Drosophila duncani Sturtevant 1918
Creators: name: Grimaldi, David A.
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Diptera
Drosophilidae
Drosophila
Drosophila duncani

description: Drosophila duncani Sturtevant, 1918b: 446.
DIAGNOSIS: Head and dorsal part of thorax largely yellowish ochre, dorsal part of pleura light fuscous brown, ventral part of pleura and legs light cream; abdominal coloration sexually dimorphic (see below); basal flagellomere with long setulae, arista with two ventral branches; frons relatively narrow (frontal index 0.69), cheek shallow (CD/ED 0.11); crossvein dm-cu close to wing margin; apex of oviscapt unmodified (margin entire); aedeagus short, stout, scaled; paraphyses long, digitate, flanking aedeagus; surstylus bilobed, small inner lobe with marginal row of prensisetae and rows of microtrichia.
DESCRIPTION: Coloration: Head: Frons dark yellowish beige, ocellar triangle slightly darker; fronto-orbital plates slightly lighter than frontal vittae. Face dull yellowish, clypeus and vibrissal angle slightly darker. Palp and proboscis very light. Antenna light, fuscous brown, pedicel slightly darker than basal flagellomere. Eye pink. Thorax: Scutum, scutellum, postnotum deep, dull yellowish to ochre, postpronotal lobe lighter; dorsal portion of pleura light, fuscous brown; katepisternum and meron cream colored. Legs entirely light, cream colored. Wing entirely hyaline, no markings; veins light fuscous brown; halter dull yellow, knob light cream. Abdominal coloration sexually dimorphic: Male with abdomen mostly black brown, shiny; all of tergite 1, anterior half of tergite 2, anteromedian portion of tergite 3 ochre; tergite 3 with median pattern (see figs. 20, 21); tergite 7 remnants and epandrium light, fuscous brown. Female with tergites 2–6 having anterior half light, cream colored, posterior half dark brown; tergites 3–6 with posterior dark band expanded into central spot, spots fused into central, dark median stripe; tergite 1 fuscous brown, tergite 7 (divided medially) dark brown, oviscapt yellow.
Head: Antenna: Scape and pedicel setulose, pedicel with two stout setae on anterior surface; basal flagellomere with long, fine, light setulae, longest ones approximately 1/2 width of flagellomere, apex of flagellomere not quite reaching to level of oral margin; arista with 5 dorsal branches, 2 ventral branches (opposite to dorsal branches 4 and 5, or nearly so), plus small terminal fork. Eye taller than long in lateral view, with dense, light interfacetal setulae. Face relatively flat, with narrow, low carina on upper portion. Vibrissa large, stout, well differentiated; subvibrissal seta approximately half the length of vibrissa. Cheek, clypeus shallow. Proboscis short, largely withdrawn into oral cavity at rest; labellum approximately to length of oral cavity; palp fairly large, bilaterally asymmetrical, with single apical seta. Frons: Of moderate length and width; fronto-orbital plates slightly shiny; frontal vittae dull, finely striate. Fronto-orbital setae well developed: proclinate slightly shorter than posterior reclinate; anterior reclinate directly lateral to proclinate, approximately 1/2 the size; posterior reclinate noticeably closer to other orbitals than to verticals. Inner vertical seta long, strongly inclinate, outer vertical strongly lateroclinate. Ocellar triangle slightly shiny; ocellar seta nearly reaching to level of ptilinum; postocellar setae convergent but not crossed.
Head measurements (N = 3): CD/ED 0.11 (0.09–0.14), ED/EW 1.22 (1.19–1.26), FD/FW 1.06 (1.02–1.12), FL/LFW 0.69 (0.65–0.77), HW/ HD 1.34 (1.29–1.39), Ocellar S-index 1.42 (1.23– 1.55), OR1/OR3 0.73 (0.62–0.79), OR2/OR1 0.48 (0.41–0.55), VT-index 1.09 (1.08–1.11).
Thorax: Setation: Acrostichal setae in 6 even rows; 2–3 acrostichals immediately anterior to transverse suture slightly enlarged. Anterior dorsocentral ca. 0.7× length of posterior dorsocentral; posterior dorsocentral midway between anterior dorsocentral and anterior margin of scutellum. Anterior scutellar seta slightly smaller than posterior scutellar; anteriors convergent; posterior (apical) scutellar setae crossing at apical third. Postpronotal lobe with 2 small setae; 2 setae very close to notopleural suture (posterior one short); 1 large seta dorsal to these. Two supraalar setae, 1 small postalar. Two large katepisternal setae, anterior one ca. 0.65× size of posterior one; small seta between these. Legs: Forefemur with 2–3 long ventrodistal setae; foretibia with short preapical dorsal seta; ctenidia on tibia and basitarsomere golden, well developed; 2–3 short, black setae at apex of probasitarsomere; male foretarsi without fine, erect setulae on dorsal surface. Midfemur without large setae, midtibia with large, stout ventroapical seta. Hind femur without large setae; hind tibia with small preapical dorsal seta. Wing: Clear, hyaline, no markings; veins light fuscous brown.
Thorax and wing measurements: 4-V index 1.61 (1.60–1.62), 5-X index 1.29 (1.23–1.42), C-index 2.67 (2.42–3.01), DC-index 0.64 (0.62– 0.67), hb-index 1.87 (1.70–1.96), S-index 0.57 (0.56, 0.57), ThL 1.11 mm (1.04–1.17), ThL/WL 0.46 (0.44, 0.49), WL/WW 2.23 (2.16–2.32).
Male Terminalia: Epandrium height nearly twice the width and length; with sparse microtrichia dorsally, none laterally; anterodorsal phragma large; ventral epandrial lobe small (apex not reaching to level of apex of surstylus), tip of lobe with large, thick, curved seta, much smaller, fine setae anterior to macroseta. Cercus small, not connected to epandrium; with ventral tuft of fine setae; no microtrichia. Surstylus apparently bilobed; with small, inner lobe having inner marginal row of ca. 14 evenly sized prensisetae, inner lobe with microtrichia on outer surface arranged roughly into irregular rows. Apparent outer, large lobe of surstylus ca. 1.5× length of inner one, with ca. 15 stiff, stout setae only on apical half (no prensisetae). Hypandrium roughly U-shaped, with 2 pairs posterior lobes, outer pair with microtrichia. Paraphyses long, digitate, extended to level of aedeagal tip, flattened at tip; with lateral row of 3–4 minute sensilla; pair of short, stout setae near base. Aedeagus short, stout, scaled; slightly shorter than aedeagal apodeme. Flat surface of ejaculatory apodeme oblique to main part of apodeme.
Female Terminalia: Oviscapt with pegs but otherwise unmodified, margin entire, no differentiation of pegs at apex; with ca. 18 pegs along margin, gradually decreased in size anteriad, 1 stout, long preapical dorsal seta. Oviprovector with sparse, small scales. Spermatheca dome shaped, with introvert extended nearly to apex of capsule.
TYPE: Holotype, female. USA: Illinois, Flat Rock, 1915, fungus, ac [AMNH accession] 5300, Type, on handwritten label: “ Drosophila duncani Sturtevant. ” In AMNH. Not dissected, in good condition.
OTHER SPECIMENS EXAMINED: USA: Nebraska: Crystal Lake Recreation Ground, at 12 mi. S.W. Hastings, 8-22, 23-50, M.R. Wheeler, lot 2069.21, portions of ≥ 4 males (terminalia) on glass slides only (no bodies), which I have labelled A to E, with A, B, D, and E having an epandrium, and C with two mounted hypandria and aedeagi. New Jersey: Morris Co., Pompton Plains, VII/23/15 through VIII/12/15, on Polyporus fungus, D. Grimaldi coll., 5♂, 3♀ (AMNH), 1♀, 1♂ dissected (nos. 82, 2, respectively). New York: Broome Co., Vestal, VI-15-82, D. Grimaldi, reared from mushroom Polyporus squamosus, 1♀, 1♂ (dissected, no. 1). Long Island [Brooklyn], Flatbush, Lost Woods, 8-9-1890, J.L. Zibriskie, 11♀, 5♂ (1♂ dissected, no. 4) (AMNH). Orange Co., Black Rock Forest [Cornwall], 17/VIII/90, Grimaldi and Stark, on old Ganoderma tsugae, 1♂ (dissected, no. 4).
COMMENTS: This is an intriguing species. It plesiomorphically has two ventral branches on the arista, and the oviscapt has a typical drosophiline structure with an entire margin, rather than the apex modified as in many Hirtodrosophila. Moreover, the hypopharyngeal bulb is not heavily sclerotized as in members of the Zygothrica genus group (which includes Hirtodrosophila) (Grimaldi, 1990), and it has a high number of posterior and medial sensilla on the cibarium (most species in the species group have a highly reduced number). Distinctive apomorphic features include the anterior reclinate orbital lateral to the proclinate; microtrichia in dense rows on the surstylus but sparse on the epandrium and entirely lacking on the cercus; and an apparent bilobed condition of the surstylus, with the inner lobe having a long row of prensisetae and outer lobe with just stiff setae. Lastly, the paraphyses are long, flanking the aedeagus, each with a row of sensilla, similar to what is seen in Scaptodrosophila, Lordiphosa, and some other basal drosophilines, although a few Hirtodrosophila (e.g., kuscheli [Brncic]) have similar paraphyses. Were it not for an egg with four filaments, mycophagy, and the setulose basal flagellomere the position of duncani in Hirtodrosophila would be highly unlikely. It is possible that H. duncani is a very basal species in the genus, but this needs to be tested with molecular data.
Patterson and R.P. Wagner (in Patterson, 1943) listed specimens they examined from Alabama, Arkansas, Mississippi, Ohio, Oklahoma, Tennessee, and Texas, cited by Vilela and Bächli (2004) but which I have not seen. These records may be correct given that this light-bodied species is fairly easy to spot with just external features.
The series of specimens that I collected in Pompton Plains, New Jersey were among a large aggregation of Mycodrosophila claytonae on a group of pliant, moist Polyporus sp. on a rotting stump (fig. 1). Other host records with specimens include Polyporus squamosus and Ganoderma tsugae (Polyporaceae). Dorsey and Carson (1956) reported a collection of 200 specimens of H. duncani at a site in West Virginia, primarily from traps baited with molasses and vinegar, although some were also collected at traps baited with cultivated fungi. This account may not be very informative of natural habits since Dorsey and Carson collected at the same traps many more Drosophila putrida and D. “transversa ” (now known to be D. recens and D. falleni in the eastern United States), despite these being strictly mycophagous species. Hirtodrosophila duncani was rare in the large study by Lacy (1982) of mycophagous drosophilid ecology in northeastern United States. Among the more than 33,000 specimens he reared from various macrofungi in Ithaca, New York, and the Smoky Mountains, Tennessee, 260 specimens were H. duncani (Drosophila falleni, D. neotestacea, and D. putrida greatly predominated).
description: Published as part of Grimaldi, David A., 2018, Hirtodrosophila Of North America (Diptera: Drosophilidae), pp. 1 in Bulletin of the American Museum of Natural History 2018 (421) on page 1, DOI: 10.1206/0003-0090-421.1.1, http://zenodo.org/record/10687866