Ditylometopa elegans Kertész

Woodley, Norman E., 2009, A review of the genus Ditylometopa Kertész (Diptera: Stratiomyidae), Zootaxa 2032, pp. 39-47 : 40-44

Ditylometopa elegans Kertész

( Figs. 1, 3 , 5, 7–11 )

Ditylometopa elegans Kertész, 1923: 115 .

Euryneura rufifrons Curran, 1934: 314 . New Synonymy.

Diagnosis. Both males and females of this species have a pair of well defined band-like pubescent markings on the fifth tergite ( Fig. 5 ). Males of D. elegans have the eighth antennal flagellomere slightly larger and more blunt apically than that of D. centralensis , and the posterior margin of the hypandrium is evenly rounded ( Fig. 8 ), rather than slightly bilobed as in D. centralensis . Females have the surface of the lower frons above the antennae more extensively tomentose than in D. centralensis , lacking well defined shiny areas; the margins of the lower frons and face have a wider strip of tomentum than in D. centralensis ; and the sutural area between the vertex and post-ocular orbits is usually darkened, with a deep groove just mediad of the suture.

Description. Male. Head black, ocellar tubercle usually brownish. Lower frons and face with extremely narrow tomentose margins, extending around lower eye margin and lower half of posterior eye margin; lower frons and face with sparse tomentum medially, ocellar tubercle with traces of fine tomentum. Silvery white pilosity present on lateral portions of lower frons and most of face that is less than length of scape and somewhat recumbent; similar hair-like setae present on gena and lower occiput but pilosity is more erect. Eyes bare. Antennae brownish, darker on outer surface; eighth flagellomere bluntly conical at apex; scape and pedicel with short, sparse black hair-like setae, especially apically, on each segment; pedicel with short, sparse pale hair-like setae on medial surface. Proboscis and palpus brownish-black, lower part of labellum dirty yellowish-white.

Thorax black, pleural sclerites just below wing base and tiny areas on postpronotal lobe and postalar callus brownish, scutellar spines yellowish. Scutum and scutellum finely granulate, not shiny; with vestiture of short, appressed black hair-like setae except on areas where longer pale golden pilosity forms a pattern ( Fig. 1 ): a quadrate spot on the presutural notopleural region; a sublateral vitta that narrows anteriorly, extending from the postalar wall anteriorly to beyond suture; and a median vitta that covers most of the disc of scutellum and narrows anteriorly to beyond suture. Pleurites with vestiture composed of mostly short, appressed silvery hair-like setae over most of surface, bare areas present on central part of anepisternum and posterior part of anepimeron; central part of anepisternum with noticeable vertical striations. Legs completely dark brownish to black, mid and hind legs with first tarsomeres indistinctly brownish to dark yellow. Wing faintly, evenly infuscated with grayish color, cell r1 (“stigma”) dark yellowish; wing blade uniformly set with microtrichia, with most of alula and small area of anal lobe near incision bare. Halter dark, dull yellowish in color.

Abdomen black, sternites more brownish, tergites with surfaces finely granulate as on scutum. Central portions of tergites with very short, inconspicuous, appressed black hair-like setae; tergites 1 and 2 with longer, mostly dark hair-like setae laterally; tergites 3 and 4 with well-defined lateral spots of golden pilosity with the posterior margin of each extending medially along suture for a short distance; tergite 5 with lateral, band-like golden markings, each expanded along posterior margin ( Fig. 5 ). Sternites with more or less uniform vestiture of short, appressed silvery hair-like setae; sternite 1 with some longer, erect hair-like setae medially.

Male terminalia with gonocoxites ( Fig. 8 ) nearly parallel-sided but tapering slightly anteriorly; posterior margin of hypandrium very slightly produced and rounded, ventrally with carina-like ridge; gonostylus simple, slightly narrowed toward apex and with outer margin arcuate; gonocoxal apodemes elongate, extending beyond anterior margin of genital capsule; phallic complex ( Figs. 9, 11 ) slender, trifid, the lobes apparently fused anteriorly, medial lobe very slightly shorter than lateral lobes, attachment structure small; epandrium ( Fig. 10 ) nearly quadrate, longer than wide, posterior margin truncate.

Body length, 5.7–6.1 mm.

Female. Differs from male as follows: Head ( Fig. 3 ) black, with wide frons as noted in generic description; upper frons, narrow lateral margins of lower frons and face and occiput along posterior and ventral margin of eye orangish-yellow. Upper frons 0.36–0.40 width of head, rugose, inflated, slightly depressed along medial line where there is a sharp, narrow, medial carina; vertex with narrow, deep depression on each side just mediad of upper corner of eye, this area darker than surrounding surface. Upper frons with scattered, recumbent black pilosity except on lower medial part where the hair-like setae are silvery; lateral margins of lower frons and much of face with short, silvery pilosity, especially dense medially on the latter. Lower frons with scattered thin tomentum, without conspicuous shiny areas; dense tomentum present on lateral margins of lower frons and face which continues ventrally along eye margin and along about lower two thirds of posterior margin of eye, wider and more conspicuous than in male. Palpus slightly larger than in male.

Thorax with scutellar spines shorter than in male, sometimes partly blackish. Golden pubescent pattern on scutum more extensive ( Fig. 3 ), with the medial and sublateral vittae extending to anterior margin, and the notopleural pilosity more extensive, extending over postpronotal lobe and coalescing with anterior portion of sublateral vitta.

Abdomen essentially as in male; cercus small, slender, first segment about twice length of second.

Body length, 5.6–6.7 mm.

Specimens examined. Type material: Ditylometopa elegans Kertész. Kertész described his species based on two female syntypes, one from Vilcanota, Peru and one from Espírito Santo, Brazil. Both were subsequently destroyed at the Hungarian Natural History Museum, Budapest in the 1956 uprising. In the interest of nomenclatural stability, and because the known species of Ditylometopa are very similar, I am hereby designating the female holotype of Euryneura rufifrons Curran as the neotype of Ditylometopa elegans Kertész , which results in their permanent synonymy. The detailed label data for this specimen is presented below.

Euryneura rufifrons Curran. The female holotype, housed at AMNH, is labeled (slashes separate individual labels): “24726/Kartabo Bartica District British Guiana 1924/ Euryneura ? TYPE rufifrons Ƥ Curran No. / Euryneura ? rufifrons Curran Det. C.H. Curran / NEOTYPE Ƥ Ditylometopa elegans Kertész, 1923 des. N. E. Woodley 2008”. The specimen is in excellent condition. Although Curran (1934: 314) stated that the specimen was collected May 26, 1924, this is not indicated on the labels (unless the first typewritten label on the specimen is the date, in which case it is incorrectly cited and should be July 26, 1924).

Other material. 1Ƥ, BOLIVIA: Santa Cruz Department, Ichilo Province, Hotel Flora y Fauna, 4–6 km SSE Buena Vista, 17°29.95΄S, 63°33.15΄W, 400–500 m, 12 November 2003, N.E. Woodley ( USNM); 1Ƥ, BRAZIL: Para, Tapajos, Boa Vista, 23 February, C.H.T. Townsend ( USNM); 2Ƥ, BRAZIL: Rondania, Fazenda Rancho Grande, 62 km S. Ariquemes, 10.32°S, 62.48°W, 165 m, 12–22 November 1991, E. M. Fisher ( CDFA, USNM); 13, ECUADOR: Napo, Reserva Ethnica Waorani, 1 km S Onkone Gare Camp, 00°39΄10ʺS, 76°26΄W, 220m, 9 October 1994, T.L. Erwin et al., insecticidal fogging of mostly bare green leaves, some with covering of lichenous or bryophytic plants in terre firme forest, Lot 912 ( USNM); 13, same data but 8 February 1995, Lot 962 ( USNM); 13, same data but 10 February 1995, Lot 1008 ( USNM); 13, same data but 4 February 1996, Lot 1414 ( USNM); 2Ƥ (paratypes of E. rufifrons ), GUYANA (as British Guiana): Bartica District, Kartabo, 23 May 1924 ( AMNH); 1Ƥ (paratype of E. rufifrons ), same data but 11 June 1924 ( AMNH); 1Ƥ, VENEZUELA: Mt. Duida, 18 November 1928 ( AMNH); 1Ƥ, VENEZUELA: T.F. Amazonas, Cerro de la Neblina basecamp, 0°50΄N, 66°10΄W, 140m, 27 January 1985, P.J. & P.M. Spangler, R.A. Faitoute, W.E. Steiner ( USNM).

Remarks. Even though the type material of Kertész (1923) has been destroyed, it is clear from his excellent description that he was describing a species of Ditylometopa with well-defined golden pubescent spots on the fifth abdominal tergite. However, there is a good possibility that his second specimen from Espírito Santo, Brazil was a species different from D. elegans that has not otherwise been recorded from the Atlantic coast of Brazil. Also, there is a questionable specimen of D. centralensis known from southern Brazil (noted below under that species). That specimen has a distinct dark spot on the knob of the halter, and Kertész (1923: 116) noted that the Espírito Santo specimen had this feature as well. For this reason, I believe that it is best to designate a neotype for Kertész’s taxon to stabilize the species concepts in the genus.

Specimens of Ditylometopa are rare in collections. The only males of D. elegans I have seen were collected by canopy fogging, so it is possible that species of the genus are normally denizens of the canopy and only occasionally occur at lower forest levels and hence are not often collected.

Figures

FIGURES 1 – 4. Habitus images of Ditylometopa species. 1, D. elegans, male. 2, D. centralensis, male. 3, D. elegans, female. 4, D. centralensis, female.

FIGURES 5 – 7. Morphological details of Ditylometopa species. 5, D. elegans, dorsal view of female abdomen. 6, D. centralensis, dorsal view of female abdomen; note: this image makes the abdominal hairs appear denser than they actually are. 7, D. elegans, posterior view of front femur of male.

FIGURES 8 – 11. Male terminalia of Ditylometopa elegans. 8, genital capsule, dorsal view. 9, phallic complex, dorsal view. 10, epandrium and post-genital segments, dorsal view. 11, phallic complex, left lateral view.