Scales cause billions of dollars in damage to U.S. crops and in control costs annually, and nearly all damaging scale pests are species that have been inadvertently introduced. Despite the importance of scales as pests, the high frequency at which they are intercepted from plants and plant material at U.S. ports of entry, and the difficulties involved in identifying them, worldwide there is a shortage of specialists who can make or confirm scale identifications.

This tool is designed to help the user identify almost any scale insect to family, and in some cases to species, without the need for expertise in the group. The tool emphasizes scale taxa important to the U.S. ports of entry. Target users include USDA APHIS pest survey specialists, identifiers at ports of entry, state and county identifiers, students, and scientists.

The first edition of this tool (Miller et al. 2007) was available on CD and on the web. This second edition introduces a number of modifications to the original tool that aim to make the identification process more user-friendly and the information on the species fact sheets and glossary easier to update. Furthermore, several species have been added to the new edition, particularly for mealybugs.

Scale Insects, Edition 2 is a portal to a variety of keys, images, fact sheets, and a glossary of terms. The fact sheets often contain photos of scales on their hosts in the field, but in order to use the key one needs to slide-mount the sample. There are four separate keys to identify slide-mounted adult females. The first one, which the non-specialist is advised to consult first, provides a means to identify a scale to the taxonomic level of family. Then the user can choose the most appropriate key for species identification. There are three keys to species: Mealybugs and Mealybug-like Scales (including Pseudococcidae, Putoidae and Rhizoecidae), Soft Scales (Coccidae), and Other Scales. The latter contains pest species in various families, but it does not include armored scales from the family Diaspididae.