Agromyza idaeiana Hardy

Agromyza idaeiana Hardy

(Fig. 69)

Material examined. MASSACHUSETTS: Franklin Co., Northfield, 276 Old Wendell Rd., 22.v.2013, em. 10– 23.ix.2013, C.S. Eiseman, ex Potentilla simplex, #CSE888, CNC392668–392671 (2♂ 2♀); Worcester Co., Sturbridge, along Route 15, 5.vi.2013, em. 1–7.ix.2013, C.S. Eiseman, ex Potentilla simplex, #CSE859, CNC358503 (1♂); WASHINGTON: Grays Harbor Co., 10.x.2012, em. 5–31.v.2013, C.S. Eiseman, ex Geum macrophyllum, #CSE431, CNC392704–392709 (3♂ 3♀); Thurston Co., Lacey, Chehalis Western Trail / 45th Ave, 8.vi.2017, em. summer 2017, E. Stansbury, ex Hydrophyllum tenuipes, #CSE4339, CNC939930–939935 (6♂).

Hosts. * Boraginaceae: Hydrophyllum tenuipes A. Heller; Grossulariaceae: Ribes glandulosum Grauer (Spencer 1990); Rosaceae: Fragaria L. (cultivated varieties), F. virginiana Duchesne, Geum * macrophyllum Willd., Potentilla gracilis Douglas ex Hook. (leaf mines only), P. * simplex Michx., Rubus L. (cultivated varieties), R. idaeus L., R. occidentalis L.; many genera of Rosoideae in Europe (Ellis 2016). Spencer & Steyskal (1986) stated that no reared specimens are known in North America and made no reference to the rearing records for Fragaria and Rubus cited by Frick (1959). The record of Potentilla gracilis is from leaf mines that were found at the same locality where a male was caught (Spencer 1981). Spencer (1990) stated that Griffiths discovered this species on Ribes glandulosum (Grossulariaceae) in Alberta; this specimen (not examined) is in the UASM with the following data: larva collected 1.8.77, emerged 7.5.78, Goose Mountain, 4300 feet, Swan Hills, Alberta, Ribes glandulosum, leg GCD Griffiths, SW62 (1♂ [abdomen missing]). Although this single rearing could be interpreted as a case of aberrant xenophagy, the occurrence of Agromyza ideaeiana on Hydrophyllum tenuipes (Boraginaceae) in Washington is evidently a recurring phenomenon. We were initially hesitant to accept this record because there were no hostplant photos or preserved leaves associated with the rearing, but in early June 2018 E. Stansbury provided us with photos of H. tenuipes leaves showing mines consistent with A. ideaeiana. He noted that these were nowhere near as common as the entirely linear mines of an undetermined Phytomyza species on the same host.

Leaf mine. (Fig. 69) Whitish; initially narrow and linear, suddenly expanding into a blotch. Frass is scattered throughout in fine, dark grains. On Geum the mines of three or more larvae may coalesce into a single large blotch.

Puparium. Reddish-brown; formed outside the mine.

Distribution. USA: CA, CO, *MA, NJ, NY, PA, UT, *WA; Canada: AB (Sehgal 1971), BC, ON, QC, YT (Boucher & Wheeler 2001); Europe; Japan. The three previous records from the eastern US (Frick 1959) were not mentioned by Spencer & Steyskal (1986).

Comments. This species is bivoltine with a pupal diapause lasting about three months from late May or June to September. It was treated by Frick (1959) and Spencer (1969) as Agromyza spiraeae Kaltenbach and by Spencer & Steyskal (1986) as A. potentillae (Kaltenbach).