Redefining generic boundaries in subtribe Eurynotina (Coleoptera: Tenebrionidae): taxonomy of the Schyzoschelus generic group

Abstract

The genus Heteropsectropus Kaszab, 1941 (Tenebrionidae: Blaptinae: Platynotini) is revised to include the following three species: H. aenescens Kaszab, 1941 (type species); H. difficilis Koch, 1954; H. longantennatus Koch, 1954. Four synonymies are proposed: H. difficilis (= H. amaroides Koch, 1954 syn. nov., = H. natalensis Koch, 1954 syn. nov., = H. transvaalensis Koch, 1954 syn. nov.) and H. longantennatus Koch, 1954 (= H. montisdraconis Koch, 1954 syn. nov.). A new genus, Muelleropsectropus gen. nov., is introduced to accommodate Schyzoschelus malaisei Koch, 1954. Additionally, the following synonomies are introduced within Schyzoschelus Koch, 1954: Schyzoschelus dumosicola (= Schyzoschelus dumosicola var. diversipenis Koch, 1954 syn. nov.) and Schyzoschelus simplicipes (= Schyzoschelus simplicipes willowmorensis Koch, 1954 syn. nov.). Diagnostic features and relations between the genera of the Schyzoschelus generic group are discussed and an identification key to the genera and the species of Heteropsectropus is provided. Ovovivipary is reported for H. difficilis and represents the 15th known case of this mode of reproduction for darkling beetles. The first description of pupal morphology for the subtribe Eurynotina is provided as well as that of the first- and later instar larvae.

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Keywords:

• Ovovivipary
• female terminalia
• larva
• pupa
• new taxa
• synonymy
• South Africa

Introduction

Darkling beetles are well known for their ability to thrive in arid environments (Koch 1962; Matthews et al. 2010; Cheli et al. 2022; Pinto et al. 2022; Raś et al. 2022; Ragionieri et al. 2023). Several groups are widely recognized and have received recent taxonomic and phylogenetic attention (e.g. Lumen et al. 2020; Kamiński et al. 2021, 2022; Johnston et al. 2022; Swichtenberg et al. 2023). However, there remain lineages that have not been treated since their initial designation, such as Eurynotina Mulsant and Rey, 1854 (Blaptinae: Platynotini) (Koch 1954a, 1954b, 1955). Consisting of 17 genera and 97 species and subspecies, this subtribe has eluded modern scrutiny until recently (Kamiński 2016; Kamiński et al. 2021; Lumen & Kamiński 2023a, 2023b). Representatives of Eurynotina inhabit different ecosystems across southern Africa (Kamiński 2016), and some (e.g. species of Eurynotus and Biolus) are ovoviviparous (Lumen & Kamiński 2023a). Despite the extreme rarity of this mode of reproduction among darkling beetles in general (only 14 examples are known), Eurynotina has not received the taxonomic and phylogenetic attention necessary for comprehensive investigation of the evolution of ovovivipary.

The lack of recent investigations concerning Eurynotina is likely driven by a deficit of reliable resources for species and genus identifications. Nearly three-quarters of currently distinguished species are known from relatively small type series, have extremely specific diagnostic features, and include very little information on variability (Koch 1954a, 1954b; Kamiński 2016). Furthermore, the available taxonomic resources are insufficiently illustrated, necessitating reliable comparative materials for identification – on both species and generic levels. We have gathered an extensive collection of Eurynotina specimens from several major natural history museums of the world, and are consecutively processing them as a part of the first author’s PhD thesis (see Lumen & Kamiński 2023a, 2023b).

This paper is focused on the Schyzoschelus generic group. In particular, we treat the taxonomy of the genus Heteropsectropus Kaszab, 1941 (Figure 1a–c) and some outstanding examples within Schyzoschelus Koch, 1954 as well as outline their generic boundaries (Figures 1e,f and 2). Previously, the only two papers concerning these taxa described seven species of Heteropsectropus based on a total of 27 specimens (Kaszab 1941; Koch 1954a). Many of these (12 specimens) represented the type species Heteropsectropus aenescens Kaszab, 1941, while the following taxa were based on single specimens: H. difficilis Koch, 1954, H. longantennatus Koch, 1954, H. montisdraconis Koch, 1954, and H. transvaalensis Koch, 1954. Since its designation, Heteropsectropus was believed to be closely allied to the genus Schyzoschelus Koch, 1954 (Kaszab 1941; Koch 1954a), and their relation appears well grounded in several morphological features, e.g. straight clypeal apex (Figure 3e), slender protibiae (Figures 1 and 2), rounded posterior angles of pronotum (Figure 3d), bordered 5th abdominal ventrite (in females), and merged parameres. Furthermore, a sister relation between Heteropsectropus amaroides Koch, 1954 and Schyzoschelus africanus (Kaszab 1941) was recovered in a recent cladistic analysis (Lumen & Kamiński 2023a). Due to their morphological distinctiveness from other Eurynotina, Heteropsectropus and Schyzoschelus were recognized as one of the three main lineages of the subtribe, and were informally referred to as the “Schyzoschelus generic group” by Koch (1954a). Delimitation between the two genera is based on the bordering of the 5th abdominal ventrite (Heteropsectropus: widely bordered in both sexes (Figure 3c); Schyzoschelus: bordered in females, where the groove is situated on the extreme apex of ventrite (Figure 3f)), the shape of epipleura (Heteropsectropus: epipleuron evenly narrowing toward apex; Schyzoschelus: epipleuron suddenly narrowed at the level of 5th abdominal ventrite), and degree of sexual dimorphism (strongly highlighted by leg modifications in Schyzoschelus (Figure 4e)) (Koch 1954a).

Figure 1. Habitus photographs of Heteropsectropus, Muelleropsectropus, and synonymized Schyzoschelus species. (a) H. longantennatus (holotype), (b) H. aenescens (specimen compared with holotype by Koch (1954a)), (c) H. difficilis (H. natalensis paratype), (d) M. malaisei. Schyzoschelus habitus, (e) S. simplicipes inset with striated abdominal ventrites (S. simplicipes willowmorensis holotype (left) and paratype (right)), (f) S. dumosicola inset without striated abdominal ventrites (S. dumosicola diversipennis holotype (left) and paratype (right)).

Figure 2. Type materials for representatives of Schyzoschelus (*for S. simplicipes and S. dumosicola see Figure 1(e,f) respectively). (a) S. aeneomicans (holotype), (b) S. braunsi (holotype), (c) S. jenkinsae (holotype), (d) S. karooensis (holotype), (e) S. kaszabi (left, dorsal and right, ventral) (paratype), (f) S. ladini (left, dorsal and right, ventral) (paratype) (g) S. sympatrius (holotype).

Figure 3. Scanning electron microscope photographs of Schyzoschelus kaszabi, Heteropsectropus difficilis, and Muelleropsectropus. (a) Schyzoschelus kazsabi – elytron (epipleura highlighted yellow, elytral stria between intervals ten and 11 highlighted red). (b and c) Heteropsectropus difficilis – elytron (epipleuron highlighted yellow), abdominal ventrite V (subapical sulcus highlighted red). (d, e, and f) Muelleropsectropus malaisei – right half of pronotum (large setae-bearing punctures indicated by arrow), head (large setae-bearing punctures indicated by arrow), and abdominal ventrite V (inset extreme apical sulcus highlighted red). Scale bars = 1 mm.

Figure 4. Scanning electron microscope photographs of Schyzoschelus kaszabi and Heteropsectropus difficilis. (a, b, d, and e) Schyzoschelus kaszabi – head (ventral), abdomen (ventral, inset close-up of striations of ventrites), close-up of mentum (prementum highlighted), and right male foreleg (arrow indicating hollowed out area). (c and f) Heteropsectropus difficilis – head (ventral), and close-up of mentum (prementum highlighted). Scale bars = 1 mm.

To begin, a revision of Heteropsectropus was necessary to address problems with the identification of voucher specimens originating from a breeding experiment conducted by workers of the Ditsong Museum in Pretoria (Schulze 1969). We associated adult specimens of an unidentified Heteropsectropus species from the pinned collection with pupae and larvae preserved in ethanol. Data on larval morphology is extremely scarce for Eurynotina (Kamiński et al. 2019b; Lumen & Kamiński 2023a), and no previous contributions provide details on pupal morphology of the group (Kamiński et al. 2018). Reliable identification required revision of the definitions of all species of Heteropsectropus. Reevaluation was conducted with reference to type materials concerning the genus, and included the first investigation of female terminalia and the application of scanning electron microscopy. Furthermore, to fully test the generic limits of Heteropsectropus, we also broadly investigated Schyzoschelus. Materials examined here imposed the need to revisit diagnostic features for both genera within the Schyzoschelus lineage.

Methods

Pinned material for the morphological examination of Heteropsectropus and Schyzoschelus presented here was acquired from the following institutional insect collections: MIIZPAN – Muzeum i Instytut Zoologii, Polskiej Akademii Nauk, Warsaw, Poland; MNHN – Muséum National d’Histoire Naturelle, Paris, France; BMNH – Natural History Museum, London, United Kingdom; SANC – South African National Collection of Insects, Pretoria, South Africa; TMNH – Ditsong National Museum of Natural History, Pretoria, South Africa. Pupae and larvae preserved in ethanol originating from breeding experiments were loaned from TMNH, and were associated with adult specimens by unique label codes. Original label data for studied specimens are provided in their respective taxonomic sections, and are condensed into single entries after their repositories (in bold). Different institutions’ holdings are separated by a period, and different records are enclosed in quotation marks and separated by commas and spaces (e.g. SANC: “specimen record 1”, “specimen record 2”. MIIZPAN: “specimen record 1”). Label data represents individual specimens unless otherwise noted.

The abdomens of adult specimens were dissected after brief incubation in 10% potassium hydroxide (KOH) solution for male and female termialia examination. Female genital tubes were stained with chlorazol black following methods of Kamiński (2021). Morphological nomenclature for larval skeletal structures follows that of Lawrence et al. (2011) and Beutel and Friedrich (2005), while terminology concerning adults has been additionally adopted after Matthews et al. (2010), with specialized terms for female terminalia following Kamiński et al. (2022). Description style follows that of Lumen and Kamiński (2023a) for imagines, Kamiński et al. (2019a) for larvae, and Kamiński et al. (2018) for pupae.

Specimens were photographed using a Canon 1000D body with extension rings and a Canon EF 100 mm macro lens, and a Nikon D3500 body with adapter for a Nikon SMZ800N microscope. Adults and larvae were further imaged using a Hitachi S3400N scanning electron microscope in the Museum and Institute of Zoology, Polish Academy of Sciences (MIIZPAN). The species distribution map was produced based on specimen label data using QGIS v. 3.16, with vector layers downloaded from the Natural Earth web page (www.naturalearthdata.com). The geographic range for the genus Schyzoschelus was projected based on distributional records (Kaszab 1941; Koch 1954a). All plates were prepared and edited in Photoshop v. 23.5.1.

Results

Based on type material and additional specimens, we propose the following synonymies within Heteropsectropus: H. longantennatus (= H. montisdraconis syn. nov.), H. difficilis (= H. amaroides Koch, 1954 syn. nov., = H. natalensis Koch, 1954 syn. nov.). The total species list for Heteropsectropus is thus: H. aenescens, H. difficilis, and H. longantennatus. Based on newly discovered male specimens, we describe a new genus (Muelleropsectropus gen. nov.) for Schyzoschelus malaisei Koch, 1954, which Koch (1954a) described based only on female specimens. We also propose the following synonymies within Schyzoschelus: S. dumosicola Koch, 1954 (= S. dumosicola diversipenis Koch, 1954 syn. nov.), S. simplicipes Koch, 1954 (= S. simplicipes willowmorensis Koch, 1954 syn. nov.). Finally, ovoviviparity is reported for the fifth time for Eurynotina and pupae from the subtribe are photographed and described for the first time along with first- and later instar larvae.

Key to the genera of the Schyzoschelus generic group

• 1. Epipleural base evenly narrowed beyond humeral angle (Figure 3a). Elytron with additional stria terminating before shoulder, resulting in 11 intervals posteriorly (Figure 3a). Ovipositor long (ratio of length of coxites 1–4 to paraprocts < 1:1) (Figure 5c). Bursa copulatrix with terminal “bulb” (Figure 5e). Schyzoschelus

  Figure 5. Heteropsectropus first-instar larva with female genitalia of Heteropsectropus difficilis and Schyzoschelus kaszabi. (a, b, and d) Heteropsectropus difficilis – first-instar larva, ovipositor (coxites and paraproct outlined), and internal genitalic structures. (c and e) Schyzoschelus kaszabi – ovipositor (coxites and paraproct outlined) and bursa copulatrix. Abbreviations: cx1–4, coxites; pr, paraproct. Scale bars = 0.5 mm.

  

  -. Epipleural base abruptly narrowed beyond the humeral angle (Figure 3b). Elytra without prematurely terminating striae – with 10 intervals. Ovipositor short (ratio of length of coxites 1–4 to paraprocts ≈ 1) (Figures 5b and 6c). Bursa copulatrix without terminal “bulb” (Figures 5d and 6a). 2

  Figure 6. Genitalia of Heteropsectropus and Muelleropsectropus. (a and c) M. malaisei – bursa copulatrix and ovipositor. (b) H. aenescens aedeagus. (d) H. difficilis aedeagus. Abbreviations: ag, accessory gland; ap, accessory pouch; bc, bursa copulatrix; cx, coxae; hk, hook; ov, oviduct; par, parameres; pr, paraproct; ps, penis; sp, spermatheca.

  

• 2. Prementum without median emargination (Figure 4f). Subapical sulcus on abdominal ventrite V present (Figure 3c). Abdominal ventrite V not concave (Figure 3c). Female without furrow running along extreme apical edge of abdominal ventrite V, and without median notch. Bursa copulatrix without additional pouches (Figure 5d) Heteropsectropus

  -. Prementum with median emargination (Figure 4d). Subapical sulcus on abdominal ventrite V absent (Figure 3f). Abdominal ventrite V slightly concave (Figure 3f). Female with furrow running along extreme apical edge of abdominal ventrite V, and with median notch (Figure 3f). Bursa copulatrix with two additional pouches on base (Figure 6a). Muelleropsectropus gen. nov.

Genus Heteropsectropus Kaszab, 1941

Heteropsectropus Kaszab, 1941: 34. Koch 1954a: 71; 1956: 27; Lumen and Kamiński 2023.

Type species

Heteropsectropus aenescens Kaszab 1941; by original designation.

Diagnosis

Heteropsectropus is well defined within the Schyzoschelus generic group of Eurynotina by the straight apical margin of the clypeus (Figure 3e), straight/unexpanded foretibiae (Figure 1), rounded basal angles of the pronotum (Figure 3d), abdominal ventrite V with a subapical sulcus (Figure 3c), and parameres with a longitudinal groove running from the apex down to the base (Figure 7c). The genus is further distinguished from other genera within the group by the following suite of characters: epipleura abruptly narrowing at the humeral region (Figure 3b) (gradually narrowing in Schyzoschelus (Figure 3a)), with a subapical sulcus on abdominal ventrite V in both males and females (Figure 3c) (present on extreme apex in females of Schyzoschelus and Muelleropsectropus (Figure 3f)), with a single large puncture bearing a strong seta above each eye (Figure 3e) (absent in Schyzoschelus except for S. ladini), flat or convex abdominal ventrite V (Figure 3c) (concave in male Schyzoschelus and Muelleropsectropus (Figures 3f and 4b)), female abdominal ventrite V without apical emargination or notch (present in Schyzoschelus, though species described based only on males require future confirmation, and in Muelleropsectropus (Figure 3f)), males with straight, unmodified tibiae – except for a patch of dense setae running down apex of hind tibiae (curved or strongly modified tibiae with setal patches in both Schyzoschelus and Muelleropsectropus (Figure 4e)), larger punctures bearing strong setae on abdominal ventrite V restricted largely to outer edge (Figure 3f) (throughout center in Schyzoschelus (Figure 4b), and present on other abdominal ventrites in Muelleropsectropus and Schyzoschelus (Figures 3f and 4b)). Heteropsectropus males also have a relatively long penis (>half the length of the parameres) and a more pronounced curvature, or hook, at the end of the penis (Figures 6b,d and 7a,c,d) (also present in Muelleropsectropus, but at most weakly pronounced in Schyzoschelus – except for S. aeneomicans, which has a long penis and pronounced hook).

Figure 7. Aedeagi of Heteropsectropus, Muelleropsectropus, and Schyzoschelus. (a) H. aenescens (ventral). (b) Schyzoschelus kaszabi (ventral). (c and d) Muelleropsectropus malaisei (dorsal and ventral respectively). Scale bars = 1 mm.

Description

Length 6.25–10 mm, width 3–4.75 mm. Color tenebrous; dark brown to black, sometimes with aeneous and/or cupreous luster. Head: Coarsely puncate, punctures closely (≤1 feature diameter) spaced; with single larger punctures bearing large setae above each eye. Epistoma apex straight, without well-defined median notch; with two large punctures bearing large setae on apical margin. Prementum without median emargination. Mentum with small ventrally projecting middle portion; lateral wings exposed. Gula with stridulatory file. Eyes constricted in middle and reniform, with impressed sulcus situated around perimeter of dorsal lobe. Antennae 11 segmented, terminal segments forming weak club; either short (extending just beyond pronotal base) or long (extending much farther); males with longer antennae than females. Prothorax: scutellum small and transversely triangular. Pronotum with broadly rounded basal angles; dorsally with few to many large, widely spaced setae and punctures situated on lateral edges. Lateral margin well defined with border running along perimeter. Hypomeron nearly smooth to finely wrinkled; with light to absent punctation. Prosternal process round without posterior projection. Pterothorax: Elytra with 10 intervals, disc relatively flat to convex. Elytral striae strongly or weakly impressed and punctate. Intervals punctate, few to no bumps or tubercles present on apical declivity. Elytral intervals visible in ventral view. Laterally reflected elytral intervals 2–4× wider than epipleura width. Epipleura broad basally, narrowing abruptly after humeral region. Apterous. Abdomen: Punctate. Punctures separated by ≥ 1 diameter. Abdominal ventrite V with subapical sulcus; males with additional, larger setigerous punctures intermixed with smaller punctures, females without median apical notch. Legs: femora laterally compressed, slightly curved and thickened. Tibiae straight and only very slightly dilated toward apex; males with strip of tomentose setae running down to apex. Tarsi with golden setae; males with weakly or strongly expanded pro/meso tarsi with ventral, tomentose pads. Male terminalia: Tegmen bipartite and without ancorae; basal portion membranous ventrally; dorsally with small, triangular membranous field at base of apical portion. In lateral view, parameres flattened toward apex, with or without slight upward curvature. Penis strongly to weakly sclerotized and with pronounced apical hook. Spiculum gastrale symmetrical and unfused along apex. Female terminalia ovipositor short; (~1:1 paraprocts to coxae ratio). Bursa copulatrix without additional pouches. One species (H. difficilis) ovoviviparous.

Distribution

South Africa: Eastern Cape, Free State, KwaZulu-Natal, and Gauteng (Figure 8).

Figure 8. Distributional map of Heteropsectropus, Muelleropsectropus, and Schyzoschelus. Range of Schyzoschelus determined using type localities (Kaszab 1941; Koch 1954a) and specimens gathered during this study and by Kamiński (2016).

Species included (3): H. aenescens Kaszab, 1941; H. difficilis Koch, 1954; H. longantennatus Koch, 1954.

Key to the species of the genus Heteropsectropus

• 1. Antennae short (at most just exceeding the base of the pronotum). Elytral striae not deeply impressed 2

  -. Antennae long (far exceeding the base of the pronotum); Elytral striae deeply impressed (Figure 1a)……………………………………Heteropsectropus longantennatus Koch, 1954

• 2. Most lateral (ventrally reflected) elytral intervals narrow (~2–3× epipleural width); parameres upturned and widened apically, penis with strong apical hook (Figue 6b)………Heteropsectropus aenescens Kaszab, 1941

  -. Most lateral (ventrally reflected) elytral intervals wide (~3–5× epipleural width); parameres flat and narrowed apically, penis with weak apical hook (Figure 6d) Heteropsectropus difficilis Koch, 1954

Heteropsectropus aenescens Kaszab, 1941 (Figures 1b, 6 b, and 7a)

Heteropsectropus aenescens Kaszab, 1941: 34. Koch 1954a: 73.

Material examined

(BMNH): “Umtata Caffraria C. Greaves, Heteropsectropus aenescens Kaszab C. Koch det. 1956, Brit. Mus. 1951–55” (with yellow circle PARATYPE label and white QR-code label with code NHMUK014663109). (TMNH): “Umtata Caffraria C. Greaves Menederes det. Peringuey” (three specimens). “15 m SE Barkley east. C.P. II.67. L.SCHULZE”, “SA KZN Kamberg 13 29.37331°S 29.62798°E 1814 m Grassland Ground Search 08-Nov-2005 III-UKZN” (two specimens, bearing two different codes: MDTP 55,645 and MDTP 1100). (TMNH): “TB#26351–29.65, 29.44, Heteropsectropus”.

Note: Though we were unable to examine the holotype described by Kaszab (1941), Koch (1954a) directly compared the “Umtata” specimens we examined with that of Kaszab and positively identified them. Additionally, comparisons of our material with both Kaszab’s and Koch’s illustrations confirmed the unique morphology of the H. aenescens aedeagus (upturned apically with a strongly sclerotized hook on the apex of the penis) (Figure 6b). Koch (1954a) also noted that the type of H. aenescens was from Gebien’s personal collection, which should be in Naturhistorisches Museum Basel (Switzerland).

Diagnosis

Heteropsectropus aenescens is often distinguished within the genus by its coppery shine. While other species also display a similar lustre, it is most commonly pronounced in H. aenescens. This species is separable from H. longantennatus by the degree of impression of the elytral striae, which are shallowly to unimpressed. Heteropsectropus aenescens has more convex elytrae than its congeners, which have an overall flatter elytral disc. The lateral edges of the pronotum can also be used to distinguish H. aenescens (with numerous large, well-defined punctures bearing large setae; few such punctures and setae in other species). The lateral-most elytral intervals reflected ventrally are also narrower in H. aenescens (~2–3× width of epipleura) compared to H. longantennatus and H. difficilis (~>3× width of epipleura). Other species are also generally wider (3–4.25 mm H. aenescens; 3.25 mm–4.75 mm H. difficilis; 3–4.5 mm H. longantennatus). The humeri of the elytra in the dorsal view are more rounded in H. aenescens compared to the other species (which are generally broader or square-shaped). The aedeagus is strongly sclerotized, with apically upturned parameres and a pronounced hook on the apex of the penis (Figure 6b) (less sclerotized, absent, and weak, respectively, in H. difficilisi (Figure 6d); parameres less strongly upturned and hook on apex of penis less pronounced in H. longantennatus). Heteropsectropus aenescens, as of this revision, is restricted to the South East region of South Africa (Eastern Cape and KwaZulu-Natal), whereas H. longantennatus and H. difficilis are distributed more northward (Figure 8).

Description

Length 6.75–9 mm, width 3–4.25 mm. Color tenebrous; dark brown to black often with aeneous and/or cupreous luster. Head: Antennae short, extending just beyond pronotal base. Prothorax: dorsally with many large, widely spaced setae and punctures situated on lateral edges. Pterothorax: Elytral striae weakly impressed; apical declivity with few to no bumps or tubercles. Laterally reflected elytral intervals ~ 2–3× wider than epipleura width. Legs: males with strongly expanded pro/meso tarsi with ventral, tomentose pads. Male terminalia: parameres narrowing from base before widening and flattening toward apex, curving upward in lateral view. Penis strongly sclerotized with pronounced apical hook.

Distribution

South Africa: Eastern Cape and KwaZulu-Natal (Figure 8).

Heteropsectropus difficilis Koch, 1954 (Figures 1c, 4 c,f, 5 a,b,d, 6 d, 9 a–k, and 10a–d).

Figure 9. Larva of Heteropsectropus difficilis. (a) Dorsal habitus. (b) head (dorsal). (c) labrum/clypeus (dorsal). (d) anterior view. (e) head (ventral). (f) mentum (close up). (g) epipharynx. (h) hypopharyngeal sclerome. (i) left foreleg. (j) meso- and metathoracic section (lateral view). (k) last abdominal segment (dorsal). Abbreviations: ab9, abdominal segment 9; c, coxa; cl, clypeus; ep, epicranial plates; f, femora; fr, frons; l, labrum; lp, labial palpus; m, mentum; mb, mandibular base; p, prementum; pt, pretarsus; sm, submentum; t1, thoracic segment 1; t2, thoracic segment 2; tr, trochanter; tt, tibiotarsus.

Figure 10. Pupa of Heteropsectropus difficilis. (a, left to right) ventral, lateral, and dorsal views. (b) dorsal head (close up). (c) abdominal gin traps (close up). (d) urogomphi (dorsal). Abbreviations: ab2, 3, abdominal segments 2, 3.

Heteropsectropus difficilis Koch, 1954a: 76.

= Heteropsectropus amaroides Koch, 1954a: 75 syn. nov.

= Heteropsectropus natalensis Koch, 1954a: 75 syn. nov.

= Heteropsectropus transvaalensis Koch, 1954a: 74 syn. nov.

Material examined

Heteropsectropus difficilis Koch, 1954: Holotype (TMNH): “Christiana Transvaal Dr. Brauns. Holotype No: 1782 Heteropsectropus difficilis KOCH difficilis Koch”.

Heteropsectropus amaroides Koch, 1954: Paratypes (TMNH): “‘N’ Kandhla Forest Zululand R.F. Lawrence Jan 1937. Paratype No: 1781 Heteropsectropus amaroides KOCH”. (BMNH): “Malvern Natal 7.97 8477? Marshall Coll. 1911–263. Heteropsectropus amaroides C.Koch Det, Koch 1954” (also with yellow circle “Paratype” label and QR code label with code NHMUK014663128).

Heteropsectropus natalensis Koch, 1954: Holotype (TMNH): “Karkloof Natal 2.97 Marshall Coll. 1911–263. Heteropsectropus natalensis C. Koch det., 1954” (also with red circle “Type” label, Red square “HOLOTYPE natalensis Koch” label, and QR code label with code NHMUK014663129.) Paratype (TMNH): same data as holotype with additional labels (Paratype No: 1779 Heteropsectropus natalensis KOCH).

Heteropsectropus transvaalensis Koch, 1954: Holotype (TMNH): “Highlands J’burg T Sept 1901 under stones Heteropsectropus transvaalensis Koch C. Koch det., 195 transvaalensis Koch”.

Additional material examined

(SANC): “Johannesberg Mondeor TVL 27-9-1959 C. H. Draper” (two specimens; one with year 1960). “Natal RT Lawrence Feb 1938”, “Nr. Balgowan Natal Jan 1953 D.W. Rorke”, (TMNH): “S.Afr., Ntl-Drakensb Cathedral Peak for. 28.57S–29.12 E 15.3.1976; E-Y: 1088 from under stones leg. Endrödy-Younga”, “Golden Gate Nat. Park I.1968. R. Jones Heteropsectropus sp. FROM INSECTARIUM NO. 807” (four adult specimens, 2 pupae, several larvae). “Golden Gate Southern O.F.S. 1.3.67. L. SCHULZE”.

Diagnosis

Heteropsectropus difficilis is the most widespread species of the genus – with its range extending from the eastern coast of KwaZulu-Natal to Johannesberg in Gauteng province. Formerly represented by four species, H. difficilis is relatively variable compared to H. aenescens and H. longantennatus. This species is most easily separable via elimination of the other two. Otherwise, H. difficilis is sharply separable by aedeagal morphology (less sclerotized and without upturned paramere apex and with weak apical hook of the penis; compared with the other species with more sclerotized aedeagi and more pronounced hooks and upturned parameres) (compare Figure 6b,d). Superficially, H. difficilis resembles H. longantennatus more in body shape (more squared elytral humeri, less metallic than H. aenescens, wider reflected elytral intervals, etc.). However, H. difficilis differs from H. longantennatus by the length of the antennae (short – at most only slightly surpassing base of pronotum; rather than long – distinctly surpassing the base of the pronotum) (compare Figure 1a–c).

Description

Imagines: Length 6.75–10.0 mm, width 3.25–4.75 mm. Color tenebrous; dark brown to black less commonly with aeneous and/or cupreous luster. Head: antennae short, extending just beyond pronotal base Prothorax: dorsally with few large, widely spaced setae and punctures situated on lateral edges. Pterothorax: elytral striae weakly impressed; apical declivity with few to no bumps or tubercles. Laterally reflected elytral intervals ~ 3–5× wider than epipleura width. Legs: males with weakly expanded pro/meso tarsi with ventral, tomentose pads. Male terminalia: parameres narrowing from base, in lateral view flattening toward apex and straight, without upward curvature. Penis weakly sclerotized with weakly pronounced apical hook.

Larval stages

First instar (extracted from bursa copulatrix) (Figure 5a). Length ≈1.5 mm. Body overall weakly sclerotized. Enclosed within thin, transparent membrane. Head: prognathous; dorsoventrally flattened; width nearly equal to prothorax. Stemmata present. Thorax: prolegs notably longer and thicker than meso- and metathoracic legs; pretarsus sclerotized. Last abdominal segment with long, thin setae on dorsal side, without row of four socketed setae along apex.

Later instars (Figure 9a–k). Length up to 13 mm, width up to 1.5 mm. Head: prognathous, distinctly retracted into prothorax; dorsoventrally flattened; width nearly equal to prothorax; sides rounded; strongly constricted before occipital foramen; yellow in apical part, strongly sclerotized basally; punctation extremely fine. Epicranial stem length approximately one-third of head capsule length; frontal sutures curved, fading in two-thirds of head length. Frons faintly punctured, with microsculpture. Epicranial plates weakly smooth, without microsculpture; each plate with two deep setose points; lateral portions moderately setose (11–13 setae present). Stemmata present. Clypeus rounded, slightly darker medially, with two deep setose points. Labrum transverse, weakly emarginate, with apical row of eight elongated setae. Epipharynx as in Figure 9g. Mandibles asymmetrical, with strongly sclerotized apices, base white and dark; left mandible with triangular premolar tooth and two distinct apical teeth; right mola reduced, with single apical tooth. Labium with distinct prementum, mentum and submentum; gula well developed, elongated and rectangular; rectangular prementum bears pair of setae in center, ligula twice shorter and subequal in width to first labial segment, labial palps 2-segmented; mentum elongated, with pair of setae at base and two pairs of longer setae lateromedially; trapezoidal submentum bears pair of setae basally. Hypopharyngeal sclerome pentagonal; bicuspidate, with apical denticle elongated; with deep depression in middle. Maxillary palpi 3-segmented. Antennae 3-segmented, second antennomere 2× longer than wide and subequal to first one. Thorax: thoracic tergites yellow, first and second segments covered with brown spots. Prothoracic tergum subquadrate, about 1.5× length of meso- or metaterga; dorsally covered with single brown spot. Meso- and metathoracic tergites wider than long. Thoracic tergites sparsely setose on dorsal surfaces. Mesothoracic spiracle simple, ovate, approximately 2.0× size of abdominal spiracles; reduced metathoracic spiracle visible. Prothoracic leg noticeably longer, thicker than meso- and metathoracic legs; prothoracic pretarsus sclerotized; tibiotarsus with two long spines on the inner side, femur with row of two spines, prothoracic trochanter with two stout spines ventroapically; prothoracic coxa without spines, laterally setose. Prothoracic pretarsus and tibiotarsus combined about 2.0× length of femur; about 1.8× length of trochanter. Meso- and metalegs not modified. Abdomen: Abdominal tergites yellow, faintly rugose, with sparse elongate seate laterally. Abdominal laterotergites with lateral margins indistinctly pigmented. Abdominal segment VIII with row of four setae basally. Pygidium rounded apically; urogomphi absent; marginal row of four socketed spines present. Pygopods short, subconical.

Pupa (Figure 10a–d)

Length (from anterior edge of pronotum to tips of urogomphi) 9–10 mm, width ~4.5 mm; body color yellow with extremely sparse brownish setae. Lateral processes of middle abdominal segments well developed, bearing posterior grinding edges. Grinding surfaces of all lateral processes situated in sagittal plane. Head: hypognathous; surface flat and glabrous; projection above antennal insertion rounded; antennae 11 segmented, terminal segments forming weak club; extending beyond pronotal base; labrum and mandibles without setation; clypeus not emarginate; last segment of maxillary palpi wide. Thorax: pronotum with broadly rounded basal angles; not setose; weakly punctured. Lateral margin well defined with border running along perimeter. Hypomeron finely wrinkled; with light to absent punctation. Prosternal process round without posterior projection. Elytral sheath glabrous; not costate; meso- and metaventrite smooth. Legs glabrous. Abdomen: all surfaces covered by extremely sparse setae; spiracles annular, vertically ovate to reniform, pigmented. Tergites 1–4 widened. Tergite 5 with subapical sulcus; 1.5× longer than tergite 4. Tergites 1–5 with grinding processes (Figure 10c). Remaining tergites without grinding surfaces. Tergite 9 short, bearing relatively short divergent urogomphi, each gradually tapered and more sclerotized toward upturned, sharp apices; cleft between urogomphi V-shaped.

Distribution

South Africa: Gauteng, KwaZulu-Natal, and Free State (Figure 8).

Heteropsectropus longantennatus Koch, 1954 (Figure 1a).

Heteropsectropus longantennatus Koch, 1954a: 76.

= Heteropsectropus montisdraconis Koch, 1954a: 77 syn. nov.

Material examined

Heteropsectropus longantennatus Holotype (TMNH): “Volksrust 1.1922.A.Rob.9 G.V.Dam. Holotype No: 1783 heteropsectropus longantennatus KOCH Heteropsectropus longantennatus Koch C. Koch Det., 195 Longantennatus Koch”.

Heteropsectropus montisdraconis Holotype (BMNH): “S.Africa R.E. Turner. Brit.Mus.1927–25. Natal: Van Beenen Drakensberg Dec.1926 HoloTYPE montis-draconis Koch unique holotype! Heteropsectropus montis-draconis Koch C. Koch Det., 195” (also bearing white QR label with code NHMUK 014663130 and red, circled “Type” label).

Additional material examined

(MIIZPAN): “−28.68741, 28.947903, 18/1/18, leg. MJ. Kaminski” (also bearing blue Tenebrionidbase QR label with ID# 26352).

Diagnosis

Heteropsectropus longantennatus is sharply separable from all other species by its geographic location (largely restricted to the Drakensberg mountain range and extending northward along the borders of KwaZulu-Natal and Free State), antennae (long – extending distinctly beyond pronotum base; short – barely exceeding the pronotum base in other species), and elytra (with strongly impressed striae; weakly impressed in other species).

Description

Length 6.25–8.25 mm, width 3–4.5 mm. Color tenebrous; dark brown to black, less commonly with aeneous and/or cupreous luster. Head: antennae long, extending beyond pronotal base. Prothorax: dorsally with few large, widely spaced setae and punctures situated on lateral edges. Pterothorax: elytral striae weakly impressed; apical declivity with few to no bumps or tubercles. Laterally reflected elytral intervals ~ 3–5× wider than epipleura width. Legs: males with weakly expanded pro/meso tarsi with ventral, tomentose pads. Male terminalia: parameres narrowing from base before widening and flattening toward apex, weakly lying flat in lateral view. Penis strongly sclerotized with weakly pronounced apical hook.

Distribution

South Africa: KwaZulu-Natal and Free State (Figure 8).

Genus Muelleropsectropus gen. nov.

Type species

Schyzoschelus malaisei Koch, 1954; here designated.

Diagnosis

Muelleropsectropus is well defined within the Schyzoschelus generic group of Eurynotina by the straight apical margin of the clypeus (Figure 3e), straight/unexpanded foretibiae, rounded basal angles of the pronotum (Figure 3d), abdominal ventrite V with a sulcus (Figure 3f), and parameres with a longitudinal groove running from the apex down to the base (Figure 7c). The genus is further distinguished from other genera within the group by the following suite of characters: epipleura abruptly narrowing at the humeral region (Figure 3b) (gradually narrowing in Schyzoschelus (Figure 3a)), sulcus present on extreme apex in females (Figure 3f) (Heteropsectropus with a subapical sulcus on abdominal ventrite V in both males and females (Figure 3c)), with a single large puncture bearing a strong seta above each eye (Figure 3e) (absent in Schyzoschelus, except for S. ladini), flat or concave abdominal ventrite V (Figure 3f) (flat to convex in Heteropsectropus (Figure 3c)), female abdominal ventrite V with apical emargination or notch (Figure 3f) (absent in some Schyzoschelus and in Heteropsectropus), males with curved or strongly modified tibiae with setal patches (straight, unmodified tibiae – except for a patch of dense setae running down apex of hind tibiae in Heteropsectropus), larger punctures bearing strong setae on abdominal ventrites with those on ventrite V restricted largely to outer edge (Figure 3f) (throughout center in Schyzoschelus (Figure 4b), and absent on other abdominal ventrites in Heteropsectropus). Aedeagus similar to Heteropsectropus (long penis with sclerotized hook at apex).

Description

Length 8.5–10 mm, width 4–5 mm. Color tenebrous; dark brown to black, sometimes with aeneous and/or cupreous luster. Head: coarsely puncate, punctures closely (≤1 feature diameter) spaced; with single larger punctures bearing large setae above each eye. Epistoma apex straight, without well-defined median notch; with two large punctures bearing large setae on apical margin. Prementum with median emargination. Mentum with small ventrally projecting middle portion; lateral wings exposed. Gula with stridulatory file. Eyes constricted in middle and reniform, with impressed sulcus situated around perimeter of dorsal lobe. Antennae 11-segmented, terminal segments forming weak club; long, extending beyond pronotal base; males with longer antennae than females. Prothorax: scutellum small and transversely triangular. Pronotum with broadly rounded basal angles; dorsally with few to many large, widely spaced setae and punctures situated on lateral edges. Lateral margin well defined with border running along perimeter. Hypomeron nearly smooth to finely wrinkled; with light to absent punctation. Prosternal process round without posterior projection. Pterothorax: elytra with 10 intervals, disc relatively flat to convex. Elytral striae strongly impressed and punctate. Intervals punctate, with few to no bumps or tubercles present on apical declivity. Elytral intervals visible in ventral view. Laterally reflected elytral intervals ~3× wider than epipleura width. Epipleura broad basally, narrowing abruptly after humeral region. Apterous. Abdomen: punctate. Punctures separated by > 1 diameter. Abdominal ventrite V without subapical sulcus; males convex with additional, larger setigerous punctures intermixed with smaller punctures, females with extreme apical groove running along edge and median apical notch. Legs: femora laterally compressed, slightly curved and strongly thickened. Tibiae slightly curved; males with apical grooves or ridges with tomentose pockets. Tarsi with golden setae and strongly expanded pro/meso tarsi with ventral, tomentose pads in males. Male terminalia: tegmen bipartite and without ancorae; basal portion membranous ventrally; dorsally with small, triangular membranous field at base of apical portion. Parameres narrowing from base before widening and flattening toward apex, curving upward in lateral view. Penis strongly sclerotized with small pronounced apical hook. Spiculum gastrale symmetrical and unfused along apex. Female terminalia: ovipositor short; (~1:1 paraprocts to coxae ratio). Bursa copulatrix with two additional pouches.

Distribution

South Africa: Mpumalanga (Figure 8).

Species included (1). M. malaisei (Koch, 1954).

Muelleropsectropus malaisei (Koch, 1954) (Figures 1d, 3 d–f, 6 a,c, and 7c,d).

Schyzoschelus malaisei Koch, 1954a: 78.

Material examined

Holotype (TMNH): “Marieps Mnt. IV: 1932 G. van Son. HOLOTYPE No: 1784 Schyzoschelus malaisei KOCH Malisei Koch”.

Additional material examined

(TMNH): “S.Afr., E.Transvaal Berlin; Karst plat. 25.31S–30.46E 4.2.1987; E-Y:2414 under fungous logs leg. Endrody-Younga”, “S.Afr; E.Tvl.Uitsoek high alt. grassveld 25.15 S − 30.34 E 12.12.1986; E-Y:2381 grassnetting leg. Endrody-Younga”, “Transvaal Mt. Anderson 29.1.1955 I.Rudebeck” (two specimens). “E.Y.Western Coll. B.M. 1924–176 Transvaal”.

Diagnosis

See diagnosis of Muelleropsectropus gen. nov.

Distribution

See distribution of Muelleropsectropus gen. nov.

Genus Schyzoschelus Koch, 1954

Schyzoschelus Koch, 1954a: 72; Koch 1956: 27; Lumen and Kamiński 2023.

Type species

Schyzoschelus kaszabi Koch, 1954; by original designation.

Species included (13): S. aeneomicans Koch, 1954; S. africanus (Kaszab 1941); S. bispinosus (Kaszab 1941); S. braunsi Koch, 1954; S. capensis (Kaszab 1941); S. dumosicola Koch, 1954; S. jenkinsae Koch, 1954; S. kaszabi Koch, 1954; S. ladini Koch, 1954; S. karrooensis Koch, 1954; S. simplicipes Koch, 1954; S. sympatrius Koch, 1954; S. validus (Fairmaire 1894).

Schyzoschelus aeneomicans Koch, 1954 (Figure 2a).

Schyzoschelus aeneomicans Koch, 1954a: 90.

Material examined

Holotype (TMNH): “‘Nutwoods’ Arminel-Alic C.P.-Walker leg. Holotype No: 1818 Schyzoschelusd aeneomicans KOCH Paracharactes aeneomicans Koch C. Koch det.,195 aeneomicans Koch”.

Schyzoschelus africanus (Kaszab, 1941).

Psectropus africanus Kaszab, 1941: 36.

Schyzoschelus africanus (Kaszab, 1941). Koch 1954a: 82.

Material examined

(TMNH): “Willowmore Capland Dr. Brauns (4 specimens)” and another specimen with the same data and two additional labels: “S.A.M. Psectropus africanus Kasz. C. Koch det. 1957”.

Schyzoschelus bispinosus Kaszab, 1941.

Psectropus bispinosus (Kaszab, 1941). Kaszab 1941: 38; Koch 1954a: 77.

Material examined

(TMNH): “CAPE col. Dumbrody. J. A. O’niel 1901 bispinosus (Kaszab)”.

Schyzoschelus braunsi Koch, 1954 (Figure 2b).

Schyzoschelus braunsi Koch, 1954a: 83.

Material examined

Holotype (TMNH): “Willowmore Capland Dr. Brauns. Holotype No: 1786 Schyzoschelus braunsi KOCH Braunsi Koch”.

Schyzoschelus capensis (Kaszab, 1941).

Psectropus capensis Kaszab, 1941: 37.

Schyoschelus capensis (Kaszab, 1941). Koch 1954a: 80.

Material examined

(TMNH): “Triangle 83, 2:20””.

Schyzoschelus jenkinsae Koch, 1954 (Figure 2c).

Schyzoschelus jenkinsae Koch, 1954a: 88.

Material examined

Holotype (TMNH): “Zwartberg C.P. nr. Avondrust Vii.1950.E.A.Pienaar Jenkinsae Koch HOLOTYPE No: 1815 Schyzoschelus jenkinsae KOCH”.

Schyzoschelus karrooensis Koch, 1954 (fig. D).

Schyzoschelus karrooensis Koch, 1954a: 79.

Material examined

Paratype (TMNH): “Oudtshoorn 7 06 PARATYPE No: 1785 Schyzoschelus Karooensis KOCH Paratypus Schyzoschelus Karrooensis C. Koch sp.n”.

Schyzoschelus kaszabi Koch, 1954 (fig. E).

Schyzoschelus kaszabi Koch, 1954a: 85.

Material examined

Holotype (TMNH): “Naauwpoort, C.P. 27-x-1948 Koch & van Son Kaszabi koch HOLOTYPE No: 1795 Schyzoschelus kaszabi KOCH”.

Additional material

(TMNH): “Bloemfontein, O.R.C. 2-9-05 G. A. K. Marshall. 1908–213”, “S.Afr.,Cape-Karoo Welwood farm 31.58 S − 24.28E 14.9.1983; E–Y:2007 groundtraps, 98 days leg. Penrith groundtrap with meat bait (2 specimens)”, “S.Afr.,Cape-Karoo Vanwykafontein farm 30.38S–25.23E 22.9.1983; E–Y:2019 groundtraps,90 days leg. Penrith groundtrap with meat bait”, “S.Afr.,Cape-Karoo woodcliff farm 31.57S–24.38E 13.9.1983; E–Y:2004 singled day leg. Penrith”. (SANC): “South Africa CP Middelburg 31.3.S 25.0 E 25/viii/1989 M de Jager AcLG1151 ex unbaited pitfalls near Pentzia spp NATIONAL COLL. OF INSECTS Pretoria.S.Afr (4 specimens, 5 additional specimens with different date: 7/IX/1989)”, “S. Africa, O.F.S. Krugersdrift Dam BLOEMFONTEIN SE 2926 Aa NATIONAL COLL. OF INSECTS Pretoria.S.Afr (2 specimens)”.

Schyzoschelus ladini Koch, 1954 (fig. F).

Schyzoschelus ladini Koch, 1954a: 88.

Material examined

Holotype (TMNH): “Resolution Albany Distr VI 1928 A. Walton. Ladini Koch HOLOTYPE No: 1805 Schyzoschelus ladini KOCH” Paratype (TMNH): same data as holotype.

Additional material

(SANC): “SOUTH AFRICA: ECape Asante Sana Game Reserve ca 41 km E Graaf-Reinett 32° 15.934’S 24°58.801E 1400 m T1S1d 23.x.2010 J.M. Midgley NATIONAL COLL. OF INSECTS Pretoria.S.Afr Midgley donation 2021”, “SOUTH AFRICA: ECape Asante Sana Game Reserve ca 43.5 km E Graaf-Reinett 32°17.092’S 24°00.521E 1024 m T2S1c 23.x.2010 J.M. Midgley NATIONAL COLL. OF INSECTS Pretoria.S.Afr Midgley donation 2021”, “SOUTH AFRICA: ECape Asante Sana Game Reserve ca 38 km E Graaf-Reinett 32°15.689’S 24°57.099E 1419 m T3S1c 23.x.2010 J.M. Midgley NATIONAL COLL. OF INSECTS Pretoria.S.Afr Midgley donation 2021”, “SOUTH AFRICA: ECape Asante Sana Game Reserve ca 41 km E Graaf-Reinett 32°15.894’S 24°58.962E 2004 m T1S4a 15.iv.2010 J.M. Midgley NATIONAL COLL. OF INSECTS Pretoria.S.Afr Midgley donation 2021”, “SOUTH AFRICA: ECape Asante Sana Game Reserve ca 43 km E Graaf-Reinett 32°15.128’S 24°00.418E 2011 m T2S5d 25.xi.2009 J.M. Midgley NATIONAL COLL. OF INSECTS Pretoria.S.Afr Midgley donation 2021”.

Schyzoschelus sympatrius Koch, 1954 (Figure 2g).

Schyzoschelus sympatrius Koch, 1954a: 84.

Material examined

Holotype (TMNH): “Willowmore cape of g. Hope Dr. Brauns. HOLOTYPE No:1789 Schyzoschelus sumpatrius KOCH synpatrius Koch”.

Schyzoschelus validus (Fairmaire, 1894).

Psectropus validus Fairmaire, 1894: 661. Gebien 1938: 391: Kaszab 1941: 35.

Schyzoschelus validus (Fairmaire, 1894). Koch 1954a: 87.

Material examined

(TMNH): “Resolution Albany Distr. VI 1928 A. Walton”, “Port Eliz. 90.49. Psectropus validus Fairm Schyzoschelus Validus (Fairm) C. Koch det., 1954”. (SANC): “Grahamstown, CP. 26-2-1955 G.A. Gill. AcC. 2992. NATIONAL COLL. OF INSECTS Pretoria.S.Afr” (MNHM): “Mars 1875 Baltrasna highl ds GRAHAMSTOWN Afrique du Sud Museum Paris Coll. P. Ardoin 1978”.

Schyzoschelus dumosicola Koch, 1954a (Figure 1f).

Schyzoischelus dumosicola Koch, 1954a: 91.

= Schyzoschelus dumosicola var. diversipenis Koch, 1954a: 91 syn. nov.

Material examined

Schyzoschelus dumosicola dumosicola Holotype (TMNH): “Algoa Bay Capland Dr. Brauns 30.8.96, Dumosicola Koch, HOLOTYPE No: 1819 Schyzoschelus dumosicola KOCH”. Paratype (NRS): same data as holotype.

Schyzoschelus dumosicola var. diversipenis Holotype (TMNH): “Algoa Bay Capland. Dr. Brauns. V.diversipenis HT Koch”. Paratype (TMNH): “Addo Bush, Juli 1919, leg. J. Drury”.

Note: In 1954b, Koch described a sympatric variation of Schyzoschelus dumosicola that slightly differed in the morphology of aedeagi from the nominal form. The name was considered subspecific under art. 45.6.4 (ICZN 1999) by subsequent authors. Kamiński (2016) elevated S. d. diversipenis to specific rank based on sympatry of the two subspecies, as his catalog could only make nomenclatural acts based on the original publication rather than specimens. Upon comparison of the type material and Koch’s (1954a) figures, we conclude that these two entities are indeed variants of the same species co-occuring in the same locality (Willowmore). We propose synonymizing the two entities.

Schyzoschelus simplicipes Koch, 1954 (Figure 1e).

Schyzoischelus simplicipes Koch, 1954a: 84.

= Schyzoschelus simplicipes willowmorensis Koch, 1954a: 85 syn. nov.

Material examined

Schyzoschelus simplicipes simplicipes Paratype (TMNH): “George dist. C.P., C. Thorne Aug. 193? Paratypus SCHYZOSCHELUS simplicipes C. Koch sp.n. (two specimens)”.

Schyzoschelus simplicipes willowmorensis Holotype (TMNH): “Willowmore, C.P. 1-XI-1948 Koch & van Son Paracharactes simplicipes ssp. willowmorensis C. Koch det., 195 KOCH ssp. willowmorensis HT Koch”. Paratype (TMNH): same data as holotype.

Note: In 1954b, Koch described the above-mentioned subspecies of Schyzoschelus simplicipes based on subtle morphological differences (i.e. width of male tarsi and density of puncatation of the head and pronotum). Upon comparison of the type specimens and Koch’s (1954a) figures, we conclude that these two entities are indeed variants of the same species co-occuring in the same locality (Willowmore). We propose synonymizing the two entities.

Discussion

Redefining taxonomic boundaries in the Schyzoschelus generic group

Many of the genera within Eurynotina are enigmatic, and are rarely collected/found in collections (Lumen & Kamiński 2023a, 2023b). In particular, the Schyzoschelus generic group has gone untreated since it was established nearly 70 years ago (Koch 1954a). This paper is the most comprehensive treatment of the group since its original designation. Despite sampling collections around the world, some taxa covered in this paper are known only from small collecting series – or singletons. As a result, taxonomic definitions are relatively “rigid”, as almost no data on their morphological variability exists. For example, the Schyzoschelus africanus species group is made up of six species centered around Willowmore, South Africa, and represents a cluster of closely related species. Koch (1954a) noted that some of them may represent recent, closely related, endemic forms. While some species have characteristics that appear to be clearly diagnosable or stable (e.g. shape of hind tibiae/femora in S. africanus and tooth of the foretibiae in S. capensis), other species are more subtle or represent variation addressed in this publication (i.e. subspecies of S. simplicipes, S. dumosicola, and S. diversipenis). We hope the results here might offer a scaffold from which additional, more comprehensive revisions can be built.

Our observations largely support characters put forth by Koch (1954a) to demarcate the Schyzoschelus generic group from other Eurynotina, i.e. straight clypeal apex (Figure 3e), slender protibiae (Figures 1, 2 , and 4), rounded posterior angles of pronotum (Figure 3d). However, other characteristics were in need of revision. Namely, the merging of parameres used by Koch (1954a) to contrast Heteropsectropus and Schyzoschelus from the Oncotus generic group is in fact a characteristic found in all Eurynotina (Lumen & Kamiński 2023a). Instead, representatives of the Schyzoschelus generic group bear a unique groove running the length of the parameres through the fused basal portion (Figure 7c). Furthermore, the bordering of abdominal ventrite V used as a key feature is varied and present in some form in genera throughout all three generic groupings of Eurynotina, i.e. Eurynotus group: Phylacastus Fairmaire, 1897; Oncotus group: Isoncophallus Koch, 1954, Menederes Solier, 1848, Stridigula Koch, 1954, Psectropus Solier, 1848; Schyzoschelus group: Schyzoschelus, Heteropsectropus, and Muelleropsectropus) (Koch 1954a, 1954b, 1955; Kamiński 2016; present paper).

Within the Schyzoschelus generic group, Koch (1954a) defined Schyzoschelus via their stronger sexual dimorphism (male modifications to legs, striae on abdominal ventrites (Figures 1e, 4b,e) and abdominal ventrite V modifications (concavity in males, extreme apical grooves in females (Figures 3f and 4b), while attributing weaker sexual dimorphism and a subapical groove on abdominal ventrite V to Heteropsectropus (Figures 1a–c and 3c). However, Koch (1954a) had misgivings about two species in particular, as they display somewhat intermediate features – Schyzoschelus malaisei (Figure 1d) and S. aeneomicans (Figure 2a). Both were described by Koch (1954a) based on a single female and male specimen, respectively. During our investigation we found new male and female specimens of S. malaisei, which enabled us to establish a firmer taxonomic position for this species and reevaluate the taxonomic boundaries between the genera of the Schyzoschelus generic group. While some of the following features have a male bias due to a shortage of specimens, they proved reliable for distinguishing relatively large species groupings: strong modification of male tibiae (curved, hollowed-out, setose, etc.) (Figure 4e), abdominal segments (I and II with striated basal border (absent (Figure 1f) or present (Figures 1e and 4b)), abdominal ventrite V concavity (absent (Figure 3c) or present (Figure 4b)), abdominal ventrite V with large punctures and strong setae on apical/outside margin only (Figure 3) (or in middle/concavity (Figure 4)), large punctures with strong setae on abdominal ventrites other than V (Figure 4) (present/absent), number of elytral intervals (10 or 11) determined by a prematurely terminating stria (Figure 3a vs. Figure 3b), size of the epipleura at the humerus (large or small, narrowing abruptly or gradually, respectively (Figure 1a,b)). Using our new suite of characters and additional specimens, it was possible to reassess diagnostic features provided for S. malaisei. Unfortunately, we did not obtain additional material outside the type for S. aeneomicans; however, while it does have setation, lustre, and aedeagal characteristics similar to Heteropsectropus, the more consistent characteristics (i.e. number of elytral rows and epipleural width) are most in line with Schyzoschelus. Since we cannot presently confidently reassess its affiliation, we chose to leave it within Schyzoschelus. Alternatively, S. malaisei showed an even stronger affinity with Heteropsectropus, so we designate a new genus (Muelleropsectropus gen. nov.) to accommodate it. Similar to S. aeneomicans, Muelleropsectropus has Heteropsectropus-like traits (i.e. head/pronotal setae and aedeagal qualities); however, Muelleropsectropus has 10 elytral intervals (vs. 11), and a wide epipleural humerus (vs. narrow). Further, female specimens made it possible to compare internal morphology between Schyzoschelus, Heteropsectropus, and Muelleropsectropus. Contrastingly, the morphology of the bursa copulatrix differs between all three: Schyzoschelus with a terminal “bulb-like” pouch (Figure 5e), Muelleropsectropus with two additional pouches (Figure 6a), and Heteropsectropus without any additional pouches (Figure 5d). It is still possible that further examination within Schyzoschelus could reveal more divisions or subsequent lumping of taxa; however, without more specimens, representatives of both sexes, etc., more action will remain impeded. The divisions and characteristics we present here (see key and diagnoses) provide clear, well-defined groupings based on the most comprehensive set of material available for future workers to use.

Variability within Heteropsectropus

Most of the diversity within Heteropsectropus (four of seven species) was based on singletons (Koch 1954a), i.e. H. difficilis, H. longantennatus, H. montisdraconis, and H. transvaalensis. Through comparison with additional material obtained as a result of this study, the variation within these taxa is easily encapsulated within fewer, more easily diagnosed, species concepts. For instance, H. montisdraconis and H. longantennatus were both described from single (male) specimens collected from localities within 160 km of one another (Koch 1954a; Kamiński 2016). Comparison of type material also revealed very little difference between the original specimens externally and internally. The case of H. difficilis, H. amaroides, H. natalensis, and H. transvaalensis proved to be more challenging. Namely, while the individual type specimens do indeed appear different, extremes concerning characters such as the “flatness” or “squareness” of the elytra described by Koch (1954a) fall well within a continuum more easily explained by variation over geographic space (Figure 8). Despite these findings, the first two groupings designated in the identification key provided by Koch (1954a) proved to be sharply and reliably separable based on some of his original characteristics, i.e. H. longantennatus + H. montisdraconis, and H. aenescens. Heteropsectropus longantennatus (= H. montisdraconis syn. nov.) is the only species of the genus with deeply impressed elytral striae and elongate antennae (Figure 1a). In the case of H. aenescens, the shape of the elytra is helpful in diagnostics, especially in conjunction with the intensity of setation on the pronotum (see Muelleropsectropus in Figure 3d) (though Koch (1954a) made no mention of this feature). The rest of the species then fell into a set of difficult-to-interpret concepts that likely suffered from diagnosing individuals. The new classification we present provides clearer concepts, and the remaining species are well diagnosable (i.e. H. aenescens, H. difficilis, H. longantennatus).

Immature stages and ovovivipary

The limits of the generic groupings with Eurynotina are important – not only for diagnostic and taxonomic purposes, but also for behavioral and ecological studies. To date, there are only 15 recorded species of Tenebrionidae that are ovoviviparous (Lumen & Kamiński 2023a; present paper). Such a rare reproductive strategy likely has interesting evolutionary origins and implications, and may be useful in phylogeny-based classification (Evangelista et al. 2019; Djernæs et al. 2020; Li 2022). As a result of our investigation here, an additional species of Eurynotina is now recorded as ovoviviparous. This discovery seems especially interesting as it concerns the second lineage within the subtribe – the other consists of closely related sister genera Biolus and Eurynotus (Lumen & Kamiński 2023a). Heteropsectropus is a more distantly related taxon, so while the evolutionary pattern and phylogenetic context of ovovivipary in Eurynotina remains uncertain, it may be more widespread in the subtribe.

Though Schulze L (1969) included a picture of an identified Heteropsectropus larva in her paper, she did not provide any detailed comments or descriptions of it. Despite an overall scarcity of materials in entomological collections for examination, Eurynotina (specifically Heteropsectropus difficilis) now represents one of the best-described examples of African darkling beetles, as the first- and later instar larvae, pupae, and adults of both sexes are now described here. Interestingly, the spikes on the last abdominal segment of the larvae are not visible in the cast of the first-instar larva, and appear in later instars during development (Figures 5a and 9k). Modifications to the abdominal segment are diagnostic for many tribes within Blaptinae (Kamiński et al. 2019a, 2021); therefore, changes to these structures throughout development may be of further diagnostic or evolutionary import. Additionally, a pale extension on the base of the mandibles may be diagnostic for the subtribe (Figure 9b,c), as it has also been observed in Eurynotus asperatus (Kamiński et al. 2019b). To date, all larvae in Eurynotina possess a wide ligula and four spikes on the last abdominal segment in later instars (Kamiński et al. 2019b). The pupa of Heteropsectropus is identifiable by morphology congruent with adults: pronotal shape strongly resembling adults, straight clypeus, and sulcus on abdominal ventrite V (Figure 10a,b).

Acknowledgments

We thank Werner Strümpher and Ruth Müller from the Ditsong Museum in Pretoria, Riaan Stals from the South African National Collection of Insects, Antoine Mantilleri from the Muséum National d’Histoire Naturelle in Paris, and Maxwell V. L. Barclay, and Dmitry Telnov from the Natural History Museum London, for their hospitality, access to material, and invaluable assistance (reference photographs, locating specimens, etc.). We also thank Magdalena Kowalewska at MIIZ PAN for SEM photographs. Specimens were collected under the permit no. OP4048/2017 (Ezemvelo KZN Wildlife). This research was funded by the OPUS 19 Project (number 2020/37/B/NZ8/02496) from the National Science Centre, Poland.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The work was supported by the OPUS 19 Project [2020/37/B/NZ8/02496].