Cerodontha (Poemyza) pygminoides Spencer, 1981

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 (Poemyza) pygminoides Spencer

Figs 555-558

Cerodontha (Poemyza) pygminoides Spencer, 1981: 183. Spencer and Steyskal 1986: 279.

Description.

Wing length 1.8-2.2 mm (♂). Female unknown. Length of ultimate section of vein M4 divided by penultimate section: 1.5-1.7. Eye height divided by gena height: 7.1-8.9. Arista short pubescent. First flagellomere small, ovate, slightly longer than high. Fronto-orbital plate ¼ frons width. Lunule minutely pitted, appearing as high as wide or slightly higher if lateral base concealed by fronto-orbital plate.

Chaetotaxy: Two ori; two ors. Orbital setulae in one row. Ocellar and postocellar setae subequal to fronto-orbitals. Four dorsocentral setae, strongly decreasing in length anteriorly, with fourth seta almost setula-like and sometimes apparently absent. One pair of prominent setae apically on each palpus.

Colouration: Setae dark brown. Head mostly brown to dark brown; if head paler, first flagellomere, anterior region of frons, face, back of head, ventral margin of gena, clypeus and palpus always darker, fronto-orbital plate, ocellar triangle, gena and pedicel light brown, and ocellar tubercle brown; if darker than surrounding frons, pigment on ocellar tubercle ill-defined and often faded (not dark and sharply delimited); soft central region of frons heavily pitted with dark brown to orange spots, always dark brown anteriorly, brownish yellow to dark brown posteriorly; pedicel sometimes yellowish apically. Body dark brown with postpronotum and notopleuron slightly paler and apices of femora light yellow for length equal to width of femur apex; wing veins light brown to yellowish, light yellow to base; halter light yellow; calypter white.

Genitalia: (Figs 555-558 ) Epandrium with small supra-anal process; fused to surstylus. Anterior portion of surstylus small, rounded, directed inwards but with longer anteroventral section; with small setae. Ventral process of subepandrial sclerites with arm as long as stout base, smooth, and with shallow outer subapical point. Basiphallus fused to venter of phallophorus; sclerotised along ventral surface of shaft, with broad, bifid apical section flanking base of mesophallus; left distal margin extended as long process. Hypophallus weakly sclerotised along surface of membranous fold and with right lateral carina; ventrally continuous with basiphallus. Paraphallus absent. Mesophallus fused to distiphallus, stem ~ 6 × longer than wide; apical chamber small, bilobate, slightly overlapping stem. Distiphallus tubule lightly sclerotised, gradually widening to broad apical cup with inner marginal row of bumps; with broad, shallow medial curve that ends very close to base.

Host.

Unknown.

Distribution.

USA: CA, CO, MD*, VA*, WV*.

Type material.

Holotype: USA. CA: Inyo Co., 2mi N of Cartago, 15.vii.1953, E.I. Schlinger (1♂, UCD). [Not examined]

Additional material examined.

USA. CO: Boulder , Flagstaff Cn., 1767 m, on side of stream, 10.vi.1961, C.H. Mann, CNC481158 (1♂, CNC), MD: Seaside, 23.vi.1931, A.L. Melander (1♂, USNM), VA: Chain Bridge, 23.iv.1922, J.R. Malloch (1♂, USNM), WV: Bluefield, 17.vi.1970, G. Steyskal (2♂, USNM) .

Comments.

The distiphallus of the eastern material examined here (Maryland male illustrated) deviates slightly from that of the holotype, being more sinuate with the apex angled ventrally, not with a relatively elongate, straight middle section and a distally pointing apex. The male from Colorado identified by Spencer illustrates an intermediate shape, suggesting that there is a continuum of morphology, although this variation should be re-examined following the collection of more material.

What is most noticeable in the re-evaluation of this species is that the previous key character used for identification in Spencer and Steyskal (1986b) does not work for specimens aside from the holotype. The length of ultimate section of vein M4 was described as being ~ 2 × length of the penultimate section in the holotype, but it is actually 1.73 in the holotype and 1.5-1.6 in the remaining specimens. While smaller than the ratio seen in the similar Cerodontha (Poemyza) attenuata Spencer, it is closer to that seen in C. (P.) inconspicua (California, Colorado, North Carolina, Utah), which mostly differs in being more matt on the thorax and having the dark, triangular spot around the ocelli very dark and clearly defined.

Figures

Figures 555 - 558. Cerodontha (Poemyza) pygminoides Spencer, male genitalia 555 external genitalia, anterior 556 external genitalia, left lateral 557 phallus, left lateral 558 phallus, ventral.