DISTRIBUTION AND HYBRIDIZATION BETWEEN CULEX-PIPIENS AND CULEX-QUINQUEFASCIATUS (DIPTERA, CULICIDAE) IN ARGENTINA

To better understand the distribution of Culex pipiens and Cx. quinque fasciatus in Argentina, samples were collected from six localities sit uated in a North-South line from Castelli (Chaco Province) to Puerto M adryn (Chubut Province). Identification was based on the morphology of male genitalia. Only Cx. quinquefasciatus was found in Castelli and E speranza, while in Rosario, 95.3% belonged to this species and 4.7% re presented hybrid forms. Southern samples included only Cx. pipiens. Wi th the purpose of verifying if Cx. pipiens and Cx. quinquefasciatus hy bridize, different crosses between the two species were performed. All crosses produced viable egg rafts. Hatching ranged from 70 to 100%, e xcept in one cross, female Cx. pipiens x male Cx. quinquefasciatus, wh ere a high incompatibility was observed (11.1% hatch). The F-1 hybrids obtained from all crosses were fertile. The finding of hybrid forms i n nature can be interpreted as evidence for subspecific status of Cx. pipiens and Cx. quinquefasciatus in Argentina.