The photos present in this App are intended to help foresters, urban landscaping employees, or others working with trees recognize some of the common pest insects affecting trees in North America and understand their life cycles and how they damage trees. The information was drawn from book, websites, factsheets, and some original literature. This App is not a guide for specialists. In many groups, such as the bark beetles and aphids, confirmation of species identity requires attention to details not visible in photos with comparisons to other similar species and use of keys. Sources for further information (websites and articles) are given at the bottom of each species' page.