Relative abundance changes in Minnesota Point coccinellid aggregations

Located at the mouth of the St. Louis River on Lake Superior in Duluth, Minnesota Point is a seven-mile long sand spit that is home to several rare and potentially declining habitats. One target of faunal studies on Minnesota Point is the phenomenon of lady beetle (Coleoptera: Coccinellidae) aggregations on the lakeside shore. In addition to being a fascinating oddity for tourists and insect enthusiasts, large gatherings of coccinellids are important for mating, migration, and overwintering. One study of coccinellid aggregations in the 1970s gathered samples consisting almost entirely of the native Hippodamia convergens (Guérin-Méneville). Also recovered were three native species now in decline throughout the eastern United States: Coccinella novemnotata Herbst, Adalia bipunctata (L.), and Coccinella transversoguttata richardonsoni Brown. In light of subsequent exotic species establishments in North America and current native coccinellid declines, this follow up survey was conducted in 2014. Twelve different coccinellid species were recovered, including three exotics: Hippodamia variegata (Goeze), Harmonia axyridis (Pallas), and Coccinella septempunctata L.. None of these species were present in the 1970s survey. The exotic H. axyridis made up the majority of coccinellids found, while Hippodamia convergens only accounted for 7% of samples. Moreover, C. novemnotata, A. bipunctata, and C. transversoguttata richardsoni were not recovered. Further work is warranted to investigate displacement of native species and the effects of exotic coccinellid establishment on Minnesota Point.