Liriomyza eupatorii (Kaltenbach)

Eiseman, Charles S., Lonsdale, Owen, Linden, John Van Der, Feldman, Tracy S. & Palmer, Michael W., 2021, Thirteen new species of Agromyzidae (Diptera) from the United States, with new host and distribution records for 32 additional species, Zootaxa 4931 (1), pp. 1-68 : 25-26

Liriomyza eupatorii (Kaltenbach)

Material examined. ILLINOIS: Cook Co., Glencoe, Chicago Botanic Gardens, 42°8′56.66″N 87°47′21.99″W, oak woodland, 21.vi.2018, em. by 25.vi.2018, J.F. Steffen, ex Symphyotrichum shortii, CNC 1135573–1135575 (2♁ 1♀); ONTARIO: Nipissing, Algonquin Provincial Park, Basin Depot, 6.vii.2018, em. 16.vii.2018, C.S. Eiseman & J.A. Blyth, ex Symphyotrichum ? cordifolium , # CSE 4778, CNC 1643629 (1♁).

Hosts. Apocynaceae : Asclepias L.; Asteraceae : Baccharis halimifolia L. , Mikania micrantha Kunth , M. scandens (L.) Willd., Solidago altissima L., S. canadensis L., S. latissimifolia Mill. , Symphyotrichum chilense (Nees) G.L.Nesom , S. cordifolium (L.) G.L.Nesom, [ S. lateriflorum (L.) Á.L̂ve & D.L̂ve, S. novae-angliae (L.) G.L.Nesom], S. praealtum (Poir.) G.L.Nesom , S. puniceum (L.) Á.L̂ve & D.L̂ve, S. * shortii (Lindl.) G.L.Nesom , Xanthium strumarium L. ( Eiseman & Lonsdale 2018). California specimens apparently reared from Callistephus Cass. (Asteraceae) have been tentatively identified as L. eupatorii ( Lonsdale 2011) ; see Comments for other likely hosts.

Leaf mine. Whitish, upper surface; long, narrow and linear; often beginning with a distinctive spiral, but this is sometimes reduced to a minute contorted area, and sometimes there is no hint of it whatsoever. The black frass is mostly in distinct, alternating strips, sometimes devolving into irregular, squiggly fragments toward the end ( Eiseman & Lonsdale 2018).

Puparium. Yellow to orange to dark brown; formed outside the mine ( Eiseman & Lonsdale 2018).

Phenology and voltinism. This species is evidently multivoltine in the USA, although all of our rearing records involve larval collections and adult emergences prior to midsummer. We have reared adults of Liriomyza eupatorii from larvae found in Oklahoma as early as 23 March, and from larvae found in Massachusetts on 11 May, 11–13 June, and 24–28 June. In New York, Scheffer & Lonsdale (2018) similarly recorded larvae only in May and June. Later dates have been observed in Canada, including an Alberta specimen emerging on 19 August from a larva collected on 4 August ( Lonsdale 2017a). In all of our rearings, adults have emerged 10–22 days after the larvae were collected.

Distribution. USA: CA, DE, GA, *IL, MA, MI, MS, MT, NC, NY, OK, PA, SC, TN, VA, WA, WV; Canada: AB, BC, MB, NB, NS, ON, QC, SK; Europe ( Eiseman & Lonsdale 2018).

Comments. We have found Liriomyza mines beginning with distinct spirals, and thus likely representing L. eupatorii , on the following additional asteraceous hosts: Ambrosia artemisiifolia L. (MA), Erigeron canadensis L. (MA, NC), Euthamia graminifolia (L.) Nutt. (MA), Senecio triangularis Hook. (ID) , Solidago rigida L. (MA), S. sempervirens L. (NY), S. simplex var. randii (Porter) Kartesz & Gandhi (NH) , Symphyotrichum firmum (Nees) G.L.Nesom (IL) , S. lanceolatum (Willd.) G.L.Nesom (MA) , S. pilosum (Willd.) G.L.Nesom (NC) , S. ulmifolia Muhl. ex Willd. (OK) , and Zinnia elegans Jacq. (NC) . Liriomyza mines without spirals, but nonetheless probably representing L. eupatorii , have been found on Solidago patula Muhl. ex Willd. (MA) .

Papp & Černý (2017) considered Liriomyza eupatorii to be synonymous with the senior L. pusilla (Meigen) , which is supported by close overall external and genitalic morphological similarity, notably including general phallic morphology, a large ejaculatory apodeme with a narrowed stem, and the occasional presence of a third ori. Liriomyza pusilla is known from Arctium L., Aster L., Bellis L., Bidens L., Callistephus Cass. , Crassocephalum Moench , Epaltes Cass. , Hypochaeris L., Synedrella Gaertn. , Tithonia Desf. ex Juss. , Vernonia Schreb. , Solidago L., and Xanthium L. ( Asteraceae ) ( Benavent-Corai et al. 2005; von Tschirnhaus & Karimpour 2006; Ellis 2020), the last two of which are also host genera of L. eupatorii . Beyond its Nearctic hosts, L. eupatorii has been reported from Aster , Eupatorium L., Helianthus L., Lapsana L. ( Asteraceae ), and Galeopsis L. ( Lamiaceae ) (Spencer 1976; Benavent-Corai et al. 2005). This synonymy follows notes of similarity by previous authors including Spencer (1971), who stated that adult morphology appeared identical, both external and genitalic, but that the form of the leaf mines was distinct. Mines of L. eupatorii typically start with a characteristic spiral, but we have observed some to lack this spiral ( Eiseman & Lonsdale 2018), as seen in L. pusilla . Spencer (1976) further differentiated the two by L. pusilla having the “mesonotum brilliantly shining black” and L. eupatorii having the “mesonotum deep black but less shining”. While these two species are clearly closely related, their synonymy may be unwarranted on the basis of minimal overlap in host genera, a relatively (but not entirely) consistent difference in larval mine pattern, and slight differences in the phallus. While no specimens of L. pusilla were available to us, descriptions and illustrations were examined from Spencer (1971) and Papp & Černý (2017). Lonsdale (2017a) noted variation in the shape of the phallus of L. eupatorii , but in all cases, the mesophallus is quite small, being narrow, stem-like, and no more than half the length of the larger distiphallus, while it is slightly longer in L. pusilla and much thicker in lateral view. Regarding the distiphallus itself, it is longer and usually widest at or past the midpoint of the segment in L. eupatorii , and shorter, rounder, and either parallel-sided or widest on the basal half in L. pusilla (also one atypical male of L. eupatorii from Alberta ( Lonsdale 2017a: Fig. 267)). Based on all of the above evidence, the two species are here considered separate (with L. eupatorii being Holarctic and L. pusilla known only from the Palearctic and Oriental regions), but because of their strong similarities, further scrutiny is certainly warranted, ideally including molecular data sets.