Undarobius Escalona & Oberprieler, 2021

Escalona, Hermes E. & Oberprieler, Rolf G., 2021, Undarobius, a new genus of cavernicolous weevils (Curculionidae: Entiminae Leptopiini) from the Undara Lava Caves in north-eastern Australia, with an overview of anophthalmic and microphthalmic Australian Curculionidae, Zootaxa 5023 (2), pp. 207-222 : 208-209

Undarobius Escalona & Oberprieler gen. n.

( Figs. 9–36 )

http://zoobank.org/ urn:lsid:zoobank.org:act:442F6299-8BD7-4FB4-8DF4-B9EFF52B5EED

Type species, by present designation: Undarobius howarthi Escalona & Oberprieler sp. n.

Diagnosis. Body longer than wide, length 4.0– 5.5 mm, somewhat flattened, covered with sparse to dense, appressed, fluted squamae and sparse, short, erect to semi-erect setae. Eyes absent ( Fig. 19 ). Rostrum dorsally not separated from head by groove (sulcus); frons indistinct; epistome short, apical margin bisinuate ( Fig. 21 ). Antennal scrobes broadly open and poorly defined ( Fig. 19 ). Scapes long, reaching apical third of prothorax in repose. Prothorax with anterior margin laterally without ocular lobes or vibrissae. Wingless. Tibiae mucronate; metatibiae without corbels or bevels. Tarsal claws free.

Description. General appearance. Body longer than wide, length 4.0– 5.5 mm, compact, robust, broad, flattened, surface without ridges, tubercles or spines ( Figs. 9–13 ). Rostrum and legs relatively long. Integument pale ferrugineous (reddish-brown) to dark brown, sparsely to densely covered with appressed, pale yellowish-brown, fluted squamae (scales) and sparse, short, erect to suberect, truncate or acute setae.

Head. Rostrum ( Fig. 19 ) ca. 3 × longer than head, oval in cross-section. Epistome slightly projecting, short, apex asymmetrically emarginate medially, base with two epistomal setae. Frons ( Fig. 19 ) indistinct, slightly domed, triangular, surface with microsculpture near apex, otherwise smooth. Epifrons ( Fig. 21 ) with indistinct but deep median groove in anterior third (between antennal sockets), asulcate in basal two thirds. Antennal sockets ( Figs. 21 ) large, not reaching rostral apex, closed laterally and open dorsally. Scrobes ( Fig. 19 ) lateral, shallow, broad, short (not extending to base of rostrum), borders poorly demarcated. Eyes absent, location marked by small glabrous area ( Fig. 19 ). Antennae ( Fig. 22 ) long, inserted near rostral apex; scapes slightly shorter than funicle and club; funicles 7-segmented, segment 1 shorter than 2, expanded apicad, 3–7 subequal, moniliform. Mouthparts imperfectly adelognathous, with maxillary stipites exposed next to base of prementum ( Fig. 20 ); mandibles ( Fig. 15 ) robust, externally paucisetose, with four long and two smaller setae, small subtriangular scar of deciduous cusp present in ventral position; maxillae ( Fig. 16 ) with single apical lobe and 3-segmented palpus, segments 1 and 2 transverse, 2 half as long as 1, 3 conical and surrounded by digitiform sensilla; prementum ( Figs. 14 , 20 ) slightly enlarged, subhexagonal, flat, asetose, labial palpi 2-segmented, ligula absent.

Thorax. Prothorax ( Fig. 24 ) about as long as wide, narrowing apicad from apical third, apically slightly constricted, forming a slight ring ventrally, anterolateral margins without ocular lobe or fringe of fine setae; pronotum slightly convex. Procoxal cavities ( Fig. 23 ) circular, medially contiguous, broadly interrupting prosternal process. Mesocoxal cavities circular ( Fig. 26 ), laterally closed by meso- and metaventrites, separated by about 0.7 × their width. Mesanepisterna and mesepimera fused but suture between them distinct. Elytra slightly longer than their joint width, medially fused but suture visible, fine, sides evenly rounded, with 10 complete striae of small, widely spaced punctures; interstriae flat, with single row of sparse, erect, spatulate setae. Metanepisterna fused to metaventrite but metanepisternal suture present as deep groove through most of their length; metepimera not exposed. Scutellar shield small, triangular, slightly convex, denuded. Wingless. Legs. Coxae with conspicuous, long stiff seta directed ventrad; procoxae ( Fig. 23 ) globular, medially contiguous. Trochanters obliquely truncate, without single long seta. Femora ( Figs. 28–30 ) slender, subcylindrical, conspicuously inflated in distal third. Tibiae long, terete, subcylindrical; protibiae ( Fig. 28 ) slightly bent inwards apically, meso- and metatibiae ( Figs. 29–30 ) straight; tibial apex with small mucro surrounded by scattered setae, without spurs, without bevel or corbel; tarsi with segment 1 longer than wide, enlarged apicad, 2 moniliform, 3 deeply lobed, claws simple, free, divergent.

Abdomen. Ventrites ( Fig. 27 ) jointly subtriangular, 1 and 2 connate but suture between them distinct, arcuate, 3–5 free; 1 in middle ca. 1.6 × longer than 2, with broad, subtruncate intercoxal process, 2 ca. 2 × longer than 3 and 4, these subequal in length, 5 longer than 3 and 4; sexual dimorphism slight, in male ventrites 1 and 2 less convex and 5 shorter, more broadly rounded. Male terminalia. Aedeagus ( Figs. 31–32 ) of pedal type; penis tubular, narrowing apicad, apex roundly acuminate, temones (apodemes) shorter than body, attached to its base in dorsal position; tegmen without parameres; endophallus without flagellum or internal sclerite; sternite VIII with hemisternites forming one plate, sternite IX with basal plate divided and subtriangular, with long apodeme (spiculum gastrale). Female terminalia. Ovipositor ( Fig. 34 ) short, weakly sclerotised, without baculi (rods); distal gonocoxites cylindrical, with apical third setose, apex with short setose stylus; spermatheca ( Fig. 35 ) sclerotised, hook-shaped, without distinct nodulus, ramus or collum, spermathecal gland sac-like, about as long as spermatheca, duct short; sternite VIII ( Fig. 33 ) with broad, spatulate plate and long thin spiculum ventrale.

Derivation of name. The name of the genus is derived from the locality of the two known species, the Undara Volcanic National Park, and the Greek noun bios, meaning life; its gender is masculine. The name Undara is an Ewamian Aboriginal word meaning ‘long way’.

Comments. Elwood Zimmerman (1912–2004) deemed these weevils to be a new genus of the former subfamily ‘Rhytirhininae’ ( Howarth 1988, Howarth & Stone 1990, Stone 2010, Stone et al. 2012), but their possession of deciduous mandibular cusps (the break planes clearly visible as flat scars) and adelognathous mouthparts (albeit imperfectly) demonstrates that they belong in the subfamily Entiminae (sensu Marvaldi et al. 2014) rather than Cyclominae (sensu Oberprieler 2010, 2014), in which the Rhythirrinini are now included as a tribe. In the key to the tribes of Australian Entiminae of Oberprieler & Zimmerman (2020), Undarobius runs to the large and poorly constituted tribe Leptopiini , but it shares no obvious characters with any known leptopiine genus in Australia and appears to occupy an isolated position in this tribe. No other anophthalmic leptopiines are known from Australia, although reduced eyes occur in the small genus Howeocis Lea (a relative of the large terricolous genus Mandalotus Erichson ) and in several other similar leaf-litter species. Undarobius currently comprises two species, but others may yet be discovered in other caves of the Undara Lava Cave system and perhaps in other cave systems in northern Queensland.

Undarobius has a most unusual shape for a cavernicolous weevil, being broad and flat with long legs, almost spider-like. Other anophthalmic cave weevils, in particular entimines such as the various Palaearctic Otiorhynchini (see, e.g., Osella & Zuppa 1998, Hlavac 2011, Hlavac & Skuhrovec 2016, Bello et al. 2021) and Laparocerini (e.g., Machado 2011a –b, Machado et al. 2017) are usually shaped like their epigean relatives or narrow and elongate with normal-sized legs. The peculiar shape of Undarobius suggests a specialised life style, possibly of crawling along the walls and even roofs of caves or among the root tresses hanging from the cave roofs, but no observations of the habits of the species are available so far.

Figures

FIGURES 9–16. Undarobius habitus and mouthparts. 9–10, 12—U. howarthi sp. n. (SL 3.8 mm, ♂) 9–10: dorsal, 12: lateral aspect; 11, 13—U. irvini sp. n. (SL 3.8 mm, ♀) 11: dorsal, 13: lateral aspect; 14– 16—U. howarthi sp. n. ♀, mouthparts, 14: labium, ventral view, 15: left mandible, dorsal view, 16: right maxilla, ventral view.

FIGURES 17–25. Undarobius howarthi sp. n., ♂, structural details. 17—head, dorsal view; 18—head, ventral view; 19—head, lateral view; 20—mouthparts, ventral view; 21—apex of rostrum, dorsal view; 22—left antenna, dorsal view; 23—prothorax, ventral view; 24—prothorax, dorsal view; 25—elytra, dorsal view.

FIGURES 26–36. Undarobius species, structural details. 26–34 U. howarthi sp. n., 26—pterothorax and elytra, ventral view; 27—ventrites, ♂, ventral view; 28—foreleg; 29—middle leg; 30—hindleg; 31—penis, dorsal view; 32—penis, lateral view; 33—sternite VIII, ♀, ventral view; 34—ovipositor, ventral view; 35—spermatheca; 36—U. irvini sp. n., spermatheca.