Leptocera argentinica, Buck & Marshall, 2009

Buck, Matthias & Marshall, Stephen A., 2009, Revision of New World Leptocera Olivier (Diptera, Sphaeroceridae), Zootaxa 2039 (1), pp. 1-139 : 20-22

Leptocera caenosa species group

Species included. L. aequilimbata Duda , L. argentinica sp.n., L. caenosa (Rondani) , L. erratica sp.n., L. erythrocera (Becker) , L. gongylotheca sp.n., L. longilimbata sp.n., L. mendozana Richards , L. neocurvinervis Richards , L. papallacta sp.n., L. sphaerotheca sp.n. The L. cultellipennis subgroup includes: L. cultellipennis (Enderlein) , L. duplicata Richards , L. ellipsipennis Richards , L. parallelipennis sp.n.

Description. Body length 1.3–4.6 mm. Body usually entirely medium to dark brown; in some species with parts of face, gena, antenna, palpus, and legs yellowish brown. Wing greyish hyaline to distinctly infuscated. Halter pale brown, apical part of knob whitish to pale brown. Anterior orbital bristle only a little shorter (ca. 0.8x) than posterior one. Usually with 1(–4) additional orbital setulae between upper orbital and inner vertical bristle (absent in L. cultellipennis subgroup); these setulae exclinate except for uppermost one which is inclinate and proclinate in some species. Palpus usually slender, inflated in two species. Arista shortto long-pubescent ( Figs. 4–6 ). Bristles of thoracic scutum well developed: Scutum with 5(–8) (rarely four) dorsocentral bristles, anterior one variable (hardly longer than surrounding hairs to strong and well developed). At least two pairs of acrostichals slightly to strongly enlarged; prescutellar acrostichals also enlarged. Bristles of posthumeral series and presutural supra-alars more or less enlarged as well. R 4+5 strongly to moderately curved up to costa. Fore tarsus with apical tarsomeres usually wider in male than in female. Mid tibia with posteroapical bristles usually short (ventral one very long in L. sphaerotheca sp.n.), ventral one absent in most species of L. cultellipennis subgroup.

Male terminalia: Sternite 5 posteriorly usually with a row of 3–15 enlarged, elongate scales (e.g., Figs. 65 , 72 ). Sternite 8 completely fused to epandrium. Male cercus developed as small, weakly sclerotized, hairy tubercle, often bearing inconspicuous, finger-like or lamellate medial processes (e.g., Fig. 95 ).

Female terminalia: Tergite 7 longer than in other species groups (i.e., at least as long as fused tergite 10 + cerci), in most species also longitudinally convex, and often with a narrow shining medial stripe (e.g., Fig. 73 ). Hind margin of sternite 7 straight. Cerci completely fused to tergite 10, the resulting plate weakly sclerotized, small and without long hairs. Spermathecae usually elongate with dilated apical portion (e.g., Figs. 43 , 53 ; spherical in two species), with bumpy or striate surface structure, spicules restricted to base.

Taxonomy. Despite their fairly uniform habitus, members of the L. caenosa group provide more external characters of diagnostic value than other New World species groups. Taxonomically important are: mid tibia chaetotaxy (especially distal and posteroapical bristles), pruinosity of scutum, width of palpus, length of pubescence of arista, coloration of frons and in brachypterous species ( L. cultellipennis subgroup) position of dorsocentral bristles and shape/venation of wing remnant. In the male terminalia the armature of sternite 5 and the shape of surstylus and cercus are distinctive. Characters of diagnostic value in the female terminalia include the shape, pruinosity and chaetotaxy of tergite 7 as well as the hind margin of sternite 7 (simple vs. thickened and shining). The species of two pairs of sibling species are separated mainly or exclusively based on the shape of the spermatheca.

Biogeography. A New World group that includes two widespread species ( L. caenosa and L. erratica sp.n.). The clade clearly originated in Andean/south-temperate South America where most of its species occur. The monophyletic L. cultellipennis subgroup is restricted to the Juan Fernández Islands. Among the mainland species only L. sphaerotheca sp.n. does not occur in South America. Within the New World the most widespread species of the L. caenosa group (and of the whole genus) is L. erythrocera , which occurs through most of North, Central and South America and the Caribbean.

Phylogeny. The L. caenosa group is newly established for a speciose clade of New World species, but this group is not as strongly supported as some of the other species groups. Putative synapomorphies include the presence of 1(–4) orbital setulae between the upper orbital and the inner vertical bristle (reversal: absent in L. cultellipennis subgroup), a relatively long female tergite 7, and spermathecae with bumpy surface structure (reversal to finely striate in L. neocurvinervis , L. aequilimbata and L. cultellipennis subgroup excluding L. parallelipennis sp.n.). Another possible synapomorphy is the fusion of sternite 8 and epandrium (shared with L. fulva group).

Biology and habitat. Only the biology of the widespread L. caenosa is known. The larvae of this species develop in a wide variety of decaying substrates (mostly carrion and excrement: Buck, 1997; Amendt et al., 2000; Bourel et al., 2004), usually in dark situations such as mammal burrows, caves, wasp nests, buried carrion and similar synanthropic habitats (basements, urinals, outhouses, septic tanks, sewage filter beds, food processing plants) ( Richards, 1930; Duda, 1938; Hackman, 1963; Fredeen & Taylor, 1964; Zuska & Laštovska, 1969; Papp, 1974; Learner, 2000). Most biological references for L. fontinalis from the New World (e.g., Howard, 1900; Usinger & Kellen, 1955; Kilpatrick & Schoof, 1957; Walker, 1957; Reed, 1958; Johnson, 1975) probably pertain to L. caenosa (see Distribution paragraph under L. fontinalis ). The immature stages of this species were described by Fredeen & Taylor (1964). Other species are rarely attracted to decaying substrates such as dung ( L. papallacta sp.n., L. erratica sp.n., L. sphaerotheca sp.n., L. erythrocera ) or carrion ( L. neocurvinervis , L. papallacta sp.n.). Some species were taken in significant numbers along the edges of streams and rivers ( L. neocurvinervis , L. papallacta sp.n., L. argentinica sp.n., L. gongylotheca sp.n.), on lakeshores ( L. neocurvinervis , L. aequilimbata , L. mendozana ) as well as in swamps, wet ditches and muddy areas ( L. argentinica sp.n.). The widespread L. caenosa and L. erythrocera are found in a wide variety of wooded and open habitats and show very little habitat specificity. Leptocera caenosa is regularly encountered in caves (22 records from U.S.A., see Material examined; also Reeves et al., 2000; Bährmann & Weber, 2008). Three species have been collected at lights ( L. erratica sp.n., L. erythrocera , L. sphaerotheca sp.n.).

Figures

FIGURES 2–6. Leptocera heads and antennae. Heads of (2) L. argentinica sp.n. (Argentina); (3) L. fulva (Costa Rica). Arista and first flagellomeres of (4) L. aequilimbata (Peru); (5) L. neocurvinervis (Chile); (6) L. caenosa (U.S.A.). ad s—additional setulae on orbit, l or—lower orbital bristle, u or—upper orbital bristle.

FIGURES 62–68. Leptocera erythrocera (62–65: Canada, 66–68: U.S.A.). Male terminalia (phallus and postgonites omitted): (62) lateral; (63) posterior; (64) ventral; (65) sternite 5. Female terminalia: (66) dorsal; (67) spermathecae; (68) ventral.

FIGURES 69–75. Leptocera gongylotheca sp.n. (Argentina). Male terminalia (phallus and postgonites omitted): (69) lateral; (70) posterior; (71) ventral; (72) sternite 5. Female terminalia: (73) dorsal; (74) spermathecae; (75) ventral. cp—finger-like process of cercus, da—desclerotized area, proc—process at base of posterior section of surstylus, sa—shining area of tergite 7.

FIGURES 94–101. Leptocera papallacta sp.n. (Ecuador). Male terminalia (phallus and postgonites omitted): (94) lateral; (95) left cercus; (96) posterior; (97) ventral; (98) sternite 5. Female terminalia: (99) dorsal; (100) spermathecae; (101) ventral. cp—finger-like process of cercus, proc—process at base of posterior section of surstylus, sa—shining area of tergite 7.

FIGURES 38–44. Leptocera aequilimbata (38–40: Argentina, 41–44: Bolivia). Male terminalia (phallus and postgonites omitted): (38) lateral; (39) posterior; (40) ventral, right cercus omitted; (41) sternite 5. Female terminalia: (42) dorsal; (43) spermathecae; (44) ventral. aps—anterior process of anterior section of surstylus, cb—cruciate bristles, ce—cercus, cp—finger-like process of cercus, ep—epandrium, fm—field of dense microtrichia, ha—hypandrial apodeme, hy—hypandrium, lp—lamellate process of cercus, pa—phallapodeme, proc—process at base of posterior section of surstylus, pss—posterior section of surstylus, S—sternite, sc—enlarged scales, se—subepandrial sclerite, T—tergite (female tergite 8 divided into two halves), vap—ventral appendage of tergite 8, vls—ventral lobe of anterior section of surstylus.

FIGURES 48–54. Leptocera caenosa (48–51: Ecuador, 52–54: U.S.A.). Male terminalia (phallus and postgonites omitted): (48) posterior; (49) sternite 5; (50) surstylus, lateral; (51) ventral. Female terminalia: (52) dorsal; (53) spermathecae; (54) ventral. ce—cercus, sa—shining area of tergite 7.