The Milwaukee Public Museum had its origin in 1883 with a group of collections presented to the City of Milwaukee by the Natural History Society of Wisconsin (NHSW) that included "1,900 Marine invertebrates, dry" and “2,690 Insects.” The collections have been managed under various departments over the years, most recently as Insect and Non-Insect Collections in the Invertebrate Zoology Department. Currently, two curators are responsible for all the invertebrate collections, approximately 800,000 specimens of which 70% are insects and 30% are other invertebrate groups that encompass a broad diversity of animals (52 zoological classes). Lepidoptera and Coleoptera comprise the largest portions of the insect collections, and Mollusca and Crustacea the largest collections of other invertebrates.
Special insect collections include the Type Collection (about 60 holotypes and 55 syntypes) of various orders, tropical Lepidoptera and gynandromorphs from James R. Neidhoefer, a worldwide collection of Sphingidae from William E. Sieker, determined Costa Rican cacao-pollinating midges (Ceratopogonidae and Cecidomyiidae) from Allen M. Young’s research. Other significant invertebrate collections include a comprehensive survey of WI crayfishes made by the WI Department of Natural Resources, Horton H. Hobbs III and Joan P. Jass, the Harold Mathiak collection of WI freshwater unionids, and the WI arachnid collection, including the historically important George W. and Elizabeth G. Peckham Collection of jumping spiders.