Pelodiaetus Jeannel, 1937

Sokolov, Igor M., 2019, A review of the genus Pelodiaetus Jeannel (Coleoptera, Carabidae, Anillini) of New Zealand, with re-description of the genus, description of a new species, and notes on the evolutionary history, ZooKeys 879, pp. 33-56 : 36-41

publication ID	https://dx.doi.org/10.3897/zookeys.879.37684
publication LSID	lsid:zoobank.org:pub:668885D2-C218-4402-B430-8672EC98E81E
persistent identifier	https://treatment.plazi.org/id/84D68944-C436-5AC9-AC61-4ACF0A5EB849
treatment provided by	ZooKeys by Pensoft
scientific name	Pelodiaetus Jeannel, 1937
status

Treatment

Pelodiaetus Jeannel, 1937 View in CoL

Pelodiaetus Jeannel, 1937: 275 (type species Pelodiaetus sulcatipennis Jeannel, 1937, by original designation).

Recognition.

The members of this genus are distinguished from the other New Zealand representatives of Anillina by the following combination of characters: eyes absent; head with long fronto-lateral carinae; antennae submoniliform, of moderate length; prosternal process slightly dilating to the blunt apex; pronotum cordiform, with prominent anterior angles and with short basal constriction anterior to the projected posterior angles; elytra with oblique longitudinal grooves; elytral apices slightly dehiscent with narrowly rounded sutural angles; pygidium exposed in apical half; 1st elytral discal seta indistinct, only slightly longer then surrounding vestiture, while 2nd and 3d discal setae always clearly visible; elytral margin with umbilicate series of 9 pores: the longest setae in the 2nd, 6th, and 9th pore positions, 7th, 8th, and 9th pores equidistant, not aligned, virtually forming obtuse isosceles triangle with 8th pore shifted towards disc. The developed fronto-lateral carinae, antennae of moderate length, projected pronotal anterior angles, grooved elytra, exposed pygidium and small size separate Pelodiaetus from endogean Hygranillus Moore. Distinct posterior angles of pronotum, dilated prosternal process and grooved elytra distinguish the representatives of Pelodiaetus from the species of Zeanillus Jeannel. Umbilicate series of nine pores, slightly dehiscent apices of grooved elytra and exposed pygidium separate the members of Pelodiaetus from the species of Nesamblyops Jeannel. An absence of the distinct tubercle anterior to the posterior angles of the pronotum and the small size separate the species of Pelodiaetus from the species of Pelodiaetodes Moore.

Description.

Size. SBL range 1.19-1.45 mm.

Habitus. Body form slightly convex, almost subparallel ( Fig. 6 View Figure 6 ), moderately elongate (WE/SBL range 0.31-0.35), head relatively wide, subequal to the width of pronotum (WH/WPm range 0.80-0.85), pronotum relatively wide, subequal to the width of elytra (WPm/WE range 0.79-0.88).

Color. Body rufo-testaceous or testaceous, appendages testaceous.

Microsculpture. Dorsal microsculpture of polygonal sculpticells with isodiametric mesh pattern throughout the dorsal surface. Development of microsculpture varies on different body parts. Head and disc of pronotum with shallow microlines, sometimes partially obliterated, while on elytra microlines are very distinct, forming well-pronounced sculpticells.

Luster. Body surface shiny.

Macrosculpture. Body surface sparsely and finely punctate.

Vestiture. Body surface covered with sparse yellowish short setae. Vestiture of elytra moderately long (around one-half length of discal setae).

Fixed setae. Primary head setae include a pair of clypeal (cs), a pair of frontal (fs), two pairs of supraorbital (ssa and ssp) and one pair of postorbital (pos) setae ( Fig. 1A, B View Figure 1 ). Mentum with two pairs of long primary (paramedial and lateral) setae ( Fig. 1C, D View Figure 1 , pms, lms). Submentum with three pairs of long primary setae (lss, prss) and a few additional shorter setulae ( Fig. 1C, D View Figure 1 ). Pronotum with two long primary lateral setae (midlateral, ls, and basilateral, bs) on each side ( Fig. 2A, B View Figure 2 ). Elytra with two distinct discal setae ( Fig. 4 View Figure 4 , ed5 and ed6), first discal seta (ed3) barely visible, scutellar (ed2) and apical (ed8) setae of normal sizes. Last three (7th, 8th, and 9th) pores (eo7, eo8, and eo9) of umbilicate series equidistant, not aligned, with 8th pore shifted towards the disc and virtually forming an obtuse isosceles triangle, the longest setae of umbilicate series in the 2nd, 6th, and 9th pore positions ( Fig. 4 View Figure 4 ). Fifth visible sternite of male with two and of female with four setae along the posterior margin.

Head ( Fig. 1A, B View Figure 1 ). Anterior margin of clypeus (cl) straight. Frontal area flat without tubercle medially near frontoclypeal suture. Fronto-lateral carinae distinct and long (fcc).

Eyes. Eyes absent.

Antennae. Submoniliform, 11-segmented, extended to about posterior margin of pronotum. Antennomeres 1 and 2 elongate, of equal length and 1.3-1.4 times longer than antennomere 3, which is slightly elongate and 1.1 times longer than antennomere 4. Antennomeres 4-10 globose, last antennomere conical and 1.7-1.8 times longer than penultimate antennomere.

Labrum ( Fig. 1A, B View Figure 1 ). Labrum (lb) transverse with almost straight, entire anterior margin with six setae apically, increasing in size from the central pair outwards.

Labium ( Fig. 1C, D View Figure 1 ). Labium with almost obliterated blunt mental tooth (mt); mentum (m) and submentum (sm) split, with mental-submental suture (mss). Glossal sclerite (gsc) without paraglossae, bisetose.

Prothorax. Pronotum ( Fig. 2A, B View Figure 2 ) cordiform, slightly convex, arcuately constricted posteriorly and moderately sinuated anterior to posterior angles, with wide marginal gutter (mg). Posterior margin of pronotum shallowly concave medially and oblique laterally. Anterior angles narrowly rounded, distinctly projecting forward. Posterior angles rectangular, projecting outwards, bearing basolateral seta anterior to angles. Widths across anterior margin slightly to moderately greater than between posterior angles at the level of basilateral setae (WPa/WPp range 1.11-1.40). Prosternum ( Fig. 2C, D View Figure 2 ) slightly protruding at the anterior margin medially, there with a group of longer setae relative to other prosternal vestiture. Prosternal intercoxal process (psp) unmargined, slightly dilated apically and widely rounded at apex.

Scutellum ( Fig. 2A, B View Figure 2 ). Externally visible, triangular, with rounded apex.

Elytra ( Fig. 4 View Figure 4 ). Elytra subdepressed, relatively long (LE/SBL from 0.56 to 0.60 among specimens) with oblique longitudinal grooves. Humeri rounded, forming an oblique angle with the longitudinal axis of body. Elytral basal margination lacking ( Fig. 2A, B View Figure 2 ). Apical half of elytra without subapical sinuation. Sutural angle of elytron narrowly rounded, making apices of elytra slightly dehiscent ( Fig. 4 View Figure 4 ).

Hind wings. Absent.

Pterothorax ( Fig. 3A View Figure 3 ). Metaventrite (mtv) moderately short, distance between meso- and metacoxae approximately equals diameter of mesocoxa. Metanepisternum (mte) slightly elongate, rectangle, with anterior margin shorter than outer margin. Metendoventrite (mes) with reduced anterior part and with lateral arms. Lateral arms U-shaped with widely divergent branches.

Legs ( Fig. 5 View Figure 5 ). Legs of moderate length, not elongated. Prothoracic legs of males with first 2 tarsomeres (ta1-2) moderately dilated apico-laterally with one row of oval articulo-setae (as) ( Stork 1980) on the ventral surface. Protibiae ( Fig. 5A View Figure 5 ) with antenna cleaner (ac) of type B ( Hlavac 1971), with both anterior (asr) and posterior (psr) apical setal rows long and with concave apico-lateral notch. Length of anterior spur (asp) slightly smaller than length of 1st tarsomere (ta1). Profemora moderately swollen. Mesotibiae ( Fig. 5B View Figure 5 ) with one long row of modified ventral setae (msms) at apical half, two terminal spurs and tibial brush (msb). Metafemora unmodified, metatibiae ( Fig. 5C View Figure 5 ) with one row of modified ventral setae (mtms) in apical half, with two terminal spurs (mts) and tibial brush (mtb). Tarsi pentamerous, 1st and 5th tarsomeres are the longest, 2 nd– 4th tarsomeres of equal length on the tarsi of all legs, 1st tarsomere shorter than combined length of 2 nd– 4th tarsomeres. Tarsal claws simple, untoothed.

Abdominal ventrites. Five visible abdominal ventrites: 2nd ventrite longest, 1.7-2.0 times longer than 3rd or 4th, 3rd and 4th equal in length; the last, 5th, 1.6-1.8 times longer than 4th. Intercoxal process of 2nd ventrite of moderate width, constricted anteriorly, subparallel before blunt apex ( Fig. 3A View Figure 3 , ipa).

Male genitalia ( Fig. 7 View Figure 7 ). Median lobe of aedeagus anopic, elongate, slightly twisted and moderately arcuate. Apex of median lobe unmodified, only slightly enlarged in dorsal view. Internal sac with weakly sclerotized copulatory sclerites represented by flagellum-like structures combined at their basal or apical parts with small sclerotized plates of various size (ds). Ostial fields or spines of internal sac absent. Parameres bi-setose. Left paramere large and broad, evenly tapered to apex, right paramere moderately long. Ring sclerite ovoid, conically tapered apically with slightly elongated, triangular, handle-like extension.

Female internal genitalia. Gonocoxite 1 asetose ( Fig. 3B View Figure 3 , gc1). Gonocoxite 2 falciform (gc2), 1.8-2.1 times longer than its basal width, moderately curved, with two ensiform (es) and one apical nematiform (ns) setae. Laterotergite (lt) with six or seven setae. Spermatheca (sp) small, weakly sclerotized ( Fig. 3B View Figure 3 , 7DH), of bean-shape. Length of spermathecal gland (sg) much greater than length of spermatheca. Spermathecal duct (sd) very long.

Included taxa. The genus comprises two species: P. sulcatipennis Jeannel, and P. nunni sp. nov.

Geographic distribution. The species of Pelodiaetus are known from the lowlands of three regions of the South Island of New Zealand ( Fig. 8 View Figure 8 ): Canterbury, Otago, and Southland. In Otago representatives of the genus deeply penetrate inland along the Clutha River valley.

Habitat. According to the label information, all specimens of Pelodiaetus were collected from washed soil samples, except one specimen, which was collected under a stone after rain. Collections were made in a vast spectrum of habitats: from improved pasture and tussocks to conifer (kahikatea and podocarp) and broadleaf ( Neopanax and beech) forests. Beetles were collected during most months of the year, except February, July, and August.

Relationships. Morphologically, the closest relative of Pelodiaetus among the New Zealand anillines is Pelodiaetodes , the two genera together forming a distinct New Zealand lineage of Anillini . Both genera share developed fronto-lateral carinae, distinct pronotal posterior angles, a dilated prosternal process, nine setae in the elytral umbilical series of pores, longitudinal elytral grooves, and are distinguished by the combination of these characters from any other New Zealand Anillina. Compared with overseas Anillini it seems reasonable to group the members of Pelodiaetus with other anillines having grooved elytra, including the Australian Illaphanus Macleay and the Madagascan Bulirschia Giachino, Malagasytyphlus Giachino, and Malagasydipnus Giachino ( Giachino 2005, 2008). Based on similarity between New Zealand Pelodiaetus and Australian Illaphanus , Jeannel (1937: 276-277) postulated that both genera had a common ancestor, and their ancestral stock inhabited East Gondwana at the time when it included modern territories of Australia, Tasmania, and, partly, New Zealand. I agree with Jeannel’s opinion and consider the representatives of the Australian genus Illaphanus as the sister-taxon to the members of the New Zealand Pelodiaetus -lineage.