Scale Insects, Edition 2 was made possible, in part, by a cooperative agreement from the United States Department of Agriculture’s Animal and Plant Health Inspection Service (USDA APHIS). A grant through the USDA Center for Plant Health Science and Technology and another infusion of funds from the USDA through Hilda Diaz-Soltero, USDA Invasive Species Liaison and Coordinator, funded an earlier version of this tool. We are grateful to Terrence Walters, coordinator of the USDA APHIS Identification Technology Program, for providing logistical support to the authors for the successful development and deployment of Scale Insects, Edition 2. Sincere thanks to Gail Coleman, Adam Holmes and Maaka Letuligasenoa (all California Department of Food and Agriculture) for administrative assistance. We also thank Gary Miller (USDA) for allowing us the use of USDA-BARC facilities and collection, and Barbara Denno (USDA volunteer) for general assistance, particularly updating ScaleNet to make our hyperlinks current. Doug Williams (The Natural History Museum, retired) provided many of the illustrations and useful advice, particularly during the first phase of this project. Finally, we wish to extend our gratitude to the reviewers of a beta version of this tool, who provided a number of valuable comments and suggestions: Ramon Dones (USDA APHIS Plant Protection and Quarantine (PPQ)), John Dooley (USDA APHIS PPQ), Laura Hartman (USDA APHIS PPQ Science & Technology), Lindsey Seastone (USDA APHIS PPQ Science & Technology), Ian Stocks (Florida Department of Agriculture and Consumer Services, Division of Plant Industry), and Natalia von Ellenrieder (CDFA).