Aphis mirabilis sp. n. (Hemiptera, Aphididae, Aphidina), a South American species resembling A. craccivora, and further data on A. tropaeoli.

We examined 1367 apterous viviparae from 151 samples to study Aphis craccivora, A. tropaeoli and a third, possibly new species in Argentina, resembling both. Principal component analysis (PCA), followed by hierarchical clustering of principal components (HCPC), revealed clusters based on 33 morphological characters of 206 selected specimens. The delimitation of possible taxonomic entities was assessed by logistic regression. PCA confirmed that A. tropaeoli is a valid species. HCPC revealed the existence of a new species distinct from A. craccivora. Recently published data on the variability of A. craccivora, mainly regarding Asian populations, are presented and discussed; the general appearance of the sexuals of this species is also presented. The new species is described with the name Aphis mirabilis Nieto Nafra and Ortego sp. n., based on apterous and alate viviparae, oviparae, and males collected in Mendoza and Neuqun (Argentina) on Adesmia volckmannii (Fabaceae), Atriplex nummularia and At. lampa (Amaranthaceae), Bougainvillea spinosa (Nyctaginaceae), and Robinia pseudoacacia (Fabaceae). This new species has also been collected on plants of another 18 species from 8 additional families, although these specimens are not included in the type series. Features to distinguish A. mirabilis Nieto Nafra and Ortego sp. n. from A. craccivora are presented together with a logistic regression model. The males of A. tropaeoli are described. The list of host plants of A. craccivora in Argentina is updated.