Phytomyza palustris, Eiseman & Lonsdale, 2018

Eiseman, Charles S. & Lonsdale, Owen, 2018, New state and host records for Agromyzidae (Diptera) in the United States, with the description of thirty new species, Zootaxa 4479 (1), pp. 1-156 : 79-80

Phytomyza palustris spec. nov.

( Figs. 49–50 , 197–198 , 348–352 )

Holotype: MASSACHUSETTS: Berkshire Co., Washington, 26.ix.2014, em. 15–30.iii.2015, C.S. Eiseman, ex Micranthes pensylvanica , #CSE1475, CNC654220 (1♂) .

Paratypes: MASSACHUSETTS: same collection as holotype, em. 15–30.iii.2015, #CSE1475, CNC654212– 654219 , CNC654221–654233 (12♂ 9♀), em. 15.iii.2015, #CSE1473, CNC564658 (1♀) .

Etymology. The specific epithet (from L. palus, swamp) refers to the wetland habitat of this fly and its host plant.

Host. Saxifragaceae : Micranthes pensylvanica (L.) Haw.

Leaf mine. ( Fig. 197 ) Upper surface, green to whitish, entirely linear, with black frass in discrete grains and irregular particles. There were multiple mines in each leaf observed, usually with the whole upper surface of the midrib mined out in addition to linear mines in the leaf blade.

Puparium. ( Figs. 50 , 198 ) Brown, normally formed within the leaf, with the anterior spiracles projecting through the epidermis. Most puparia were formed on the lower surface of the leaf blade, but a few were found on the upper surface of the midrib. A single female (CSE1473) emerged from a puparium that was formed outside the leaf and was found attached to the lower leaf surface.

Distribution. USA: MA.

Adult description. Wing length 2.3–2.6mm (♂), 2.3–2.7mm (♀). Eye height divided by gena height: 2.5–4.3. Eye very sparsely short-haired. First flagellomere rounded. Orbital plate ill-defined; with slightly more pronounced gray/silvery pruinosity. Orbital spot broadly ovate to subrectangular, posterior ocelli widely spaced. Very slight epistoma. Notum pruinose. Vein dm-cu absent.

Chaetotaxy: Two ors, two ori (anterior ori approximately 2/3 length).

Coloration: ( Fig. 49 ) Setae dark brown. Body with slight gray/beige pruinosity. Head partly yellow with brown/beige tint that is darker on lunule; pedicel and scape brown with rusty tint; first flagellomere, ocellar spot, back of head, clypeus and ventral line on gena dark brown; posterolateral corner of frons dark brown to base of inner vertical seta, continuing anteriorly as stripe along outer margin of otherwise yellowish orbital plate; orbital stripe sometimes restricted to eye margin with mottling at base of setae, but usually with extensions to base of ors and sometimes ori; face brown to dark brown; palpus brown. Thorax dark brown, postpronotum and notopleuron paler with rusty tint and yellowish mottling. Calypter margin dirty white, hairs brown. Haltere light yellow. Coxae dark brown with apex of fore coxa yellowish apically; femora brown, sometimes with yellowish mottling, apices light yellow with either fore femur or all femora with apical spot as long as wide or slightly longer; tibiae brown with base and apex paler, with fore tibia palest and hind tibia darkest; tarsi light brown to yellowish on fore leg, brown on hind leg, intermediate on mid leg. Abdomen dark brown.

Genitalia: ( Figs. 348–352 ) Surstylus small, rounded, fused to epandrium, setose on inner face. Postgonite simple, one medial seta and one subapical socket. Phallophorus flanked by one pair of irregular sclerotized bands. Basiphallus composed of one pair of sclerites with tapered apices and irregular margins; left sclerite wrapped ventrally around shaft before midpoint; right sclerite with split, irregular base approximate to distal margin of phallophorus. Hypophallus with medial paired sclerites that are confluent at base of large, longitudinally split, membranous flagellum; broader and darker at base, distally with one pair of sclerotized bands following base of flagella, laterally with one pair of short, narrow, curved processes with irregular outer margin. Mesophallus indistinct, fused to distiphallus. Distiphallus long, narrow, dark, linear, upcurved on flattened, split distal half.

Comments. Phytomyza palustris is mostly dark with a grayish-beige pruinosity, the frontal vitta, gena, postgena and inner orbital plate are brownish-yellow, the face, pedicel and scape are paler brown, and the femora apices are variably yellow, at least with the fore femur widely yellow. The anterior ori is slightly reduced, the eye is very sparsely short-haired, and the genitalia are highly diagnostic: the paraphalli are absent, the hypophallus is dominated by a long, stout flagellum with a complex basal sclerotized structure including one pair of short, narrow curved arms, and the mesophallus and distiphallus are fused to form a narrow dark sclerite that is flattened and split apically ( Figs. 351, 352 ). The notum is covered with a relatively heavy dusting of pruinosity, keying it to P. agromyzina in Spencer & Steyskal (1986) , which has highly dissimilar genitalia. Very similar morphology is seen in related Nearctic saxifrage-miners with a shinier notum ( P. mitellae Griffiths and P. tiarellae Griffiths—see Griffiths (1972)), but none match the derived structures seen here.

Figures

FIGURES 44–50. Figures 44–45. Phytomyza hatfieldae spec. nov.; 44: puparia; 45: adult female. Figures 46–47: P. hydrophyllivora spec. nov.; 46: puparium; 47: adult male. Figure 48: P. loewii Hendel, puparium. Figures 49–50: P. palustris spec. nov. 49: adult male; 50: empty puparium.

FIGURES 189–199. leaf mines; 189: Phytomyza hatfieldae spec. nov. in Osmorhiza claytonii; 190: P. hydrophyllivora spec. nov. in Hydrophyllum canadense; 191: P. hydrophyllivora in Hydrophyllum virginianum (yellow puparium at tip of leaf serration, upper right); 192: P. linnaeae (Griffiths) in Linnaea borealis (transmitted light); 193: P. loewii Hendel in Clematis virginiana; 194: P. minuscula Goureau in Thalictrum pubescens; 195: P. omlandi Scheffer & Lonsdale in Gelsemium sempervirens; 196: P. palmeri spec. nov. in Symphoricarpos orbiculatus (transmitted light; puparium at upper left); 197: P. palustris spec. nov. in Micranthes pensylvanica; 198: same, five brown puparia in blisters on lower leaf surface (whitish object along left side of midrib is a coniopterygid cocoon); 199: P. penstemonis Spencer in Penstemon digitalis.

FIGURES 348–352. Phytomyza palustris spec. nov., male genitalia; 348: external components, posterior; 349: postgonite, left lateral; 350: hypandrium, ventral; 351: phallus, ventral; 352: phallus, left lateral.