Drosophila trispina Wheeler, 1949

Grimaldi, David A., 2022, The Drosophila funebris Species Group in North America (Diptera: Drosophilidae), American Museum Novitates 2022 (3988), pp. 1-28 : 21-23

Drosophila trispina Wheeler, 1949

Figures 1D , 2D , 4D , 5E , 6F, G, 6K , 7D , 8E , 9E

Drosophila trispina Wheeler, 1949: 180 .

DIAGNOSIS: Facial carina broad, bulbous, noselike. Aedeagus: lateral lobes short and broadly rounded, not curved posteriad; apical lobe longer and more slender than in other species of group, without large inner spine at apex; distiphallus more slender in lateral view. Male cercus with large gap between spine 1 and 2, with 4–5 spines total. Oviscapt lightly sclerotized, ventral margin with slight emargination; with about 32 marginal pegs; spermathecal capsule with fine papillae.

DESCRIPTION: (N = 4, all measured specimens from type series), body size, ThL 1.10 mm (0.98–1.17); wing length, 2.11 mm (1.91–2.27)

HEAD: Significantly broader than deep, HW/HD 1.39 (1.32–1.48). Eye dull red, with dense ommatrichia; ovoid, ED/EW 1.31 (1.29–1.43). Frons, face dull, dark yellow (carina lighter), antenna slightly darker (flagellomere 1 with fine, whitish microtrichia); frontal-orbital plates and ocellar triangle slightly shiny. Frons short, FL/LFW 0.72 (0.71–0.74), broadened posteriorly, UFW/LFW 1.32 (1.28–1.38), with fine setulae near ptilinal suture. Proclinates slightly divergent, length more than 2× that of anterior reclinate, OR 1 /OR 2 2.42 (2.21–2.62), proclinate shorter than posterior reclinate, OR 1 /OR 3 0.74 (0.70–0.80). Anterior reclinate posterolateral to proclinate, separated by distance slightly larger than diameter of socket. Posterior reclinates slightly divergent. Inner vertical in line with tangent running through ipsilateral proclinate and posterior reclinate. Verticals nearly equal in size, VT-index 0.96 (0.91–1.04); inner vertical strongly inclinate, outer vertical lateroclinate and almost directly posterior to inner one. Postocellar setae strong, convergent; ocellar setae significantly longer than postocellars, Ocellar S-Index 1.39. Antennal pedicel with 2 strong setae (1 proclinate, 1 lateroclinate); arista with 4–5 dorsal, 3 ventral branches. Carina relatively broad, CL/CW 3.9 (3.2–4.6), protruding, bulbous and noselike. Vibrissa slightly larger than subvibrissa, vibrissa index 0.94 (0.93–0.95). Cheek short, ED/CD 7.5 (6.6–8.6). Palp entirely yellow, asymmetrical, dorsal margin flat and ventral margin convex with 3 strong setae. Labellum with ~10 pseudotracheae; occiput brown.

THORAX: Scutum and scutellum dark yellowish to faint brownish, dark tan; slightly shiny. Acrostichals in 8 rows; short row of 3 acrostichals anterior to anterior dorsocentral slightly thicker and longer than others (same for transverse row of 4 acrostichals in front of transverse suture). Two long postpronotal seta, lower seta larger than upper, h-index 0.81 (0.80–0.84). Three notopleural setae, longest ones are 2 anterior setae; 1 short, anterior supraalar seta, 1 long posterior supraalar. Posterior katepisternal seta significantly longer than anterior, S-index 0.59 (0.55–0.65). Posterior dorsocentral significantly longer than anterior, DC-index 0.62. Posterior scutellar setae slightly longer than anterior, Scut-index 0.86 (0.83–0.92), anterior pair parallel, posterior pair crossing ~0.3× their length. Legs light yellow; fore femur with 3 fine ventral setae, 2 lateral ones. Male protarsus without longer, curved setulae; midtibia with long, thick ventroapical seta, smaller dorsal-preapical seta; hind tibia with 1 fine, preapical-dorsal seta.

WING: Entirely hyaline, of moderate length relative to body size WL/ThL 1.91 (1.89–1.94), wing relatively broad WL/WW 2.12 (2.07–2.18); C-index 2.47 (2.38–2.55); hb-index 1.78 (1.67–1.88); 4-V index 1.28 (1.25–1.31); crossvein dm-cu distant from wing margin, 5X-index 1.27 (1.20–1.38). Halter light.

ABDOMEN: Pigmentation sexually dimorphic. Male: Tergites 1–3 with most of central area dark yellow; tergites 4–7 entirely dark, shiny brown; epandrium dark yellowish. Female: Tergites more yellow than brown, tergites 1 and 2 all yellow; tergites 3–5 with brown band on posterior margins, each with median gap of yellow; tergites 6 and 7 dark brown, with yellow anterior band; tergite 8, paraprocts, oviscapt light yellow.

MALE TERMINALIA: Epandrium lightly sclerotized, devoid of microtrichia, short, flattened (not capsulate); dorsolateral phragma well developed; ventral lobe very small, with 2 short, thick, stiff setae at apex. Cerci protruding, lobelike, lacking microtrichia, setae dense and long (lengths ~equal to thickness of cerci). Cercus with 4–5 heavily sclerotized spines; one large, dorsal spine far separated from others (~3× thickness of spine), group of 3–4 straighter spines ventrally (in one specimen left cercus was missing one of spines in ventral group). Surstylus most distinctive in group of N. American species: ventral margin not broadly rounded, apex of surstylus narrow; with 8 slender prensisetae on inner margin, 10 thick other setae. Hypandrium lightly sclerotized, lateral margins narrowed in middle; posterior width ca. 2× the anterior width; gonopod with 1 long, fine seta and one minute one. Aedeagus with shaft of uniform thickness, apex of aedeagus not as bulbous in lateral view as macrospina and limpiensis ; apex with pair of lobes spreading 3.5× width of shaft; lobes short, rounded, partly serrate on margin and neck; distal lobes with coarse serrations, lacking large medial tooth seen in other species. Aedegal apodeme sclerotized, relatively short, 0.7× length of main part of aedeagus (without apical lobes). Ejaculatory apodeme small, bent at right angle, both portions approximately equal in length.

FEMALE TERMINALIA: Oviscapt not heavily sclerotized, with slight depressions along dorsal and ventral margins in lateral view; apex narrowed; 30–32 pegs along margin, plus 4 slightly longer ones on dorsolateral portion of valve. Spermatheca slighly bulb shaped, sclerotized, introvert long, ~0.85× length of capsule, with fine papillae on surface of capsule.

TYPES: Holotype, male: United States: California, Earp/ MR Wheeler, June 1948 / [lot]1858.5. In NMNH, not examined. Wheeler (1949) mentioned that the holotype was taken from the same isofemale culture that yielded the paratypes (below).

SPECIMENS EXAMINED: Paratypes, 4M, 2F (1 of each dissected), in AMNH: USA: California, Earp / MR Wheeler, June 1948 / [lot]1858.5. Field notebooks from former UT collection contains more detailed locality for this lot: “Traps set in brushy, woody grove along Colorado River, at Kinders’ Camp, at 4 mi [6.4 km] NW Earp, Calif., Coll. 6-14-48” (~34.2777°, -114.2326°) .

DISTRIBUTION: Known only from the type series.

COMMENTS: Wheeler (1949: 181–182) mentioned that D. trispina can hybridize with D. limpiensis , but they produce sterile male offspring; when the female parent is trispina this yields offspring with reduced viability or that are inviable. The type locality of this species along the Colorado River, separating Arizona and California, is low, hot desert of approximately 120–150 m elevation.

Figures

FIG. 1. Heads, frontal views, of native North American species of the Drosophila funebris group. A. D. limpiensis (ex: type locality: Limpia Canyon, Texas). B. D. macrospina (ex: Rochester, NY). C. D. subfunebris (ex: type series: Pasadena, CA). D. D. trispina (ex: type series: Earp, CA). To the same scale.

FIG. 2. Heads, lateral views, of native North American species of the Drosophila funebris group. A. D. limpiensis (ex: Limpia Canyon, TX). B. D. macrospina (ex: Piqua, OH). C. D. subfunebris (ex: Pasadena, CA). D. D. trispina (ex: Earp, CA). To the same scale.

FIG. 4. Epandria (male) of native North American species of the Drosophila funebris group; posterolateral views (to same scale). A. D. limpiensis (ex: Limpia Canyon, TX). B. D. macrospina (ex: Magazine Mtn., AR). C. D. subfunebris (ex: Pasadena, CA). D. D. trispina (ex: Earp, CA).

FIG. 5. Male genitalia of native North American species of the Drosophila funebris group, ventral views (to same scale). A. D. limpiensis (ex: Limpia Canyon, TX). B. D. macrospina (ex: St. Catherine’s Island, GA). C. D. macrospina (ex: Rochester, NY). D. D. subfunebris (ex: Pasadena, CA). E. D. trispina (ex: Earp, CA).

FIG. 6. External details of male terminalia, A–G: Cercal spines, right lateral views; H–K: Surstyli, lateral views. All to same scale. A. D. limpiensis (ex: Limpia Canyon, TX). B. D. limpiensis (ex: Patagonia, Arizona). C. D. macrospina (ex: New Orleans, LA). D. D. macrospina (ex: Piqua, OH), dashed line indicates spine sometimes missing. E. D. subfunebris ex: Pasadena, CA). F. G. D. trispina (ex: Earp, CA), G. showing right cercus with one less spine. H. D. limpiensis (ex: Limpia Canyon, TX). I. D. macrospina (ex: New Orleans, LA). J. D. subfunebris (ex: Pasadena, CA). K. D. trispina (ex: Earp, CA).

FIG. 7. Aedeagi with aedeagal apodemes, ejaculatory apodemes (B, D, E), lateral views (all to same scale). A. D. macrospina (ex: Magazine Mtn., AR). B. D. macrospina (ex: Rochester, NY). C. D. limpiensis (Limpia Canyon, TX). D. D. trispina. E. D. subfunebris.

FIG. 8. Detail of apices of aedeagi (ventral views) of native North American species of the D. funebris group (all to the same scale). A. D. limpiensis. B. D. macrospina (ex: New Orleans, LA). C. D. macrospina (ex: Piqua, OH). D. D. macrospina (ex: Missouri). E. D. trispina. F. D. subfunebris.

FIG. 9. Female terminalia (oviscapts, spermathecal capsules, and minutely scaled oviprovector membrane [internal]) of North American species of the D.funebris group (all to same scale).A. D. funebris (introduced). B. D.limpiensis. C. D. macrospina (spermatheca of limpiensis and macrospina is identical). D. D. subfunebris. E. D. trispina.