Holotype (female): Iran: Mazandaran Province, Haraz road, 10 km north east Abali, 35°50'N; 51°58'E, h 2360m, swept from flower heads of Centaurea behen, 20 May, 2011, S. Mohamadzade Namin leg. (JAZM).

Paratypes: 1♀, same collection data as in holotype, reared from flower heads of Centaurea behen Linnaeus, collected 13 September, 2008 & emerged 22 September 2008; 1 ♂, 1 ♀, Alburz Province, Chaloos road, Nesa, 36°04'N; 51°19'E, h 2200m, 22 June 2009, swept from Centaurea behen; 15 ♂, 18 ♀, same collection data as in holotype, 20 May, 2011, S. Mohamadzade Namin leg. (JAZM; some paratypes are deposited also in MHNG, SIZK, ZISP and first author's personal collection).

Head: Yellow, except ocellar triangle, occiput and slender part of arista black. Length: height: width ratio = 1: 1: 1.25. Frons brown; face whitish yellow; Antenna yellow, scape with blackish setulae at dorso-apical margin; first flagellomere light yellow, 1.6 times as long as wide and distinctly rounded antro-ventrally; arista bare. Compound eye about as high as long. Gena 1.1 times as high as length of first flagellomere. Proboscis capitate with black setae. Two frontal and one orbital setae present. Postocellar, postocular, vertical and genal setae black and acuminate. Frons with black setulae around frontal setae (Fig. 4).

Thorax: General color black; mesonotal scutum densely covered with gray microtrichia and black setulae. Notopleura shining black. Pleuron black; only stripe in anterior half of anepisternum and postpronotal lobe yellow. Scutellum yellow; slightly convex, corners of scutellum black. Subscutellum and mediotergite black. All setae on thorax black and acuminate. Scutellum with 4 equal black setae; basal setae placed in yellow area. Halter yellow.

Wing: Hyaline with 3 well developed dark brown crossbands. Subbasal band reduced and only present as darkening near apex of cell bm and rarely bcu. Discal crossband complete, crossing wing from pterostigma through R-M crossvein into posterior margin. Preapical crossband complete, reaching posterior margin. Apical band well developed. In females, preapical and apical crossbands in 56.2% of type material fused in cell r1 (Fig. 2), in 31.2% fused in r1 and r2+3 (Figs 1, 11) and in 12.5% fused in r1, r2+3 and anterior half of r4+5 cells (Fig. 3). In males, preapical and apical crossbands in 33.3% of specimens fused in cell r1, in 50% fused in r1 and r2+3 and in 16.6% fused in r1, r2+3 and anterior half of r4+5 cells. In one male of type series discal and preapical crossbands narrowly joined in r1 cell and in one female and one male discal and preapical crossbands narrowly connected at posterior margin of wing. Pterostigma yellowish. Distance between crossveins about 1.4 as long as dm-cu crossvein. R4+5 with 1 setula ventrally at node.

Legs: Completely yellow; fore femur in 60% of females and 55% of males with black stripe in dorsal side. All setae and setulae blackish (Figs 9, 10). Fore femur with two dorsal and one ventral rows of setae.

Abdomen: General color black, sparsely microtrichose, subshining with black setulae. Posterior margin of abdominal tergites, especially tergites 5–6 with long black setae. Oviscape 1.25 times as long as preabdomen, shining black with black hairs. Aculeus narrow, 11 times as long as wide, apically rounded, apex with two pairs of indistinct steps, as in Figs 5, 6, 13, 14. Tergite 5 of males as long as two preceding tergites with long setae in posterior margin.Epandrium as in Figs 8, 12 and glans as in Figs 7, 15.

Measurements: Male: BL= 3.5–4 mm (average 3.8), WL = 3.5–4.5 mm (average 3.9); female: BL= 4.5–6 mm (average 5.3), WL= 4–4.9 mm (average 4.3), AL = 1.5–2 mm (average 1.9) (n = 5).

The species is named in honour of Dr Bernhard Merz, an outstanding Swiss dipterist, in recognition of his invaluable contribution into study of the order Diptera, especially family Tephritidae.

The new species is similar to Urophora campestris Ito (Japan), Urophora sachalinensis (Shiraki) (Russia and Japan), Urophora stylata Fabricius (Worldwide), Urophora tsoii Korneyev and White (Russia) and Urophora vera Korneyev and White (Armenia), sharing similar wing pattern (3 well developed crossbands and indistinct subbasal crossband, with apical and preapical crossbands fused along anterior margin of wing), yellow femora and antenna and black notopleura, differing in the shape of aculeus apex. Apex of aculeus in Urophora sachalinensis, Urophora stylata and Urophora vera has one pair of steps. Urophora campestris and Urophora tsoii (both occurring in the Far East of the Palaearctic Region) possess two pairs of distinct steps, whereas the aculeus tip in Urophora merzi sp. n. has two pairs of smoothed, almost indistinct steps. Also the new species is similar to Urophora jaculata Rondani (Italy and Greece), sharing similar aculeus apex and host plants of the genus Centaurea, differing in the subbasal crossband strongly reduced to a darkening near bm cell (distinct and reaching R1 in Urophora jaculata).

All the compared species are associated with different host plants: Urophora campestris, Urophora sachalinensis and Urophora stylata are associated with Cirsium spp., Carduus spp. and Galactites tomentosa; Urophora tsoii and Urophora vera with Serratula spp. and Urophora jaculata with Centaurea solstitialis (Korneyev and White 1999, 2000) whereas Urophora merzi sp. n. is associated with Centaurea behen.