Liriomyza asclepiadis Spencer

Liriomyza asclepiadis Spencer

(Fig. 134)

Material examined. KANSAS: Riley Co., Konza Prairie Biological Station, 3.vii.2015, em. by 19–20.vii.2015, C.S. Eiseman, ex Asclepias viridis, #CSE1741, CNC654491–654493 (1♂ 2♀); MASSACHUSETTS: Franklin Co., Northfield, 42.646572, -72.428259, 21.vi.2016, em. 6–10.vii.2016, C.S. Eiseman, ex Asclepias exaltata, #CSE2710, CNC654109–654111 (2♂ 1♀); Orange, along Shingle Swamp Brook (42.561394, -72.299578), 11.viii.2016, em. 26–29.viii.2016, C.S. Eiseman, ex Asclepias incarnata, #CSE2952, CNC638897 (1♂).

Hosts. Apocynaceae: Asclepias * exaltata L., A. incarnata L., A. syriaca L., A. * viridis Walter (Spencer 1969). The record of A. speciosa Torr. (Spencer 1969; Lonsdale 2017) refers to Liriomyza subasclepiadis Spencer (Spencer & Steyskal 1986). See comments for other possible hosts.

Leaf mine. (Fig. 134) Spencer (1969) originally described the mine as an irregular, partly interparenchymal blotch with frass in scattered black grains, frequently with numerous larvae in a single leaf. Spencer & Steyskal (1986) described it as a small, predominantly regular blotch mine, with greenish diffused frass. It is possible that the discrepancy has something to do with Spencer’s including L. subasclepiadis in his original concept of L. asclepiadis, but our own observations indicate that the mine can differ depending on the host species. The mines we observed on Asclepias incarnata were small, irregular, and largely interparenchymal, appearing greenish with associated reddish discoloration, sometimes mottled with whitish on the upper surface. There was little evident frass. The mines on A. exaltata, A. syriaca and A. viridis are entirely on the upper surface, whitish suffused with green to varying degrees, with dark green to black frass in scattered grains or irregular lumps. Mines are at least sometimes initially linear, but this portion is almost always obliterated by the blotch before long.

Puparium. Yellow to orange; formed outside the mine.

Distribution. USA: IN, *KS, MA, NH, NY; Canada: ON, QC. The record of ID (Lonsdale 2017) is erroneous; IN was intended (Spencer 1969). See comments for other (tentative) distribution data.

Comments. The record of this species from Asclepias ovalifolia Decne. in Minnesota (Spencer & Steyskal 1986) is based on empty leaf mines. To this we can add A. subverticillata (A. Gray) Vail (CO) and A. tuberosa L. (KS). We have also seen mines (including photographs posted to www.BugGuide.net) on A. exaltata in IA, on A. syriaca in CT, MD, OH, PA, WI, and NB, and on A. viridis in OK. These records should be confirmed by rearing, given that two other Liriomyza species are known to form blotch mines on Asclepias. Liriomyza peleensis Spencer was reared from A. incarnata at Point Pelee, Ontario, and L. subasclepiadis from A. speciosa Torr. in Yakima Co., Washington (Spencer 1969; Spencer & Steyskal 1986). Spencer (1969) stated that numerous larvae of L. peleensis feed together in a single leaf, “forming a large blotch with frass scattered irregularly in greenish-black grains”, characterizing those of L. asclepiadis as “similar, though smaller”. Neither this description nor the single geographic datapoint for L. peleensis seem sufficient to separate the two with confidence. The mine of L. subasclepiadis is described as irregular and interparenchymal, “frequently partially linear, with frass detectable in 2 lines of strips, but often develop[ing] into [a] secondary blotch; mine appears greenish and may be difficult to detect as a true mine” (Spencer & Steyskal 1986). This largely agrees with our observations of L. asclepiadis on A. incarnata, but the linear portion and strips of frass would be distinctive if present.