Western flower thrips, Frankliniella occidentalis Pergande, is a well known pest in California and is polymorphic for color, with populations varying from nearly black to pale yellow. This type of color polymorphism has been noted throughout the global distribution of this insect. Several hypotheses have been proposed for why these color morphs occur, i.e. variation in temperature or host plant, or genetic differences within the species. We have compared sequence data from the nuclear genes ITS and 28S and the mitochondrial genes COI and 16S to analyze genetic variation among western flower thrips from many regions of California, as well as selected populations from Europe, Australia and several states in the USA. A dendrogram revealing the relationship between color polymorphism and genetic similarity in western flower thrips will be presented.