Agromyza parca Spencer

(Figs. 11, 12, 110, 111, 240–242)

Material examined. CONNECTICUT: Litchfield Co., Norfolk, Aton Forest, Bull Pasture, 42.028400, −73.135659, 18.vi.2022, em. 7.vii.2022, C.S. Eiseman & J.A. Blyth, ex Glyceria striata, # CSE7585, CNC5173427 (1♀); MARYLAND: Colesville, 1.viii.1976, W.W. Wirth, USNMENT01540659 (1♀, USNM), Lavale, 9.v.1970, G. Steyskal, USNMENT01540660 (1♂, USNM); MASSACHUSETTS: Berkshire Co., Mount Washington, Yagar Pond, 42.117961, −73.443367, 28.vi.2024, em. 11.vii.2024, C.S. Eiseman, ex Glyceria canadensis, # CSE8893, CNC2130721 (1♀); Windsor, 30.vii.2014, em. 14.viii.2014, C.S. Eiseman, ex Glyceria melicaria, # CSE1322, CNC384892 (1♀); Middlesex Co., Concord, 17.vii.1961, W.W. Wirth, USNMENT01540656–8 (2♂ 1♀, USNM).

Hosts. Poaceae: Glyceria canadensis (Michx.) Trin., G. *melicaria (Michx.) F.T.Hubb., G. striata (Lam.) Hitchc. (Eiseman & Lonsdale 2018). The undetermined Poaceae host of the Iowa specimens listed by Eiseman et al. (2021) was likely also a Glyceria sp., based on the habitat (stream margin) and what is visible of the leaves in our photographs of the larval mines (Fig. 111). Our previous records of A. parca from Dichanthelium spp. (Eiseman & Lonsdale 2018; Eiseman et al. 2021) refer to A. dichanthelii sp. nov. (see above).

Leaf mine. (Figs. 110, 111) Several eggs are laid in close proximity, without associated host-feeding punctures in the examples we have seen. The larvae initially form narrow mines toward the leaf apex, sooner or later reversing direction and merging to form a whitish- to yellowish-green blotch that may occupy the full width of the leaf. Fine, closely spaced, granular frass is deposited throughout the mine. In some cases, mines are on the abaxial leaf surface, but the leaf is twisted so that the mined portion faces upward.

Puparium. (Fig. 12) Reddish-brown to blackish-brown; formed outside the mine. Posterior spiracles distantly separated, with 3 narrow, widely separated pores. Also see Guglya (2025, including Figs. 17–18).

Phenology and voltinism. Larvae collected in Iowa, Massachusetts, and Connecticut in mid- to late June, mid-July, and late July emerged as adults (Figs. 11, 240–242) 13–23 days later (Eiseman & Lonsdale 2018; Eiseman et al. 2021).

Distribution. USA:CT, IA, MA, MD, NC,TN (Eiseman &Lonsdale2018; Eiseman et al. 2021); Ukraine (Guglya 2025). Of the specimens reported for this species in Lonsdale (2021), only five from Maryland and Massachusetts are retained in this species, as listed above. Some of the specimens from Maryland are now paratypes of A. dichanthelii, as are all specimens reared from Dichanthelium, as well as the males from the District of Columbia, Connecticut, and New Jersey; one female from Connecticut is also tentatively placed in that species. The remaining females could not be confidently placed, and are identified as “ Agromyza sp. ”; these are from Connecticut, Maryland, New Hampshire, and New York. Grigoryan & Hovhannisyan (2025) reported A. parca from Azerbaijan and stated that it is “quite widespread in the Palearctic region, China, Japan, [and] the Nearctic region,” citing Nartshuk (2019). The latter publication in fact makes no mention of A. parca, and we are unable to confirm the identification of the Azerbaijan material based on the images provided by Grigoryan & Hovhannisyan (2025), especially given the novel host genera reported. Guglya (2025) noted that N. Grigoryan was unable to determine the true source of the distribution records that were erroneously attributed to Nartshuk (2019), and we presume they referred to another species.

Comments. Eiseman & Lonsdale (2018) discussed a Massachusetts female as “ Agromyza sp. 5,” but we are now satisified that it represents A. parca.

Although Agromyza parca so far has been found exclusively on Glyceria spp. in North America, Guglya (2025) has reared specimens that appear entirely consistent with this species from Setaria viridis (L.) P.Beauv. in Ukraine. No Agromyza species has been reared from Setaria in North America, although two species that occur here, A. albipennis and A. nigrella (Rondani), have been reported from this host genus elsewhere (Spencer 1972; Ellis 2024). Several Old World Setaria species are common in New England, and CSE has occassionally found Agromyza mines on S. pumila (Poir.) Roem. & Schult. in Massachusetts and Vermont, but no adult emerged from the single puparium obtained.