Metoponia robertsoni

Daniels, Greg, 2016, A new genus and two new species of soldier fly (Diptera: Stratiomyidae: Chiromyzinae) from Australia, one found infesting sugarcane in central Queensland, Zootaxa 4092 (2), pp. 572-582 : 574

Metridius Daniels nov. gen.

( Figs 1–21 )

Type species. Metridius robertsoni nov. sp., by present designation.

Diagnosis. This genus can be separated from the other Australian Stratiomyidae by the following combination of characters: Eyes distinctly separated in both sexes and with sparse ommatrichia. Flagellomeres indistinct, at most represented by slight dorsal and/or ventral indentations; the first flagellomere is sometimes present in M. robertsoni nov. sp. Wings of male lacking discal medial cell, vein M3 absent; females apterous. Scutum of female without dorsal sutures and scutellum absent; scutum of male with usual sutures and scutellum present. Male terminalia ( Figs 6–8 ) small; aedeagus single pronged. Gonocoxite medially attenuate distally, extending almost to apex of aedeagus. Epandrium ( Figs 8 , 26 ) with prominent posterior corners. Female terminalia ( Figs 13–15 ). Ovipositor not apparent; sternite 8 viewed ventrally, is convex and longer than combined length of tergites 8 and 9.

Description. Male ( Figs 1–8 , 22–26 ). Head ( Figs 1–2 , 23 ). Yellow-brown with short erect setae; transversely broadened; ocellar tubercle black or black brown and raised above vertex. Frons visible when viewed laterally especially in M. robertsoni nov. sp. Frontal index 0.5–0.8. Ratio of frons width to head width 1.0:2.0–2.6. Eyes distinctly separated and with sparse ommatrichia. Flagellomeres indistinct, at most represented by slight dorsal and/or ventral indentations; the first flagellomere is sometimes present in M. robertsoni nov. sp.

Thorax about 1.5 times longer than wide and entirely yellowish brown or deep brown, with scutellum, humeral callus, postalar callus and laterotergite yellowish. Anepisternum shining, mostly devoid of setae. Wings ( Figs 4 and 24 ) about 2.5–3.0 times longer than wide and lacking discal medial cell and vein M3. Legs yellowish. First tarsomere on all legs shorter or longer than tibia.

Abdomen yellowish uniformly covered with short suberect setae. Male terminalia ( Figs 6–8 , 25–26 ) broadly triangular to subquadrate. Cerci one segmented. Gonostyli concave distally. Aedeagus single pronged. Gonocoxite medially attenuate distally, extending almost to apex of aedeagus.

Female ( Figs 9–15 ). Differing from male by being apterous and lacking halters, scutellum and most lateral thoracic pleura. Head (figs 9–10). Frontal index 0.6–0.7. Ratio of frons width to head width 1.0: 2.5–2.6.

Thorax. Scutum without dorsal sutures and scutellum. Wings absent, halters absent. Legs shorter than male and first tarsomere shorter than tibiae.

Abdomen. Terminalia ( Figs 13–15 ). Ovipositor is not apparent; sternite 8 viewed ventrally is convex and longer than combined length of tergites 8 and 9.

Etymology. The name of the genus comes from the Greek metridios, filled with seed, pertaining to the enlarged ovaries of the type species which occupy most of the abdominal and thoracic cavities.

Geographic Distribution. Australia (Queensland and New South Wales).

Comments. Metridius nov. gen. differs from Inopus in having eyes with sparse ommatrichia; in males the flagellum is at least three times as long as the combined length of the scape and pedicel, and the eyes are distinctly separated; females are apterous and lack scutal sutures and scutellum. From Boreoides and the Chiromyza group, Metridius nov. gen. differs in having an almost flat frons. Female Boreoides are micropterous, having vestiges of the wings and halters, in M. robertsoni nov. sp. they are entirely absent. The ovipositor of Boreoides and many Chiromyza is comprised of segments 5–8; in Inopus the ovipositor is comprised of segments 7 and 8, while in Metridius nov. gen. the ovipositor is not well developed. Sternite 8 in Chiromyza , Inopus and Boreoides is more or less flat and tapers distally, in Inopus it is almost square, in Boreoides and Chiromyza it is about twice as long as wide; in Metridius nov. gen. sternite 8 is convex, its length subequal to its basal width, and the apical margin about half the basal width. Tergite 8 and sternite 8 are subequal in length in Boreoides , Inopus and Chiromyza ; in Metridius nov. gen., the combined length of tergites 8 and 9 approximates the length of sternite 8.

Figures

FIGURES 1 – 8. Metridius robertsoni nov. sp., male paratypes. (1). Head, lateral view. (2). Head, anterior view. (3). Lateral habitus. (4). Wing. (5). Antenna. (6). Genital capsule, dorsal view with epandrium, proctiger and cerci excluded. (7). Genital capsule, ventral view. (8). Epandrium, proctiger and cerci. Abbreviations: aed, aedeagus; ce, cercus; ep, epandrium; gonocx, gonocoxite; gonost, gonostylus; pr, poctiger. Scale bar, 0.25 mm.

FIGURES 9 – 15. Metridius robertsoni nov. sp., female paratypes. (9). Head, lateral view. (10). Head, frontal view. (11). Lateral habitus. (12). Dorsal habitus. (13). Terminalia, dorsal view. (14). Terminalia, lateral view. (15). Terminalia, ventral view. Abbreviations: ce, cercus; st, sternite; tg, tergite. Scale bar, 0.2 mm.

FIGURES 16 – 21. Metridius robertsoni nov. sp., larva. (16). Head and thoracic segment 1, dorsal view. (17). Abdominal segment 3, dorsal view. (18). Anal segment, dorsal view. (19). Head and thoracic segment 1, ventral view. (20). Sternites 5 and 6, ventral view. (21). Anal segment, ventral view. Abbreviations: pdl, primary dorsolateral seta; pvl, primary ventrolateral seta; spa, sternal patch; st, sternite; sdl, secondary dorsolateral seta; svl, secondary ventrolateral seta. Scale bar, 1.0 mm.

FIGURES 22 – 26. Metridius mcalpinei nov. sp., male paratypes. (22). Lateral habitus. (23). Head, lateral view. (24). Wing. (25). Genital capsule, dorsal view with epandrium, proctiger and cerci excluded. (26). Epandrium, proctiger and cerci. Abbreviations: aed, aedeagus; ce, cercus; ep, epandrium; goncx, gonocoxite; gonst, gonostylus; pr, poctiger. Scale bar, 0.25 mm.