The inheritance of nymphal colour/pattern polymorphism in the leafhoppers Eupteryx urticae (F.) and E. cyclops Matsumura (Hemiptera: Auchenorrhyncha)

Nymphal colour/pattern polymorphisms are described in two cicadellid leafhopper species in the genus Eupteryx (Curt.). Eupteryx urticae (F.) exhibits three phenotypes (black, orange and white), while E. cyclops (Mats.) is polymorphic for pattern (ranging from completely pale to entirely black). There is no apparent parallel variation in the adults reared from these different phenotypes. The polymorphic variation reaches its full development in the last two nymphal instars, although it is possible to score earlier stages in certain cases. Crossing experiments revealed that part of the variation in E. urticae is controlled by a sex-linked gene, with orange dominant to black. Experiments with the white phenotype were inconclusive. In E. cyclops, the polymorphism is controlled by three genes, two autosomal and one sex-linked, each exhibiting complete dominance with epistatic interactions between them. A limited number of crosses between E. cyclops stock from Britain and Finland suggested that the loci controlling the polymorphism in the two countries are probably homologous. The theoretical implications of these findings are discussed.