Phytomyza ilicicola 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

Phytomyza ilicicola Loew

Figs 784-786

Phytomyza Ilicis Loew, 1863: 54 [preoccupied by Curtis 1846].

Phytomyza ilicicola Loew, 1872: 291 [new name for Phytomyza ilicis Loew]. Hendel 1920: 168 [as possible synonym of Phytomyza ilicis Curtis], Frick 1952a: 426, 1957: 205 [lectotype designation], 1959: 429; Kulp 1968: 16; Spencer 1969: 246; Spencer and Steyskal 1986: 213; Scheffer and Wiegmann 2000: 249; Lonsdale and Scheffer 2011: 1189; Scheffer and Lonsdale 2018: 88; Scheffer et al. 2021: 62.

Phytomyza obscurella var. ilicicola . Melander, 1913: 270.

Phytomyza ilicis . Misidentification. Frost, 1924: 76.

Description.

Wing length: 1.7-2.1 mm (♂), 1.9-2.1 mm (♀). Vein dm-m absent. Eye height divided by gena height: 3.5-6.5. Vein dm-m absent; veins R2+3 and R4+5 crowded relatively close to anterior margin of wing. Ocellar tubercle wider than long (often subrectangular), with space between posterior ocelli wider than 3 × width of ocellus; ocellar triangle indistinct, barely larger than tubercle. Fronto-orbital plate narrow with inner margin smooth and slightly convex. Cheek narrow, but distinct.

Chaetotaxy: Two ori, anterior 1/2 length of posterior; two ors. Ocellar and postocellar setae at least as long as fronto-orbitals, but thinner. Four to six scattered rows of acrostichal setulae. Four dorsocentral setae, one presutural, decreasing in length anteriorly.

Colouration: Body covered with greyish pruinosity that is denser on thorax, especially dorsally; pruinosity coppery postsuturally, bluish presuturally and on anterodorsal corner of anepisternum (colour differences often difficult to see in poorly preserved material). Head mostly grey with brown to yellowish tint; back of head, clypeus, palpus, ocellar triangle and scape dark brown; pedicel and first flagellomere dark brown to black; lunule sometimes paler than frons; frons with thin reflective pruinosity appearing white to dark grey depending on individual and angle of view; posterolateral corner of frons dark to base of inner vertical seta, often with narrow band extending to base of posterior ors; fronto-orbital plate sometimes with spot posterior to base of anterior ors and posterior ori, or with most of plate dark grey excluding anterior and anterolateral margins; face yellowish medially, whitish to dark grey or brownish laterally and on parafacial; gena usually very pale, strongly contrasting remainder of head, sometimes with yellowish tint, less commonly greyish. Thorax dark brown with pruinosity as mentioned above. Halter white. Calypter white with margin and hairs grey to brownish. Legs brown with yellowish tint, with femora darker and fore and mid tibiae and tarsi paler, at least medially; if predominantly pale, then apex of fore femur and faint supra-alar spot on scutum also pale. Abdomen dark brown.

Genitalia: (Figs 784-786 ) Surstylus short, rounded and relatively narrow; fused to epandrium but with suture evident along anterior margin. Epandrium broadly rounded and setose and with small dorsomedial protuberance ("epandrial process") above anus. Cercus small, setose, and narrow. Subepandrial sclerite divided medially, each side with dark dorsal arm that is contiguous ventrally with flatter, pointed ventral process. Hypophallus membranous and sac-like with one pair of floating lateral sclerites that are subrectangular, curved and ~ 4 × longer than wide with margin irregular. Mesophallus nearly 6 × longer than wide at midpoint and slightly longer than distiphallus. Paraphallus with dark basal section and very flat, pale, nearly indistinct distal plate approaching mediobasal surface of mesophallus. Arms of distiphallus separate, not strongly diverging at base and curved dorsally. Ejaculatory apodeme with base bulging, stem very short, and blade well-developed with marked gradation in pigment distally; sperm pump with transverse sclerite with ends thick, dark, and produced.

Hosts.

Aquifoliaceae - Ilex aquifolium , I. opaca ; possibly I. vomitoria ( Scheffer et al. 2021).

Distribution.

Canada: ON. USA: DC, DE, FL, GA, KY, MA, MD, NC, NY, OH, PA, SC; leaf mines only: CT, TN, VA.

Type material.

Lectotype: USA. DC: "Loew Coll.", [Osten-Sacken], Type No. 13431 (1♀, MCZ).

Additional material examined.

USA. USA. NC: Scotland Co., Laurinburg, St. Andrews University , 25.ii-4.iii.2016, T.S. Feldman, Ilex opaca , em. 18-25.iii.2016, #CSE2387, CNC653938-653941 (1♂ 3♀, CNC), VA: Falls Church, 5.v.1969, [illegible], mines Ilex opaca em. 5-11.v.1969, CNC480100 (1♂ 1♀, CNC). Also see Lonsdale and Scheffer (2011) .

Comments.

Phytomyza ilicicola is collected with relative frequency compared to other holly-mining agromyzids in the Delmarva states, all of which belong to the P. ilicis species group. This group was recently revised in North America by Lonsdale and Scheffer (2011), who included discussions on life history and host use. This followed molecular treatments of the group by Scheffer and Wiegmann (2000) and Scheffer and Hawthorne (2007), and the description of a related species feeding on Gelsemium ( Gelsemiaceae ) in North Carolina, P. omlandi Scheffer and Lonsdale ( Scheffer and Lonsdale 2011). Scheffer et al. (2021) provided a thorough analysis of the host plant use and diversification in the group. Of the 12 Nearctic species in this group, P. ilicis was introduced into the western Nearctic from Europe and eleven native species occur in the eastern United States. An additional undescribed species from Florida and North Carolina mentioned in Scheffer et al. (2021) on Ilex amelanchier is not considered here. Nine of the eleven described native species occur in the Delmarva states: P. ditmani , P. glabricola , P. ilicicola , P. leslieae , P. lineata , P. nemopanthi , P. opacae , P. verticillatae , and P. wiggii .

The species group is tentatively treated as monophyletic on the basis of Ilex -feeding, widely separated posterior ocelli, and overall genitalic morphology. The eleven native Nearctic species are further allied on the basis of a subrectangular ocellar tubercle and a bump above the anus on the epandrium ( Lonsdale and Scheffer 2011).

Figures

Figures 778 - 786. Phytomyza ditmani Kulp, male genitalia 778 external genitalia, left lateral 779 phallus, ventral 780 hypandrial complex, left lateral 781 - 783 P. glabricola Kulp, male genitalia 781 external genitalia, left lateral 782 phallus, ventral 783 hypandrial complex, left lateral 784 - 786 P. ilicicola Loew, male genitalia 784 external genitalia, left lateral 785 phallus, ventral 786 hypandrial complex, left lateral. Originally published in Lonsdale and Scheffer (2011).