The Terrestrial Mollusc Key was specifically designed to assist in the identification of adult terrestrial slugs and snails of agricultural importance. The key also includes species of quarantine significance as well as invasive and contaminant mollusc species commonly intercepted at U.S. ports of entry. This key is designed for federal, state and other agencies or organizations within the U.S. that are concerned with the detection and identification of molluscs of significance. This key includes 33 families and 128 species. It should be noted that this key is not inclusive of all mollusc pests, as new species of interest arise almost daily.

The list of species included in this tool was generated based on pest species reported in scholarly publications by Barker 2002, Cowie et al. 2009, and Godan 1983 as well as commonly intercepted species documented in the port of entry interception data from US Department of Agriculture, Animal and Plant Health Inspection Service, Plant Protection and Quarantine division (USDA-APHIS-PPQ) and the Florida Department of Agriculture and Consumer Services (FDACS) -Division of Plant Industry.