I found this large empty blotch mine on Maianthemum stellatum. On close examination I finally located an empty single white, elongated egg similar in appearance to those attributed to the fly Synchysa tricincta. However it was on the underside of the leaf near the edge adjacent to the red asterisk in the photo, not near the basal part of the leaf. It is also apparently very early for this species. I've searched leaves of this and all related plants species in the area but have not yet found any other mines.