Phylacastus Fairmaire, 1897

Lumen, Ryan & Kaminski, Marcin Jan, 2023, Taxonomic revision of the genus Phylacastus Fairmaire (Tenebrionidae, Eurynotina): shortfalls of anatomical nomenclature with notes on aedeagal homology, ZooKeys 1138, pp. 1-27 : 1

Genus Phylacastus Fairmaire

Phylacastus Fairmaire, 1897: 116. Koch 1954a: 275; 1954b: 2; 1956: 27; Kamiński 2016: 245.

Type species.

Phylacastus striolatus Fairmaire; by monotypy.

Diagnosis.

Within Eurynotina , Phylacastus largely resembles Eurynotus and Capidium Koch. All three have relatively sharp basal pronotal angles, rather than broadly rounded as is the case in the rest of Eurynotina ( Kamiński 2016: fig. 2). The only other exception is Oncotus Solier which, while some representatives have basal angles of the pronotum similarly shaped, is separable by prosternal process shape (rounded rather than angular in lateral view ( Kamiński 2016), body shape (much rounder/transverse than Phylacastus ), tibial morphology (foretibia greatly expanded apically and with a sharp lateral projection; Kamiński 2016), and coloration (species may be bicolored and/or very pale or testaceous in color). Phylacastus can be easily separated from all other subtribal representatives by the presence of (at most) weak tubercles on the apical declivity of the elytra (Figs 1 , 2 ), the form of the prosternal process which is angular rather than rounded in lateral view ( Kamiński 2016: fig. 2D), and the pronotum with basal angles present rather than absent/rounded) ( Kamiński 2016: fig. 2J).

Eurynotus , the most closely affiliated genus according to Koch (1954a), can be separated from Phylacastus by body size ( Eurynotus ~9-20 mm long and ~5-12 mm wide, versus Phylacastus 4-8 mm long and ~2.75-4 mm wide ( Koch 1954a; Kamiński 2016); pronotal hind angles ( Eurynotus prominently produced often rearward projecting; less prominent and not rearwardly projected in Phylacastus ; Kamiński 2016), tibial morphology ( Eurynotus with slender/narrow tibiae lacking coarse spines on ventral surface of foretibia; dorsoventrally flattened and apically expanded tibiae with coarse spines on the underside of the foretibia in Phylacastus ( Kamiński 2016), elytral sculpturing ( Eurynotus with coarse or well-defined tubercles in most species; while most species of Phylacastus lack well-defined tubercles ( Kamiński 2016). Finally, Eurynotus lacks a subapical sulcus on abdominal ventrite V, which is present in all Phylacastus species (Fig. 3F, G ).

Capidium can be separated from Phylacastus most reliably via the structure of the prosternal process and abdominal ventrite V (prosternal process rounded and not produced in Capidium , angular and produced in Phylacastus ( Kamiński 2016), and subapical sulcus absent in Capidium (present in Phylacastus ); additionally, although Capidium also is defined by angular basal angles of the pronotum ( Kamiński 2016), the angles are usually more produced. Finally, the elytral sculpturing and tuberculation of representatives of Capidium (when present) are stronger than in Phylacastus .

Genus redescription.

Length 4-8 mm. Shining to dull; colored tenebrous; reddish to dark brown/black. Head: epistoma with well-defined median notch. Transition between clypeus and frons gradual and smooth along lateral edge, or with slight depression. Coarsely punctate, punctures large and closely spaced, separated by ≤ 1 feature diameter. Mentum with enlarged, ventrally projecting middle portion parallel-sided to slightly narrowing apically with reduced/slightly hidden lateral wings. Gula with stridulatory file. Eye constricted in middle and reniform, with strong to weakly impressed sulcus situated around posterior perimeter of dorsal lobe. Antennae with 11 antennomeres, terminal members forming weak club. Prothorax: pronotum base straight, with basal angles roundly produced. Without lateral depression or flattening along margins. Hypomeron at most only finely sculptured and finely punctured, dull to shining. Prosternal process angulate in lateral view, weakly produced or rounded at apex, with clear sulcus running perimeter, projecting at most only weakly toward midcoxae. Pterothorax: scutellar shield small and transversely triangular. Elytra not costate, with or without shallow or weakly defined punctate striae. Intervals punctate, without microtubercles; weak to well-defined tubercles (when present) only on apical declivity. Interval X terminating before reaching elytra base. Epipleura without microtubercules, broad basally, narrowing apically. Apterous. Abdomen: punctate. Ventrite V with sulcus running parallel to apical perimeter. Legs: femora slightly curved and expanded toward apex. Tibiae dorsoventrally compressed. Meso- and metatibia slightly curved. Foretibia dilated triangularly toward apex with coarse spines underneath. Male terminalia: tegmen bipartite with or without ancorae (small ancorae present in one species); basal portion membranous ventrally; dorsally with small, triangular membranous field at base of apical portion. Parameres fused dorsally at base, apical opening (in dorsal view) small or broad (Fig. 4 ). In lateral view, parameres flattened toward apex, with or without slight curvature. Female terminalia: paraprocts nearly as long or slightly longer than coxites I-IV, coxite IV reflected dorsally with gonostyli present (Fig. 5 ); bursa copulatrix divided into two sections by median constriction (bilobate) or not (Fig. 6 ), with or without additional "accessory pouch" situated near to spermatheca and accessory glands.

Species included

(5). Phylacastus ancoralium sp. nov., P. crypticoides , P. makskacymirowi sp. nov., P. rhodesianus , P. striolatus .

Distribution.

Southern Africa (Lesotho, South Africa, Zimbabwe) (Fig. 7 ).

Figures

Figure 1. Dorsal habitus of Phylacastus species A Phylacastus ancoralium sp. nov. holotype B Phylacastus makskacymirowi sp. nov. C Phylacastus crypticoides D Phylacastus rhodesianus E Phylacastus striolatus lectotype. Scale bars: 1 mm.

Figure 2. Phylacastus lateral aspect photographs and close-up of apical elytral tubercles and striae A Phylacastus ancoralium lateral angle B P. ancoralium close-up of elytra apical declivity C P. rhodesianus lateral angle D P. rhodesianus close-up of elytra apical declivity E P. striolatus lateral angle F P. striolatus close-up of elytra apical declivity.

Figure 3. Diagnostic features of Phylacastus species A-C mentum (Median keel red, middle portion and lateral wings blue and green respectively) D-E prosternal process F-G abdominal ventrite V A, D, F Phylacastus crypticoides B P. makskacymirowi C P. rhodesianus E P. ancoralium G P. striolatus. Scale bars: 0.1 mm

Figure 4. Phylacastus species spp. aedeagi A-D aedeagus dorsal view E, F aedeagus Ventral view A, H Phylacastus striolatus B, G P. ancoralium (ancorae highlighted blue) C P. rhodesianus E P. crypticoides D, F P. makskacymirowi (subapical sutures highlighted blue). Median lobes highlighted green. Scale bars: 0.2 mm.

Figure 5. Phylacastus ovipositor (dorsal). Right Phylacastus ancoralium Left P. crypticoides. Abbreviations: C - Coxae (1 - 4); Prct - Paraprocts. Scale bars: 1 mm.

Figure 6. Phylacastus internal female structures A Phylacastus striolatus B P. crypticoides C P. ancoralium. Abbreviations: Ag - Accessory gland, Ap - Accessory pouch, Bc - Bursa copulatrix, Ov - Oviduct, Sp - Spermatheca.

Figure 7. Phylacastus species distribution map. P. ancoralium (blue star), Phylacastus crypticoides (black circle), P. makskacymirowi (red diamond), P. rhodesianus (pink square), P. striolatus (yellow triangle).