Cerodontha (Cerodontha) dorsalis (Loew)

Lonsdale, Owen, 2021, Manual of North American Agromyzidae (Diptera, Schizophora), with revision of the fauna of the " Delmarva " states, ZooKeys 1051, pp. 1-481 : 1

Cerodontha (Cerodontha) dorsalis (Loew)

Figs 106 , 508-512

Odontocera dorsalis Loew, 1863: 54.

Cerodontha dorsalis . Melander, 1913: 249; Malloch 1913: 331; Hendel 1931: 269; Curran 1934: 163; Frost 1936: 318.

Cerodontha (Cerodontha) dorsalis . Frick, 1952a: 399, 1959: 399; Spencer 1969: 143; Spencer and Steyskal 1986b: 91; Boucher 2002: 581; Scheffer et al. 2007: 771; Scheffer and Lonsdale 2018: 87; Eiseman and Lonsdale 2018: 41.

Cerodonta femoralis Meigen, 1838. Misidentification (in part). Melander 1913: 249.

Description

(Fig. 106 ). Wing length 2.0-2.4 mm (♂), 2.0-2.9 mm (♀). Length of ultimate section of vein M4 divided by penultimate section: 0.8-1.1. Eye height divided by gena height: 2.6-3.7. Arista relatively stout and thickened on basal 1/2, distinctly thicker than width of distal 1/2. First flagellomere slightly longer than high, longest subdorsally, where segment ends in pronounced spine; sometimes very stout apically, appearing almost subrectangular, but often more gradually tapering to apex; distal margin to distal 1/2 of ventral margin with relatively long, white hairs. Fronto-orbital plate slightly visible laterally, with anterior region more strongly projecting, continuing as narrow parafacial; cheek evident on anterior 1/2 of gena.

Chaetotaxy: One ori, slightly inset, usually also with additional weak ori anteriorly; two subequal ors. Orbital setulae sparse, in single row; partially reclinate, but becoming erect to proclinate anteriorly. Postocellar subequal to fronto-orbitals. Ocellar longer than fronto-orbitals. Four dorsocentral setae, slightly decreasing in length anteriorly. Anterior notopleural seta, lateral scutellar seta, acrostichal seta and acrostichal setulae absent.

Colouration: Setae black. Base colour of head light yellow to slightly whitish, contrasting rest of body; yellower between fronto-orbital plates on frons, on face, palpus, scape, pedicel and gena; first flagellomere dark brown; fronto-orbital plate with narrow dark brown marking posterolaterally to base of anterior or posterior ors; posterolateral corner of frons dark brown to dorsal margin of eye and outer vertical seta; clypeus yellow to brown with lateral arms usually browner; back of head dark brown. Notum mostly dark brown with sparse grey pruinosity, but often with yellowish to distinctly yellow pattern, usually including a vestige of the following: most or all of posterior margin, one pair of postsutural intra-alar stripes and one stripe between dorsocentral rows to approximate level of the second dorsocentral seta that continue to transverse suture along dorsocentral rows as one pair of very narrow lines; at least part of notopleuron and scutellum (usually wide central stripe) yellow, and postpronotum yellow with dark anteromedial spot that may predominate; metanotum usually yellow lateral scutellum. Pleuron dark brown with at least part of anepisternum yellow. Legs yellow with tibiae and tarsi light brown to brown. Halter white. Calypter margin greyish, hairs brown. Abdomen dark brown.

Variation: Darker forms differ as follows: dark posterolateral spot on frons sometimes reaching base of inner vertical seta; scutum, scutellum and anepisternum entirely dark, sometimes excluding yellowish medial marking on scutellum; femora sometimes with dark striping or mottling, at least basally. Paler forms with distinct yellow markings on notum; scutellum widely yellow medially with lateral margins dark; anepisternum usually entirely yellow with venter sometimes darker, katepisternum entirely yellow or with variable dark brown ventral spot.

Genitalia: (Figs 508-512 ) Epandrium rounded, without process protruding above anus. Cercus small, setose. Surstylus setose, produced inwards anterodorsally. Subepandrial sclerite with one pair of strong setae and one pair of stout ventrolateral processes; rounded apically and with shallow outer subapical point. Hypandrium thin, halves approximate, with one pair of sockets on inner lobe. Postgonite small, bare. Phallophorus not much longer than wide, narrower to base, left distolateral margin more produced. Basiphallus with one broad left lateral sclerite slightly extending onto dorsal and left ventolateral surfaces. Hypophallus asymmetrical, with left sclerite darker, well-defined and with regular margin; right sclerite much larger but irregular, ill-defined, with minute sclerotised patches and hairs distally, and with base narrow, darker and discrete; clear tubule emerging from between sclerites. Mesophallus with dark, swollen irregular base enclosing apex of duct; otherwise cylindrical with basal 1/2 swollen, narrowest point at 2/3 length, and distoventral margin produced basally as thick lip. Distiphallus entirely divided into one pair of long tubules equal to length of phallophorus + basiphallus; somewhat S-shaped with basal curve short and apex directed anterodorsally; distal 1/3 thicker, darker, barrel-shaped, with narrow seam ventromedially. Ejaculatory apodeme with short, stout base and stem, blade relatively small with clear margin; sperm pump with one pair of sclerotisations continuing onto base of duct.

Hosts.

Poaceae - Agrostis , Avena , Bromus , Dactylis , Dichanthelium , Digitaria , Echinochloa , Ehrharta , Eleusine , Elymus , Eragrostis , Hordeum , Lolium , Panicum , Phalaris , Phleum , Poa , Secale , Setaria , Sorghum , × Triticosecale , Triticum , Zea ( Frick 1959; Spencer and Steyskal 1986b; Eiseman and Lonsdale 2018).

Distribution.

Canada: AB, BC, MB, NB, NS, ON, QC, SK. USA: "probably present in all states" ( Spencer and Steyskal 1986b). Brazil. Colombia. Ecuador. Guatemala. Jamaica. Mexico. Peru. Puerto Rico. Eastern Russia. Mongolia.

Type material.

Holotype: USA. DC: "51, DC, Loew Coll, dorsalis" (1♀, MCZ; type no. 13,433). [Not examined]

Additional material examined.

Canada. AB: Waterton Lakes National Park, 49°5'N, 113°53'W, 1347 m, meadow, 5.vi.2005, Goulet and Boudreault, CNC480672, CNC480676 (1♂ 1♀, CNC), BC: Agassiz, Res. Sta., rhodo patch, 49°15'N, 121°46'W, 23.vii.2004, S.A. Marshall, Malaise trap, CNC287186, CNC287220, CNC287251, CNC287283 (2♂ 2♀, CNC), Mt. Kobau , 49°5'N, 119°38'W, fallow field, 23.v.2005, Goulet and Boudreault, sweeping, CNC480673-480685 (11♂ 1♀, CNC), Osoyoos, 49°2'N, 119°27'W, alfalfa, 26.v.2005, Goulet and Boudreault, site 8, CNC480687 (1♀, CNC), Apex Mt. Ski Area , 2.viii.2004, 49°28'56"N, 119°56'04"W, J.E. Swann (1♂, CNC), MB: Aweme, Criddle homestead, 49°43'N, 99°35'W, mixed grass prairie, 24.vii.2007, H. Goulet, sweeping, CNC480686 (1♂, CNC), Assiniboine River Conservation Area , 49°40'42.48"N, 99°36'46.56"W, 1.vi.2007, Goulet, Boudreault and Fernandez, CNC352493 (1♀, CNC), NB: Madawaska Co., Saint-Jacques, Baisley Rd. at QC border, 27.vii.2013, O. Lonsdale, CNC271171, CNC271188 (2♂, CNC), ON: Moose Factory, 51°16'N, 80°36'W, 11.vi.1949, D.P. Whillans, CNC_ Diptera 109362 (1 ex, CNC), Ottawa, 3.vi.2007, J.R. Vockeroth, CNCDiptera164460 (1♂, CNC), Algonquin Provincial Park, Whitefish Lake Group Campground , 45°33'47.01"N, 78°26'13"W, 414 m, 28.vi-2.vii.2008, J.andA. Skevington, Malaise trap, CNC339235, CNC339249 (1♂ 1♀, CNC), Almonte, Burnt Lands Provincial Park, 45°15'43"N, 76°9'8"W, 5.vii.2015, O. Lonsdale, sweeping, CNC454712 (1♂, CNC), Sudbury Dist. , Killarney Provincial Park, Cranberry Bog Trail, 46°1'8"N, 81°23'42"W, 1.ix.2014, O. Lonsdale, CNC380415 (1♀, CNC), Sudbury Dist. , Killarney Provincial Park, Lake of the Woods Trail, 46°6'36"N, 81°11'48"W, 2.ix.2014, O. Lonsdale, CNC380790, CNC380793 (2♂, CNC), SK: Maple Creek , mowed grass, 15.vii.2005, J.R. Vockeroth, CNCDiptera166564 (1♂, CNC), 7 km E Leask, 10.viii.2005, J.R. Vockeroth, CNCDiptera193131 (1♀, CNC), Cypress Hills Provincial Park, E Block, 9.vii.2005, J.R. Vockeroth, CNCDiptera166367 (1♂, CNC) . USA. CO: Chaffee Co., Poncha Springs, South Arkansas River , 8.vii.2015, em. by 21.vii.2015, C.S. Eiseman, ex × Triticosecale , #CSE1777, CNC634812 (1♀, CNC), Boulder Co. , Corona Pass, 3230 m, marshy meadow at timberline, 6.vii.1961, J.G. Chillcott, CNC480693 (1♂, CNC), Doolittle Ranch, Mt. Evans , 2987 m, 12.vii.1961, C.H. Mann, CNC480720 (1♂, CNC), 27.vii.1961, J.G. Chillcott, CNC480717-480719, CNC480722 (4♂, CNC), 3.viii.1961, CNC480725 (1♀, CNC), 8.vii.1961, C.H. Mann, CNC480721, CNC480723, CNC480724 (1♂ 2♀, CNC), Echo L., Mt. Evans , 3230 m, 11.viii.1961, C.H. Mann, CNC480696 (1♀, CNC), 12.viii.1961, CNC480694 (1♂, CNC), 24.viii.1961, CNC480695 (1♂, CNC), Idaho Springs, 5mi SW, 2621 m, 27.vii.1961, C.H. Mann, CNC480713 (1♂, CNC), Lake Co. , Independence Pass, 3688 m, tundra, 31.vii.1961, J.G. Chillcott, CNC480714 (1♂, CNC), 8.viii.1961, B.H. Poole, CNC480715, CNC480716 (2♂, CNC), Mt. Evans , 3566 m, timberline, 22.vii.1961, W.R.M. Mason, CNC480698 (1♀, CNC), 3962 m, on tundra, 28.vii.1961, C.H. Mann, CNC480699 (1♀, CNC), 4267 m, 4.viii.1961, B.H. Poole, CNC480697 (1♀, CNC), Nederland, 3mi N, 2590 m, marshy stream margin, 2.vii.1961, J.G. Chillcott, CNC480711 (1♀, CNC), dry gravelly meadow, CNC480710 (1♂, CNC), Nederland, Science Lodge, 2895 m, 27.vi.1961, B.H. Poole, CNC480712 (1♀, CNC), Nederland, 2529 m, seepage area, 5.vii.1961, J.G. Chillcott, CNC480700-480709 (7♂ 3♀, CNC), Niwot Ridge, nr. Ward, 3444 m, 28.vi.1961, C.H. Mann, CNC480690, CNC480692 (2♂, CNC), Vernon Cn., nr. Golden, 2194 m, 31.vii.1961, C.H. Mann, CNC480688, CNC480689, CNC480691 (2♂ 1♀, CNC), 2003, CNC484171 (4 ex, CNC), CT: Litchfield Co. , Canaan, Falls Village , 21.vii.2015, em. 27.vii.2015, C. Vispo, ex Elymus , #CSE2170, CNC564678 (1♂, CNC), NC: Clingmans Dome, 35°35'45"N, 83°29'54"W, 6500', 28.v.1999, J.R. Vockeroth, CNCDiptera193694 (1♀, CNC), Durham Co. , Durham, Pelham Rd. , 29.iv.2017, em. ~ 17-22.v.2017, T.S. Feldman, ex Dichanthelium , #CSE3675, CNC939801-939802 (2♀, CNC), 29.iv.2017, em. ~ 17.v.2017, T.S. Feldman, ex Elymus virginicus , #CSE3676, CNC939821 (1♀, CNC), 13.v.2017, em. 19.v.2017, T.S. Feldman, ex Dichanthelium dichotomum ssp. nitidum , #CSE3693, CNC939803 (1♀, CNC), Scotland Co. , Laurinburg, St. Andrews University , 18.iv.2017, em. 18.v.2017, T.S. Feldman, ex Agrostis hyemalis , #CSE3685, CNC939750 (1♂, CNC) .

Comments.

Cerodontha dorsalis is widespread in North America, and the only member of the subgenus found east of Manitoba and Colorado. The subgenus is more diverse in the western Nearctic, where differentiating C. dorsalis from congeners can be difficult, requiring measurements of body size and examining the relative width of the arista, frons and parafacial. Dissection of the male is the most reliable method of diagnosis, with the large, thickened apical section of the distiphallus being unique.

Figures

Figures 99 - 106. 99 Cerodontha (Butomomyza) angulata (Loew), head, anterior 100 Cerodontha (Phytagromyza) frankensis Spencer, head, anterior 101 Cerodontha (Poemyza) muscina (Meigen), head, anterior 102 Cerodontha (Poemyza) incisa (Meigen), head, anterior 103 Cerodontha (Icteromyza) longipennis (Loew), head, anterior 104 Cerodontha (Xenophytomyza) illinoensis (Malloch), head, anterior 105 Cerodontha (Dizygomuza) morosa (Meigen), head, anterior 106 Cerodontha (Cerodontha) dorsalis (Loew), (K. Matz - Utah, Salt Lake City).

Figures 508 - 512. Cerodontha (Cerodontha) dorsalis (Loew), male genitalia 508 external genitalia, anterior 509 ejaculatory apodeme 510 hypandrium and postgonite, ventral 511 phallus, ventral 512 phallus, left lateral.