Phytomyza tigris Eiseman & Lonsdale 2018, spec. nov.

Phytomyza tigris spec. nov.

(Figs. 54, 211, 372–376)

Holotype. MASSACHUSETTS: Franklin Co., Northfield, 42.647594, -72.428414, 29.vi.2016, em. 12.vii.2016, C.S. Eiseman, ex Tiarella cordifolia, #CSE2741, CNC654112 (1♂).

Paratypes. MASSACHUSETTS: Franklin Co., Northfield, 42.647594, -72.428414, 8.vii.2016, em. 10.vii.2016, C.S. Eiseman, ex Tiarella cordifolia, #CSE2734, CNC638898 (1♀); 29.vi.2016, em. 8.vii.2016, #CSE2724, CNC659972 (1♂).

Additional material examined. NEW YORK: Columbia Co., Copake Falls, 20.vii.2014, em. 29.vii.2014, C.S. Eiseman, ex Tiarella cordifolia, #CSE1240, CNC384837 (1♀).

Etymology. The specific epithet refers to the puparium’s striped pattern, which is reminiscent of that of a tiger, Panthera tigris (L.).

Host. Saxifragaceae: Tiarella cordifolia L.

Leaf mine. Long, linear, whitish, on the upper leaf surface. The brown frass is in discrete, closely spaced grains, sometimes obscured by a broad central band of brown discoloration.

Puparium. (Fig. 54) Pale with dark brown transverse bands; formed within the leaf in a small chamber on the lower surface with the anterior spiracles projecting through the lower epidermis. The bands were very pale in one Massachusetts specimen (CSE2724); the puparia from New York were dark brown at collection time, appearing pale with dark banding when empty.

Distribution. USA: MA, NY; we have found leaf mines in OH.

Adult description. Wing length 1.8mm (♂), 2.2mm (♀). Eye height divided by gena height: 5.5–6.4. First flagellomere small, rounded, with minute ill-defined tuft of slightly longer hairs above midpoint. Orbital plate weakly defined, slightly shiny, slightly wider at base of fronto-orbitals. Notum subshining. Vein dm-cu absent.

Chaetotaxy: Two ors, one ori. Ocellar and postvertical setae subequal to ors. Four dorsocentral setae, decreasing in length anteriorly with fourth seta half length of first seta. Acrostichal setulae in four irregular, relatively sparse rows.

Coloration: (Fig. 54) Setae dark brown. Head dark brown (more pronounced in female), frontal vitta, gena and postgena brownish-beige. Thorax dark brown, anteromedial margin of notopleuron slightly paler. Calypter white, hairs light brown. Haltere light yellow. Legs dark brown, female hind tibia slightly paler medially. Abdomen dark brown.

Genitalia: (Figs. 372–376) Surstylus small, rounded, fused to epandrium, small setae on inner face. Postgonite simple, one medial seta and one subapical socket, inner lobe serrated distally. Phallophorus flanked by one pair of weak bands. Basiphallus divided between two sclerites twisted along same axis with bases approximate. Hypophallus with two sclerites nearly as long as meso+distiphallus, upcurved, left sclerite with strong subbasal point. Mesophallus indistinct, fused to distiphallus. Distiphallus linear, narrow, divided longitudinally along length, weaker and slightly divergent apically.

Comments. Other species known from Tiarella include Phytomyza sp. 7 from Oregon, which differs in cephalic and thoracic chaetotaxy, the color of the frons (orange between orbital plates, not dark brown), and the darker, bushier calypter margin. The Alaskan P. tiarellae Griffiths appears to agree more closely in description and will key to the same position in Spencer & Steyskal (1986), but in the new species, the gena is higher, there are more rows of acrostichal setulae, the hypophallus is split between two upcurved sclerites (left sclerite with strong pointed basal process), and the fused mesophallus and distiphallus are straight, narrow and divided medially along their length (Figs. 375, 376). In both Phytomyza sp. 7 and P. tiarellae, the ventral surface of the puparium has a dark longitudinal stripe, not a series of transverse stripes as in P. tigris. Host species also differ, with P. tiarellae known from Tiarella trifoliata and Phytomyza sp. 7 known from T. trifoliata var. unifoliata.