Many species belonging to family Apiaceae are host plants for species of aphids, included species of Aphis Linnaeus, 1758 (Aphididae Aphidina), which have different distribution and are diverse in trophic preferences, some species are endemic and other cosmopolitan, several ones are polyphagous and other are more or less stenophagous. No records of aphids exist on plants of apiaceous genus Gymnophyton Clos. This genus is South American and include few species, only six in the South Cone (Blackman & Eastop, 2016; Instituto de Botánica Darwinion, 2016).

Aphids belonging to genus Aphis have been collected in last years in Argentinean localities on Gymnophyton polycephalum (Gillies & Hook.) Clos, which is known in the provinces of Salta, Catamarca, La Rioja, San Juan and Mendoza, from North to South (Instituto de Botánica Darwinion, 2016). They present peculiar features that permit to us establish a new species (see above the taxonomic discussion).

Aphis cuyana López Ciruelos & Ortego, sp. n.

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APTEROUS VIVIPAROUS FEMALES, big form (Figs. 1A, 1E): From 127 specimens, which 76 have been measured. When alive caramel to brown with dorsal bright spots. When mounted, specimens have parts and sclerites more or less pigmented (see above). Metric and meristic features in Table 1. Head, including clypeus and mandibular and maxillar lames and rostrum brown. Frons nearly flat or sometimes gently sinuated. Antennal segment I, II, VI and apex of V more or less dark brown, like head. Other antennal segments pale. Rostrum reaches nearly to the hind leg coxae. Its ultimate segment is darker than the other and has 2 accessory setae lateral to grove. Coxae, trochanters, tarsi, apex of tibiae, brown like head; front and medial femora homogenously light brown, paler than coxae; hind femora with half or two thirds distal part darker than anterior femora and as dark as coxae and trochanters. Prothorax and mesothorax with individual brown entire or fragmented transverse dorsal band. Metathorax with brown fragmented transverse band, sometimes reduced to marginal sclerites. First segment of tarsi with 2 or 3 setae. Dorsum of abdominal segments 1–6 with individual spinopleural transversal and irregularly edged patches, which can be coalescent one another in different ways, come up to form a patch with unsclerotized intersegmental spots. Abdominal segments 1–4 without marginal sclerites. Small antesiphuncular and postsiphuncular patches, sometimes fragmented in sclerites. Abdominal segments 7 and 8 with individual transverse bands carrying spinules. All segmental sclerotization as dark as head. Intersegmental and spiracular sclerites always conspicuous and dark brown. Hind tibae of several specimens of spring sample ARG-1101 carries 1–7 (exceptionally up to 12 and one specimen with 17 and 25) well defined, small and pale scent plates; these specimens also carry an exceptional higher number setae on abdominal segment 8. Marginal prothoracic tubercles, smaller than the triommatidium, but more voluminous than marginal tubercles on abdominal segments 1 and 7. Intermediate abdominal segments without marginal tubercles. Siphunculi tapered on proximal half and subcylindrical on distal one, little longer than cauda, homogeneously dark brown to black, darker other body part, with scales and small flange. Genital and anal plates dark brown. Cauda finger-shaped, with slight constriction and medial edges more or less parallel. Setae in general robust and pointed.

APTEROUS VIVIPAROUS FEMALES, small form (Figs. 1B, 1F): From 66 specimens, which 13 have been measured. When alive similar to “big” females, but without bright spots. When mounted very pale because have not segmental dorsal sclerotization (reduced to a small transverse band on abdominal segment 8 and sometime setiferous pale sclerites on segment 7), and the pigmentation of intersegmental and spiracular sclerites, antennae in general, rostrum, trochanters and femora is more less intense than the “big” females. Siphunculi subcylindrical and cauda triangular. Metric and meristic features in Table 1.

ALATE VIVIPAROUS FEMALES (Figs. 1C, 1D): From 12 specimens, which 11 have been measured. Similar to apterous viviparous “big” females, more intense and wide pigmented. Ocelli surrounded by a dark ring. Segments of antennal flagellum with strong imbrication. Antennal segment III with 6–12 secondary sensoria ventrally aligned along the segment, and segment IV sometimes with 2–4 secondary sensoria. Spinopleural patches slender and completely individualized. Round marginal patches on abdominal segments 2–6. One specimen of sample 732 has 1 marginal tubercle on abdominal segment 2. Siphunculi subcilindrical. Other quantitative features in Table 1.

BIOLOGY: Gymnophyton polycephalum (Gilles & Hook.) Clos is at the moment the only host plant for Aphis cuyana sp. n. It should be holocyclic without host alternation, as usual in the species of this genus in mountain areas of Argentina. The species presents during summer one or several generations of apterous viviparous females that are smaller and paler than the spring or autumnal generations, adjectival aestivating, dwarf, small, like the South American A. mendocina Mier Durante & Ortego, 2006, A. eucollinae López Ciruelos & Ortego, 2016, A. melosae Mier Durante & Ortego, 1999, or the North American A. rubicola Oestlund, 1887, or several European species, e.g. A. hieracii Schrank, 1801, A. confusa Walker, 1849, A. lambersi (Börner, 1940), A. ruborum (Börner, 1931) (see Mier Durante & Ortego 1999; Blackman & Eastop, 2016).

DISTRIBUTION: It is possible that the new species is present in the area where its host plant grows.

ETYMOLOGY: The specific epithet cuyana, is an adjective that means inhabiting on the Argentinean region of Cuyo (entire or in part current provinces of San Juan, San Luis, Mendoza and La Rioja).

TAXONOMIC DISCUSSION: Aphis cuyana sp. n. is the 56th species of Aphis, in current sense of genus, recorded from South America, twenty-two are introduced and 34 are native (Ortego et al., 2013; López Ciruelos et al., 2016; Nieto Nafría et al., 2016a, 2016b; González Rodríguez et al., 2017). To establish the taxonomic identity of the new species, several characteristic of its apterous viviparous “big” and “small” females are confronted with selected more evident characteristics of other 55 species of Aphis and three close relatives belonging to genera Andinaphis and Protaphis (Table 2); firstly (1) presence (in A. cuyana) or lack of marginal tubercles on abdominal segment 7 and presence (in A. cuyana) or absence of posterior setae on genital plate, or (2) lack (in A. cuyana) or presence of marginal tubercles on abdominal segments 2–4, or (3) lack (in A. cuyana) or presence of marginal sclerotization on abdominal segments 2–4, and subsequently other qualitative or quantitative features if it were necessary.