Sphaeronina

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 : 154-160

Sphaeronina Casey

Figures 349–403

Sphaeronina Casey, 1905: 54 . [Cited as Sphaeronia; Genera included: Scopaeodes Sharp, 1876 , Sphaeronum Sharp, 1876 , cited as Sphaeronium nomen nudum]. Type genus: Sphaeronum Sharp, 1876 .

— Newton and Thayer, 1992: 61 (cited as synonym of Lathrobiina).

DIAGNOSIS. Sphaeronina can be separated from all other subtribes and genera by the wide, triangular, deep, ctenidial concavity of the protibia that has three, wide, diagonally transverse combs (figs. 350, 351), the large, heavily sclerotized, dorsally directed, basally wide, apically tapered and obtuse hypopharyngeal peg (figs. 370–372, 386–388, 397–398), the denticle arising from the ventral surface of the left mandible (figs. 374, 390–391, 400), and the groove on the outer edge of the mandibles. The hypopharyngeal peg and ventral mandibular denticle appear to be unique features. In addition to the preceding characters, the genera of the Sphaeronina are explicitly excluded from the Scopaeina by the absence of cephalic paraocular trichobothria and tripartite ligular lobes.

Although occurring elsewhere in the Paederinae , eight other homoplasic features aid recognition and support definition of the subtribe. The (1) neck is narrow, about one ninth to one sixth as wide as the head (figs. 349, 364, 381, 382, 392, 403), (2) gular sutures are confluent (fig. 403), (3) gena has a hollowed surface, (4) pronotum is ovoid (fig. 349, 355, 363, 381), (5) pronotal marginal ridge is absent, (6) probasisternum is long, moderately to strongly rounded with the surface adjacent to the procoxae slightly to moderately swollen (fig. 355, 393), (7) procoxa has a carina on the mesial surface (figs. 380, 385, 394), (8) exposed surface of the scutellum lacks or has few setae and is wide basally and notably slender apically (fig. 378), and (9) slender, acute tip of the lateroapical process of tergum IX is strongly bent dorsally (figs. 360, 379).

The head of Sphaeronum , Typhloleleupius Fagel, 1964 , and Coecoscopaeus Coiffait, 1982 , has a submarginal, postocular groove (figs. 365, 366, 403) on the lateroventral surface. Some species of Tripectenopus Lea, 1918 , have a short, feeble groove or ridge in the same position and some have only a hint of a groove or ridge or lack it entirely. The profurcasternum of Typhloleleupius , Tripectenopus , and Coecoscopaeus is long, slender, tapered posteriorly, and widely separated from the hypomeron (fig. 393), while for Sphaeronum the profurcasternum is long and wide and touches the hypomeron (fig. 355). All the genera have a deep, wide subantennal hollow on the gena between the eye and the mandibular base.

DESCRIPTION. Body length 2.7– 12 mm.

Head (figs. 349, 362, 364, 381, 392) elongate, longer than wide; lateral margin long and broadly rounded. Cephalic trichobothria absent.

Neck petiolate (figs. 362, 382); nuchal groove abruptly and strongly constricted and proximad occiput strongly enlarged; nuchal groove about one ninth to one sixth as wide as greatest width of head; nuchal groove without longitudinal carinae; nuchal ridge absent.

Gular sutures confluent (fig. 403).

Submentum with medial surface broad, flat, and delimited laterally by submarginal ridge.

Antenna not geniculate; flagellar antennomeres tending to moniliform.

Gena, between eye and mandibular base, with wide, deep subantennal hollow.

Mandibles strongly dentate (figs. 373–376, 389–391, 399–402); mandibular denticles not in dorsoventral alignment along mesial edge, arranged on two planes (see denticles on left of fig. 390); left mandible with large denticle on ventral surface (figs. 374, 390, 400) and with more denticles than right; right mandible with small to tiny denticle on ventral surface or ventral denticle absent and marked by slight tumescence.

Maxillary palpus with second palpomere gradually expanded apically; third palpomere (figs. 356, 383, 396) slightly flattened dorsoventrally and pedunculate, with slender, curved base and expanded, clavate to capitate, apically; fourth palpomere asetate and conical to nipplelike, with broad base.

Labium with first palpomere shorter than second and slightly less thick; second palpomere long and stout (figs. 370, 387, 398); third palpomere slender and without setae; mentum small and transverse (fig. 354); dorsal surface with comb of contiguous setae extending from apex of paraglossa onto and reaching base of hypopharynx; anteromedial surface with hypopharyngeal peg; hypopharyngeal peg large, strongly sclerotized, dorsally directed, with wide base and tapered apically to obtuse apex (figs. 370–372, 386–388, 397–398; tripartite, ligular lobe absent; no specimens of Coecoscopaeus available for dissection).

Prothorax ovoid and longer than wide (figs. 349, 355, 363, 382, 393); widest at anterolateral angles or near middle of lateral margin; anterolateral angle moderately to poorly developed; lateral margins gradually convergent posteriorly from middle or anterolateral angles.

Pronotal marginal ridge absent.

Probasisternum (figs. 355, 393) long and moderately to strongly rounded; surface anterior to procoxae slightly to moderately swollen; transverse prosternal carina in front of procoxae at posterior margin of acclivity; midlongitudinal ridge absent.

Length of probasisternum, measured from its anterior margin to anterior edge of procoxal cavity, greater than the distance between anterior margin of profurcasternum and posterior margin of notum.

Notosternal suture present or absent.

Prohypomeron with short to long postprocoxal lobe; hypomeronal transverse ridge present; submarginal ridge absent.

Intercoxal carina well developed, with acute, knifelike ventral edge.

Profurcasternum long, tapered posteriorly and widely separated from hypomeron (fig. 393) or long, expanded laterally, and touching hypomeron (fig. 355); apex reaching to anterior margin of mesoventrite.

Procoxal cavity open or closed.

Mesospiracular peritreme small, moderately sclerotized, separated from hypomeron and each other, and separated from or partially covered by furcasternum.

Elytral epipleural ridge absent; submarginal ridge present; posterior margin with densely to sparsely populated row of setae.

Scutellum without or with few setae; base wide, apical half slender (fig. 378).

Mesoventrite without midlongitudinal carina; mesoventrite with deep to feeble median depression; surface without ridges (fig. 368) or with remnants of prepectal, mesanapleural, and mesotransventral ridges; suture separating pteroventrites present or absent (figs. 367, 368).

Procoxa with mesial carina near base (figs. 380, 385, 394).

Protibia (figs. 350, 351) with large, triangular lobe on basal half; mesial surface of lobe deeply, broadly concave; ctenidial concavity with three, wide, diagonally transverse combs.

Profemur with large, diagonal ridge on anteroventral edge; ridge with comb of closely spaced setae on ventral edge.

Protarsomere with setae ventrally, but without densely setose pad. Protarsomere, mesotarsomere, and metatarsomere 4 not expanded beneath metatarsomere 5.

Metatibial apex with one or two apical combs.

Abdominal segments III to VII with tergum and sternum of each segment separated; segments III to VII with two pairs of lateroventrites.

Sternum II short and trilobed.

Sternum III with basal, midlongitudinal, rounded or acute carina extending posteriorly; basal transverse ridge present; sublateral carina absent.

Sternite IV without glandular opening.

Tergum IX (figs. 357, 358, 377; see Janák, 2013: figs. 41, 45, 55) with posterior margin deeply emarginate; middorsal base fused or divided; emargination occupied by tergum X; lateroapical process (figs. 360, 377, 379) tapered gradually to acute apex with apical portion slen- der and strongly (most species) to gradually curved dorsally (a few species), apical portion long (most species) to short (few species).

Tergum X (figs. 357, 358, 377; see Janák, 2013: figs. 41, 45, 55) more or less trianguloid or trapezoidal and exposed with basal margin slightly covered by IX.

Aedeagus symmetrical (fig. 356); parameres absent; basal piece absent (examined only for one species of Sphaeronum and one of Typhloleleupius ).

Segment IX (fig. 359) of female with median or lateral gonocoxal plate; “vulvar apparatus” proximad of gonocoxal plate(s) (examined only for one species of Sphaeronum and one of Typhloleleupius ).

Spermatheca not examined.

DISCUSSION. Coecoscopaeus , Tripectenopus , and Typhloleleupius , all have a tapered profurcasternum (fig. 393) widely separated from the prohypomeron, whereas Sphaeronum has a wide profurcasternum (fig. 355) contiguous with the prohypomeron. Despite that major distinction, the four genera share two characters found nowhere else and many others found in few paederine genera. The four genera share so many characters that scarcely any remain to distinguish them from each other. Unique to the subtribe is the massive, heavily sclerotized, hypopharyngeal peg (figs. 370, 386, 397) and prominent denticle arising on the ventral surface of the left mandible (figs. 374, 390, 400).

Casey (1905: 54) proposed Sphaeronina (cited as Sphaeronia) for two Neotropical genera described by Sharp (1876), Sphaeronum and Scopaeodes , with six and two species respectively, all from Brazil. Thereafter, the subtribal name was ignored for more than a century. Bernhauer and Schubert (1912: 278) and Blackwelder (1939a: 114) placed Scopaeodes among paederine genera now in the Cryptobiina. In a checklist, Blackwelder (1944: 126) included Scopaeodes in the Cryptobiina (cited as Cryptobii). There is ample support for that placement. Sphaeronum was included, without subtribal assignment, in lists of genera by Bernhauer and Schubert (1912: 276) and Blackwelder (1939a: 116). Later ( Blackwelder, 1944: 128; Blackwelder and Arnett, 1974: 76) Sphaeronum was included in the Echiasterina Casey, 1905 (cited as Echiasteres) or between Echiaster Erichson, 1839 , and Pinophilus Gravenhorst, 1802 ( Blackwelder, 1943: 374) . The name Sphaeronina (or Sphaeronia) evaporated from the literature until Newton and Thayer (1992: 61) cited it without comment as a synonym of the Lathrobiina. Twenty years later, Sphaeronum , the type genus of Sphaeronina , was again included in the Echiasterina ( Navarrete-Heredia et al., 2002: 285); the name Sphaeronina was not cited.

In the present work Sphaeronina is resurrected, redefined, and reconstituted with three genera that had been associated with or thought to be similar to Scopaeus , or listed as incertae sedis. More than 35 years ago in the AMNH collections I brought the South American Sphaeronum and Australian Scopaeodracus Scheerpeltz together in the Sphaeronina . In 2007 after briefly examining undissected paratypes of the type species of the African Typhloleleupius I concluded that it and Scopaeodracus were probably synonyms because they shared so many characters, and no obvious features separated them. However, my tentative identification of Scopaeodracus was based on Scheerpeltz’s (1935) description; I had and have seen neither type material of the taxon nor reliably identified specimens. Until the present work I had seen no specimens of Tripectenopus or Coecoscopaeus .

Since Al Newton had collected in South Africa and Australia, I wrote to him seeking specimens of Coecoscopaeus , Scopaeodracus , Typhloleleupius , and Tripectenopus . He responded by lending seven specimens of an unnamed species of Typhloleleupius and a specimen of each of two species of Tripectenopus , and by generously providing a list of Australian species originally assigned to Domene that belonged in Tripectenopus . In this work these transfers are based on his examination of the relevant types. Britton (1974: 87) suggested Tripectenopus and Typhloleleupius might be synonyms. Newton (in litt., June 27, 2009) considered Tripectenopus and Scopaeodracus to be synonyms. Although Newton did not know Coecoscopaeus, Frisch did. He had borrowed a syntype of the only known species and helped arrange a loan of that specimen to me. Once able to study specimens of Coecoscopaeus , Tripectenopus , and Typhloleleupius , I was astonished by the remarkable number of characters shared with Scopaeodracus and Sphaeronum and the overall similarity of appearance of the five genera. That discovery and the availability of relevant examples of the five genera lead me to explore their morphology to try to determine their subtribal affiliation.

Although no reasons, no characters, were offered to support moving Sphaeronum to Echiasterina ( Blackwelder, 1944: 128; Blackwelder and Arnett, 1974: 76) the assignment may have been based on the laterally expanded profurcasternum that touched the hypomeron, a feature typical of genera of Echiasterina. However, the profurcasternum is enlarged and touches the prohypomeron in, for example, Astenus , Brachynetes , Cephalochaetus , Haplonazeris , Nazeris , Pachymedon , Sunesta , and, along with other genera of the Astenina and Stilicopsina , as well as some species of Rugilus . So, although a wide, hypomeron-contiguous profurcasternum is a useful apomorphy, it is homoplasic and alone insufficient for generic placement. Sphaeronum is excluded from Echiasterina because the labrum in that subtribe is strongly dentate and has a ridge across the base, and the third and fourth maxillary palpomeres are fusiform and acicular respectively. Sphaeronum lacks the preceding features. Furthermore, the Echiasterina differs from the Sphaeronina as follows: the outer surface of the mandibles lacks a groove, the left mandible lacks a ventral denticle, the hypopharyngeal peg is absent, the anterior margin of the hypopharynx has a row of small, spinelike setae, the two protibial ctenidia or combs are arranged longitudinally, the protibia lacks the enlarged ctenidial concavity, and the anterior portion of the probasisternum is short and wide.

Coecoscopaeus , Scopaeodracus , Sphaeronum , Tripectenopus , and Typhloleleupius comprise a clade, a hypothesis of a monophyletic group, a subtribal taxon supported by characters stated above in the Diagnosis. Most of those characters are homoplasic in the Paederinae except for the hypopharyngeal peg, ventral denticle of the left mandible, and form of the scutellum. The defining characters presented in the diagnosis are discussed in the following paragraphs. Although some are homoplasic they, nonetheless, help to define the group.

LABIUM: The hypopharyngeal peg (fig. 397, 398) is unique in the Paederinae . I have seen it in none of approximately 150 disarticulated paederine genera. Among the Lathrobiina some genera (for example Acalophaena , Achenium , Domene , Lathrobium , Lobrathium , Pseudolathra , Throbalium , and scattered among a few genera of other subtribes) have, near the anterior margin of the hypopharynx, a minute, apically acute, anterodorsally directed spine. It is unclear whether this spine has anything to do with the hypopharyngeal peg of Sphaeronina . Is it a precursor or does it just happen to be in roughly the same position? For Sphaeronina a specimen of one species of Sphaeronum , Tripectenopus , and Typhloleleupius , was dissected. For Coecoscopaeus coecus I examined only one syntype and could neither dissect nor move the mouthparts nor was I unable to see dorsal structures on the labium. However, the left mandible of C. coecus has a large ventral denticle; on the strength of the unique mandibular character the genus is included in the Sphaeronina . That placement is supported by the homoplasic characters cited in the diagnosis for the subtribe.

MANDIBLES: A denticle originating on the ventral surface in the Sphaeronina appears to be unique in the Paederinae . All but one of the denticles of the mandibles of the Sphaeronina are on the medial edge where they are slightly out of alignment (fig. 390). The left mandible of Coecoscopaeus , Sphaeronum , Tripectenopus , and Typhloleleupius has a large denticle originating on the ventral surface (figs. 389–391). The right mandible may or may not have a small denticle or bump arising from the ventral surface. The outer margin of both mandibles of the sphaeronine genera has a groove that begins near the base and extends toward the mandibular apex. The mandibular denticles of the mesial edge of most paederines are aligned with the medial edge of the mandible; for some few, the denticles are only slightly out of alignment with the medial edge (see, e.g., Astenus , Echiaster , Ecitocleptis , Nazeris , Pinophilinus , Scopaeodes , Serrolabis , Throbalium , etc.); none were found with a denticle arising from the ventral surface. For most other genera the outer surface of the mandibles lacks a well-defined groove. Some genera have a feeble to shallow groove on the outer surface (e.g., Achenomorphus , Charichirus , Deroderus , Dolicaon , Eustilicus , Medon , Pseudolathra , Scopobium , Scymbalium , Serrolabis , Stilicoderus , Rugilus ), but none of those examined have the deep, well developed groove featured in Sphaeronina .

NECK: The neck of genera of Sphaeronina is about a ninth to a sixth as wide as the head (figs. 349, 382). A modest number of paederine genera have a slender neck. If a slender neck is defined as less than a fourth as wide as the head this feature occurs in the subtribes Astenina , Cryptobiina, Echiasterina, Medonina , Scopaeina, and Stilicina in, for example, such genera as Acanthoglossa , Echiaster , Eustilicus , Opithes , Panscopaeus , Ronetus , Rugilus , Scopaeodes , Scopaeus , Stilicastenus , Stilomedon , etc. Although not unique, it clearly supports the definition of Sphaeronina .

GULAR SUTURES: The gular sutures are confluent along their entire length in the Sphaeronina (fig. 403). This homoplasic condition is widely scattered in the subfamily. The species of Domene (Spelaeomene) and Domene (Canariomene) have partly confluent gular sutures. Among other paederine entirely or partially confluent gular sutures are found in the Astenina , Cryptobiina, Echiasterina, Procirrina , Stilicina, and Stilicopsina . Example genera with confluent gular sutures include: Astenus , Bolbophites , Brachynetes , Deroderus , Dibelonetes , Dibelophacis , Echiaster , Ecitonides , Eurysunius , Eustilicus , Haplonazeris , Megastilicus , Mimophites , Monocrypta , Myrmecosaurus , Nazeris , Ophitodum , Ophryomedon , Procirrus , Ronetus , Rugilus , Stamnoderus , Stilicoderus , Stilicopsis , Stiliphacis , Stilosaurus , Sunesta , and Synecitonides .

PROTHORAX: The probasisternum (figs. 355, 393) of the genera of Sphaeronina lacks a midlongitudinal ridge and is notably long, strongly rounded transversely and, for all but Coecoscopaeus , swollen near the procoxae. The probasisternum among other paederines is short, flat, or slightly rounded transversely, and may or may not have a midlongitudinal ridge. The probasisternum of genera of the Sphaeronina (fig. 393) is distinctly longer than in other paederines (figs. 98, 345; also see Acanthoglossa , Astenus , Domene , Echiaster , Neolindus ; Neomedon , Ochthephilum , Oedichirus , Paederus , Pinobius , Pinophilus , Rugilus , Stilicopsis , and many others).

The pronotum of Sphaeronina lacks a pronotal marginal ridge. This homoplasic character is scattered throughout the Paederinae and found in some genera of most subtribes. Examples of a few genera in which all or some species lack the ridge are Astenus , Chetocephalus , Echiaster, Monista , Orus , Paederus , Procirrus , Rugilus , Scopaeus and Stilicopsis .

PROCOXA: The base of the procoxa has a small, transverse carina on the mesial surface. This carina seems to conveniently fit under the lateral edge of the long, tapered basisternum/furcasternum. I have seen this feature elsewhere in the Paederinae and have wondered if it was a means of stabilizing coxal rotation when the leg is in use.

PROTIBIA: Protibial grooming combs and, opposite it, a femoral ridge with a comb, are characteristic of the Paederinae . In the subfamily, the protibial ctenidia or combs are arranged across (see, e.g., Astenus , Dolicaon , Domene , Homaeotarsus , Lobrathium , Micrillus , Paederus , Pinophilus , Procirrus , Rugilus , and many others) or extend along most of the length (a few examples: Cephalochaetus , Echiaster , Eustilicus , Neolindus , Pseudastenus , Ronetus , Stamnoderus , Stilicopsis , Stilomedon , and many others) of the protibia. For most genera with transverse combs the depression is slight to moderate; species with longitudinal protibial combs lack or have a feeble to weak depression; some genera lack a ctenidial depression (see, for example, most genera of the Cryptobiina, also Dacnochilus , Paederus , Neolindus , etc.) and the combs are on the unmodified surface. For most species the depression is feeble to shallow to moderately deep and the tibia is not expanded or is slightly to moderately enlarged in the vicinity of the combs. Among the subtribes the range of variation of the transverse protibial grooming combs is greatest in the Lathrobiina. The protibial grooming structure is particularly notable for Domene where, perhaps, all the species have a large, deep, protibial, ctenidial concavity. I have examined specimens of only 13 of the 86 species and protibial illustrations for perhaps a dozen more (see illustrations in: Peyerimhoff, 1949: 82; Español, 1970: 371; 1972: 52; Outerelo, 1985: 105; Oromí and Hernández, 1986: 131, 137; Hernández and Medina, 1990: 289, 291; Salgado and Outerelo, 1991: 211; Wunderle, 1992: 147; Hernández and Oromí, 1993: 67; Hernando and Comas, 2014: 106; and Serrano et al., 2015: 405). The protibia of all of them has an enlarged, deep, ctenidial concavity that is presumably characteristic of the genus. Outside of Domene the only other paederine taxa with the dramatically wide, deep, “scooped-out,” ctenidial concavity of the protibia are the genera of Sphaeronina (figs. 350, 351; Scheerpeltz, 1935: 641; Britton, 1974: 86). This homoplasic feature is one of the defining traits of the Sphaeronina and suggests possible affinity between it and elements of the Lathrobiina, a poorly defined subtribe in serious need of careful morphological study.

SCUTELLUM: The exposed dorsal surface of the scutellum of Sphaeronina is wide basally; the lateral margins are sinuate, then abruptly constricted at about the apical third to form a tapered lobe apically (fig. 378; see Britton, 1974: fig. 2). This configuration does not seem to occur in other genera of the subfamily. The scutellum of species in most other genera is wide to moderately wide gradually tapering to the apex.

Domene: Few of the 86 valid species currently included in Domene (extracted from my unpublished catalog of the Paederinae ) were available for study; among those available each was represented by only a couple of specimens of which only one could be dissected. That deficit has prevented proposing a suitable definition of the genus. Only two specimens of one species of Domene (Canariomene) jonayi Hernández and Medina, 1990 , were available for study, but not dissection. No examples of Domene (Spelaeomene) or Domene (Lobramene) were available. Few species and few specimens of Domene (Lathromene) were examined. Only one male and female of Domene (Domene) scabricollis Erichson, 1840 , could be dissected. That species lacks the hypopharyngeal peg and the ventral denticle of the left mandible and is omitted from Sphaeronina . There exists the potential that one or more species currently assigned to Domene might belong in Sphaeronina . That possibility awaits availability of material for dissection.

GENERA INCLUDED: Coecoscopaeus Coiffait, 1982 , Sphaeronum Sharp, 1876 , Tripectenopus Lea, 1918 , and Typhloleleupius Fagel, 1964 .

Figures

FIG. 349. Sphaeronum pallidum. Habitus.

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

FIGS. 352–361. Sphaeronum sp. c. 352. Labrum. 353. Maxillary palpus. 354. Labium, ventral. 355. Prothorax. 356. Aedeagus, dorsal. 357. Tergites IX, X, male. 358. Tergites IX, X, female. 359. Genital segments, ventral,

FIGS. 362–369. Sphaeronum spp. a, b, c. 362. Head. 363. Pronotum. 364. Head. 365. Head, left lateral. 366. Head, enlarged, left lateral. 367. Metaventrite, anterior with posterior mesoventrite. 368. Mesoventrite and anterior metaventrite. 369. Metaventrite, posterior.

FIGS. 370–376. Sphaeronum sp. c. 370–372. Labium, hypopharynx. 370. Lateral. 371. Anterior. 372. Dorsal. 373–376. Mandibles. 373. Ventral, right. 374. Ventral, left. 375. Dorsal, left. 376. Dorsal, right.

FIGS. 377–380. Sphaeronum. sp. c. 377. Tergites IX, X, male. 378. Scutellum, female. 379. Tergite IX, lateroapical process, lateral, female. 380. Procoxa, dorsal end, male.

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.

FIGS. 392–396. Typhloleleupius. 392. T. doryloides, right proleg omitted. 393–396. T. nr. minutus. 393. Prothorax. 394. Procoxa, anteromesial. 395. Labrum. 396. Maxillary palpus, fourth palpomere missing.

FIGS. 397–402. Typhloleleupius nr. minutus. 397–398. Labium, hypopharynx. 397. Lateral. 398. Anterior. 399–402. Mandibles.

FIG. 403. Typhloleleupius nr. minutus. Head, ventral.