Chaetonerius serratus, Sepúlveda & Souza, 2019

Sepúlveda, Tatiana A. & Souza, Diego De S., 2019, A new species of Chaetonerius Hendel (Diptera: Neriidae) from Northeast Madagascar, Zootaxa 4656 (2), pp. 389-392 : 390-391

Chaetonerius serratus sp. n.

urn:lsid:zoobank.org:act:FA9B1036-C136-427F-AC18-5DE3E55F4A60

Diagnosis. Arista brown and bare, positioned apically; first flagellomere ovate, elongate ( Fig. 1 ); underdeveloped antennal base ( Fig. 2 ); several setulae between anterior margin of frons and anterior fronto-orbital seta; four well-developed fronto-orbital setae, equidistant; lateral occiput brown, with one well-defined median yellow stripe and one ventral narrow yellow stripe; one postocular seta; postgena with a dense group of long yellow setae from behind the genal seta toward occipital foramen; thorax dorsally with narrow dorsocentral yellow stripe, converging on scutoscutellar suture; thorax with median wide brown stripe ( Fig. 3 ); mid and hind coxae brown; femora brown; abdomen brown, with two longitudinal yellow stripes.

Male (HOLOTYPE). Body 7.8 mm length. Head. Inner process of pedicel finger-like. Frontal vitta mostly black, with small yellow area on anterior margin, narrowing posteriorly. Anterior fronto-orbital seta positioned very close to anterior margin of fronto-orbital plate; anterior fronto-orbital seta short, half the length of the second one. In anterior view, upper face yellow dorsally, dark-brown ventrally ( Fig. 2 ); lateral face yellow with dark brown spot under scape; six occipital setae increasing in length dorsally on one side and three setae on the other. Thorax. Four well-developed dorsocentral setae increasing in length toward scutellum, being the dorsocentral pre-scutellar almost twice the length of dorsocentral pre-sutural and same length as apical scutellar seta. Scutellum trapezoidal, with margins rounded; posterior margin measuring approximately half of distance between dorsocentral pre-scutellar setae. Pleuron mostly brown, except for one yellow stripe from dorsal half of proepisternal lobe, notopleura, dorsal anepisternum to wing base. Prosternum with one ventral black seta and two yellow setulae. Anepisternum with several black setulae on posterior half. Katatergite brown. Katepisternum with two ventral setae, one long and one short. Fore coxa yellow, with a row of four anterolateral spine-like setae; mid and hind coxae brown. Wing. 6.5 mm long, 1.8 mm wide; slightly infuscate apically ( Fig. 4 ). Legs. Femora brown. Fore femur with anteroventral spine-like seta, interspersed between two or three short and one long inserted in a small tubercle ( Fig. 5 ). Tibiae brown; fore tibia with two lines of short and thick setae on posterior margin. Abdomen. Sternite 6 brown and visor-shaped, expanded over a very small proximal region of epandrium. Syntergosternite 8 yellowish-brown, shiny; half the length of epandrium ( Fig. 6 ). Epandrium yellowish-brown; distal margin of epandrium reaching posterior half of fifth abdominal segment ventrally. Surstylus linear, about two thirds the length of cercus. Cercus wide and linear, slightly tapering distally; as long as one third the length of epandrium. Phallapodeme linear ( Fig. 7 ). Pregonite linear. Postgonite rounded, with rows of 2−3 spines; slightly sclerotized basally. Distiphallus partially sclero- tized; bifurcated on distal half, always joined medially by membranous area; ending in one sclerotized spike and one thin membranous flexible tube; at level of the sclerotized spike, with one dorsal membranous spike ( Fig. 8 ).

Variation (PARATYPE). Body 6.5 mm length. Wing 5.9 mm length, 1.5 mm width. Five occipital setae on one side, four on the other.

Female. Unknown.

Etymology. The specific epithet is from the Latin word serratus , referring to the thick setae present on the ventral margin of fore femur, which resemble the cutting face of a saw. It should be treated as a noun in apposition.

Type material. HOLOTYPE, ♂ COLL. MUS. TERVUREN, N. E. Madagascar: Ambodivoangy , x.1959, J. Vadon [ RMCA] ( Fig. 9 ) . PARATYPE, 1 ♂, same data as the holotype [ RMCA]. Distribution. Madagascar (Antsiranana Province). Discussion. According to Sepúlveda & de Carvalho (2019), the faint frontogenal suture can provide valuable taxonomic information for the differentiation of groups of species in Neriidae from the East African islands. The authors suggested that species with the frontogenal suture extending anteriorly beyond the parafacial and almost reaching the antennal socket are closely related. C. serratus sp. n., not only bear an extended frontogenal suture, but also have underdeveloped antennal base, a feature similarly found in C. ebejeri . Apart from the features included in the key to differentiate C. ebejeri from C. serratus sp. n., the distal distiphallus of both species is also very different, with the latter bearing a particularly long flexible tube.

Figures

FIGURES 1−9. Chaetonerius serratus sp. n. (holotype): 1. Head lateral; 2. Head anterolateral; 3. Thorax dorsal; 4. Wing; 5. Fore femur, anterior view; 6. Postabdomen, lateral; 7. Postabdomen, ventral; 8. Distal portion of distiphallus, dorsal and ventral view; 9. Habitus. Abbreviations: distph, distiphallus; cerc, cercus; epand, epandrium; hypd, hypandrium; phapod, phallapodeme.