Chaetonerius alluaudi (Giglio-Tos)

Sepúlveda, Tatiana A. & De Carvalho, Claudio J. B., 2019, Chaetonerius Hendel (Neriidae: Diptera) from the East African islands with description of four new species from Madagascar and the Comoros, Zootaxa 4567 (1), pp. 130-146 : 137-138

Chaetonerius alluaudi (Giglio-Tos)

Nerius alluaudi Giglio-Tos 1895: 366 .

Chaetonerius alluaudi ; Enderlein 1922: 146.

Diagnosis. Antennal base absent. Several setulae between anterior margin of frons and anterior fronto-orbital seta. Face yellow with median sagittal brownish-yellow to blackish-brown stripe ( Fig. 3 ). Occiput brown with median yellow stripe densely white pruinose and submedian stripe of white pruinescence, beginning in posterior margin of eye and fading away posteriorly ( Fig. 2 ). Proepisternal lobe with anterodorsal protuberance. Dorsal katepisternum slightly yellow. Katatergite yellow. Vein dm-cu slightly oblique. Coxae yellow ( Fig. 5 ). Abdomen with two very wide longitudinal yellow stripes, divided by very narrow brown stripe. Sternite 6 expanded over proximal half to two thirds of epandrium. Outer margin of pregonite with triangular kink on distal third. Surstylus half the length of cercus. Cercus lanceolate ( Fig. 21 ).

Male. Male body brown and yellow with regions of dense white pruinescence in thorax dorsal and pleuron; males from Réunion with darker body and legs. Body length 4.0– 6.5 mm ( Fig. 18 ).

Head. Sagittal stripe in face dark brown to blackish-brown in specimens from Réunion. Anterior margin of frons straight; fronto-orbital plate yellow, covered by dense white pruinescence; three fronto-orbital setae equidistant or anterior and middle fronto-orbital setae slightly more distant that middle and posterior fronto-orbital setae; anterior fronto-orbital seta length nearly half of posterior fronto-orbital seta; frontal vitta mostly blackishbrown, except for median yellow stripe narrowing towards ocellar triangle; vertex brown, bordered laterally by yellow stripe with white pruinescence extending from fronto-orbital plate to occipital foramen, delineating the brown median occipital sclerite ( Fig. 4 ); area around insertion of outer vertical seta slightly inflated ( Fig. 1 ); lateral occiput with variable number of setae: postocular setae from 1 to 4 but mostly with one long and one short postocular setae in one side and two shorts in the other side while occipital setae from 3 to 5 but mostly with four occipital setae. Postgena with yellow setulae laterally and sparse black setulae near occipital foramen. Faint frontogenal suture fades out below parafacial ( Fig. 3 ). Palpus yellow. Antennae. Arista brown with base white to completely brown, covered by short pubescence; arista inserted sub-apically; first flagellomere wide ovate with wide apex; scape and pedicel short, length together is near half of first flagellomere.

Thorax. Dorsal longitudinal stripe of gray pruinescence divided medially by two brown stripes fading postsuturally ( Fig. 6 ). Scutellum trapezoid with curved margins; length of distal margin between scutellar apical setae, half the distance between prescutellar dorsocentral setae; discal scutellar seta same length as anterior notopleural seta. Pleuron mostly brown, with yellow stripe from dorsal half of proepisternal lobe to wing base, extending to posterior anepisternum, anterior anepimeron and dorsal katepisternum ( Fig. 5 ). Proepisternum yellow with yellow setulae; ventral margin with one yellow setula and one seta as long as anterior notopleural seta. Anepisternum and katepisternum with yellow setulae posteriorly. Wings. Infuscate around reaching point of veins R 2+3 and C; length 1.2¯ 1.8 mm and width 3.9¯ 5.8 mm. Legs. Fore coxa with two anterolateral setae (three on males from Réunion). Femora brown with yellow ring on distal third; fore femur with short spine-like anteroventral setae increasing in size discretely as they approach the apex.

Abdomen. Tergites brown with two dorsal wide yellow longitudinal stripes, divided by median narrow brown stripe; sternite 6 brown, visor-shaped ( Fig. 21 ). Distal margin of epandrium, reaching anterior half of third abdominal segment ventrally; surstylus linear; cercus with very pointed apex, measuring half the length of epandrium; outer margin of phallapodeme linear; postgonite rounded with rows of 4¯5 spines and slightly sclerotized basally; distiphallus mostly sclerotized and linear, with a median narrow membranous area, terminating in a partially sclerotized spine and a short and wide membranous tube.

Female. Body length 5.6–6.6 mm. Fore coxa with one and sometimes two anterolateral setae or even only one seta on one side; fore femur with several prominent anteroventral setae and two spine-like in apical third; femora dark with rings on distal third only slightly differentiated. Oviscape yellow with black apex.

Type Material. (lost). Type locality: Seychelles Island .

Material examined (51 specimens). Seychelles: 2♂ 7♀ 1?, (1) Illes Séchelles Solhou-ette: Mare Cochons , forêt endemique 500m, 2¯ 8.vii.1972 (2) Coll Mus Tervuren Miss. Zool belge aux Sécgelles-PLG Benoit et J. J. van Mol [ RMCA, 489, 488, 525, 518, 520, 521, 526, 519, 524, 517] ; 2♀, (1) Illes Séchelles Solhou-ette: Mt. Dauban, for. endemique vers. Est 600m, 5¯ 6.vii.1972 (2) Coll Mus Tervuren, Miss. Zool belge aux Sécgelles-PLG Benoit et J. J. van Mol [ RMCA, 523, 522] . Madagascar: 1♂ 7♀, (1) N. Ambohitra 800m Joffreville , 9–12.iv.1991, A. FRIEDBERG & FINI KAPLAN (2) SMNH-TAUI 205774, 205630, 205768, 205767, 205766, 205765, 205764, 205763, 205773 [TAUI, 745, 744, 743, 742, 741, 740, 734, 735]; 1♂, (1) Antananarivo, Park Tsimbazada , 18°56´S 47°31´E, 6.xi.2007, A. FREIDBERG (2) SMNH-TAUI/ 205630 [ TAUI, 874] ; 1♀, (1) Ivoloina , viii.62, tomate (2) Madagascar [ USNM, 1542] ; 2♀, (1) RÈP. MALGACHE, TAMATAVE, Ivoloina , 1.viii.1972, L. & R. Blommers (2) RMNH Leiden ex collection ZMAN [ RMNH, 1712, 1708] ; 3♀, Brickaville , vii.58, Sigwalt [ MNHN, 1158, 1156, 1513] ; 1♂ 1♀, Ranomafana N. P., 21°16'S, 47°27'E, 18.iv.1994, M. Wasbauer [ NMSA, 1679; UCDC, 1602] . Réunion: 2♀, (1) General sweeping: secondary vegetation (2) Mare Longe , research station, 27m, 21°21'43"S, 55°45'51"E, 6.xi.2015, M. J. Ebejer [ ME, 1829, 1830] ; 1♂, (1) General sweeping: riverbed (2) Rivière St. Suzanne, 20°56'53"S, 55°35'02"E, 4.xi. 2015, 360m, M. J. Ebejer [ ME, 1831] ; 2♂ 1♀, (1) Malaise trap: lowland tropical rainforest (2) Mare Longue, réserve naturelle at: 21°21'08"S, 55°44'20"E, 7¯ 10.xi. 2015, 270m, A. H. Kirk-Spriggs (3) Entomology Dept. National Museum, P.O. Box 266, Bloemfontein 9300, South Africa (4) BMSA (D) 75365, 75364, 75363 [BMSA, 1848, 1849, 1847]; 2♂ 9♀, (1) Hanging trap baited rotten fish; lowland, tropical rainforest (2) Mare Longue, réserve naturelle at: 21°21'08"S, 55°44'20"E, 23–28.x. 2015, 270m, A. H. Kirk-Spriggs (3) Entomology Dept. National Museum, P.O. Box 266, Bloemfontein 9300, South Africa (4) BMSA (D) 78105, 78101, 78106, 78107, 78109, 78110, 78111, 78104, 78102, 78100, 78099 [BMSA, 1850, 1857, 1851, 1853, 1852, 1858, 1859, 1856, 1860, 1854, 1855 (dissected)]. Mauritius: 2♀, (1) Vacoas ― 5.10.63, 27.3.1961 ―, C. M. Courtois (2) NATIONAL COLL . OF INSECTS, Pretoria, South Africa [ SANC, 1678, 1328] ; 1♂ 1♀, (1) Beau Bassin , 12.9.1939, M. Courtois (2) NATIONAL COLL . OF INSECTS, Pretoria, South Africa [ SANC, 1603, 1604 (dissected)] ; 1♀, (1) Ile d´Ambre , 7.ii.65, C. M. COURTOIS (2) NATIONAL COLL . OF INSECTS, Pretoria, South Africa [ SANC, 1677] .

Distribution. Seychelles, Madagascar (Diana Region, Alaotra-Mangoro Region, Atsinanana Region, Vatovavy-Fitovinany Region), Réunion, Mauritius.

Comments. Barraclough (1993a) mentions that it was not possible to access the type material of C. alluaudi , despite having unsuccessfully sought out every institution in which it could have been deposited. For that reason, this species was not discussed in his revisionary work. Moreover, the species has never been redescribed by any author.

Lamb (1914) has been the only one to address comments on morphology of C. alluaudi by describing how he identified the species by the presence of three thoracic dorsal gray stripes, being the median stripe narrower. The same character was used by Giglio-Tos (1895): “ Chez l´un des exemplaires, lhe thorax a trois lignes grises longitudinales, dont la mediane beaucoup plus êtroite; chez l´autre, ces lignes manquent et on voit deux petites lingnes latérales fauves très peu distinctes qui ne rejoignent pas la suture transversale du thorax ”. This character, together with its exclusive record from Seychelles Island, allows us to believe that the species described by Giglio- Tos (1895) corresponds to material recorded here as C. alluaudi . Our study allows us to confirm it can be easily differentiated from other species from East African islands by having three thoracic dorsal gray stripes longitudinally. Furthermore, other characters such as mid and hind coxae yellow and shape of cercus, which is long and lanceolate ( Fig. 21 ), can help differentiate C. alluaudi .

Figures

FIGURES 1–6. Chaetonerius alluaudi. 1. Head laterodorsal; 2. Head lateral; 3. Head lateroventral; 4. Head dorsal; 5. Thorax lateral; 6. Thorax dorsal.

FIGURES 21–25. Male genitalia of Chaetonerius of the East African islands, lateral and ventral views, square showing the zoomed apex of distiphallus (out of scale). 21. C. alluaudi [SANC, 1604]; 22. C. ebejeri [CSCA, 2246]; 23. C. kirkspriggsi [CSCA, 2241]; 24. C. kotrbae [USNM, 1633]; 25. C. madagasikara [USNM, 466].

FIGURES 16–20. Male habitus of Chaetonerius of the East African islands. 16. C. kirkspriggsi (HT); 17. C. ebejeri (HT); 18. C. alluaudi [BMSA, 1858]; 19. C. madagasikara (HT); 20. C. kotrbae (HT). Abbreviation: HT, holotype.