The huge geographic variation in diapause suggests it has an underlying genetic basis, a feature further revealed by selection experiments that are successful in both increasing and decreasing the diapause incidence as well as modifying other attributes of diapause. Genetic crosses between lines with different diapause characteristics reveal diverse inheritance patterns. While some such crosses reflect a simple Mendelian-type pattern, polygenic inheritance patterns are more commonly revealed. Examples of dominance and incomplete dominance abound and a few examples can be found showing diapause traits linked to recessive alleles. Likewise, both sex-linkage and autosomal inheritance are noted in some examples. Mapping quantitative trait loci is a powerful technique for identifying single nucleotide polymorphisms associated with diapause. Results of such analyses elegantly demonstrate the complexity of the diapause response as well as the large number of chromosomal sites that have both major and minor impacts on diapause.