Aphidini (Hemiptera: Aphididae) living on Senecio (Asteraceae), with descriptions of a new genus and three new species

The species of Aphidini living on Senecio L. in South America are reviewed. Pehuenchaphis gen. nov. is described; it is an Aphidina genus characterized mainly by the siphunculi on abdominal segment VI when present and by its radicicolous way of life. The type species of the genus Pehuenchaphis agilissima sp. nov. is described and the new combination Pehuenchaphis americana for Seneciobium americana Mier Durante and Ortego is established. Aphis senecionicoides E.E. Blanchard is redescribed and its neotype is established. Aphis papillosa sp. nov. with very large marginal papillae and Aphis malalhuina sp. nov. with short siphunculi are described and differentiated from the previously known Aphis intrusa Ortego and A. senecionicoides. A key for the apterous viviparous females of these seven species and Andinaphis paradoxa Mier Durante et al. is given.