Poecilominettia octovittata ( Williston, 1896 )

Soares, Matheus M. M., Gaimari, Stephen D., Corrêa-Neto, José De J., Limeira-De-Oliveira, Francisco & Rafael, José A., 2024, Insect (Hexapoda) diversity in the oceanic archipelago of Fernando de Noronha, Brazil: Lauxaniidae (Diptera), Zootaxa 5537 (1), pp. 1-23 : 15-21

Poecilominettia octovittata ( Williston, 1896)

( Figs. 7–8 )

Sapromyza octovittata Williston, 1896: 382 . Type locality: Saint Vincent (West Indies). Lectotype female (designated by Gaimari & Silva 2020), Natural History Museum, London, United Kingdom (examined SDG).

Poecilominettia sp. 2 ( Rafael et al. 2020).

Diagnosis. Easily differentiated from the other congeneric species by the distinct pattern of spots on the thorax, wing and abdomen ( Fig. 7A, B ); femora yellow, tibiae with a ventral brown spot near base ( Fig. 7A, B ); anterior margin of wing dark brown ( Fig. 7F ); surstylus ovoid, 1.5X longer than wide at widest point, with 2 pointed processes, 1 at middle of inner edge and 1 at apex ( Fig. 8A, B ).

Redescription. Head ( Fig. 7A–E ). Mostly yellowish, except frons with a narrow central dark brown median stripe extended from ocellar triangle to edge of lunule, subparallel to tapered anteriorly; face with an ovoid, median dark brown spot at lower margin; and with dark brown spot in area of gena and bottom of parafacial. Head 1.6X higher than long, 1.3X wider than high, 1.1X wider than scutum; eye 1.4X higher than long; gena height (directly below eye) 0.2X eye height. Vertex silvery-yellow pruinose, rounded; inner vertical seta long and strong, about 1.5X longer than outer vertical seta, with distance between them about 1/3 that from inner vertical seta to central vertex. Ocellar triangle dark brown, small, slightly raised, placed slightly in front of vertex, at same level as inner vertical seta; ocelli subequal in size and arranged in small equilateral triangle, covered with few tiny setulae. Ocellar setae proclinate and divergent, weak. Postocellar setae cruciate, slightly longer than ocellar seta. Two rows of short postocular setulae. Median occipital sclerite with silvery pruinosity and supracervical setae above occipital foramen. Frons 1.2X wider than long, frons flat, curved evenly into facial plane; with 2 strong reclinate fronto-orbital setae, posterior seta slightly longer than anterior seta, located near midpoint between inner vertical seta and anterior seta; anterior seta closer to lunule than to posterior seta; frons setulose at anterior 1/2, wholly bronzy pruinose except for central brown stripe. Lunule low, straight. Antenna mostly orangish-yellow, except scape and arista dark brown; scape with few short dorsal setae; pedicel with 1 long dorsal seta at middle length, with crown of short setae at apex and 3–4 long ventral setae; first flagellomere about 1.6X longer than high, and about 2X longer than scape and pedicel combined, with rounded apex; arista inserted dorsobasally on first flagellomere, covered with short and sparse rays. Gena with dense row of strong setae along ventral edge, extended onto lower parafacial; postgena with short and strong setae. Face about 1.2X wider than long, face and parafacial silvery pruinose, except parafacial darkened ventrally. Clypeus orange, narrow. Maxillary palpus and labellum brown, ventral surface of maxillary palpus with rows of long setae.

Thorax ( Fig. 7A, B, E ). Scutum slightly arched, about 1.2X longer than wide; scutellum about 1/3 as long as scutum, with width at base about 1.75X greater than length; scutum orangish-yellow, with dorsocentral and supra-alar brown stripes, pale yellow on postpronotum through notopleuron; scutellum pale yellow with dark brown lateral stripes as extended through dorsocentral stripes of scutum; pleural region mostly orangish-yellow, except anterodorsal quadrant of anepisternum, upper margin of katepisternum, lower margin of anepimeron, and meron dark brown. Chaetotaxy: 0+3 dorsocentral setae, anterior seta slightly shorter than middle seta, located close to transverse suture, middle seta located at midpoint between posterior seta and anterior seta; prescutellar acrostichal seta present, weak; 1 postpronotal seta; 2 notopleural setae, in anterior and posterior corners, anterior seta slightly longer than posterior; 1 postsutural intra-alar seta present; 1 presutural and 1 postsutural supra-alar setae; 2 postalar setae, in anterior and posterior corners; 7–8 irregular rows of acrostichal setulae between dorsocentral setal rows, row of setulae along dorsocentral area present, and setulose outside dorsocentral row; proepisternal seta present, strong; anepisternum with anepisternal seta along posterior edge, otherwise setulose in posterior 2/3; anepimeron bare; 2 katepisternal setae present, both strong, posterior one slightly stronger, katepisternum otherwise setulose through middle, and with group of long ventral setae, close to the coxa; 2 pairs scutellar setae, anterior setae subparallel, posterior setae cruciate. Legs ( Fig. 7A, B ). Pale yellow, except all tibiae with a ventral brown spot near base. Fore femur with posteroventral row of long and strong setae, about 1.5X longer than width of femur, posterior and posterodorsal rows of setae from base to apex, shorter and thinner than posteroventral row of setae; ctenidium absent. Mid femur with anterior row of short and strong setae in apical 1/2, and with 1 short curved posteroventral preapical seta. Hind femur with anteroventral row of short setae in apical 1/3 and 1 anterodorsal long preapical seta. All tibiae with preapical dorsal seta, strongest on mid tibia; mid tibia with 1 longer preapical ventral seta, as long as dorsal seta; hind tibia with 1 short apical ventral spur. Wing ( Fig. 7A, F ). Mostly hyaline, except dark brown in anterior 1/3 (through cells sc, r 1, and most of r 2+3) and curved around distal part of wing to the tip of vein M 1, on crossveins rm and dm-m, and with a spot at the midpoint of the distal part of vein M 1. Veins dark brown, except yellow in basal veins and sections of veins R 4+5 and M 1 ( Fig. 7F ). Length 3.5 mm; 2.5X longer than high. Cell dm about 4X longer than crossvein dm-m. Crossvein r-m located at midpoint of cell dm. Vein R 4+5 ending at wing tip, subparallel with veins R 2+3 and M 1. Crossvein dm-m straight, located slightly basal to midpoint between crossvein r-m and tip of vein M 1. Vein M 4 about 0.2X as long as crossvein dm-m. Vein CuA+CuP short, about 1/2 length of vein A 1.

Abdomen ( Fig. 7G, H ). Tapered gradually after segment 4; mostly yellow, except for lateral margins of syntergite 1+2 and tergites 3–6 dark brown forming a narrow stripe, paired semicircular brown spots along posterolateral margins of syntergite 1+2 and tergites 3–6, and central brown macula on tergites 3–6 forming a narrow stripe. Tergites covered with short setulae, longest and strongest along posterior edges of syntergite 1+2 and tergites 3–6. Sternites pale yellow to white, except lateral margins of sternites 3–5 dark brown, sternite 1 bare, sternites 2–5 setulose, with slightly longer setae at lateral margins; sternites 2–5 each slightly wider than long, subequal in width sternite to sternite; sternite 6 a membranous transverse strip. Male genitalia ( Figs. 7G , 8A–D ). Pale yellow, epandrium dorsally with rectangular dark brown spot at middle. Syntergosternite 7+8 simple, bare, transversely saddle-shaped. Epandrium simple, saddle-shaped; mostly bare, with median row of short setae and with row of long setae at posterior edge, 2X longer than widest point. Surstylus large, leaf-shaped in lateral view, 1.5X longer than wide at widest point, with 2 medially-pointed processes, inner process at middle of inner edge and apical process at apex, with sparse short setulae in posterior 1/2, close to the inner process and with 2 short inner setae above the process. Subepandrial sclerite narrow, about 5X longer than wide. Cercus short, ovoid, heavily setose. Ejaculatory apodeme long and narrow, weak sclerotized. Phallus mostly tubular, widened towards apex, about 2X longer than wide; apex of distiphallus with short, sclerotized teeth, 2 apical long and pointed teeth, apparently articulated with distiphallus, 1 short and stout tooth at base of distiphallus. Hypandrium a narrow transverse band. Postgonite short, rounded and weak sclerotized, with small seta.

Female: Similar to male. Sternite 6 pale yellow to white, except lateral margin dark brown (as in sternites 3–5) ( Fig. 7K ). Female terminalia ( Figs. 7I, J , 8E–H ). Tergite 7 not fused to sternite 7. Tergite 8 narrow, somewhat saddle-shaped, weakly sclerotized, with posterior row of setae. Sternite 8 somewhat quadrangular, lateral edges curved, heavily setose, dark brown, except for median rectangular yellow area. Epiproct narrow, with row of strong setae. Hypoproct simple, semicircular, heavily setulose. Spermathecae round, with configuration 1+2, paired spermathecae; surface smooth.

Material examined. BRAZIL, Pernambuco, Fernando de Noronha: Capim-Açu , 03°51′17″S – 32°26′26″W, 09–24.vi.2019, large Malaise trap, J.A. Rafael, F. Limeira-de-Oliveira & L.C. Castro (7 ♂, 36 ♀, INPA; 1 ♂, 3 ♀, AMNH; 1 ♂, 3 ♀, CSCA; 1 ♂, 3 ♀, USNM; 1 ♂, 3 ♀, SDG) ; same data, except 08–27.x.2019 (1 ♀, dissected, INPA) ; same data, except 03°51′30″S – 32°25′50″W, 01–09.vi.2019, varredura [sweeping], J.A. Rafael, F. Limeira-de-Oliveira & D.M.M. Mendes (9 ♀, INPA) ; Sueste Mangue , 03°51′30″S – 32°25′50″W, 01–09.vi.2019, armadilha luminosa [light trap] (3 ♂, 7 ♀, INPA) ; same data, except 20–27.ii.2020, Malaise trap, J.A. Rafael, F. Limeira-de-Oliveira & P.C. Grossi (1 ♂, 4 ♀, INPA) ; Trilha Sancho , 03°51′30″S – 32°25′50″W, 01–09.vi.2019, Malaise trap, J.A. Rafael, F. Limeira-de-Oliveira & D.M.M. Mendes (11 ♂, 2 dissected, 17 ♀, 2 dissected, INPA; 1 ♂, 1 ♀, AMNH; 1 ♂, 1 ♀, CSCA; 1 ♂, 1 ♀, USNM; 1 ♂, 1 ♀, SDG) ; same data, except CDC-UV light trap (2 ♂, 3 ♀, INPA) ; same data, except Caracas (1 ♀, INPA) . Additionally, 16,422 specimens from nearly all localities and dates in ethanol.

Remarks. Poecilominettia octovittata is easily recognized by the patterns of stripes and spots on the head and body, and by the wing pattern of being darkened anteriorly, on the crossveins, and in the distal part of vein M 1, as well as the distinctive characteristics of the male genitalia (particularly the shape and structure of the surstylus and the phallus) and female terminalia (particularly the paired darkened patches on sternite 8). The species was described from Saint Vincent (West Indies), and later recorded from Brazil ( Gaimari & Silva, 2020). This is by far the most abundant lauxaniid in Fernando de Noronha, after nine months we collected 16,548 specimens in all traps, representing 87,6% of the specimens collected, with 13,416 in Capim-açu, 2,769 in Sancho and 363 in other localities of the archipelago. It is worth noting that Fig. 7B is a living specimen photographed in Olho d’Água das Flores, in the state of Alagoas, being the first record of this species from the state (https://www.inaturalist.org/ observations/140062464).

Discussion. The genus Poecilominettia comprises 81 described species, all found in the Neotropics except for three strictly Nearctic species, and with 56 of the Neotropical species found in Panama, and 10 recorded in Brazil ( Gaimari & Silva 2020). The revisionary work of Broadhead (1989) represents the most comprehensive treatment of the genus, with a key to species and illustrations for most species. Broadhead (1989) also discusses the biology of the species of this genus, finding that adults feed on fungal hyphae and fungal spores, based on examination of food particles found in the pseudo-tracheal canals and gut contents. She also discusses the idea that although their larval habits are not known, they are generally thought to develop within the tissues of fall, decaying leaves. Some species of the genus are also known to feed in decaying matter in birds’ nests ( Miller & Foote 1975, Miller 1977). Further, Miller & Foote (1976) provide details of the morphology of immatures for a species of Poecilominettia .

Figures

FIGURE 7. Poecilominettia octovittata (Williston, 1896). A, C–H male (INPA), B (living female from municipality of Olha d’Água das Flores, state of Alagoas), I, J female (INPA). A, B. Habitus, lateral view; C, D. Head anterior and lateral views, respectively; E. Head and thorax, dorsal view; F. Wing; G. Male terminalia, posterior view; H. Male abdomen, dorsal view; I–J. Female abdomen, dorsal and ventral views respectively. Abbreviations: afrs = anterior fronto-orbital seta; dc str = dorsocentral stripe; ep spt = spot on epandrium; fc spt = facial spot; kpt s = katepisternal seta; flgm 1 = first flagellomere; ot = ocellar triangle; sal str = supra-alar stripe. Photograph B provided by Alenilson Rodrigues.

FIGURE 8. Poecilominettia octovittata (Williston, 1896). A–D male (INPA), E–H female (INPA). A, B. Epandrium in posterior and lateral views, respectively; C, D. Internal appendages in lateral and anterior views, respectively; E–G. Female terminalia in lateral, dorsal and ventral views, respectively; H. Spermathecae.Abbreviations: bp = basiphallus; cerc = cercus; dp = distiphallus; e = epiproct; epand = epandrium; h = hypoproct; hypd = hypandrium; ej apod = ejaculatory apodeme; te = teeth of distiphallus; st = sternite; tg = tergite; pgt = postgonite; sur = surstylus.