trochantofemoral articulation not developed into spur. Protibiae with lateral teeth decreasing in size from apical to basal tooth; all lateral teeth apart from one another and always clearly directed laterally ( Fig. 15B, F ); protibial spur present, articulate, bifurcated at apex, internal branch of bifurcation much longer than external branch, which is only indicated ( Fig. 15B, F ). Mesofemora lacking brush of setae on posterior edge ( Fig. 17B ); near posterior edge umbilicate punctures surrounded by diffuse microsculpture (as in rest of tegument of mesofemora). Mesotibiae with internal edge with sparse setae not forming a clear row ( Fig. 18B ). Metafemora simple, lacking posterior spur ( Fig. 19C ). Metatibiae smooth at base, without row of sharp teeth ( Fig. 20B ).

Distribution

Patches of coastal lowland Atlantic Forest in the Brazilian states of Bahia and Espírito Santo ( Fig. 4 ).

Ecoregions. Bahia Coastal Forests.

Collection sites. Brazil – Bahia: Maraú (Área de Proteção Ambiental Baía de Camamu), Porto Seguro (Reserva Particular do Patrimônio Natural Estação Veracel), Potiraguá, Santa Teresinha, Uruçuca (Parque Estadual da Serra do Conduru), Valença; Espírito Santo: Linhares (Reserva Natural Vale).

Intraspecific variation

The most remarkable geographical variation presented by S. opatroides concerns colouration, particularly that of the venter ( Fig. 2 ). Throughout much of the distribution of the species, including the only population known from Espírito Santo (Linhares) and several localities in Bahia (Porto Seguro, Potiraguá, Santa Teresinha and Valença), populations of S. opatroides show silky reflections of reddish and olivaceous tonalities over much of the predominantly brown dorsum, particularly at the outer limits of the head and pronotum, at the base and outer limits of the elytra, and on the entire pygidium, while the venter bears a strong reddish metallic sheen covering the legs, hypomeron, prosternum, meso- and metaventrites and abdominal ventrites ( Fig. 2 ). In a very limited region in southeast Bahia, however, more specifically in Maraú and Uruçuca, specimens are always much darker, show at most only some discreet reddish and olivaceous reflections on the dorsum and, most interestingly, completely lack the ventral metallic sheen seen in the other populations; instead, their venter is usually dark brown, sometimes even entirely black ( Fig. 2 ). Unless this colour variation evolved in the mentioned populations during the 20 th century (which does not seem to be the case, since Harold’s 19 th century specimen of Colonychus shows this darker ventral colouration), the lectotype and only known paralectotype of S. opatroides , whose provenance labels state only “ Bahia ” and “ Brésil ”, respectively, most probably did not come from the southeastern region of that state, since their venter shows the more typical metallic colouration of the other populations of the species.

Initially, we investigated the possibility that the populations of southeast Bahia could represent a different species than S. opatroides , but our results show that this is probably not the case, since no other morphological or phenological features were shown to vary along with the ventral colouration. Indeed, for some yet unknown reason, dung beetle populations in the Atlantic Forest, especially in its more or less northern half, seem to be particularly prone to exhibit geographical colour variation, and some species such as Sylvicanthon obscurus (Schmidt, 1920) ( Cupello & Vaz-de-Mello 2018), Canthon (Goniocanthon) smaragdulus (Fabricius, 1781) ( Nunes et al. 2018) and Phanaeus (Notiophanaeus) splendidulus (Fabricius, 1781) ( Edmonds 1994; Edmonds & Zídek 2012; and personal observations of the authors) are well-studied examples of this phenomenon. We believe that the interpopulational variation seen in S. opatroides is, therefore, just another instance of this general pattern, and future collections will reveal whether there exists a geographical intergradation between the two colour phases of S. opatroides observed in this paper and, if not, whether intermediate populations show individuals of both possibly-discrete phases.

Apart from colour, the only other noteworthy variation observed in S. opatroides concerns allometric differences in the sexual secondary characteristics of males. As usual in Scarabaeinae , smaller males have such features disproportionally less developed than larger males and, consequently, the smaller the males, the more similar they are to females. Thereby, in small males, profemora tend to have lessdeveloped anterior spurs (sometimes only one tiny spur is present instead of two), protibiae tend to be less twisted, the metafemoral spur tends to be shorter and protibiae tend to be less projected apically. However, no allometric variation was observed in the shape of the paramera or of the internal sac sclerites.

Remarks

It is remarkable that, although only relatively few specimens are known for this species, and most of them collected in the 21 st century, a large amount of mislabelling and many erroneous geographical records are found in collections and the literature. The NMPC male allegedly collected in Honda (Tolima, Colombia), for instance, is certainly mislabelled; this wrong provenance information was probably what led Vladimir Balthasar to identify it, with uncertainty, as S. punctatus (“ Streblopoides cf. punctatus ”, as stated on one of its labels). Additionally, the MNHN male labelled “ Natal ”, which possibly refers to the capital city of the Brazilian state of Rio Grande do Norte, is also probably incorrect as no other specimens are known from the region north of Bahia State. As for the literature, Paulian’s (1939) record of S. opatroides from Oxapampa (Pasco, Peru) is certainly incorrect and possibly refers to either a misidentified S. punctatus or a mislabelled S. opatroides ; although this specimen originally belonged to the Boucomont collection, which is currently housed in the MNHN ( Horn et al. 1990a), neither we nor Halffter & Martínez (1966) were able to locate it. The incorrect record given by Paulian (1939) was repeated by Balthasar (1941, 1951), Pereira & Martínez (1956), Vulcano & Pereira (1964, 1967) and as recently as Ratcliffe et al. (2015). As noted earlier by Halffter & Martínez (1966), this species should be removed from the list of Peruvian dung beetles.

Although only one syntype was found by Paulian (1939), Halffter & Martínez (1966) and ourselves in the MNHN, the museum that currently houses the Van Lansberge collection ( Horn et al. 1990b), the original type series of S. opatroides certainly consisted of more than one specimen, since Van Lansberge (1874a) discussed the sexual dimorphism of the species (and it is worth noting that, based on his description, he correctly differentiated the sexes). Indeed, a second syntype was found by MC in the RBINS originating from the J. Thomson collection, whose Scarabaeoidea were incorporated into the RBINS in 1878 ( Horn et al. 1990b). Notwithstanding our ignorance as to the whereabouts of the other syntypes, we decided to designate the only male syntype known to us, the MNHN specimen, as the lectotype of S. opatroides . We could recognize these two specimens as part of the type series because they both bear identification labels clearly handwritten by Van Lansberge (see examples of Van Lansberge’s handwriting in Horn et al. 1990b). However, it is interesting to note that the lectotype came to the MNHN not via the Van Lansberge collection, but rather the Edgar von Harold and R. Oberthür collections, meaning that Harold probably received this specimen directly from Van Lansberge after the latter’s studies for the description of the species.

The BMNH specimen from Espírito Santo was collected by the 19th-century French naturalist JeanThéodore Descourtilz (1796–1855), who from 1829 until his death lived in southeastern Brazil and travelled extensively, particularly in search of birds, across that region ( Sick 1997). Before arriving at the BMNH, that specimen belonged to the collection of Alexander Fry (1821–1905), who lived and worked in Rio de Janeiro until 1854 (Max Barclay, pers. comm. to MC, Sep. 2019) and developed his Coleoptera collection largely by purchasing specimens. Therefore, it is not difficult to imagine that Fry bought his specimen of S. opatroides directly from Descourtilz while they were both living in the same region or through some intermediate. Be it as it may, the Fry collection was eventually bequeathed to the BMNH ( Horn et al. 1990a) and that is why the Descourtilz specimen is housed there. What makes this specimen unique is that not even the old beetle collection of the MNRJ, the institution for which Descourtilz worked as a travelling naturalist for a brief period between 1854 and 1855 ( Sick 1997), housed specimens collected by him (MC, pers. obs. between 2009 and 2017).

Ecology

As stated above for the genus, almost nothing is known about the behaviour of S. opatroides . Indeed, until the 1990s only six specimens were known apart from the syntypes, one third of them with erroneous provenance data (an MNHN male and the NMPC male), another third without locality content (the MNHN female and Harold’s MNHN “ Colonychus ” specimen), and the final third with fairly general information (“ Bahia ” for the MZSP male and “ Espírito Santo ” for the BMNH female). The specimens collected over the past three decades, however, have shown that S. opatroides is a coprophagous species attracted to human faeces used as bait in pitfall traps and that lives in patches of lowland forests (recorded from 10 up to 800 m a.s.l.) across a limited range along the Brazilian states of Bahia and Espírito Santo ( Fig. 4 ). Adults of the species seem to be active throughout the year, since specimens have been collected in every month except August, October and December. As discussed above, S. opatroides is probably a nocturnal forager, judging from the morphology of its eyes (with a very wide dorsal portion) and its dull dorsal colouration; indeed, Audino et al. (2014) recorded the species as nocturnal in their surveys. The data obtained by the latter authors also show that S. streblopus can be relatively abundant in mature forests (particularly primary forests, but also present in old secondary ones), but is absent from more disturbed environments such as mid- and early-succession stage forests and pastures. Nothing more is known about the natural history of S. opatroides .

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. 2. Geographical variation in Streblopus opatroides van Lansberge, 1874. Individuals from a few localities in southeast Bahia (Maraú and Uruçuca) have a different ventral colouration from individuals belonging to other populations, being much darker and not showing the typical red metallic colouration seen in specimens from other localities in Bahia and Espírito Santo.

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

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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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).