Macrostomus chelicercus, Rafael & Marques, 2021

Rafael, José Albertino & Marques, Dayse Willkenia A., 2021, Four new species of Macrostomus Wiedemann and a checklist of Empididae s. str (Diptera) from Peru, Zootaxa 4981 (3), pp. 506-530 : 516-517

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Macrostomus chelicercus

sp. nov.

Macrostomus chelicercus sp. nov.

( Figs 8A–N View FIGURE 8 , 9A–E View FIGURE 9 )

Diagnosis. Male. Thorax with mesonotum, scutellum and mediotergite shiny brown to black; postpronotal lobe and mesopleuron shiny yellow; pronotum and notopleuron partially shiny brown to black and partially yellow; mid and hind femora and tibiae slightly curved; hind femur clavate from basal 2/3; tergite 8 short, with shallow basal sinus, sinuose posteriorly; anterior cercus with U-shaped cercal bridge; posterior cercus cheliform, distinctly inward and forward curved, bifid at apex; phallus distinctly longer than hypandrium.

Description. Holotype ♂ ( Fig. 8A View FIGURE 8 ). Body length 3.2 mm; wing length 3.0 mm. Head dichoptic. Frons shiny black narrower than width of anterior ocellus, narrower ventrally. One pair of proclinate ocellar setae. Face as wide as frons ventrally, less shiny black than frons, slightly gray pruinose. Postcranium shiny black, sparsely gray pruinose, except dorsal postocular margin shiny without pruinescence. Inner and outer vertical setae broken. Gena with 2 small setae and postgena with 1–2 minute setae. Antenna velvety brown to black with postpedicel short setulose. Proboscis mainly yellow. Palpus brown to black. Thorax ( Fig. 8A View FIGURE 8 ) shiny brown to black dorsally, partially on pronotum, entirely on mesonotum, partially on notopleuron, entirely on scutellum and mediotergite; shiny yellow on postpronotal lobe, partially on notopleuron and entirely on mesopleuron. Thoracic chaetotaxy: 3 antepronotals; 1 postpronotal stout and 1–2 minute; 4 dorsocentrals, with posterior pair stouter; 1 presutural supra-alar; 0 postsutural supra-alar; 1 postalar stout, 1 minute; 2–3 small proepisternals; 1 notopleural stout, 1 weaker; 2 pairs of scutellars, outer pair weaker; 4 laterotergitals. Legs ( Figs 8A, B View FIGURE 8 ) shiny yellow except apices of mid and hind femora, distal half of hind tibia, mid and hind tarsi brown to black. Mid and hind femora and tibiae slightly curved. Hind femur clavate from basal 2/3. Mid tibia with slender anterodorsal distal seta; hind tibia with 1 short seta at basal fourth and 2 longer setae at distal fourth; hind tarsomere 1 with 3 longer dorsal setae at distal half. Wing ( Fig. 8A View FIGURE 8 ) hyaline, slightly brown infuscate at pterostigma and apex of cell r 2+3. Veins M 1, M 2 and CuA+CuP evanescent. Distal section of vein M 4 longer than vein dm–m length. Cell dm elongate, somewhat truncate. Halter yellow with knob brown. Abdomen ( Fig. 8A View FIGURE 8 ) with tergite 1 and base of tergite 2 shiny yellow, remaining shiny brown to black. Tergite 8 ( Figs 8C–E View FIGURE 8 ) short, with shallow basal sinus, sinuose posteriorly. Sternite 8 ( Figs 8E, F View FIGURE 8 ) with posterolateral saddle-shaped projection. Tergite 8 narrowly articulated anterolaterally with sternite 8 ( Fig. 8E View FIGURE 8 ). Epandrium ( Figs 8G, H View FIGURE 8 ) with posterodorsal lobe higher than anterodorsal lobe, latter with small rounded mesial lobe and longer setae posteriorly and dorsally, without anterodorsal nor anteroventral cleft. Anterior cercus ( Fig. 8G View FIGURE 8 ) subtriangular, wider dorsally, with slightly longer setae dorsally and triangular mesial process of anterior cercus touching each other but not fused ( Figs 8I, J View FIGURE 8 ); cercal bridge U-shaped ( Fig. 8I View FIGURE 8 ). Median cercus ( Fig. 8G View FIGURE 8 ) somewhat translucent, subsquare, upward directed with longer marginal setae; posterior cercus ( Fig. 8G View FIGURE 8 ) cheliform, distinctly inward and forward directed with apex bifid. Ventral projection of cercus ( Fig. 8J View FIGURE 8 ) short, transversely positioned, with 3–4 stout distal setae. Dorsal hypoproctal lobe ( Figs 8J, K View FIGURE 8 ) large, with slender marginal setae; ventral hypoproctal lobe inconspicuous. Hypandrium ( Figs 8L, M View FIGURE 8 ) in lateral view slightly wider distally, apex with two protuberances, anterior shorter and reclined; posterior margin of hypandrium with 7 uniseriate setae. Ejaculatory apodeme ( Fig. 8L View FIGURE 8 ) with dorsal lamella slightly higher than ventral lamella. Phallus ( Figs 8L, M View FIGURE 8 ) distinctly longer than hypandrium.

Female. One specimen in poor condition appears to be conspecific with male specimens. Body and wing length not measured. Frons shiny black slightly wider than anterior ocellus width, narrower ventrally. Face slightly narrower than frons, slightly gray pruinose. Postcranium shiny black, entirely sparsely gray pruinose. Legs shiny yellow with apices of distal tarsomeres brown. All legs not curved, nor clavate. Wings damaged. Abdomen entirely shiny black. Tergite 8 damaged, apex with deep distal sinus ( Figs 9B, D View FIGURE 9 ). Tergite 9+10 ( Figs 9A, B View FIGURE 9 ) short with distinct basal sinus. Sternite 8 ( Figs 9A, C View FIGURE 9 ) somewhat truncate distally, with incision laterally and mid-longitudinal hyaline stripe ventrally, stripe almost reaching apex. Sternite 10 with basal sinus. Cercus cylindrical. Genital fork ( Fig. 9E View FIGURE 9 ) simple rod-shaped, slightly wider distally. Genital chamber predominantly membranous.

Geographical records. Peru (Cuzco).

Type Material examined. HOLOTYPE ♂, labelled: “ PERU, Cuzco, Quincemil, Rio Araza , 13º21′18″S – 70º53′22″W, 1000 m ” / “ 22–26.viii.2012, sweep, J.A. Rafael, R.R. Cavichioli ” / “ Holotype ♂ Macrostomus chelicercus Rafael & Marques ” ( Fig. 8N View FIGURE 8 ) ( MUSM) GoogleMaps . PARATYPES: 1♂ and 1♀, same data as holotype (1♂ INPA, 1♀ MUSM); Cusco Estacion Biologica Villa Carmen , Oroya, S. side, 1.89111°S 71.41046°W, 572 m, MT, 12–16.xii.2013, A.L. Norrbom, B.D. Sutton (1♂ CNC) GoogleMaps .

Holotype condition. Pinned, glued on small card, in good condition; abdomen dissected, stored in microvial with glycerin.

Etymology. From Greek chele = claw and cercus = cercus, refers to the cheliform shape of the posterior cercus.

Remarks. Macrostomus chelicercus sp. nov. is best placed in the M. amazonensis species-group as described by Rafael & Cumming (2015). In the key presented by Rafael & Cumming (2015) it runs to couplet 2 of M. acreanus Rafael & Cumming, 2015 by having the mesopleuron yellow. Both species have a short tergite 8 with shallow basal sinus. Macrostomus chelicercus sp. nov. differs by the cercal bridge U-shaped (versus dome-shaped in M. acreanus ), anterior cercus subtriangular (versus longitudinally elongate), posterior cercus inward and forward directed with apex bifid (versus vertically elongate with apex simple). Nevertheless, Macrostomus chelicercus sp. nov. appears to be more related with M. xavieri Rafael & Cumming, 2015 by the short tergite 8 with shallow basal sinus, mesial process of anterior cercus small and posterior cercus inwardly curved. Macrostomus chelicercus sp. nov. differs by cercal bridge U-shaped (versus somewhat bilobate in M. xavieri ), anterior cercus subtriangular (versus vertically elongate), posterior cercus inwardly and forwardly directed with apex bifid (versus inwardly curved with apex simple). Additionally, M. chelicercus sp. nov. differs from both species by the distinctly crooked hind femur, with denser, short, stouter dorsal and ventral setae at curved area and by the slightly curved mid and hind femora and tibiae. In CNC, there is an additional new species which keys to M. chelicercus sp. nov. (B.J. Sinclair pers. comm. 2020). The specimens are from Peru, Manu Wildlife Centre, Bamboo Trial, 30.x.2006, 12°17′08″S 70°54′14″W, J.H. Skevington (4♂, CNC).


Instituto Nacional de Pesquisas da Amazonia


Canadian National Collection of Insects, Arachnids, and Nematodes