During urban grid surveys in September 1982, San Diego County biologists discovered a new invading whitefly on avocado. Ray Gill, insect taxonomist for the California Department of Food and Agriculture (CDFA), identified the new invader as Tetraleurodes sp. Steve Nakahara of the United States National Museum then confirmed both the identification and the fact that the whitefly was new to California. Gill and Nakahara agree that this whitefly is the same undescribed species known from the Caribbean, Central America, Florida, and Mexico. The whitefly The adults of both sexes of the invading Tetraleurodes sp. bear red wing patterns, prompting the common name, red-banded whitefly. Several other species of Tetraleurodes are found in southern California, including the mulberry whitefly, T. mori (Quaintance), acacia whitefly, T. acaciae (Quaintance), and Stanford whitefly, T. stanfordi (Bemis). The red-banded whitefly can be distinguished from these three species in southern California by both adult and larval characters. The red patterns on the wings are unique to the red-banded whitefly and are readily visible. Late larval stages of all four species are a characteristic jet black, surrounded by a white marginal fringe. However, red-banded whitefly larvae, which develop on the undersides of maturing avocado leaves, produce a copious white marginal fringe that curls up and partially covers the dorsum. The white fringe of mulberry, acacia, and Stanford whitefly larvae generally lies flat on the leaf surface and is not as prominent. Additionally, of the three named species of Tetraleurodes previously in southern California, only mulberry whitefly has been recorded from avocado. Therefore, host plant association is a partially reliable means of identifying the red-banded whitefly.