Agromyza isolata Malloch

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 : 11

Agromyza isolata Malloch

( Figs. 2 , 70–71 )

Material examined. VERMONT: Chittenden Co. , South Burlington, Winooski Gorge, 29.vi.2014, em . 15.vii.2014, C.S. Eiseman, ex Populus balsamifera , #CSE1176, CNC384839–384841 (3♂); Williston, Mud Pond, 28.viii.2016, em. 18–19.ix.2016, C.S. Eiseman, ex Populus balsamifera , #CSE3000, CNC654500–654504 (2♂ 3♀).

Hosts. Salicaceae : Populus balsamifera L., P. deltoides W. Bartram ex Marshall, P. × jackii Sarg., P. trichocarpa Torr. & A.Gray ex. Hook., Salix bebbiana Sarg. (leaf mines only), S. lucida Muhl. ( Spencer 1969; Spencer & Steyskal 1986). Spencer (1969) caught an adult female on P. tremuloides .

Leaf mine. ( Figs. 70–71 ) “Large irregular blackish blotch, with several larvae normally feeding together” ( Spencer 1969). In our first collection of this species, the mines were not distinguished in the field from those of Agromyza albitarsis (see Comments). In our second collection, six very small, brown, irregular mines were found near the center of a leaf blade ( Fig. 70 ). These expanded to large, irregularly lobed, pale greenish-brown blotches that partially coalesced, none of them quite reaching the leaf margins when complete ( Fig. 71 ). The frass was in scattered black grains and irregular particles.

Puparium. ( Fig. 2 ) Yellow to yellowish-brown, 1.9–2.0 mm by 0.9–1.1 mm; formed outside the mine.

Distribution. USA: CA, CO, MN (leaf mines only), PA, *VT, WA; Canada: AB, ON, QC, SK.

Comments. In 2014 we collected mines of this species on Populus balsamifera along with similar mines that yielded adults of Agromyza albitarsis . At the time of collection, the mines were all assumed to represent the same fly species, and those of A. isolata were not photographed. When the larvae had emerged, the differences in the puparia of the two species were obvious; those of A. albitarsis were substantially larger and were reddish-brown rather than yellow ( Fig. 2 ). The leaf from which we reared A. isolata in 2016 also contained a single larva of what we believe was A. albitarsis , forming a large, greenish mine along the leaf margin. It formed a puparium that was substantially larger than those of A. isolata , but no adult emerged.

Figures

FIGURES 1–6. 1. Agromyza diversa Johnson, adult male. Figure 2: puparia; A. isolata Malloch (left), A. albitarsis Meigen (right). Figures 3–4: A. fission spec. nov.; 3: adult male; 4: empty puparia. Figures 5–6: A. soka spec. nov.; 5: adult male; 6: puparium.

FIGURES 63–74. leaf mines; 63: Agromyza albitarsis Meigen in Populus balsamifera; 64: A. ambrosivora Spencer in Helianthus annuus; 65: A. aristata Malloch in Ulmus rubra; 66: A. bispinata Spencer in Elymus hystrix; 67: A. diversa Johnson in Laportea canadensis; 68: A. fission spec. nov. in Celtis occidentalis; 69: A. idaeiana Hardy in Geum macrophyllum; 70: A. isolata Malloch in Populus balsamifera, young mines (left) with probable A albitarsis mine at leaf margin; 71: same Populus balsamifera leaf with completed mines, A. isolata to left of midrib and probable A. albitarsis to right; 72: A. parca Spencer in Dichanthelium clandestinum; 73: A. pseudoreptans Nowakowski in Urtica dioica; 74: A. pudica in Dichanthelium scoparium.