Tripectenopus Lea

Herman, Lee, 2023, Generic Revisions Of The Scopaeina And The Sphaeronina (Coleoptera: Staphylinidae: Paederinae: Lathrobiini), Bulletin of the American Museum of Natural History 2023 (460), pp. 1-195 : 170-175

Tripectenopus Lea

Figures 351 , 381–391

Tripectenopus Lea, 1918: 83 (species included: caecus ). Type species: Tripectenopus caecus Lea , fixed by monotypy.

— Scheerpeltz, 1933: 1270 (catalog). — Blackwelder, 1939a: 122 (type species). — Blackwelder, 1952: 397 (type species).

Scopaeodracus Scheerpeltz, 1935: 638 . Type species: Scopaeodracus handschini Scheerpeltz, 1935: 646 , fixed by original designation and monotypy. New synonym.

— Blackwelder, 1952: 347 (type species).

DIAGNOSIS: Tripectenopus has two apical, metatibial combs; both Sphaeronum and Coecoscopaeus have one. Tripectenopus has a deep, longitudinally furrowed, mesobasisternal depression; the mesobasisternal depression of both Sphaeronum and Coecoscopaeus is barely discernible. The prohypomeron and profurcasternum of Tripectenopus are separated ( Britton, 1974: fig. 6); they touch in Sphaeronum (fig. 355). These three characters do not distinguish Tripectenopus from Typhloleleupius .

Tripectenopus and Typhloleleupius are most conveniently and clearly separated by the Indian Ocean; the former is confined to Australia, the latter to southern Africa and Madagascar. Few morphological features separate them. The labrum of Tripectenopus is deeply emarginate and edentate (fig. 384; Scheerpeltz, 1935: 4 a). The labrum of Typhloleleupius has a large, submedial, apically acute ( Janák, 2013: fig. 21) to small, apically rounded denticle (fig. 394) submedially on the anterior margin. None of the articles published on Typhloleleupius and Tripectenopus present characters or discussion to aid separation. Until now the two genera have never been compared or associated with each other.

Other possibly distinguishing characters, two of which have been cited as diagnostic for Tripectenopus , are all subtribal features that permit separation from other Paederinae . They include the confluent gular sutures ( Scheerpeltz, 1935: fig. 3a), absence of the pronotal marginal ridge, presence of the hypomeronal ridge of the postprocoxal lobe, the trilobed anterior margin of sternum II, the strongly sclerotized, dorsally directed, hypopharyngeal peg (figs. 386–388), and the enlarged grooming concavity of the protibia (fig. 351; Scheerpeltz, 1935: fig. 4h).

DESCRIPTION: Body length 3.2–11.0 mm (from Lea, 1918: 85, 1923: 29–31; Scheerpeltz, 1935: 647; Britton, 1974: 86).

Head (figs. 381, 382; Scheerpeltz, 1935: fig. 1a; Britton, 1974: fig. 5) with lateral margin gradually rounded to basal angles or to neck; basal angle broadly to strongly rounded or absent; basal margin slightly to strongly rounded and slightly to strongly emarginate medially or with small median lobe; anterolateral surface with or without temporal ridge; temporal ridge, when present, fine, short, and extending posteriorly from lateral surface of supraantennal hump onto temple; lateroventral surface with or without submarginal furrow or ridge; furrow or ridge, when present, moderately long, posteriorly extended, and well separated from basal angle of head.

Dorsal cephalic surface (fig. 382) with dense to moderately dense punctation; punctation distinct and moderately coarse; punctation present or absent from midlongitudinal strip; microsculpturing present and distinct to feeble; pubescence fine and with scattered coarse, long, macrosetae.

Clypeal margin of males with large ( Britton, 1974: fig. 5), apically rounded, conical horn mesiad of supraantennal hump or horn replaced by tumescence (fig. 382); female with small to slight tumescence in place of horn.

Labrum deeply emarginate and edentate (fig. 384).

Eyes present and with many ommatidia, reduced to one ommatidium (fig. 382, evident as small, ocelluslike bump on right side), or absent ( Britton, 1974: 86); multifaceted eyes with setae.

Neck width across nuchal groove about one sixth as wide as greatest width of head.

Maxillary palpomere 4 small, conical (fig. 383).

Labrum deeply emarginate and edentate (fig. 384).

Prothorax about one fifth to one third longer than wide.

Pronotum (fig. 382) with punctation moderately dense to dense and uniform, but absent from midline; microsculpturing distinct, weak, or absent; surface with low, midlongitudinal ridge; median ridge moderately developed basally, weak or absent medially, absent anteriorly; median ridge with or without slight groove.

Notosternal suture present and weakly developed ( Britton, 1974: fig. 6).

Prohypomeron moderately densely punctate; postprocoxal lobe moderately long, nearly vertical, apex rounded, surface without setae; transverse hypomeronal ridge present and broadly curved.

Profurcasternum long, narrow, tapered posteriorly, widely separated from hypomeron ( Britton, 1974: fig. 6).

Procoxal cavity open posteriorly.

Elytra shorter to longer than pronotum.

Mesoventrite without midlongitudinal carina; mesobasisternum with broad, median depression; basisternal depression with strong, midlongitudinal furrow.

Procoxa with mesial carina near base (fig. 385).

Metatrochanter without spines on posterior margin.

Metafemur without spinelike setae on inner edge.

Metatibia without spinelike setae on inner edge; apex with comb on inner and outer sides.

Tergum VIII with or without palisade fringe.

Tergum IX with apex of lateroapical process long to short; tergum IX of male with middorsal base fused (female not examined).

Segments IX and X not examined.

Aedeagus not examined (illustrated for T. occultus: Britton, 1974: 85 ).

Spermatheca not examined.

DISTRIBUTION AND HABITAT: Although Tripectenopus is widespread in Australia and has been collected in New South Wales, Northern Territory, Queensland, South Australia, and Western Australia, the genus is known by few specimens from few localities. Although specimens of the genus have been rarely collected, but it is anticipated that more, perhaps many more, species will be described.

Little is known about the habitat or where specimens and species might be found, but the few data available suggest deep litter of the forest floor for at least some species. Specimens of Tr. torrensensis were collected from river debris ( Blackburn, 1891: 75) and from a flooding river in Queensland ( Lea, 1923: 29). Tripectenopus occultus was taken from a cave in Western Australia ( Britton, 1974: 85); both species lack eyes. Among unidentified specimens I examined, two were attracted to lights and one was collected from forest floor leaf and log debris. The only known elevational record is 1580 meters for an unidentified specimen collected in New South Wales. Three species were collected near rivers.

DISCUSSION: When Lea (1918: 83) described the monotypic, Australian Tripectenopus he included many of the essentials that define the subtribe Sphaeronina : the ovate head, moniliform antennomeres, narrow neck, elongate prothorax, enlarged protibial grooming lobe, and small scutellum. His illustrations depict several of these diagnostic features. Lea also noted that Tripectenopus caecus was apterous and eyeless. He did not state the sex of the type, but since he described none of the external features typical of males, the specimen may be a female. He placed the genus near Domene and thought Tr. caecus looked like an exaggerated Domene torrensensis Blackburn, 1891 ; he separated the two by the presence or absence of eyes.

Scheerpeltz (1935: 638) published a detailed eight-page description with 10 illustrations permitting recognition of the Australian monotypic Scopaeodracus , but not separation from Tripectenopus . Among noteworthy characters are the form of the head and pronotum, the confluent gular sutures, bilobed labrum, narrow neck, large grooming structures of the protibia and profemur, and ventral denticle of the mandibles; all are features of the subtribe. Scheerpeltz did not refer to Tripectenopus and placed his new genus near Scopaeus .

Tripectenopus occultus Britton, 1974 , was the second species described in the genus. Britton included most of the same diagnostic features for the genus relevant to the gular sutures, protibiae, eyes, antennae, and procoxal concavity, cited by Lea and Scheerpeltz. Britton listed the narrow neck as a feature of the Paederinae , but, though widespread, it is neither a defining nor the more common condition of the subfamily. This species was the first among the three genera for which males were known and described. After studying the type species of Typhloleleupius, Britton opined that it and Tripectenopus might be synonyms. Except for male specific features and the anophthalmy, the characters Britton used to define Tripectenopus are those that distinguish the subtribe.

Omitting a brief comment by Britton (1974: 87), Tripectenopus , Scopaeodracus , and Typhloleleupius were not compared with or considered in the context of one another by anyone. Many of the published characters for each are either found widely among paederines or are possessed by each of the three genera and are considered herein to define the Sphaeronina . Among the Australian species I find no characters to suggest there are two genera. I agree with Newton’s supposition (in litt., June 27, 2009) that the two are synonyms and hereby formally synonymize Tripectenopus and Scopaeodracus .

For the Australian Tripectenopus and southern African and Madagascan Typhloleleupius there appear to be no characters that separate them as clearly as their respective geographical locations. The structural diagnostic features distinct to each are few and variable. Some characters are present in one genus but are whispers in the other. The two genera share most characters. Britton (1974: 87), who studied the type species of Typhloleleupius , thought the two might be synonyms because he found no distinguishing features, but most of the characters he used are subtribal and shared by the four, now included genera. Some possible discriminatory features published by Janák (2013) or discovered during the present study are considered in the following six paragraphs.

(1) All known species of Typhloleleupius are eyeless ( Ty. doryloides , Ty. minutus , Ty. podocarpus ) or have one ommatidium ( Ty. capensis , Ty. elongatus ). Among Tripectenopus there are eyeless species ( Tr. caecus , Tr. occultus ) and species with multifaceted eyes ( Tr. microps , Tr. pectinatrix, Tr. handschini , Tr. torrensensis ). The presence, reduction, or absence of eyes is strongly correlated with the habitat and is insufficient as a generic level characteristic.

(2) The anterolateral portion of the head of Typhloleleupius has a fine temporal ridge on the side of the head that originates on the side of the supraantennal hump and extends posteriorly onto the temple. The surface below this ridge was described as a “longitudinal furrow” by Janák (2013: 82 and fig. 4; in litt., August 28, 2019). However, as the ridge is more evident than the furrow emphasis is placed on the “temporal ridge.” In dorsal view images of Ty. doryloides , Ty. minutus , and Ty. podocarpus ( Janák, 2013: figs. 9, 10, 15, 16) the temporal ridge can be seen as a black line along the lateral periphery of the head beginning near the antennal insertion. Both the type of Ty. doryloides and Typhloleleupius near minutus have a temporal ridge. An Australian species of Tripectenopus with one corneal lens has an identical, but shorter, temporal ridge. Lea (1918: 84) mentioned a feeble, oblique ridge on the side of the head of Tripectenopus caecus . Species of Tripectenopus with eyes lack a temporal ridge, which suggests it may be confined to eyeless or reduced-eye species. The presence of these ridges and grooves in species of both regions make them unsuitable generic features.

(3) The clypeal margin of males of Typhloleleupius has a small, conical, apically rounded horn mesiad of the antennal insertion ( Janák, 2013: figs. 8, 10, 14); the horn is smaller in the females ( Janák, 2013: figs. 14, 16). In the same position on the clypeus of males of Tripectenopus the horn is large ( Britton, 1974: fig. 5) or reduced to a small bump and on females a slight tumescence is present (fig. 382).

(4) According to the illustration of the labrum of Typhloleleupius doryloides ( Janák, 2013: fig. 21) the anterior margin is emarginate medially with a broad denticle on each side. Janák’s (2013) descriptions of all the species indicate a rather prominent “denticle” or “lobe” adjacent to the median emargination. In my notes for the type of Ty. doryloides , the labrum has a broad, apically rounded denticle adjacent to the median emargination. The labrum of Typhloleleupius near minutus is deeply emarginate and the anterior margin has a small boss, bump, lobe, or denticle (fig. 395), but lacks longer, larger, more apically pointed denticles. The labrum of four unidentified species of Tripectenopus and Tr. handschini (Scheerpeltz) (1935: fig. 4a) has a deeply emarginate, bilobed anterior margin (fig. 384) and none has a denticle or lobe adjacent to the emargination.

(5) The submarginal lateroventral region of the head of the type of Ty. doryloides has a furrow or groove extending from near the base of the mandible posteriorly (as in figs. 365, 366). This groove was not recorded by Fagel (1964) or Janák (2013). The groove is present in Typhloleleupius near minutus (as in figs. 365, 366). The dark shadow near the ventral edge of Janák’s (2013) figure 4 is in the correct position and was affirmed to be a furrow by Jiri Janák (in litt., September 1, 2019); Janák also reported that he has an undescribed species with a similar furrow. Among the four unidentified species of Tripectenopus the submarginal, lateroventral groove is absent from three. One species has a weak ridge with an adjacent feeble impression, one has a short, shallow, barely perceptible impression, one has neither a ridge nor impression, and the fourth has a shallow, distinct furrow passing beneath and beyond the eye.

(6) Based on the published lateral view images of the two genera, Tripectenopus ( Britton, 1974: fig. 4) and Typhloleleupius ( Janák, 2013: figs. 25, 31, 33, 46), the aedeagus appears to offer no differential characters.

In summary, I am deeply skeptical that the species of these two regions should be assigned to separate genera. Not one of the preceding characters supports recognition of two genera. Two genera are maintained here only because they are separated by about 10,400 kilometers of ocean. No morphological characters have been found to support recognition. The presence, reduction, or absence of eyes is largely habitat related. The temporal and submarginal grooves and ridges are variable and found on species in both regions. The clypeal “horns” are mere variable bumps and might not even distinguish species. The labral dentition might separate species, but in some the denticles are the slightest of “bumps.” Even in Scopaeus , a genus of many species with highly developed, large, long, apically acute denticles, includes species with lobes that are regarded denticles only by a stretch of imagination. The aedeagus offers no help.

Figures

FIG. 350–351. Proleg, left. 350. Sphaeronum sp. a. 351. Tripectenopus sp.

FIGS. 381–385. Tripectenopus spp. 381. Habitus, legs omitted. 382. Head and prothorax, legs omitted. 383. Maxillary palpus. 384. Labrum. 385. Procoxa, mesial surface.

FIGS. 386–391. Tripectenopus sp. 386–388. Labium, hypopharynx. 386. Lateral. 387. Dorsal. 388. Anterior. 389–391. Mandibles, left. 389. Dorsal. 380. Mesial. 391. Ventral.