Macrostomus trilineatus, Rafael & Marques, 2019

Rafael, José Albertino & Marques, Dayse Willkenia Almeida, 2019, Five new species of Macrostomus Wiedemann and a checklist of Empididae (s. str.) (Diptera) from Bolivia, Zootaxa 4567 (2), pp. 251-275 : 270-273

Macrostomus trilineatus sp. nov.

( Figs 13 A–Q)

urn:lsid:zoobank.org:act:DEC371FE-B2EC-4107-9C54-67298D08B242

Diagnosis. Thorax shiny yellow with a mid-longitudinal black stripe from pronotum to level of transverse suture, between dorsocentral row of setae and paired submedian black stripes from anterior dorsocentral seta to scutoscutellar suture; tergite 8 with a short projection posteriorly, with apex rounded and longer setae surrounding and on the projection; posterodorsal lobe of epandrium with two stouter spatulate apical setae; anterior cercus multilobate.

Description. Holotype male ( Fig. 13A , before abdomen macerated). Body length 3.7 mm; wing length 3.8 mm. Head narrowly dichoptic. Frons shiny black, slightly narrower than anterior ocellus width. One pair of proclinate ocellar setae. Face less shiny black than frons, as wide as width of anterior ocellus. Postcranium somewhat narrow, shiny black, entirely sparsely gray pruinose. Inner vertical seta as long as outer vertical and postocular setae. Antenna velvety black with postpedicel short pubescent. Proboscis shiny, reddish-brown, almost 2X longer than head height. Palpus brown to black, upcurved. Gena with 2 setae and postgena with 1–2 setae. Thorax shiny yellow, yellow pruinose, with mid-longitudinal black stripe ( Fig. 13B ) from pronotum to level of transverse suture and paired submedian black stripe from anterior dorsocentral seta to scutoscutellar suture; midlongitudinal stripe placed between row of dorsocentral setae and paired submedian black stripe placed between dorsocentral and supra-alar row of setae. Scutellum yellow. Thoracic chaetotaxy: 3–4 antepronotals; 1 postpronotal stout, 2–3 minutes; 4 dorsocentrals, posterior pair longer; 1 presutural supra-alar; 1 postsutural supra-alar; 1 postalar; 1–2 proepisternal; 1 notopleural stout, 2 weaker; 2 pairs of scutellars, outer pair weaker; 4 laterotergitals with posterior seta weaker. Legs, predominantly shiny yellow, with ventral shiny black spot on all trochanters; apex of femora darker, mainly on hind femur; all tibiae and tarsi dark brown to black. Legs longer setae: fore coxa with 1 posteroventral near apex; fore tibia with 1 ventral at apex; mid tibia with 1 anterodorsal and 1 posterodorsal at basal third; hind femur with 1 anterodorsal and 1 anteroventral at distal third; hind tibia with alternating anterodorsal and anteroventral along entire length; hind tarsomere 1 with 1 anterodorsal, 1 posterodorsal distally and 4–5 ventrally, both shorter than dorsal seta. Wing ( Fig. 13A ) light brown infuscate along costal margin, darker at pterostigma; veins M 1 and M 2 somewhat distinct. Last section of vein M 4 longer than dm–m length. Vein CuA+CuP somewhat evanescent distally. Halter with stem dark yellow, knob dark brown. Abdomen ( Figs 13A, C ) shiny black, except basal sternites yellow. Tergites with longer setae posteriorly. Tergite 8 ( Fig. 13D ) in dorsal view with short projection distally, with apex rounded, with longer setae surrounding and including projection; in lateral view with distinct ventral keel ( Fig. 13E ) connected to cercal bridge. Sternite 8 with deep basal excision ( Fig. 13F , sinus outlined). Tergite 8 loosely connected to respective sternite ( Fig. 13E ). Epandrium ( Figs 13G, H, I ) with longer setae posteriorly; anterodorsal lobe stouter and longer than posterodorsal lobe; without anterodorsal cleft and with distinct anteroventral excision; posterodorsal lobe with two stouter spatulate apical spine–like setae besides other slender setae; small transverse sclerite between anterodorsal lobe of epandrium and anterior cercus ( Fig. 13J , arrow in figure). Anterior cercus ( Figs 13H, I ) well sclerotized, upwardly directed, multilobate, with longer setae on distal half; when viewed anteriorly ( Figs 13J, K ) emitting mesially stout, wide, curved arm connected to small, somewhat less sclerotized fused mid-longitudinally sulcate cercal bridge; cercal bridge ( Fig. 13L ) projected posteriorly in dorsal view. Median cercus subglobose ( Fig. 13I ), somewhat membranous with dorsal and mesial setae. Posterior cercus up and forward curved ( Figs 13I, M ), bifid; external arm entirely black; internal arm yellow on distal half. Ventral projection of cercus ( Figs 13J, K ) wider and less sclerotized dorsally, stouter ventrally, with distinct posterior setae medially on more sclerotized area; emitting dorsal branch with yellow distinct setae apically, setae visible in posterior view ( Fig. 13I ) when components dissected. Dorsal and ventral lobes of hypoproct somewhat connected, both short setose. Hypandrium ( Figs 13O, P ) expanded laterally in connection point with epandrium, with wide gonocoxal apodeme and seven slender posterior setae medially (mostly broken), microsetulose posterodorsally; apex wider with distinct distally backward directed spine-like projection. Ejaculatory apodeme (Fig. 130) tetralamellar with dorsal lamella wider than ventral one. Phallus same length of hypandrium with apex curved and thin.

Female. Unknown.

Geographical records. Bolivia (La Paz).

Type material examined. HOLOTYPE ♂: “ BOLIVIA, La Paz, Chulumani, cloud forest above 2000 m ”; “ Chulumani , 29.vi. [19]79”; “QR code: NHMUK 010864613 ”; “ Holotype ♂ Macrostomus trilineatus Rafael & Marques ” ( Fig. 13Q ) (NHMUK). PARATYPE: Bolivia: Same data as holotype, NHMUK 0 10864614 (1♂, NHMUK, dissected) .

Holotype condition. Pinned, double mounted. Abdomen dissected, in microvial with glycerin.

Etymology. From the Latin tri = three and linea = line, which refers to the three longitudinal stripes on the scutum.

Variation. Paratype specimen with thoracic submedian black stripe ending before scutoscutellar suture and all stripes narrower.

Remarks. Characters allowing a well-founded placement are presently not available for M. trilineatus sp. nov. It differs remarkably from other known Macrostomus species by the epandrium posterodorsal lobe with two stouter spatulate apical spine-like setae, by the presence of a small sclerite between anterodorsal lobe of epandrium and anterior cercus (not seen in other Macrostomus species). On the basis of the black longitudinal stripes on the thorax of M. trilineatus sp. nov., this species appears related to M. lineatus Rafael & Cumming, 2006 described from Ecuador and Peru. It differs by the three longitudinal black stripes on the scutum (versus one mid-longitudinal black stripe in M. lineatus ); tergite 8 projected distally (versus somewhat elongate and bifid); hypandrium wider distally and without medial projection (versus narrow distally, with medial posterior projection).

Figures

FIGURE 13. Macrostomus trilineatus sp. nov. holotype ♂. A. Habitus, lateral view, before abdomen macerated; B. head, lateral view and thorax, dorsal view; C. Apex of abdomen, lateral view; D. Tergite 8, dorsal view; E. Tergite and sternite 8, lateral view; F. Sternite 8, outlined, ventral view; G. Epandrium, partially broken, lateral view; H. Terminalia, lateral view; I. Terminalia (epandrium, hypandrium and phallus removed), right lateral view; J. Cercal bridge of anterior cercus, subepandrial sclerite and apex of ventral projection of cercus, anterior view (small transverse sclerite between anterodorsal lobe of epandrium and anterior cercus indicated by a small black arrow); K. Cercal bridge of anterior cercus and apex of ventral projection of cercus, posterior view; L. Cerci, dorsal view; M. Cerci, right laterodorsal view; N. Anterior cercus and subepandrial sclerite, anterior view; O. Hypandrium, ejaculatory apodeme and phallus, lateral view; P. Hypandrium, posterior view (alveoli setae highlighted); Q. Holotype labels. Scale bars, figures A = 1 mm; B = 0.5 mm; C = 0.3 mm; D–P = 0.2 mm.