Arganthomyza acuticuspis Roháček & Barber, 2013

Roháćek, Jindřich & Barber, Kevin N., 2016, Nearctic Anthomyzidae: a monograph of Anthomyza and allied genera (Diptera), Acta Entomologica Musei Nationalis Pragae (suppl.) 56, pp. 1-412 : 79-83

Arganthomyza acuticuspis Roháček & Barber, 2013

( Figs 106 , 110–125 )

Arganthomyza acuticuspis Roháček & Barber, 2013: 18 .

Type material. HOLOTYPE: ♂, “ USA:NM: Torrance Co., Manzano Mts , 12 mi W Manzano [34°37.4'N 106°24.8'W], Red Canyon Cmpgd, 8000', 27–30.viii.1993, J. E. O’Hara, malaise trap ” and “ HOLOTYPUS ♂, Arganthomyza acuticuspis sp.n., J. Roháček & K. N. Barber det. 2011” [red label] ( CNCI, intact, see Fig. 106 ) . PARATYPES: 2 ♂♂ 9 ♀♀ ( AMNH, CASC, CNCI, DEBU, LEMQ, OSAC, UCRC, WFBM) (details in ROHÁĆEK & BARBER 2013).

Diagnosis. Male 2.24–2.78 mm, female 2.30–3.05 mm. Mostly blackish brown ( Fig. 106 ), sparsely grey microtomentose and distinctly shining; face, parafacialia, gena, postgena, ventral margin of occiput, mouthparts, haltere entirely and frons, antennae, legs largely contrasting ochreous, yellow or whitish yellow. Frontal triangle relatively short and narrow, reaching anterior third (its brown part only half) of frons. Mid and hind basitarsus without short thickened setae. T1 and T2 almost separate, only laterally partly fused. T3–T5 subequal, broad, bent onto ventral side of abdomen. Wing hyaline ( Fig. 125 ). Reference to the genitalia is necessary to conndently distinguish this species from A. disjuncta and A. socculata , although colour characters can differentiate taxa in its own species group.

Male genitalia (see Figs 110–116 for details). Epandrium ( Figs 110, 111 ) brown to blackish brown, higher than long and relatively broad. Gonostylus ( Figs 111, 116 ) nat, ochreous yellow, of elongate subtriangular lateral outline (in maxium extension view) with acute apex; very slightly bent medially ( Fig. 110 ), markedly less than in A. bivittata and A. duplex . Postgonite narrow, long, with apex bent posteriorly ( Fig. 112 ); nlum of distiphallus with longitudinal sclerites only partly fused and basally dilated ( Fig. 115 ).

Female postabdomen and genitalia (see Figs 117–124 for details). T7 and S7 completely fused into largely dark brown ring-shaped tergosternum T7+S7 ( Figs 118, 119 ), anteroventrally with long, dark, nnely sinuate transverse ledge-like band and spiracles situated at its lateral ends ( Fig. 119 ). Ventral receptacle ( Fig. 121 ) slender and elongate, of the same general form as in A. bivittata and A. duplex , with middle part curved and somewhat ringed, and long terminal part simply tubular and apex vermicularly twisted. Spermathecae (1+1) short-pyriform to subcylindrical ( Figs 117, 120 ), both of the same size, each more or less constricted in proximal third, with dark transversely striated (striae interrupted) surface in distal two-thirds, and with a number of small dark spines in narrower basal part around duct insertion; duct with cervix distinct but weakly sclerotized.

Discussion. Arganthomyza acuticuspis is supported as basal in the A. duplex group, which also includes A. bivittata and A. duplex ( ROHÁĆEK & BARBER 2013: Fig. 173 ; ROHÁĆEK & TÓTHOVÁ 2014: Fig. 1 ).

Arganthomyza acuticuspis differs distinctly from both of its closest relatives by its uniformly dark brown pleuron, among many other internal characteristics. However, it is more similar externally to both A. disjuncta and A. socculata . The key above is necessary for absolute separation of these three species but because A. acuticuspis appears to be restricted to the southwestern United States (Arizona, New Mexico), it is distantly allopatric with the northwestern A. socculata (Alaska) , and these two species should not be confused. In contrast, the female of A. acuticuspis can be readily distinguished from that of A. disjuncta which has the S7 separated from T7 (fused in A. acuticuspis ) while the shape of the gonostylus is usually enough to separate the males of these two (narrowly sympatric?) species.

Biology. Virtually nothing is known about the biology of this species. Generally, habitats are open meadows dominated by grasses and wildnowers bordering and surrounded by coniferous forests (based on photographic information from Dr. James O’Hara, CNCI). This generalized habitat is more reminiscent of the open “grassy” habitat of A. disjuncta than of other members of the A. duplex group that are associated with a more mesic mixed forest with dense herbaceous undergrowth (at least in eastern North America). Flight period runs minimally from 15 June (Arizona: Rustler Park) to 27–30 August (New Mexico: 12 mi W Manzano) but this short period is probably an artifact of insufncient data.

Distribution. This poorly collected species is known only from elevated sites (7100' to 8950' = 2164 to 2728 m) in Arizona and New Mexico in the southwestern United States of America (see Table 2, Fig. 600 ).

Figures

Figs 106–109. Holotype males of the Nearctic species of the Arganthomyza duplex group. 106 – A. acuticuspis Roháček & Barber, 2013; 107 – A. bivittata Roháček & Barber, 2013; 108 – A. duplex Roháček & Barber, 2013 (all laterally); 109 – A. bivittata, head and thorax dorsally. Photo by J. Roháček. Adapted from ROHÁĆEK & BARBER (2013: Figs 1, 3, 5, 6).

Figs 110–116.Arganthomyza acuticuspis Roháček & Barber, 2013, paratype male (USA:New Mexico).110 – external genitalia, caudally; 111 – the same, laterally; 112 – hypandrial complex, laterally; 113 – transandrium, caudally; 114 – apex of nlum, subventrally (widest extension); 115 – aedeagal complex, laterally; 116 – gonostylus, sublaterally (widest extension). Scales = 0.1 mm. Adapted from ROHÁĆEK & BARBER (2013: Figs 67–73).

Figs 117–124. Arganthomyza acuticuspis Roháček & Barber, 2013, paratype female (USA: New Mexico). 117 – spermatheca; 118 – postabdomen, dorsally; 119 – the same, ventrally; 120 – spermatheca; 121 – ventral receptacle, laterally; 122 – internal sclerites, ventrally; 123 – the same, laterally; 124 – female genital chamber and apex of postabdomen, laterally. Scales = 0.2 mm (Figs 118, 119), 0.1 mm (Figs 121–124) and 0.05 mm (others). Adapted from ROHÁĆEK & BARBER (2013: Figs 74–81).

Figs 125–127. Wings of the Nearctic species ofArganthomyza. 125 – A. acuticuspis Roháček & Barber, 2013, paratype male, wing length 2.5 mm (USA: New Mexico); 126 – A. bivittata Roháček & Barber, 2013, paratype male, wing length 2.8 mm; 127 – A. duplex Roháček & Barber, 2013, paratype male, wing length 2.6 mm (both Canada: Ontario). Photo by K. N. Barber. Adapted from ROHÁĆEK & BARBER (2013: Figs 167–169).

Figs 168–175. Arganthomyza disjuncta Roháček & Barber, 2013, paratype male (Canada:Alberta). 168 – external genitalia, caudally; 169 – base of phallapodeme, dorsally; 170 – external genitalia, laterally; 171 – hypandrial complex, laterally; 172 – transandrium, caudally; 173 – apex of nlum of distiphallus, anteroventrally (widest extension); 174 – aedeagal complex, laterally; 175 – gonostylus, lateroventrally (widest extension). Scales = 0.05 mm (Figs 173, 175) and 0.1 mm (others). Adapted from ROHÁĆEK & BARBER (2013: Figs 122–128).

Fig. 1. Anthomyza dichroa sp. nov., male, general habitus (Canada: Ontario: Sault Ste. Marie, Bristol Place Park), body length ca. 2.5 mm. Based on photograph by J. Roháček.

Fig. 600. Map of North America showing unique distributions of six species representing Clusters 5 to 10. Cluster 5: Anthomyza occidentalis sp. nov.; Cluster 6: A. concolor (Thomson, 1869); Cluster 7: A. furvifrons sp. nov.; Cluster 8: Fungomyza buccata Roháček & Barber, 2004; Cluster 9: Arganthomyza acuticuspis Roháček & Barber, 2013; Cluster 10: Arg. socculata (Zetterstedt, 1847). Many of the west coastal localities are shared between A. occidentalis and A. concolor with several records of the latter not visible.See “Distributional patterns” for explanation of Clusters.