In our recent study on the aphid fauna of the Aysén del General Carlos Ibáñez del Campo region (Nieto Nafría et al., 2020), we reported that some samples collected in January 2019 had only been identified to genus level, and that a more thorough study would be necessary to ensure their specific identities.

Specimens of three of those samples exhibit clear features of Uroleucon Mordvilko, 1914 (Aphididae, Macrosiphini), but their precise characteristics do not fit those of any described species of the genus, per Nieto Nafría et al. (2019), Mier Durante et al. (2020).

Thirty-two species of Uroleucon are known in South America, including U. littorale Blanchard, 1939 and U. ambrosiae (Thomas, 1878). Uroleucon littorale is a poorly defined species that may be synonymous with another South American species (Blackman & Eastop, 2020). Uroleucon ambrosiae (Thomas, 1878) is represented in South America by its subspecies, U. ambrosiae lizerianum (Blanchard, 1939) while its nominotypical subspecies is found in North America. Twenty-three of these 32 species (79%), being known only from South America, are presumably indigenous to the continent. Thirty of the 32 species have been recorded from Chile or Argentina: 20 from Chile and 23 from Argentina. Almost all those species are represented in the aphid collection of the University of León, and the relevant specimens have been examined for this study.

We employed standard protocols for collection, rearing, ethanol preservation, slide preparation, and morphometric study, which have been employed in previous works (Nieto Nafría et al., 2019; Mier Durante et al., 2020). Microphotographs were taken using a smartphone through an eyepiece adapted to an Olympus CX41 microscope and were subsequently adjusted with Corel Photo-Paint 2018 and Microsoft Publisher 2010 software.

Geographical coordinates and altitudes were obtained or validated using the Google Earth Pro computer tool, version 7.3.2.

Spanish orthography, diacritics included, was retained in the names of localities and political-administrative entities (region, provinces and communes). The official name of the region, Aysén del General Carlos Ibáñez del Campo, is abbreviated to Aysén from here on.

All specimens examined belonging to both new species were designated as holotypes or paratypes and are listed in the “type material” section of each species.

Uroleucon chiliotrichi sp. n.

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Fig. 1

Type material. Holotype, apterous viviparous female (labelled with the number 5 of sample CHI-467, on a slide with a paratype), CHILE, Aysén region, Coyahique province, Coyhaique: Coyhaique Alto (45º31’ S, 71º33’ W, 770 m a.s.l.), on Chilotrichum diffusum; 13-January-2019; Mier Durante, Nieto Nafría and Ortego leg.; Universidad de León collection (León, Spain).

Paratypes, 9 apterous viviparous females, same data and depository as the holotype.

Apterous viviparous females (Fig. 1A-H). Based on 10 specimens. Colour when alive pale green with dark brown antennae and brownish green siphunculi and cauda. Body 2.29–2.99 mm and pear-shaped with long antennae and legs and very conspicuous siphunculi and cauda. Mounted specimens more or less very light brown with pigmented appendages, dorsal thoracic and abdominal sclerites, siphunculi, subgenital and anal plates and cauda, as detailed below. Setae on dorsum of body and antennae, and most of those on the legs very pale, thin and with truncate apices; other setae more or less pointed. Marginal tubercles absent. Frons sinuous, because it is shallow and the medial tubercle almost as high as the lateral ones. Cephalic dorsum with two anterior and four posterior setae. Head, with clypeus and mandibular and maxillary laminae, and also antennal segments I and II, the very proximal part of antennal segment III, and most of rostrum light brown, contrasting greatly with the rest of segment III and the remaining antennal segments, which are dark brown. Antennal segments I to III smooth, segment IV somewhat striated, segments V and VI imbricated. Antennal sensoria round, with thick walls; primary sensoria ciliate; secondary sensoria small, non-protruding, more-or-less aligned and limited to the proximal half or two thirds of antennal segment III. Rostrum reaching past middle coxae; ultimate and pre-ultimate rostral segments (IV+V and III, respectively, in Blackman & Eastop, 2020) darker than two proximal rostral segments. Legs smooth except tarsi; mostly pigmented like the head, with tarsi and distal portion of tibiae darker. Thoracic and abdominal dorsum with light brown setiferous sclerites, pigmented like the cephalic dorsum; spiracular sclerites light brown; intersegmental muscular sclerites brown. Marginal setiferous sclerites on abdominal segments 1 to 5 and sclerites on abdominal segment 8, sometimes joined; pre- and post-siphuncular sclerites absent. Siphunculus cylindrical with broad base, very thin, brown to dark brown (darker than the rest of the body, except the distal antennal segments), very rough over most of its length (only with isolated spinules on its proximal quarter), short apical portion with relatively big polygonal cells (5 to 8 rows with 6 or 7 cells per row), and a small flange. Subgenital plate pale brown. Anal plate and cauda less pigmented than siphunculi. Cauda lanceolate, broad at middle, with thin setae, lateral setae much longer than dorsal ones. Quantitative data are in Table 1.

Alate viviparous females, oviparous females, males.

Unknown.

Bionomics . Chiliotrichum diffusum (G. Forst.). Kuntze (Asteraceae, Asteroideae) is the only host plant known of the species. There are no data on its life cycle.

Distribution . The species is known only from its type locality. It is possible that it is present wherever Chiliotrichum diffusum can be found, that is, in the southern half of Chile and in Argentinean Patagonia and Tierra del Fuego, but so far only Brachycaudus helichrysi (Kaltenbach, 1843) has been found on that plant (Nieto Nafría et al., 2004).

Etymology . The specific name chiliotrichi is the name in genitive of the plant-host genus of the aphid.

Taxonomic discussion, with identification key . Apterous viviparous females of Uroleucon chiliotrichi sp. n. are morphologically similar to U. bereticum (Blanchard, 1922), U. macolai (Blanchard, 1932) and U. mendocinum (Mier Durante & Ortego, 2007) that occupy the last two couplets in the identification key to apterous viviparous females of Uroleucon species found in South America (Nieto Nafría et al, 2019, with modifications by Mier Durante et al., 2020). That key is here modified to include Uroleucon chiliotrichi sp. n.

Uroleucon amigoi sp. n.

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Figs. 2-3

Type material. Holotype, apterous viviparous female (labelled with the number 5 of sample CHI-467, on a slide with an oviparous female paratype), CHILE, Aysén region, Capitán Prat province, Cochrane: Valle La Tranquera (47º37’ S, 72º56’ W, 180 m a.s.l.), on Adenocaulon chilense; 19-January-2019; Mier Durante, Nieto Nafría and Ortego leg.; Universidad de León collection (León, Spain).

Paratypes, 2 apterous viviparous females, 12 oviparous females, 3 alate viviparous females CHILE, same data as that of the holotype; and 1 apterous viviparous female, CHILE, Aysén region, Capitán Prat province, Cochrane: road 9, 10 km N from Los Ñadis bridge (47º31’ S, 72º51’ W, 80 m a.s.l.), on Adenocaulon chilense; 19-January-2019; Mier Durante, Nieto Nafría and Ortego leg.; Universidad de León collection (León, Spain).

Apterous viviparous females (Fig. 2A-2I). Based on 4 specimens. Colour when alive dark brown with hyaline antennae, legs and cauda. Body 2.85–3.54 mm, pear-shaped and with long antennae and legs and conspicuous siphunculi and cauda. Mounted specimens more or less light brown with noticeably dark siphunculi and more or less pigmented dorsal thoracic and abdominal sclerites, subgenital and anal plates, and cauda, as detailed below. Setae on antennae, dorsum of body, and most of those on the legs very pale, thin, with apices truncate; other setae more or less pointed. Marginal tubercles absent. Frons with a marked sinus, conspicuously divergent lateral tubercles, and low medial tubercle. Cephalic dorsum with two anterior and four posterior setae. Head, antennal segment I, and proximal part of antennal segment III light brown; clypeus, mandibular and maxillary laminae, antennal segment II, distal part of antennal segment III and antennal segments IV to VI brown. Antennal segments I and II delicately rough; most of antennal segment III smooth; a small distal portion of segment III, and antennal segment IV with stretch marks; segments V and VI imbricated. Sensoria round; primary sensoria ciliate; secondary sensoria poorly aligned on the ventral face of most of antennal segment III, variable in size, with relatively thick margins and protruding disk. Rostrum reaching hind coxae; ultimate and pre-ultimate segments (IV+V and III, respectively, in Blackman & Eastop, 2020) brown, darker than previous segments, relatively narrow. Legs smooth except tarsi; mostly pigmented like the head, with tarsi and very distal portion of tibiae darker. Thorax with marginal patches and spiracular sclerites light brown, and intersegmental muscular sclerites brown. Abdomen with light brown small or very small setiferous sclerites and post-siphuncular sclerites; intersegmental sclerites usually inconspicuous, if present they are small and darker than stigmatic sclerites. Siphunculi dark brown (they are by far the most pigmented structure), cylindrical and thin, with broad base, very rugose non-reticulated part, long apical portion with polygonal cells (which are relatively small, 12 to 25 cells per row), enlarged apex, and very small flange. Subgenital and anal plates pale brown. Cauda lanceolate, broad at middle, weakly pigmented (no more than the cephalic dorsum), with thin and pale setae, marginal setae much longer than dorsal ones. Quantitative data are in Table 1.

Alate viviparous females (Fig. 3). Based on 3 specimens. Colour when alive similar to that of apterous viviparous females, but with darker antennae. Body 3.09–3.53 mm. When mounted they are similar in general appearance to apterous viviparous females, with dark thorax and darker antennae (the pale basal portion of antennal segment III is very small), distal half of both front and middle femora, distal quarter of hind femora, marginal patches on abdominal segments 2 to 4 or 5, and intersegmental sclerites. Quantitative data are in Table 1.

Oviparous females (Fig. 2J). Body length 3.20– 3.38 mm. Similar to apterous viviparous females when alive and mounted, with more setae on subgenital plate and slightly swollen proximal part of the hind tibiae bearing most of scent plates, (36)54– 73, diverse in size and form. Quantitative data are in Table 1.

Bionomics . Uroleucon amigoi sp. n. lives on the stems of Adenocaulon chilense Less. (Asteraceae, Mutisioideae), forming relatively compact groups in which individuals of Macrosiphun euphorbiae (Thomas, 1878) (Aphididae, Macrosiphini) may be mixed. The species produces oviparous females early in mid-January.

Distribution . The species is only known from its type localities, both in the Capitán Prat province (Aysén region, Chile), although its distribution may extend further north and south, accompanying its host plant, which is known from the Biobío region of Chile and Neuquén province of Argentina in the north, to the extreme south of the continent.

Etymology . The species is dedicated to Francisco-Javier Amigo Vázquez, botanist at the University of Santiago de Compostela (Spain), connoisseur of the flora of southern Chile, who identified the host plant of both species described here.

Taxonomic discussion, with identification key . Apterous viviparous females of Uroleucon amigoi sp. n. are similar to U. muermosum (Essig, 1953) and U. eumadiae Delfino, 2005, species placed in couplet 8 of the identification key to apterous viviparous females of Uroleucon species found in South America (Nieto Nafría et al, 2019, with modifications by Mier Durante et al., 2020), which is here modified as follows to include Uroleucon amigoi sp. n.

Only Uroleucon adenocaulonae (Essig, 1936) has been recorded on species of Adenocaulon (Blackman & Eastop, 2020). Specimens of this species also have very dark and heavily ornamented siphunculi and, when alive, also are more-or-less reddish brown, but the distribution of this species and that of U. amigoi are widely disjunct: U. adenocaulonae is known from Idaho, Washington, Oregon and California (U.S.A.). The more appreciable morphological differences between U. adenocaulonae and U. amigoi (Essig 1936; Robinson, 1985; Blackman & Eastop, 2020) are shown in Table 2.