Amauromyza abnormalis (Malloch)

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

Amauromyza abnormalis (Malloch)

Figs 413-417

Agromyza abnormalis Malloch, 1913a: 320.

Phytobia (Amauromyza) abnormalis . Frick, 1952a: 393, 1959: 378.

Amauromyza abnormalis . Spencer, 1969: 158; Bautista-Martinez et al. 1997: 461.

Amauromyza (Cephalomyza) abnormalis . Spencer, 1981: 148; Spencer and Steyskal 1986b: 273; Boucher 2012b: 737; Černý et al. 2020: 200.

Description.

Wing length 1.8-2.2 mm (♂), 2.2-2.7 mm (♀). Length of ultimate section of vein M4 divided by penultimate section: 1.3-2.5. Eye height divided by gena height: 2.3-3.1. Gena broad, ventral margin straight, highest posteriorly. Epistoma ~ 2/3 length of clypeus with anterior margin relatively straight. Fronto-orbital plate and parafacial projecting, visible laterally but less pronounced than in A. karli . First flagellomere ~ 1/3 longer than high and with anterodistal corner slightly to indistinctly angulate. Lunule height <1/2 width. Distance between cross-veins distinctly longer than dm-m. Thorax with light pruinosity.

Chaetotaxy: Three ori (uncommonly two or four); two ors. Postocellar and ocellar setae as long as ors. Setulae on tubercle slender, as long as ocellus. Orbital setulae short and indistinct to absent, reclinate. Four dorsocentrals: one presutural, posterior two well-developed, posterior-most slightly longer, anterior two short. Acrostichal setulae in four scattered rows.

Colouration: Setae dark brown. Entire body (including knob of halter, which is only paler around sutures) brown except as follows: gena, parafacial, lunule and frons light brown; lateral and posterior margins of frons darker, with dark stripe on margin extending to surround bases of fronto-orbitals; clypeus and lower margin of gena very dark and shiny; face darker towards centre. Calypter margin and hairs pale brown.

Genitalia: (Figs 413-417 ) Hypandrium stout and broadly arched; inner lobe weakly sclerotised, separated by suture and with several medial setae on narrow, well-sclerotised strip. Halves of basiphallus separate, plate-like; hypophallus weakly sclerotised, split. Paraphallus small, lobate, membranous. Mesophallus approximately as long as wide, slightly compressed dorsoventrally. Distiphallus dense, dark, globular; surrounded by minute spinules apically and larger spicules basally (also see comments below). Ejaculatory apodeme broad on distal 2/3 with margin pale; stem broad; sperm pump bowl-shaped, broadly rounded, lightly sclerotised.

Hosts.

Amaranthaceae - Amaranthus ( Benavent-Corai et al. 2005).

Distribution.

Canada: BC, MB, NB*, ON, QC. USA: AZ, CA, CO*, DC, IA, KS, MD*, MO*, NM. Mexico. Germany ( Černý et al. 2020). While previously reported Palaearctic records of A. abnormalis were determined to represent A. chenopodivora Spencer ( Spencer 1976; Boucher 2012b), Černý et al. (2020) listed specimens of A. abnormalis collected at a single locality in Germany that they suggest result from introduction of its New World host Amaranthus retroflexus in Europe.

Type material.

Holotype: USA. DC: Washington, vi.1903, "97270, on aphid", "on roots of Amarantha " (1♀, USNM; type No. 15583).

Paratype: USA. KS: Twilight, Lawrence, July, E.S. Tucker (1♀, USNM).

Additional material examined.

Canada. CANADA. BC: Robson , 13.vi.1952, H.R. Foxlee, CNC358588 (1♀, CNC), MB: Brandon, 10.viii.1958, J.G. Chillcott, CNC358587 (1♀, CNC), NB: Dannebrog, 18.viii.1960, W.F. Rapp (1♀, USNM), ON: Chatham, 29.viii.1928, A.B. Baird, 18333A, CNC358590 (1♀, CNC), Ottawa, 11.vii.1957, J.E.H. Martin, CNC358589 (1♀, CNC), QC: Abbotsford, 19.vi.1937, G. Shewell, CNC358591 (1♂, CNC) . USA. CO: Custer Co., 10 mi SW of Wetmore, 8.viii.1973, G.F. and S. Hevel (1♀, USNM), IA: Ames , 16.viii.1924, H.L. Sweetman, “2690” (1♀, USNM), Mills Co. , 2mi SW Glenwood, 27.viii.1969, R.R. Pinger (1♂, USNM), MD: Montgomery Co. , 4mi S of Ashton, Malaise trap, G.F. and J.F. Hevel, 6.ix.1981 (1♂, USNM), 31.v.1986 (1♂, USNM), MO: Boone Co. : Columbia , Malaise trap, 7am-4pm, 9.ix.1967, P.D. Parker (1♂, USNM), Columbia, Malaise trap, F.D. Parker, 17-31.viii.1968 (1♂ 1♀, USNM), 16-31.vii.1968 (1♂ 2♀, USNM), 1-15.vii.1968 (1♂, USNM), 6.vii.1968 (1♀, USNM), 6.ix.1968 (1♀, USNM), 7.viii.1968 (4♀, USNM) .

Comments.

Amauromyza abnormalis , an internal stem borer, is a widespread species that can be distinguished from other Delmarva Phytomyzinae by an entirely or predominantly dark halter. Other Amauromyza with brown maculations on the halter are known only from California, and the halter of Nemorimyza maculosa (Malloch) is mostly white with a brown spot.

The shape of the distiphallus of the dissected male from Maryland is of an intermediate morphology between those illustrated from California and Quebec in Spencer and Steyskal (1986b), being quite similar to the New Mexico specimen photographed in Boucher (2012b). These intermediates support the concept of a single morphologically variable species, not two separate species, as suggested by Spencer and Steyskal (1986b).

While tentatively treating the European representatives of Amauromyza abnormalis as conspecific with the new World fauna, Spencer (1976) later considered them distinct, placing them in the new species A. chenopodivora Spencer. Aside from a difference in host plant genus ( Chenopodium album ), he made this distinction on the basis of slight variation in the male genitalia. The male examined by Sasakawa (1961) has a strong resemblance to the illustration in Spencer (1971) and it is likely that Spencer would have also classified these as A. chenopodivora . The illustration of the Californian male in Spencer and Steyskal (1986b), however, has a very strong resemblance to the British male illustrated by Spencer (excluding a slight strengthening of the apex of the basiphallus and a basal proliferation of spinules on the membrane surrounding the distiphallus), and it is uncertain as to what specifically he used as evidence to differentiate the two. The status of A. chenopodivora was treated in Boucher (2012b), who examined material from Sweden and found that the specimens were slightly larger with differences in the phallus and concluded that they were distinct from those in the Nearctic.

Figures

Figures 413 - 417. Amauromyza abnormalis (Malloch), male genitalia 413 hypandrium and postgonite, ventral 414 ejaculatory apodeme 415 hypandrial complex, left lateral 416 phallus, ventral 417 phallus, left lateral, of males from California (left) and Quebec (right), from figures in Spencer and Steyskal (1986 b).