Collections of specialized (high fidelity) mimetic Syrphidae in northern Michigan revealed 19 species associated with 18 flowering plants. Almost 97% of these syrphids were taken on seven plant species or species groups, all with conspicuous white or yellow blossoms, and all but one with aggregate inflorescences. Pastinaca sativa (Umbelliferae) is visited by many mimetic syrphids in northern Michigan but by very few in central Illinois; the opposite is true of Sambucus canadensis (Caprifoliaceae). In northern Michigan mimetic syrphids exploit a sequence of blossoming plants that more or less replace each other as the season progresses. The cooling effect of Lake Michigan slows the development of vegetation and the appearance of mimetic. syrphids along the shore by over two weeks as compared to a transect only 6.5 to 17 km inland. Because of the normally cooler temperatures in northern Michigan, syrphids appear on flowers later in the day and remain there longer than they do in central Illinois
