( Figs. 40–42)
Lithocolletis ledella Walsingham 1889: 79. Phyllonorycter ledella (Walsingham) — Davis 1983: 10.
Leaf mine. An upper-surface blotch, becoming wrinkled when mature ( Figs. 40–41).
Hosts. Ericaceae: Rhododendron columbianum (Piper) Harmaja, R. groenlandicum (Oeder) Kron & Judd.
Distribution. Canada: AB, BC, NB, ON, QC, SK, YT; USA: CA, ME, MI; Greenland.
Review. Walsingham (1889) reared the type series from “somewhat folded mines, occupying the whole upper side of leaves of Ledum glandulosum ” (= Rhododendron columbianum) collected in Mendocino Co., California. This species has since been recorded from Quebec and Greenland, where it has been reared from Rhododendron groenlandicum ( Handfield 1997; Karsholt et al. 2015; De Prins & De Prins 2019), as well as from British Columbia ( Pohl et al. 2015), Yukon, Alberta, and Ontario ( Pohl et al. 2018). An aborted mine on R. groenlandicum apparently representing Phyllonorycter ledella was photographed in Saskatchewan ( Dombroskie 2017), and Adam (2019) reared adults from this host in New Brunswick (Fredericton, York Co.). Karsholt et al. (2015) stated that the distribution of P. ledella includes “north-eastern and western USA,” but apart from Michigan specimens listed in Appendix 1 of Landry et al. (2013), there are no specific literature records from states other than California. CSE has found old mines on R. groenlandicum in Maine (Steuben, Washington Co.; Figs. 40–41).
Comments. In Greenland it has been suggested that Phyllonorycter ledella may have a two-year life cycle, with larvae hibernating in non-deciduous leaves ( Karsholt et al. 2015). Adults have been found in Greenland from late July to early August. The available records from Canada and the US similarly only account for one generation: Dombroskie (2011) photographed what appears to be a mine containing a feeding larva of P. ledella in Ontario on 8 May; the Quebec specimen shown by De Prins & De Prins (2019) was reared from a larva or pupa collected on 10 May (the adult emerged on 29 May according to J.-F. Landry, in litt.); the New Brunswick specimens emerged from 15 to 18 June from mines collected on 22 May ( Adam 2019); and the type series emerged in June from mines collected in the same month ( Walsingham 1889).