Sphaeronum Sharp

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 : 161-167

publication ID	https://doi.org/ 10.1206/0003-0090.460.1.1
persistent identifier	https://treatment.plazi.org/id/FA4F87B1-E1B1-FF5D-0A1A-C21BFE0DF966
treatment provided by	Felipe
scientific name	Sphaeronum Sharp
status

Treatment

Sphaeronum Sharp View in CoL

Figures 349 View FIG , 350 View FIG , 352–380 View FIGS View FIGS View FIGS View FIGS

Sphaeronum Sharp, 1876: 224 View in CoL (species included: opacum View in CoL , depressifrons View in CoL , carinifrons View in CoL , elongatum View in CoL , carinicolle View in CoL , pallidum View in CoL ). Type species: Sphaeronum pallidum Sharp View in CoL , fixed by Casey (1905: 55) by subsequent designation.

— Duvivier, 1883: 167 (catalog). — Casey, 1905: 55 (characters). — Bernhauer and Schubert, 1912: 276 (catalog). — Blackwelder, 1939a: 101, 116, 121 (key; checklist; type species). — Blackwelder, 1943: 231, 374 (key; characters; type species). — Blackwelder, 1944: 128 (checklist of species, Latin America).

— Blackwelder, 1952: 355 (type species).

— Blackwelder and Arnett, 1974: 76 (checklist; North America; Central America; West Indies). — Navarrete-Heredia, Newton, Thayer, Ashe, and Chandler, 2002: 285 (characters in key to genera for Mexico; general notes; unnamed species in Mexico).

Sphaerinum Sharp, 1876: 36 View in CoL , 224 (Nomen nudum. See discussion below under “Synonymy”).

— Blackwelder, 1943: 374 (synonym of Sphaeronum View in CoL ). — Blackwelder, 1952: 355 (synonym of Sphaeronum View in CoL ; type species).

— Blackwelder and Arnett, 1974: 76 (synonym of Sphaeronum ).

DIAGNOSIS: The head of most species of Sphaeronum has a rectangulate “basal extension” of the posterior margin; the extension is small (fig. 364) to moderately large (fig. 362) to large, easily separating the genus from all other Sphaeronina . A few species of the genus lack the extension.

Sphaeronum also can be separated from Tripectenopus and Typhloleleupius by the presence of the mesial, apical, metatibial comb and the short, medially bent postprocoxal lobe. The profurcasternum of Sphaeronum is expanded and contiguous with the prohypomeron (fig. 355). With these characters the species of Sphaeronum that lack the basal cephalic extension can be distinguished from other sphaeronines. Tripectenopus and Typhloleleupius both have two apical, metatibial combs, a deep depression with a midlongitudinal furrow on the mesoventral basisternum, and a nearly vertical postprocoxal lobe. The profurcasternum of both Tripectenopus and Typhloleleupius (fig. 393) is wide basally, tapers posteriorly, and is well separated from and does not touch the hypomeron. Species of Sphaeronum have a prominent, submarginal, subocular groove on the lateroventral margin of the head that extends from the hypostomal ridge (figs. 365, 366), near the base of the mandibles, to the neck. Typhloleleupius has a lateroventral, submarginal, cephalic groove that is less strongly developed than for Sphaeronum . Some species of Tripectenopus lack the submarginal groove and some have a short, shallow, poorly developed groove and others have a modest ridge in the same vicinity. The eyes of Sphaeronum lack setae, whereas the eyes are setate for species of Tripectenopus with multifaceted eyes.

The Neotropical Sphaeronum is separated from the North African Coecoscopaeus by the short, medially bent postprocoxal lobe and the wide, laterally expanded, profurcasternum that touches the prohypomeron. Although most species of Sphaeronum have a cephalic extension, at least two do not, nor does Coecoscopaeus . The neck of Sphaeronum of species with the cephalic basal extension is attached to the ventral surface, just below the posterior margin (fig. 365). The neck of Coecoscopaeus is attached to the midhorizonal plane of the posterior margin of the head.

DESCRIPTION: Body length 2.7– 12 mm.

Head (figs. 362, 364) with lateral margin gradually rounded to basal angle or cephalic basal extension; basal angle broadly to strongly rounded or absent and head gradually tapered to cephalic basal extension; basal margin slightly emarginate or with wide, medial, apically truncate, cephalic basal extension; species with emarginate basal margin with slight to moderate medial swelling in place of basal extension.

Cephalic basal extension (figs. 362, 364, 365) present or absent; basal extension wide to moderately wide and with long to short, straight to emarginate lateral margin; dorsal edge of lateral margin carinate or rounded; posterolateral angle tumescent; surface with middorsal carina or tumescence.

Lateroventral surface of head with deep, narrow, submarginal, subocular groove extending posteriorly from hypostomal ridge near base of mandible to posterior margin of head and to neck.

Dorsal surface (fig. 362, 364) with moderately dense to dense, fine to coarse punctation; midline with or without punctation or partially punctate; microsculpturing feeble and sparse or absent; pubescence moderately dense to dense.

Clypeal margin (fig. 362) without or with small bump or tumescence mesiad of supraantennal hump.

Eyes present and with many ommatidia; eyes without setae.

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

Maxillary palpomere four (fig. 353) small, nipple shaped, broad basally then strongly tapered and short, compressed, truncate apically.

Labrum (fig. 352) with anterior margin truncate and with abrupt median emargination or broadly emarginate and emargination beginning near lateral margin and continuing to middle; anterior margin with or without lobe like denticle.

Prothorax with length about twice width.

Pronotum (fig. 363) with simple, fine to coarse punctation; punctation moderately dense to dense, more or less uniform, but absent from midline; microsculpturing present, strong and dense to sparse and weaker, or absent; surface with low, midlongitudinal ridge from near base extending anteriorly for half to two thirds of length; ridge without punctation and with or without fine median groove.

Notosternal suture absent (fig. 355) or represented by faint, feeble ridge or narrow, shiny strip or disruption of microsculpturing; remnant of suture present as short groove extending posteriorly from lateroventral edge of anterior margin of probasisternum.

Prohypomeron with anterior surface sparsely to densely and finely to coarsely punctate; postprocoxal lobe short, acute apically, pubescence sparse to dense or absent, and strongly bent medially and leaning toward profurcasternum; prohypomeronal transverse ridge strongly developed and bordered dorsally by distinct hypomeronal groove; submarginal ridge absent.

Profurcasternum (fig. 355) broad, extending to and touching, but not fused to hypomeron; profurcasternal intercoxal keel extending beyond posterior margin as tricarinate, apically acute lobe.

Procoxal cavity (fig. 355) closed posteriorly by expanded profurcasternum.

Elytra shorter than or subequal to pronotum.

Mesoventral basisternum (fig. 368) without midlongitudinal carina; surface with shallow to barely discernible median depression.

Metaventrite (fig. 367) with mesopericoxal ridge present laterally; metakatepisternal processes (fig. 369) short and rounded apically.

Meso-metaventral junction absent or possibly evident as slightly pale diagonal strips (figs. 367, 368).

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 side.

Tergum VIII with palisade fringe on posterior margin.

Tergite IX with lateroapical process sharply (figs. 360, 379) to gradually bent dorsally.

female. 360. Tergites IX, X, lateral. 361. Sternite IX, male.

MALE: Tergum IX of male with middorsal base divided (figs. 357, 377).

Sternite IX (fig. 361) of male triangular with emargination of posterior margin.

Aedeagus (in ventral view) oval, symmetrical, with ventral process; parameres absent; basal piece absent.

FEMALE: Tergite IX (fig. 358) of female with middorsal base fused; median gonocoxal plate (fig. 359) triangular and apical margin with narrow notch.

Spermatheca not examined.

DISTRIBUTION AND HABITAT: Sphaeronum is known from Paraguay and Bolivia north to Mexico and Cuba. Most specimens examined and six of the seven described species are from Brazil, one is from Cuba. I have examined unidentified specimens from Bolivia, Peru, Venezuela, and Mexico. It is possible the genus will be found in the northern provinces of Argentina from Misiones to Salta and Jujuy.

The species seem to be infrequently collected. Of the six Brazilian species described by Sharp (1876: 225–229), four were based on one specimen each, one on two specimens, and the sixth on 10 specimens; the Cuban species was also based on one specimen ( Blackwelder, 1943: 375). For none of the described species was the collecting habitat stated. Nearly all the specimens for which collecting data were available were taken at lights. One specimen was taken in “human dung” ( Brazil), another from forest floor litter ( Brazil), and a third from a rotten fig ( Peru). The paucity of specimens and dearth of habitat information may hamper discovery of new specimens .

NOMENCLATURE: In the first of his two-part work on the Staphylinidae of the Amazonian Valley, Sharp (1876: 36) proposed Sphaerinum for six species but described neither the genus nor species. Had at least one of the species been characterized, Sphaerinum would have been an available name ( ICZN, 1999: Article 12.2.5). In the second part Sharp (1876: 224–229) described the seven taxa, including the genus, abandoned the name Sphaerinum and replaced it with Sphaeronum because he erroneously decided the former was preoccupied by Sphaerina Erichson. Sharp (1876: 224) cited Sphaerinum as a synonym of Sphaeronum , but neither use of the former made it available.

DISCUSSION: Only seven named species are named in the genus, but among the rather limited material I’ve examined are at least several more undescribed ones. Most of these specimens were collected at lights and, as seems commonly the case, most are females. For several species no males are represented among the samples.

The cephalic “basal extension” of most species is large and prominent with a strongly developed midlongitudinal carina or tumescence. Two species lack the cephalic extension, for one there is a tumescence in its place, and for a few the cephalic extension is distinct, but short. The carina of the lateral edge is absent in some species, the median carina is a tumescence in some and absent in a few. All the species have a postocular (or slightly subocular), lateroventral, submarginal, cephalic groove that extends the length of the head from the eye. The neck (fig. 365) is attached just below the dorsal edge of the posterior margin of the cephalic basal extension so the nuchal groove is covered and can be viewed only by tilting the head downward. The neck of those without the extension is attached normally.

Some species have a supraocular groove that extends to just beyond the posterior margin of the eye and in one the groove reaches nearly to the base of the head; the ridge along the ventral edge of the groove reaches the neck in all species examined. The postprocoxal lobe of Sphaeronum is one of the shortest I’ve seen in the entire subfamily. Sharp (1876: 225, fn.) observed the ligula appeared to be “entirely corneous” but was unsure about that because the structure had become distorted during dissection. He may have seen the ventral surface of the hypopharyngeal peg, which, until now, was not used or mentioned again.