Aphis sibirica, Stekolshchikov & Novgorodova, 2019

Stekolshchikov, A. V. & Novgorodova, T. A., 2019, A new species of Aphis (Homoptera: Aphididae: Aphidina) from Siberia, Zoosystematica Rossica (China) 28 (2), pp. 323-332 : 324-331

Aphis sibirica sp. nov.

( Figs 1–11)

Holotype. Apterous viviparous female, Russia, “ Aphis sibirica sp. nov., 15.VII.2018, Irkutsk Prov., Ol’khonskiy Distr., near Elantsy Vill., Rhinanthus serotinus aestivalis (N.W. Zinger) Dostál , on the stem at the top of the plant, leg. A. V. Stekolshchikov”, No. 10996 [collection number in ZIN], slide No. 22, specimen No. 2 [right specimen].

Paratypes. Russia: Novosibirsk, combined heat and power plant No. 5, ash-and-slag dump, 20.VII.2017, at Odontites vulgaris Moench , 7 apt. (ISEA, No. 14671), 20.VII.2017, at Odontites vulgaris Moench , 27 apt. (ISEA, No. 14672), 20.VII.2017, at Medicago sp. , 5 apt. (ISEA, No. 14808), 24.VII.2017, at Odontites vulgaris Moench , 1 apt. (ISEA, No. 14676), 24.VII.2017, at Odontites vulgaris Moench , 27 apt. (ISEA, No. 14810), 25.VII.2017, at Odontites vulgaris Moench , 16 apt. (ISEA, No. 14681), 25.VII.2017, at Elaeagnus rhamnoides (L.) A.Nelson, 25 apt. (ISEA, No. 14683), 25.VII.2017, at Medicago sp. , 6 apt. (ISEA, No. 14811), 26.VII.2017, at Odontites vulgaris Moench , 10 apt. (ISEA, No. 14812); Irkutsk Prov., Ol’khonskiy Distr., near Elantsy Vill., 15.VII.2018, at Pedicularis palustris opsiantha (Ekman) Almq. , 19 apt., 3 al. (ZIN, No. 10994), at Rhinanthus serotinus aestivalis (N.W.Zinger) Dostál , 74 apt., 2 al., 2 alatif. apt. (ZIN, No. 10996), 16.VII.2018, Euphrasia pectinata Ten., 5 apt., 2 al. (ZIN, No. 11009).

Description. Apterous viviparous female. Body broadly elliptical, 1.5–2.1 (1.6–1.9) times as long as wide. Live individuals gray, brown, brownish-gray or brownish gray green, with distinct waxy pulverulence; specimens fixed in alcohol dirty gray green or brownish gray green; bases and apices of antennae, and sometimes apices of 3rd–5th antennal segment, femora of middle and hind, or only hind legs, apices of tibia, tarsi, siphunculi and cauda dark. Cleared specimens with dark brown head, 1st antennal segment, coxae, apices of tibiae and tarsi of all legs, femora of middle and hind legs (except for bases), peritremes on abdomen, intersegmental muscle sclerites on thorax and I–V abdominal tergites, siphunculi, anal and subgenital plate, and cauda; with brown 2nd antennal segment, apices of 3rd–5th antennal segments, 6th antennal segment, two last segments of rostrum, trochanters of all legs, dorsal part of fore femora, bases of tibiae, and sclerites and bands on thorax and abdomen. Pronotum often with sclerotised band which sometimes thin and almost interrupt- ed in midline; abdominal tergite VIII always with band which sometimes thin; abdominal tergite VII almost always with band and postsiphuncular sclerites; abdominal segments I, V and VII often with small marginal sclerites; and some or all abdominal tergites occasionally with sclerites sometimes forming short sclerotised bands. Surface of head, dorsal sides of thorax, abdominal tergites I–VII reticulate; contour of cells on thorax and abdominal tergites I–VI formed by wide irregular line, and on tergite VII, by flat fused large spinules. Surface of abdominal tergite VIII with long rows of small pointed spinules which partially fusing and forming scales. Surface of ventral side of thorax smooth; the same of abdomen with long rows of small pointed spinules sometimes forming strongly stretched reticulate cells. Setae on dorsal and ventral sides of thorax and abdomen finely point- ed; numbers of marginal setae 0–2, 1–3, 1–4, 1–3, 1–3, 1–3, 0–2 on each side of abdominal segments I–VII, respectively. Marginal tubercles present on prothorax, I and VII segments of abdomen, usually large, but sometimes small, and in one specimen (0.4% of all specimens) marginal tubercles on segment VII completely absent; marginal tubercles on other segments absent and only one specimen with two marginal tubercles on abdominal segment VI, and one specimen with one tubercle on segment III. Head with epicranial coronal suture or with clear traces of epicranial coronal suture. Frontal tubercles distinct but not well developed; antennal tubercles relatively high; median tubercle not surpassing the level of antennal tubercles. Setae on head finely pointed. Antennae 6-segmented, or very rarely 5-segmented as result of incomplete fusing of 3rd and 4th segments; 1st, 2nd and base of 3rd antennal segment slightly wrinkled, almost smooth, 3rd (except base) and 4th–6th segments with large scales. Antennae without secondary rhinaria. Setae on antennae pointed or more often finely pointed. Rostrum reaching meso- or metathorax. Ultimate rostral segment elongate wedge-shaped, with straight or slightly concave sides, 1.64–2.67 (1.91–2.23) times as long as its basal width. Legs normally developed; setae on tarsi pointed; setae on coxae, trochanters, femora and tibiae finely pointed. Chaetotaxy of first tarsal segments 3, 3, 3 in 53% of specimens, 3, 3, 2 in 20% of specimens, and first tarsal segments on one hind leg with two and on other legs with three setae in 27% of specimens. Arms of mesosternal furca connected by wide base. Spiracles reniform. Siphunculi almost cylindrical, gradually tapering towards apex, sometimes very slightly S-shaped, with relatively small, but distinct flange. Surface of siphunculi imbricated, covered by rough scales which sometimes formed by partially fused large pointed spinulae. Subgenital plate oval, with finely pointed setae. Setae on anal plate finely pointed. Cauda finger-shaped, with distinct constriction in basal third, with rounded apex and long finely pointed setae.

Measurements of the holotype. Body – 2017× 1178, antenna – 1128: III – 273 × 30 (in middle), IV – 167, V – 164, VI – 107+266; hind femur – 508, hind tibia – 873; siphunculus – 182×52 (in middle); cauda – 291×154 (at base) ×129 (before base). Additional measurements are given in Table 1.

Alate viviparous female. Body elliptical, 2.1– 2.2 times as long as wide. Live individuals dirty gray green or brownish gray green, with weak waxy pulverulence dorsally; head, thorax, antennae, femora of middle and hind, or only hind legs, apices of tibia, tarsi, siphunculi and cauda dark. Thorax of cleared specimens dark brown, 2nd– 6th antennal segment (except pale base of 3rd segment) brown. Abdomen always with sclerotised band on tergites VI–VIII, with sclerites on some or all abdominal tergites, and with large marginal sclerites on abdominal segments II–VII; sclerites on I–V abdominal tergites sometimes forming short sclerotised bands often interrupted in the midline, band on tergite VI short; marginal sclerites and band on segment VII always fused. Surface of head and thorax smooth, slightly wrinkled; abdominal tergites I–VI smooth, with rare spinulae on sclerites and sclerotised bands, and with flat or pointed large spinules on marginal sclerites, sometimes forming cells. Antennae 6-segmented, 2nd antennal segment with small scales on ventral side. Third antennal segment with 9–19 (13.5– 16.4) secondary rhinaria, 4th segment with 0–5 (0.8–2.8) secondary rhinaria, and 5th segment without rhinaria. Secondary rhinaria round or oval, with internal diameter of very different sizes (8–23), very weakly protuberant, with external diameter 4.0–8.0 times as long as their height. Rostrum reaching mesothorax. Cauda conical at basal half, with a more or less distinct constriction almost in middle and finger-shaped in distal half, with rounded or almost pointed apex.

Alatiform apterous viviparous female. Antennae with 0–9 (5.3) small (internal diameter 8–13) secondary rhinaria on 3rd antennal segment.

Mode of life. The life cycle is unknown. Near Novosibirsk, the aphids were collected on the stem (mainly at its apex) of Odontites vulgaris Moench ( Orobanchaceae ), on which they formed colonies. Small colonies were also found once at the apex of the shoot of Elaeagnus rhamnoides (L.) A. Nelson ( Elaeagnaceae ), and two times on the stems of Medicago sp. ( Fabaceae ).

In the Irkutsk Province, the aphids were collected from Pedicularis palustris subsp. opsiantha (Ekman) Almq. , Rhinanthus serotinus subsp. aestivalis (N.W. Zinger) Dostál , and Euphrasia pectinata Ten. (all three species from the family Orobanchaceae ). Colonies of aphids on all three species of host plants were located at the top of the stem or between flowers and were visited by ants.

It is very likely that Aphis sibirica sp. nov. is a wide oligophagous species inhabiting plants of the family Orobanchaceae . This is evidenced by the fact that of the twelve samples of this species, nine colonies were found precisely at the species of Orobanchaceae , and only three smaller colonies were located on the plants of other families. Furthermore, these last three samples were collected on the territory of the ash-and-slag dump at the initial stages of its self-revegetation. The extreme conditions which are usual for such technogenic landscapes could have caused disruption of the food specialisation of aphids.

Diagnostic characters. Twelve species of Aphis were previously recorded on plants of the family Orobanchaceae : A. asclepiadis Fitch, 1851 , A. coffeata Mamontova, 1979 , A. craccivora Koch, 1854 , A. fabae Scopoli, 1763 , A. frangulae Kaltenbach, 1845 , A. gerardiae (Thomas, 1879) , A. gossypii Glover, 1877 , A. illinoisensis Shimer, 1866 , A. nasturtii Kaltenbach, 1843 , A. pediculariphaga Pashtshenko, 1994 , A. septentrionalis Pashtshenko, 1994 , and A. solanella Theobald, 1914 , but only four of them, A. coffeata , A. gerardiae , A. pediculariphaga , and A. septentrionalis , live strictly on plants of this family, whereas the others are polyphagous species. These four species can be easily distinguished from A. sibirica by the ratio of siphunculi to cauda: only in A. coffeata , the minimum value of this ratio reaches 0.90 (vs. 0.36–0.91 in A. sibirica sp. nov.), while in the other three species, it is significantly more than 1. In addition, A. coffeata and A. pediculariphaga differ from the new species in a large number of setae on the abdominal tergite VIII: 3–8 and 5–8, respectively (vs. 2–3 in A. sibirica sp. nov.), and A. septentrionalis has a smaller number of setae on the cauda: 4–7 (vs. 7–19 in A. sibirica sp. nov.). Also, A. pediculariphaga often has marginal tubercles on the abdominal segments II–VI (vs. marginal tubercles are very rarely present in A. sibirica sp. nov.) and the secondary rhinaria on 3rd–5th antennal segments of the apterous vivipara (vs. secondary rhinaria is completely absent in A. sibirica sp. nov.).

Aphis illinoisensis , which is heteroecious holocyclic in USA and migrates from Viburnum prunifolium ( Baker, 1917) to species of the family Vitaceae , was once found at Agalinis laevigata ( Favret et al., 2010) , a species belonging to Orobanchaceae . This aphid species is also easy to distinguish from A. sibirica sp. nov. by very long siphunculi which are 0.25–0.40 of the body length and more than twice as long as the cauda.

Specialised, non-polyphagous species of the genus Aphis are not known from Elaeagnus . At the same time, three species known from Medicago ( A. medicaginis Koch, 1854 , A. coronillae Ferrari, 1872 , and A. yangbajaingana Zhang ex Zhang et Zhong, 1981 ) are easily distinguishable from A. sibirica sp. nov. by the long siphunculi, significantly exceeding the length of the cauda.

Among polyphagous species, the new species is close to the aphids of the so-called Aphis fabae group and is most similar to A. fabae itself. However, the new species can be distinguished by the following characters: the ratio of the length of 3rd antennal segment to the length of the cauda, the ratio of the length of siphunculi to the length of the cauda (this ratio is rarely less than 0.90 in A. fabae ); the presence of the constriction at the cauda (which are not constricted in A. fabae ); the presence of two and only extremely rarely one or three setae on the abdominal tergite VIII (this tergite has four to seven or very rarely two to three setae in A. fabae ), most individuals of A. sibirica sp. nov. have three setae on the first segment of the hind tarsus (vs. two setae in A. fabae ). Some morphological characters that can differentiate these two species by the apterous viviparous females are given in Table 2. Aphis sibirica can be easily distinguished from A. solanella , the species close to A. fabae , by the short siphunculi: in A. sibirica , they are 0.36–0.91 as long as the cauda, 0.06– 0.12 as long as the body, and 1.54–3.78 as long as their diameter in the middle of the length (for A. solanella , 1.30–1.90, 0.13–0.20, and 3.50–7.50, respectively).

Etymology. The specific epithet sibirica is a feminine singular adjective derived from the geographical name of Siberia, where the new species was collected.

Distribution. Known from Western (Novosibirsk Province, Novosibirsk) and Eastern (Irkutsk Province, Ol’khonskiy District, near Yelantsy Village) Siberia.