Chrysotus angustifrons (Robinson) Robinson, 2010

Capellari, Renato Soares & Amorim, Dalton De Souza, 2010, Re-description and new combination of five New World species of Chrysotus Meigen, with comments on the Neotropical genus Lyroneurus Loew (Diptera: Dolichopodidae), Zootaxa 2520, pp. 49-65 : 50-53

Chrysotus angustifrons (Robinson) , comb.nov.

( Figs. 1–4 , 18 )

Diaphorus angustifrons Robinson, 1975: 93 .

Diagnosis. Male: Eyes approximate, but not contiguous above the antennae; vt absent; apex of CxI yellow, covered by long pale setae; femora mainly brown, except apices; pulvilli I and II as long as t5, claws present; abdominal sternites with long vestiture, St8 without striking bristles. Hypandrium constricted after emerging from epandrium, dorsal surface serrate; arms of postgonite covered by microtrichia; cercus rounded.

Type material examined. Holotype ɗ: DOMINICA, Layou R. mouth. 8.iii.1965, W.W. Wirth, leg ( USNM). Paratypes, 2 ɗ, 2 Ψ, Layou R. mouth, 18–24.iii.1965; 1 ɗ, Layou R. mouth, 9.i.1965 ( USNM).

Re-description. Male. Body length: 2.5–3.2 mm. Wing: 2.2–2.4 mm long, 0.9–1.0 mm wide. Head. Dichoptic, frons converging at middle, as wide as ocellar mound, becoming wider above and below (mssc), metallic green; face as broad as broadest width of frons, metallic green, covered by silvery pruinosity; palpus yellow, with some brownish setulae; proboscis brown, with many pale setulae; 1 pair of divergent, strong oc and 1 pair of minute poc; vt absent, 1 pair of pavt; row of pale pocl, occiput slightly concave, lower surface with many long scattered pale setae. Antenna brown, scape conical, short; pedicel short, with crown of setulae at apex, dorsalmost longer; postpedicel rectangular, clearly pubescent, stylus bi-articulated at base, also pubescent. Thorax. Shining green. Mesonotum around median and transverse suture, anepisternum and katepisternum with bronze reflections; notopleuron with bluish reflection; mesopleura weakly covered by silvery pruinosity. Ac irregularly biseriate, extending to between 4th and 5th pairs of dc; 6 pairs of long dc, except 1st pair short; 1 pre- and 1 sutural ia; 1 pre- and 2 post-sutural sa; 1 large pa with 1 minute anterior seta; 2 npl; anterior end of mesonotum with few setulae on each side of median suture; 3 pprn, 1 very strong and 2 minute; lower surface of proepisternum with 2–3 pale setae, ventralmost longer; upper surface of proepisternum in front of anterior spiracle bare; scutellum light green, with pair of strong medial scutellars and 1 pair smaller laterad, about 1/4 as long as medial scutellars. Wing ( Fig. 18 ). Membrane hyaline. C ending at wing apex; R1 ending on basal third of wing; R2+3 not bent anteriorly at distal end; R4+5 and M parallel, R4+5 only slightly bent before reaching C; CuAx ratio, 0.5; A1 present, not reaching wing margin; anal angle slightly enlarged. Lower calypter and cilia yellowish; halter yellow. Legs. I: 1.7, 1.6, 1.1, 0.5, 0.3, 0.2, 0.1. II: 1.8, 1.9, 1.2, 0.6, 0.3, 0.2, 0.1. III: 2.3, 2.4, 0.8, 0.6, 0.3, 0.3, 0.2. Basal 3/4 of CxI, CxII and CxIII, trochanters, femora (except apical 1/5-1/4 of FI, FII and extreme tip of FIII) brown, somewhat shining green; tarsi brown from apex of t1; apex of CxI, tibiae and base of tarsi yellow. Anterior surface and outer edge of CxI covered by many long pale setae; anterior surface of CxII with 1 conspicuous lateral seta at base and with diagonal row of black setae descendent internally; lateral of CxIII with 1 long, black basal seta and 1 minute pale seta apically. FI with row of 6–8 pv on apical third; FIII with 1–2 anterior setae more conspicuous at apex. TI with 1 minute ad at base, ventral surface with short serration; TII with 1 large ad at base; TIII with irregular row of dorsal setae and 5-7 larger setae. Apical tibial setae: 0, 2, 3. Pulvilli slightly developed, as long as t5 on I and II; claws present on all legs. Abdomen. Shining green, inferior margins of Tg2–4 lighter; Tg2–5 dorsally with some bronze reflections. Tergites covered by short bristles, those of distal margins slightly stronger. Tg6 pubescent. St2–4 covered by long pale bristles, those of St5 shorter. St8 with pale setae on distal margin. Hypopygium ( Figs. 1–2 ). Anterior margin of epandrium straight at level of emergence of hypandrium; lateral epandrial lobe slightly projected, bearing 2–3 setae, basiventral seta present; surstylus short, 2 strong spines and 1 seta medially at apex, 1 dorsal seta near middle. Proximal portion of hypandrium with short projection; distal portion constricted after emerging from epandrium, dorsal surface serrate. Arms of postgonite as long as anterior processes and covered by microtrichia. Cercus short, rounded, pale brown. Female. Body length: 2.4–2.7 mm. Wing: 2.3–2.4 mm long, 0.9 mm wide. Very similar to males, except as noted. Frons as broad as face, about 1.5 times as high as broad, clypeal suture evident; palpus yellow, brownish basally; vt present, dorsal 6-7 pocl black. Legs. I: 1.7, 1.7, 1.0, 0.4, 0.3, 0.2, 0.1. II: 2.2, 2.0, 1.1, 0.5, 0.3, 0.2, 0.2. III: 2.4, 2.4, 0.8, 0.6, 0.3, 0.2, 0.1. Apex of FI without row of pv; TII with 1 large ad and 1 mintue dorsal seta near base, 1 short ventral seta near middle; TIII with 2 ad on basal half and 3–4 dorsal to pd setae. Apical tibial setae: 0, 3, 4. pulvilli not developed. Terminalia ( Figs. 3–4 ). Anterior margin of Tg6–7 with deep inverted U-shaped incision (c.f. Fig. 15 ). Tg8 and St8 divided into two rod-like sclerites, St8 sclerites connected mesally by sclerotized bridge; dorsal surface of acantophorites (Tg10) with crest of 5 rhomboid spines and 1 seta laterally.

Comments. The habitus of C. angustifrons is very similar to that of C. robustus and C. wirthi . It can be distinguished from these two species by the presence of only pale setae on the anterior surface of CxI, as well as by the hypopygium morphology: surstylus shorter (about the same length in C. robustus ), arms of postgonite shorter and covered by microtrichia (in C. robustus only a few proximally) and rounded cercus.

Figures

FIGURES 1 – 4. Chrysotus angustifrons (Robinson) comb. nov. 1 – 2. Male hypopygium, paratype (1, ventral view; 2, left lateral view). 3 – 4. Female oviscapt, paratype (3, dorsal view; 4, right lateral view). Scale bars: 0.1 mm.

FIGURES 18 – 25. Wings of Chrysotus and Lyroneurus. 18. C. angustifrons (Robinson) comb. nov., male paratype. 19 – 20. C. maculatus (Parent) comb. nov. (= Diaphorus maculipennis Robinson) (19, male; 20, female). 21. C. robustus (Robinson) comb. nov., male paratype. 22. C. spectabilis (Loew), male. 23. C. wirthi (Robinson) comb. nov., male paratype. 24 – 25. L. adustus (Wiedemann), male. Scale bars: 1.0 mm.

FIGURES 13 – 15. Chrysotus spectabilis (Loew), specimen from Dominica, B. W. I., female oviscapt (13, 15 dorsal view; 14, right lateral view). Scale bars: 0.1 mm.