Drosophila macrospina Stalker and Spencer, 1939

Grimaldi, David A., 2022, The Drosophila funebris Species Group in North America (Diptera: Drosophilidae), American Museum Novitates 2022 (3988), pp. 1-28 : 5-13

Drosophila macrospina Stalker and Spencer, 1939

Figures 1B , 2B , 3A–D , 4B , 5B, C ; 6C, D, I ; 7A, B , 8B–D , 9C

Drosophila macrospina Stalker and Spencer, 1939: 110 . Subsequent refs: Mainland, 1942 (hybrid sterility); Patterson, 1943 (redescription, internal reproductive organs, immature stages, chromosomes); Patterson and Wagner, 1943 (distribution); Patterson and Stone, 1952 (distribution);

Miller et al., 2017 (identification, eastern distribution); Werner et al., 2020a, 2020b (identification, biology);

Drosophila macrospina ohioensis Spencer, 1940: 304 . NEW SYNONYM.

DIAGNOSIS: Very similar to Drosophila limpiensis . Postocellar setae slightly to strongly convergent to crossing; male with lateral lobes of distiphallus broader and more protruding than in D. limpiensis (especially at the apex); apical lobes with more lateral serrations; large gap between largest (dorsalmost) cercal spine (1) and next one (2) (gap is ~width of spine 2, vs. with barely any gap); ventral epandrial lobe with 4–5 small setae (vs. 2 thick ones in limpiensis ). Female: oviscapt dark, sclerotized as in limpiensis . No distinction between the two species is apparent in the surstyli or female terminalia.

DESCRIPTION: Body size, ThL 1.12 mm (0.92–1.30); wing length, 2.25 mm (1.95–2.74).

HEAD: significantly broader than deep HW/HD 1.39; frons short, FL/LFW 0.74 (0.69–0.82), UFW/LFW 1.39 (1.30–1.51). Eye dull, light red, with dense ommatrichia, proportions in lateral view ED/EW 1.26 (1.16–1.34). Frons, face, antennae dull, pollinose, light brown; frontal-orbital plates and ocellar triangle slightly shiny, FOPs (frontal-orbital plates) and carina lighter. Frons with small, scattered setulae on anterior half. Proclinates parallel, shorter than posterior reclinates. Ipsilateral proclinate, posterior reclinate, and inner vertical in line. Anterior reclinate posterolateral to proclinate, closer to proclinate than to posterior reclinate. Posterior reclinates slightly divergent. OR 1 /OR 2 2.32 (1.8–2.8); OR 1 /OR 3 0.69 (0.62–0.82). Inner verticals strongly inclinate, outer verticals strongly pointed posterolaterad; verticals nearly equal in length, VTindex 0.97 (0.92–1.07). Postocellars very strong, slightly convergent to strongly convergent and even cruciate for ~0.5× their length. Ocellar setae long, tips reaching slightly past ptilinal suture; setal sockets lie between anterior and posterior ocelli. Antennal pedicel with 2 larger setae (1 proclinate, 1 lateroclinate), plus ca. 12 smaller setulae; pedicel without long, fine setae on mesal surface; basal flagellomere with fine setulae short; arista with 4–5 dorsal and 3 ventral branches. Carina narrow, CL/CW 5.33 (3.6–6.5), edge slightly flattened, lying below level of flagellomere 1. Two pairs strong vibrissae present, vibrissa longer than subvibrissa, vibrissaindex 0.77 (0.65–0.88); 7–8 small setae on cheek, anterior margin of cheek darker; cheek shallow, ED/CD 8.90 (6.85–10.8). Clypeus U-shaped, shiny. Palp yellowish, asymmetrical, ventral margin convex, with 2–3 longer setae; dorsal margin flat. Mentum dark yellow, shiny, with ~10 long, fine setae. Labellum with 8–9 pseudotracheae. Occiput dark yellow and light brown.

THORAX: ThL males 1.06 mm (0.89–1.15mm; N = 9), ThL females 1.29 mm (1.24–1.40 mm; N = 4). Scutum and scutellum light brown (centrally lighter for scutum), faintly pollinose, dull not shiny; pleura slightly lighter, especially katepisternum. Acrostichals in 8 rows between dorsocentrals; anterior to dorsocentral is row of 4–5 acrostichals slightly thicker and longer than others; transverse row of ~4 acrostichals 1.4–2.0× length of others anterior to transverse suture. 2 postpronotal setae, lower one larger than upper, h-index 0.82 (0.76–1.0), thinner than notopleurals; 3 notopleural setae, 2 at ventral edge of notopleural suture, posterior seta short. Supraalar setae: 1 short, 1 long; 2 large katepisternal setae, anterior one significantly shorter than posterior dc, S-index 0.68 (0.62–0.75), with small seta between them and a vertical row of ~10 small setulae. Dorsocentral setae: large, well developed, anterior pair significantly shorter than posterior pair, DC-index 0.65 (0.51–0.70); scutellum with anterior pair of setae slightly shorter than posterior, Scutindex 0.91 (0.86-0.94), posterior scutellars slightly to strongly convergent. Legs yellow; fore femur with 3–4 long ventral setae, 1 fine, preapical dorsal seta; male fore tarsus without longer, erect, recurved setulae. Mid tibia with thick ventroapical seta, shorter preapical dorsal seta; hind tibia with 1 fine preapical dorsal seta. Wing: relative to body size, WL/ ThL 2.00 (1.85–2.18); relatively broad, WL/WW 2.19 (2.11–2.23); C-index 2.98 (2.65– 3.30); hb-index 1.96 (1.70–2.23); 4V-index 1.53 (1.41–1.62); distance of crossvein dm-cu from wing margin, 5-X-index 1.25 (1.08–1.42). Halter light.

ABDOMEN: Pigmentation sexually dimorphic; male tergites almost entirely dark blackish brown, shiny, with faint lighter areas in middle of tergites 1–3; epandrium and cerci lighter; sternites light. Female tergites with dark band on posterior half of each segment, anterior half light; dark band on tergites 2–4 with slightly median interruption, tergite 6 with middle of dark band enlarged; tergites 7, 8 light, yellowish, paraprocts slightly darker; oviscapt dark, especially at base.

MALE TERMINALIA: Epandrium lightly sclerotized, devoid of microtrichia, short and somewhat flattened (not capsulate); dorsolateral phragma well developed; ventral lobe small, closely pressed to surstylus, with 4–5 short, stout setae at apex. Cerci well developed, projecting well beyond margins of epandrium, lacking microtrichia, with many long setae; ventral margin with 3 heavily sclerotized spines, 3 smaller ones ventrally (sometimes 2), a large one apically (twice the size of other 2); no gaps between smaller spines; gap between smaller and large spine large, ~1.5× thickness of large spine. Surstylus well developed, with row of 9–10 peglike prensisetae, 8–14 thick setulae laterally. Hypandrium well developed, lightly sclerotized, anterior end narrowed to ~0.60× width of posterior end; gonopods (postgonites/paraphyses) with longer seta posteriorly, small seta (~0.5× the length) mesally; inner lobe of gonopod more sclerotized; pair of narrow sclerites attached to posteromedial corners of hypandrium, not connected in middle. Aedeagus with slender neck of uniform thickness, moderately arched in lateral view; apex with medial lobe (roughly triangular in shape), pair of lateral, winglike lobes, and pair of serrate, apical lobes. Lateral lobes with fine scales/serrations on lateral margins and at base near neck; these lobes hardly sclerotized; “wingspread” 5.0× (mean) thickness of aedeagal neck (range 4.3–6.0). Distal pair of lobes of aedeagus flattened, with irregular teeth/serrations on lateral, mesal and apical margins, ones on apex largest (generally 2–3 very large teeth). Aedeagal apodeme sclerotized, straight, slightly shorter than aedeagus. Ejaculatory apodeme small, bent at right angle, both arms approximately equal in length.

FEMALE TERMINALIA: Oviscapt heavily sclerotized (especially at base), with ~30 small, densely spaced marginal pegs, plus 3–4 discal ones; oviprovector membrane with sparse, fine scales. Spermathecal capsule heavily sclerotized, no exterior microtexture, with introvert reaching almost to apex; inserted portion of spermathecal tube sclerotized.

TYPES: Neotype, male: United States: Louisiana: 0.5mi E Miss. River, New Orleans, VI/12/41, 1112.6, GB Mainland, MR Wheeler/M.R. Wheeler, W.K. Baker/ Neotype, Drosophila macrospina , det. D. Grimaldi, 2022. Dissected by D.A.G., in AMNH. Stalker and Spencer (1939) mentioned that the original, type culture, established from a female collected on fungus and from which “type and gonotypes” were made, was from Austin, Texas. As for D. subfunebris (below), no types of macrospina occur in the AMNH, NMNH or other institutions, so a neotype is designated here. Specimens from the published type locality were not available.

SPECIMENS EXAMINED: All in AMNH. United States: Arkansas: Logan Co., Magazine Mtn. , 2750 ft., D. Grimaldi, Collected on 9/VI/92 at 2200’ with banana bait, 1M (dissected) . Georgia: Crooked River State Park, VI/28-VI/29/53, WB Heed, MR Wheeler; Liberty Co., St. Catherine’s Is. 11-20/IV/88, D. Grimaldi, 4M, F (1M dissected) . Louisiana:. 5mi E Miss. River, New Orleans , VI/12/41, 1112.6, GB Mainland, MR Wheeler / MR Wheeler, WK Baker. 7 M, F (1 M dissected) . Mississippi: Claiborne Co., VI/5/50, H.D. Stalker, W.P. Spencer (1F) . Missouri: Webster Groves , IX/50, H.D. Stalker, W.P Spencer (1M, dissected) . New York: Rochester , Highland Park, J. Jaenike, F 1 of isofemale culture coll. 16/VI/2016, 4M, 4F (1M dissected) . Ohio: Piqua , July 1948, JT Patterson, 1035.3 (4M,F; 3 dissected) . Oklahoma: 10 mi NE Tulsa , V/2/41, AB Blair, 996.3 (2F) . South Carolina: 2 mi. SW Cross Anchor , VII/13-VII/4/53, W.B. Heed, M.R. Wheeler 2321.8b (1F) .

DISTRIBUTION: Patterson and Wagner (1943) mapped 45 records of macrospina in North America, which was updated by Patterson and Stone (1952). Their westernmost records are from Del Rio, Texas; Moclova, Cuahuila, Mexico; north to the northwest corner of Nebraska and Fort Peck Dam in northern Montana. The record from Albuquerque, New Mexico, may be due to a higher latitude and altitude in that area or to a zone of overlap with limpiensis , but needs to be confirmed. Although it was not recorded from Florida on their maps, records from Georgia and Florida were mentioned, but, regrettably, very few of the specimens from most of their localities were saved. Miller et al. (2017) added eastern records farther north, in southern Québec, Canada, and Rochester, New York. The species is abundant in eastern Texas, the Mississippi valley, Ohio, Michigan, east to coastal Carolinas and New Jersey—essentially encompassing the eastern half of North America from ~ 48° N to ~ 27° N latitude.

Mainland (1942) used stocks of macrospina for his crossing experiments from the following localities, some series of which are in the AMNH collection (above): United States: Arkansas: Petit Jean St. Park [Conway] (35.1204°, -92.9379°) ; Florida: Tampa (~28.0886°, -82.3224°) ; Louisiana: New Orleans (30.3003°, -90.7120°); Mississippi: Columbus (33.5215°, -88.4060°); Ohio: Overton [Chester Township] (40.8662°, -82.0053°) ; Texas: Austin (~30.3109°, -97.8234°), Del Rio (29.3802°, -100.8930°) .

COMMENTS: Spencer (1940) made the name D. macrospina ohioensis apparently available as a brief mention within a review article on Drosophila speciation, as an example of “interfer- tile races/subspecies...” in which “these two subspecies [m. macrospina and m. ohioensis ] cross readily and the hybrid offspring are quite fertile.” Types were not designated, though a diagnosis was given. His observations were based on a culture of two males and two females that he collected “ 6 mi. north of Overton, Ohio ” (Overton is a small town ca. 7 mi NW of Wooster, Ohio: 40.8662°, -82.0053°). He distinguished between the two subspecies based on features now known to be quite intraspecifically variable in Drosophila , particularly coloration.

Mainland (1941) did not distinguish these subspecies because he found no sterility in crosses between m. macrospina and m. ohioensis ; he reported soon afterward ( Mainland, 1942) a slight reduction in fertility between them. Subsuming D. macrospina ohioensis under the species is based not only on the reports of complete hybridization, but also my observations in which no consistent morphological differentiation was found. Fortunately, several specimens of “ ohioensis ” are in the AMNH collection, from Piqua, Ohio (culture 1035.3, collected by J.T. Patterson), and there is no distinction between the aedeagus of these flies and macrospina from other localities (the apex of the hypandrium is slightly narrowed, but this is quite variable in Drosophila ; also, the middle cercal spine is rather small). It would be ideal to compare mitochondrial DNA sequences of flies from these localities.

Stalker and Spencer (1939) mentioned that D. macrospina flies were “subject to ‘catalyptic’ fits when the container is disturbed,” but I did not observe this in the cultures examined. Drosophila macrospina seems to never be particularly abundant in its primary habitat, which is forests; the natural hosts are unknown. It can easily be bred in the lab. Geographic variation in the genetics of D. macrospina and limpiensis would be very useful for examining any zones of overlap and introgression.

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. 3. Drosophila macrospina thorax and abdomen (all ex: Rochester, NY). A. Head and thorax, dorsal. B. Thorax, lateral. C. Abdomen, male. D. Abdomen, female.

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.