Agromyza varifrons Coquillett, 1902

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

Agromyza varifrons Coquillett

Figs 236-242

Agromyza varifrons Coquillett, 1902: 189. Frick 1952a: 374; Spencer 1969: 59; Spencer and Steyskal 1986b: 269; Scheffer and Lonsdale 2018: 85.

Description.

Wing length 1.7-2.2 mm (♂), 1.8-2.3 mm (♀). Length of ultimate section of vein M4 divided by penultimate section: 0.9-1.0. Eye height divided by gena height: 3.5-10.0. Arista pubescent. First flagellomere small and rounded, without pale tuft of hairs. Fronto-orbital plate slightly projecting (more so anteriorly). Ocellar triangle small and rounded.

Chaetotaxy: Two ori; two ors. Orbital setulae in one row. Ocellar and postvertical setae subequal to fronto-orbitals. Two strong dorsocentral setae, with second seta ~ ¾ length of first seta; much weaker third dorsocentral not much larger than acrostichal seta. Acrostichal seta ~ 2 × length of setulae. Acrostichal setulae in 8 scattered rows, tapering posteriorly to level of first dorsocentral. Mid tibiae without posteromedial setae.

Colouration: Setae dark brown. Antenna yellow to orange; first flagellomere darker orange with basal margin paler and with small brown curved spot around base of arista posteriorly and along outer surface. Frons yellow with posterolateral corner and posterior margin dark brown; orbital plate darker, brownish orange behind anterior ors, becoming darker posteriorly, and with narrow brownish line continuing anteriorly along eye margin beside ori; ocellar spot rounded, dark brown, slightly larger than tubercle; remaining posterior 1/2 or less of frontal vitta brownish orange, becoming darker posteriorly, sometimes with this dark region restricted to large circle around ocellar spot. Lunule light yellow. Gena yellow with ventral brownish line. Parafacial yellow. Face whitish yellow. Mouthparts yellow; clypeus with brown tint that is darker laterally. Postgena, back of head and remainder of body mostly dark brown; body subshiny. Apex of fore femur yellowish orange for length equal to width of femur apex; apex of mid femur narrowly paler brown apically; tibiae sometimes paler brown with base and apex yellowish, and mid tibia sometimes with yellow mottling medially; tarsi yellow, becoming more brown tinted on posterior legs; wing veins brown; halter yellow with orange-brown tint on stem; calypter margin and hairs brown.

Variation: Posterior 1/2 of frons brownish in holotype and FL specimen. IL male with first flagellomere entirely light yellow, head brighter and scutum shiny.

Genitalia: (Figs 236-242 ) Epandrium as long as high; fused to small, inwardly directed surstylus. Cercus large, well-developed, venter of inner surface covered with tubercle-like setae. Hypandrium with large apical apodeme and narrow basal arms; medially with weakly sclerotised region connected to L-shaped inner lobe bearing row of minute setae. Postgonite in lateral view with short, flat globose body with extremely long tail; inner surface with apically setose shelf. Phallophorus elongate cylindrical, apicodorsal margin irregularly sclerotised to base of basiphallus. Basiphallus with small left basolateral plate partially fused to large dorsal plate that is strongly curved ventrally at base and with medial and apical lobes that wrap along right lateral surface of shaft. Ejaculatory duct widening to mesophallus, which is round, bulbous, and clear with thick triangular sclerotisation ventrally. Distiphallus composed of one pair of upturned “wings” that nearly meet ventrally and are very narrowly connected dorsally; each wing with small, dark, smooth base expanding into densely haired, distally pointed lobes. Ejaculatory apodeme weakly sclerotised, with broad slanted base and short stem grading into thick blade with faint apical striations; sperm pump with slight basal sclerotisation.

Hosts.

Cannabaceae - Celtis laevigata . Possibly Ulmus Americana ( Ulmaceae ) ( Eiseman 2021).

Distribution.

Canada: ON, QC. USA: AK, DC, FL, IA, IL, KS, MS, NY, PA, TX, VA*.

Type material.

Holotype: USA. DC: "District of Columbia" (1♀, USNM).

Additional material examined.

USA. FL: Hialeah , em. 10.v.1963, mine Celtis laevigata , 22.ix.1963 (1♂ 1♀ [same pin, with puparia]), Gainesville , Newman's Lake , 26.iv.1952, O. Peck, CNC352994 (1♂, CNC), Hialeah , 22.ix.1963, mine Celtis laevigata , Em. 5.x.1963, [K.A. Spencer], CNC352996 (1♂ 1♀ [with puparia], CNC), IL: [illegible], 15.v.1919 (1♀, USNM), NY: Suffolk Co., Stony Brook Village , larva coll. 19.vi.1993, S.J. Scheffer, 93-187 (1♂ [illustrated], USNM), eclosed 9.vii.1993 (1♂, USNM), eclosed 8.vii.1993 (1♀, USNM), eclosed 10.vii.1993 (3♂, USNM), eclosed 11.vii.1993 (1♀, USNM), elcosed 17.vii.1993 (1♂, USNM), TX: Kerrville, 4.iv.1959, J.F. McAlpine, CNC352995 (1♂, CNC), Welder Wildlife Ref. nr Sinton, 19-23.iii.1965, J.G. Chillcott, CNC352997 (1♀, CNC), VA: Fairfax Co. , Turkey Run Park, nr. mouth of Turkey Run, 38°57.9'N, 7°09.4'W, Malaise trap, 26.iv-2.v.2007, D.R. Smith (3♀, USNM), Turkey Run Park, 0.3 km W mouth Turkey Run, 38°58'N, 77°09.6'W, Malaise trap, D.R. Smith, 18-30.v.2007 (1♀, USNM), 29.iii-25.iv.2007 (1♂, USNM), Great Falls Park, quarry, 38°59.1'N, 77°14.8'W, Malaise trap, D.R. Smith, 24.iv-2.v.2007 (3♂ 1♀, USNM), 10-17.v.2007 (1♂, USNM), 3-10.v.2007 (1♂, USNM) .

Comments.

This species is clearly allied to Agromyza aristata , being similar in external and male genitalic morphology. The anterior portion of the head is mostly pale, the cercus is covered with small tubercle-like setae along the anterior surface, and the mesophallus is a ventral band separate from a curved, plate-like distiphallus. The most immediate difference in the genitalia is the densely haired distiphallus and short mesophallus, but the hypophallus has an apical apodeme, the basiphallus is also strongly curved and irregular in outline, the postgonite broadly lobate (lateral view) and the ejaculatory apodeme is well-developed. Externally, the pale portions of A. aristata are light yellow, not orange to yellowish, and the legs are extensively yellow.

Figures

Figures 236 - 242. Agromyza varifrons Coquillett, male genitalia 236 ejaculatory apodeme 237 external genitalia, ventral 238 external genitalia, left lateral 239 postgonite, lateral (1 / 2 size) 240 hypandrium, ventral (1 / 2 size) 241 phallus, left lateral 242 phallus, ventral.