Book excerpt: This publication treats the species of Trialeurodes known from North America. In this region the genus is of particular interest because of its wide distribution, the number and diversity of its food plants, and the injuriousness of certain species. It is the largest aleyrodid genus known on the continent, and all species now known in the Nearctic Region presumably are indigenous to it or are Neotropical species whose northern limits extend into that Region. Characteristics of interest are modifications in papillae and in the vasiform orifice exhibited by some its members, and also the unusual parthenogenetic behavior of one of them.