Ctenostylum fuscomaculatum Rafael, Pimentel & Godoi

Rafael, José Albertino, Pimentel, Therezinha De Jesus, Godoi, Fabio Siqueira P. & Machado, Renato Jose Pires, 2009, The enigmatic genus Ctenostylum Macquart with the description of a new species from the Brazilian Amazon Basin and a checklist of world Ctenostylidae species (Diptera), Zootaxa 2026, pp. 63-68 : 65-68

Ctenostylum fuscomaculatum Rafael, Pimentel & Godoi , n. sp.

( Figs. 1–12 )

Female. General coloration yellow with head and thorax brown spotted. Head nearly as bulky as thorax ( Figs. 1–3 ). Frons yellow with brown spots at base of anterior prominence and at apex, near antennae. Frons with small yellow lateroclinate setae laterally, and with rather deep incised median line and dark brown to black bifid prominence anteriorly. Ocelli absent. Ocellar tubercle slightly protuberant with distinct tuft of brown setae. Postcranium yellow with yellow setae, brown spotted dorsally and ventrally, with longer setae on dorsal brown spot. No series of postocular setae can be distinguished from occipital setulae. Lunule large, subshining, distinctly small setulose. Antennal sockets separated by node-like carina. Face yellow, margined with brown ventrally, with median sclerotized zone more or less differentiated from lateral zones that are transparent and converge near antennal sockets. Eye brown-reddish, large, with small subequal facets. Antenna very short ( Fig. 4 ). Pedicel with anterodorsal protuberance with long and distinct setae. Flagellum with deep depression in which arista is inserted. Arista very complex, with dendritic branching (fan-shaped). Mouthparts entirely absent. Thorax ( Figs. 5–6 ) mainly yellow, with brown margin on mesonotum, entire scutellum, and extreme dorsal and ventral parts of mesopleuron. Mesoscutum with numerous short yellow reclinate setulae, and erect supra-alar and postalar tuft of dense dark setulae. Notopleuron bare. Scutellum with numerous yellow setulae dorsally, and one pair of dense and dark setulae posteriorly. Proepisternum and proepimeron bare. Prothoracic spiracles rounded, almost bare. Postpronotal lobe with two small setae. Posterodorsal margin of anepisternum, median part of anepimeron and katepisternum setulose. Legs (only right fore leg, except tarsi, and right hind leg present) yellow, but fore coxa brown anteriorly. Legs elongate, with small setae. Fore and hind tibiae without apical spurs. Hind femur attenuated distally and hind tibiae attenuated basally. Wing ( Fig. 7 ) narrowed basally, without alula. Veins yellow, membrane yellow basally and along costal margin, the remaining part hyaline. Costa with subcostal break. Costal vein extending to vein M.

Sc vein incomplete. Vein R1 with sparse, weak setulae. Cell r1 with four distinct crossveins forming five small closed cells; the first hyaline window in this cell at least 3.5x longer than other hyaline windows. Crossvein rm near the middle of cell dm and at level of vein R1. Anal vein (A) incomplete. Base of vein M rather evanescent leaving cell bm open anteriorly. Abdomen yellow, rather oval. Tergites ( Fig. 8 ) rather membranous; tergite 1 more sclerotized laterally; tergite 6 reduced to tranverse line of setae. Sternites ( Fig. 9 ) more membranous than tergites. Sternite 1 V-shaped. Sternite 2 distinct and remaining sternites distinguisable only by clusters of setae. Terminalia ( Figs. 8–11 ) with segment 7 enlarged, well sclerotized, not completely fused laterally ( Fig. 8 ). Distal eversible tube membranous with two more slender parts, the first representing segment 8; distal segment wider distally ( Fig. 10 ), with short, setulose, and quite blunt fused cerci dorsally ( Figs. 10–11 ). Internal eggs as illustrated ( Fig. 12 ).

Material examined. Holotype Ƥ (pinned): BRASIL, Pará [state], Serra Norte, H-1 Canga, 23–26.i.1986, Armadilha suspensa [= suspendable trap], 16 m (rectangular printed white label). Ctenostylum fuscomaculatum , HOLÓTIPO (rectangular printed red label). Deposited at MPEG.

Etymology. From Latin fuscus = brown, dark; maculatus = spotted. Refers to the brown-spotted head and thorax.

Discussion. McAlpine (1989) wrote that sexual dimorphism of the head in Ctenostylidae may affect eye size, and facial and antennal structures. He compared both sexes of Furciseta, in which the eyes were very much larger in the male with the anterior ommatidia enlarged and the frons narrowed to accommodate the eyes, and concluded that similar dimorphism is to be expected in Ctenostylum . This prediction is here supported as the female studied, unlike the males, has a wide frons and ommatidia of subequal size. The female specimen studied disagrees in many characters with Macquart’s and Bigot’s descriptions of C. rufum and we do not believe that they are sexually dimorphic characters.

Ctenostylum fuscomaculatum n. sp. differs from C. rufum in the brown-spotted head and thorax; the supra-alar tuft of dense dark setulae; the tuft of dense, dark scutellar setulae on each side of centre; and the four crossveins in cell r1. Ctenostylum rufum has six or seven crossveins.

Ctenostylum fuscomaculatum n. sp. differs from the undescribed male from Costa Rica by being generally yellow in coloration; the head and thorax are brown spotted; cell r1 has four crossveins; and vein r-m is placed near the midpoint of cell dm. The Costa Rican Ctenostylum is generally brownish in coloration; the head and thorax are unspotted; cell r1 has seven crossveins; and r-m crossvein is positioned distally beside cell dm.

Ctenostylum rufum was collected at “banks of Amazon River”, which varies from 60 meters elevation in Manaus to sea level in Belém, while C. fuscomaculatum n. sp. was collected around 500 km south of Amazon River in a highland forested area 500 – 700 meters above the sea level, presently being explored by a mining company.

Investigation of the phylogenetic relationships of this species with other ctenostylids is beyond the scope of this study, but Ctenostylum seems to be a basal group in that the sclerites of female segment 7 are not completely fused, as in other genera.

Figures

FIGURES 1 – 7. Ctenostylum fuscomaculatum, n. sp., holotype. 1, head, frontal view; 2, head, lateral view; 3, head, dorsal view; 4, antennae; 5, thorax, dorsal view; 6, thorax, lateral view; 7, wing.

FIGURES 8 – 12. Ctenostylum fuscomaculatum, n. sp., holotype. 8, abdomen, dorsal view; 9, abdomen, ventral view; 10, distal abdominal segment, lateral view; 11, cerci, ventral view; 12, internal egg.