An unusual chromosome system in a leafhopper (Homoptera auchenorrhyncha)

An unidentified species of the genus Austroagalloides is shown to have 7_II+1_IV instead of the normal 11_II+XO configuration at metaphase I of meiosis in males. The quadrivalent manifests two types of pairing which ensures regular disjunction; normal chiasma-type pairing and distance pairing. It is suggested that the 7_II+1_IV form is derived from the 11_II+XO form by a series of fusions.