Sclerocoelus bucki Kuwahara, Marshall & Paiero, 2025, sp. nov.
Creators: name: Kuwahara, Gregory K.
name: Marshall, Stephen A.
name: Paiero, Steven M.
Publisher: name: Zenodo
Year: 2025
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Diptera
Sphaeroceridae
Sclerocoelus
Sclerocoelus bucki

description: Sclerocoelus bucki sp. nov.
urn:lsid:zoobank.org:act: 58504FAC-2EF1-4C5D-B489-CBE2693CFED4
Figs 5G, 26–28
Etymology
This name is in honour of Dr Matthias Buck, an esteemed colleague with whom field trips to Ecuador and Costa Rica yielded the type of this and other Sclerocoelus species.
Material examined
Holotype
COSTA RICA • ♂; Cartago, Tapantí National Park; 1550 m a.s.l.; 7–12 Oct. 1999; Marshall and Buck leg.; pans in fallen tree; MNCR debu00107951.
Paratypes
BOLIVIA – La Paz • 3 ♂♂; 23 km NE of Caranavi; 14 Apr. 2001; S.A. Marshall leg.; roadside/stream sweep; CBFC • 1 ♂; Zongo; 16°06′32″ S, 68°04′30″ W; 18 Apr. 2001; S.A. Marshall leg.; roadside, sweep cut foliage; DEBU.
COSTA RICA – Cartago • 1 ♂; same data as for holotype; MNCR • 1 ♂; Tapantí National Park, La Esperanza del Guarco; 17–18 Aug. 2001; S.A. Marshall leg.; DEBU • 1 ♂; Tapantí National Park, near Catarata trail; 1450 m a.s.l.; 4 Oct. 1999; S.A. Marshall leg.; roadside, sweeping leaf litter; DEBU. – Heredia • 1 ♀; 6 km ENE of Vara Blanca; 10°11′ N, 84°07′ W; 2000 m a.s.l.; 11 Mar. 2002; MNCR • 3 ♂♂; Moravia, near border of Braulio Carrillo National Park; 3–4 Mar. 1996; L. Masner leg.; creek bed, yellow pans; MNCR.
ECUADOR – Napo • 1 ♂; SierrAzul Lodge, 14 km W of Cosanga; 5 Nov. 1999; S.A. Marshall leg.; QCAZ. – Pichincha • 3 ♂♂; 7 km SE of Nanegalito, trout farm ‘San Jose’; 1500 m a.s.l.; 27–30 Oct. 1999; S.A. Marshall leg.; riverine forest, sweeping treefalls; QCAZ • 2 ♂♂; Bellavista Cloud Forest Reserve; 0°01′13″ S, 78°40′30″ W; 2200 m a.s.l.; 1 May 2011; S.A. Marshall leg.; pans near treefall; DEBU • 3 ♂♂, 1 ♀; Bellavista Reserve; 0°00′54″ S, 78°40′56″ W; 2200 m a.s.l.; 1 May 2011; S.A. Marshall leg.; treefall; QCAZ • 1 ♂; Bellavista Reserve; 0°01′13″ S, 78°40′30″ W; 2200 m a.s.l.; 9–13 May 2009; S.A. Marshall leg.; DEBU.
PERU – Cusco • 9 ♂♂, 12 ♀♀; Cock-of-the-Rock Lodge, NE Paucartambo; 13°03′18″ S, 71°32′42″ W; 1120 m a.s.l.; 4–9 Nov. 2007; D. Brzoska leg.; flight-intercept trap; DEBU • 5 ♂♂, 7 ♀♀; same data as for preceding; MUSM • 2 ♂♂, 3 ♀♀; Wayqecha Biological Station, ~ 9 km NE of Challabamba; 13°10′ S, 71°35′ W; 2800 m a.s.l.; 13–15 May 2007; S.A. Marshall leg.; MUSM. – Junín • 1 ♂; Pampa Hermosa Lodge, 22 km N of San Ramon; 10°59′18″ S, 75°25′30″ W; 1220 m a.s.l.; 24–27 Nov. 2007; D. Brzoska leg.; flight-intercept trap; DEBU.
Description
BODY (Fig. 26A). Length 2.6–3.9 mm. Head dark brown, lower third of frons, frontal vitta, and gena orange; face and antennae orange-brown. Frontal width 2.2–2.3× frontal height. Three pairs of strong interfrontal bristles surmounting a very fine fourth pair; anterior orbital 0.4–0.5× length of posterior. Palpus yellow. Eye large, greatest height about 4.0× shortest genal height. Thorax dark brown, scutum with paler lateral edges. Two pairs of dorsocentral bristles (anterior pair distinct, 0.5× length of posterior pair) separated by 6–7 rows of acrostichal setulae. Membrane around prosternum bare. Legs brown, fore and hind tibiae darker. Fore femur with 3–4 large ventral preapical setae. Ventral surface of male mid tibia with two rows of stout setae in apical third. Wing (Fig. 5G) moderately infuscate. CS2 subequal to CS3. Halter brown.
MALE ABDOMEN (Figs 26B–C, 27). Dark brown, posterior edges of tergites sometimes slightly desclerotized. T2–5 and S2–4 uniformly long-setose with large posterolateral setae. S5 rectangular, 1.2× length of S4, posterolaterally long-setose with a short, dark, posteromedial patch of dense setulae flanked by posterior rows of setae. Anterior flange of S6+7 small, 1.3× as long as wide. Sclerite A large, posteriorly deeply cleft and densely setulose; sclerites B dark, arched; sclerite C absent; sclerite D small, dark, triangular, articulating with sclerite E; sclerite E large, dark, rectangular, and densely setulose posteriorly; sclerite F elongate, articulating with right posterior edge of S5; sclerite G elongate, narrow; ring sclerite small but well sclerotized. Epandrium small, 0.3× length of S8, height 1.5× maximum length and 0.8 × maximum width, long-setose, posteroventral corner slightly emarginate; anal fissure rounded; perianal pads weakly developed. Pseudocercus absent; halves of subepandrial sclerite very gently curved and medially fused. Subcercus very large, subtriangular in posterior view and rectangular in lateral view, ventral half concave, posterior surface setulose with a small preapical lobe. Hypandrium with long, sinuate anteromedial apodeme. Surstylus stout, subtriangular, basal two-thirds bulging and laterally setose, apical third flattened and blade-like, in line with inner surface of basal part. Postgonite unusually long, longer than distiphallus, very broad, apex truncate with a small anterolateral lobe. Phallapodeme long, sinuate; basiphallus inverted L-shaped, bent at almost a right angle; distiphallus short, largely membranous with a flattened dorsal sclerite and a pair of sinuate ventrolateral sclerites.
FEMALE ABDOMEN (Fig. 28). T7 broad, simple; T8 entire but dorsally desclerotized, giving the appearance of two lateral sclerites, posterolateral corners slightly expanded posteriorly. Epiproct broad but short, posteromedially cleft, and setulose in posterior half. Cercus short, apically pointed with long apical and dorsal setae. S7 broad, posteromedially pointed with four large posterior setae; S8 entirely membranous/ absent. Three spermathecae, bulb elongate, cylindrical, very finely striate with deep invaginations on both ends (basal invagination deeper than apical, ends meeting but separate).
Distribution
Neotropical: Bolivia, Costa Rica, Ecuador, Peru.
Remarks
The very large and simple subcerci, distinct from the narrow but complete subanal plate, are distinctive of Sclerocoelus bucki sp. nov.; other identifying characters of S. bucki include the densely setulose, bilobed genital pouch sclerite A, posteriorly densely setulose sclerite F, and very broad postgonite. Although Sclerocoelus bucki ranges from Bolivia north to Costa Rica, most records are from the South American Andes, where we have repeatedly collected it by sweeping over green leaf litter or pan trapping below the still-green foliage of fallen trees. The clade of five species (S. altus sp. nov., S. bucki, S. lazulita sp. nov., S. penai sp. nov., and S. xynos sp. nov.) to which S. bucki belongs is almost entirely Andean and is generally associated with wet plant material in cloud forest or alpine habitats.
description: Published as part of Kuwahara, Gregory K., Marshall, Stephen A. & Paiero, Steven M., 2025, A revision of the genus Sclerocoelus Marshall (Diptera: Sphaeroceridae), pp. 1-277 in European Journal of Taxonomy 979 on pages 33-34, DOI: 10.5852/ejt.2025.979.2803, http://zenodo.org/record/14980852