Dryxo margaretae Cogan 1968

Dryxo margaretae Cogan

Dryxo margaretae Cogan, 1968:360; 1980:661 [Afrotropical catalog].—Mathis and Zatwarnicki, 1995:116 [world catalog].

DIAGNOSIS.—This species is distinguished from congeners by the following combination of characters: inner vertical seta subequal or slightly longer than outer vertical seta; postpronotal seta absent; R stem vein bearing about 6 long, thin setulae along posterior margin basad of humeral crossvein; male hindbasitarsus with several long, slender setae toward base, setae becoming shorter and much sparser toward apex; male 2nd hindtarsomere bearing long, slender setae on dorsal surface; katepisternal seta well developed, length subequal to notopleural seta; tergites 3 and 4 with dark band along posterior margin, at least in middle, band sometimes connected laterally with anterolateral spot or spot separate; and tergite 1 with medial patch of short, dorsally erect setulae.

DESCRIPTION.—Large to very large shore flies, body length 7.10–9.30 mm; generally blackish brown dorsally but with considerable areas gray.

Head: Generally densely microtomentose. Frons mostly to almost entirely gray to tan, sometimes with some blackish brown maculation, especially posteriorly as 2 short, parallel stripes extended obliquely anterolaterally from posterior ocellus and adjacent lateral area of vertex; inner vertical seta subequal or slightly longer than outer vertical seta; ocelli arranged in equilateral triangle. Antenna blackish brown, usually with some gray to tan microtomentum dorsally; arista white to tannish white basally, bearing 11–13 dorsal rays. Face, parafacial, gena, and microtomentose-covered portion of clypeus concolorous, whitish gray, contrasting with darker-colored frons; face bare except for series of setulae paralleling frontal suture; parafacial with transverse, golden brown to blackish brown stripe or maculation at level of antennal base, thereafter ventrally concolorous with face. Eye slightly higher than wide. Gena high, height slightly more than eye height, anterior portion concolorous with face and parafacial, becoming whiter posteriorly; gena-to-eye ratio 0.52–0.56. Clypeus with dorsal of medial portion bare.

Thorax: Mesonotum generally mottled, mostly dark brown, with some gray to tannish gray areas, especially peripherally and along setal tracks, bases of setae blackish brown; scutum mostly brown to blackish brown, with some gray areas sometimes evident, usually as short stripes along acrostichal and dorsocentral tracks; scutellum generally and extensively blackish brown, only mediobasal, somewhat triangular area whitish gray; anepisternum generally concolorous with rest of pleural area, sometimes slightly darker, lacking maculation in middle. Postsutural supra-alar seta well developed but slightly shorter than postalar seta; anepisternal setae 1–3, thinly developed; katepisternal seta well developed, length subequal to notopleural seta. Wing hyaline; R stem vein bearing 5–7 short, thin, pale setulae dorsally; vein R1 with short, sparse setulae along length; costal-vein ratio 0.29–0.33; M-vein ratio 0.56–0.62. Leg color variable; femora blackish brown with moderately dense whitish gray microtomentum; tibiae blackish brown apically, basal portion yellowish red, thinly invested with whitish gray microtomentum; tarsi blackish brown dorsally, yellowish orange to orange ventrally, apical tarsomeres becoming blackish gray; forebasitarsomere of male normally developed, similar to basitarsomeres of mid- and hindlegs; foretarsomeres 2–5 of male normally developed, not greatly expanded apically, width much less than length; lateroapical setae of foretarsi of male tapered; hindbasitarsus and tarsomere 2 of male bearing sparse patch of long, slender setae posterodorsally; hindtarsomere 2 of male bearing some long setae along dorsum; tarsomeres of midleg bearing long setae lateroapically, aligned with plane of leg, length of setae subequal to width of tarsomere at apex.

Abdomen: Tergites 3 and 4 with dark band along posterior margin, at least in middle, band sometimes connected laterally with anterolateral spot, or spot separate; 1st tergite with medial patch of short, dorsally erect setulae. Male terminalia (Figures 39–41): epandrium in posterior view (Figure 39) rounded arch-shaped, narrow dorsally and slightly angulate, arms wider at dorsolateral level, ventrally becoming narrower; cercus ovoid, wider subventrally; presurstylus in posterior view (Figure 39) broadly triangular, length about 1.5 times basal width, dorsomedial angle narrowly produced, short, medial margin with 2 step-like processes, ventral apex broadly rounded, lateral margin very shallowly arched; postsurstylus in lateral view (Figure 41) wide and angulate basally, bearing shallow, setulose lobe just beyond midlength; inner lobe of bilobed apex wider and slightly longer than outer lobe, essentially bare of setulae; aedeagus in lateral view (Figure 41) with base moderately wide, immediately narrowed, especially on inner surface, external surface with recurved, narrow lobe at midlength, apex irregularly and relatively broadly rounded; aedeagal apodeme in lateral view (Figure 41) with keel shallow, ridge-like, with long, narrow extension toward attachment with hypandrium, bifurcate arms at attachment with hypandrium long; hypandrium somewhat wide and deep.

TYPE MATERIAL.—The holotype male is labeled “Holo-type [round label with red submargin]/Madagascar[.] [Tamatave:] Est[,] Sahasoa Fampanambo 80m[,] dct Maroansetra[,] 26–29.III.58[,] B. Stuckenberg/Dryxo margaretae sp. n. det. B. H. Cogan 1967 [species name and “1967” handwritten].” The holotype male is pinned directly, is in excellent condition (right midleg missing), and is deposited in the MNHN. Two paratypes (1, 1; NMSA) bear the same locality data as the holotype. Other paratypes are as follows: MADAGASCAR. Toamasina: Moramanga (=Mamaranga), Perinet (Niagarakely Forest), Dec 1955, B.R. Stuckenberg (2, 1; BMNH, NMSA).

OTHER SPECIMENS EXAMINED.—Afrotropical. MADAGASCAR. Fianaratsoa: Ranomafana (600 m), 18–20 Jan 1990, W.E. Steiner (1 2; USNM); Ranomafana (7 km W; 900 m), 8–21 Oct 1988, 20–24 Mar 1990, W.E. Steiner (7, 4; USNM). Toamasina: Maroansetra, Dec 1949, J. Vadon (3; MRAC).

DISTRIBUTION.—Afrotropical: Madagascar.