Metopolophium sabihae Prior 1976

Metopolophium sabihae Prior, 1976

(Figs. 26–32, Tab. 4)

Material. 1 fund., No. 10151, Somnitel’naya Bay, 13.vii.2006, sand and pebble river floodplain with forbs, sweeping; 6 fund., No. 10152, the middle course of the Mamontovaya River, 20.vii.2006, dry southern slope of the ridge with forbs-willow-grassy tundra-steppe vegetation, sweeping; 1 ovip., No. 10153, Somnitel’nye Mountains, 13.vii–14.viii.2006, dry southern slope of the hill with forbs-grassy tundra-steppe vegetation, pitfall traps; 1 fund., No. 10154, from the same locality and the same data as No. 10153; 1 ovip., No. 10155, from the same locality as No. 10153, 16.vii–14.viii.2006, pitfall traps; 1 ovip., No. 10156, from the same locality as No. 10153, 14.vii–15.viii.2006, pitfall traps; 1 fund., No. 10281, from the same locality as No. 10152, 9–19.vii.2006, pitfall traps; 1 ovip., No. 10283, from the same locality as No. 10151, 19–31.vii.1988, river valley with forbs-grassshrubby (dryad, willow) vegetation, pitfall traps; 1 fund., No. 10293, from the same locality as No. 10153, 30.vii–7.viii.2006, pitfall traps.

Description. Fundatrix. Body broadly elliptical, 1.6–1.8 times as long as wide. Colour in life pale green. Cleared specimen with 3rd antennal segment except for its base (sometimes 3rd segment gradually darkened from base to apex), 4th–6th antennal segment, apices of tibia and tarsi dark brown; 2nd antennal segment, two last segments of rostrum, femur (except for its base), tibia, apex of siphunculus near flange dark; head, coxa, trochanter, band on abdominal segment VIII, peritreme, siphunculus, subgenital and anal plates, and cauda light brown. Sclerites and bands on abdominal tergites absent, except for a faintly sclerotized, almost invisible band on abdominal segment VIII. Head and dorsal side of thorax and abdominal tergites I–VI smooth, weakly wrinkled; tergites VII–VIII with rows of partially fused pointed spinules forming short scales; ventral side of thorax smooth; ventral side of abdomen with long rows of small spinules, sometimes forming strongly stretched cells. Setae on dorsal surface of thorax and abdomen weakly capitate or blunt, rod-shaped; on ventral surface, pointed or finely pointed; abdominal tergite III with 4–8 (5.0–5.6) dorsal setae. Marginal tubercles present on prothorax in 6 specimens (2 specimens out of 11 with 2 tubercles); one tubercle present on mesonotum in 1 specimen, on metanotum in 1 specimen, and on abdominal segment II in 1 specimen; marginal tubercles small and flat. Head with distinct traces of epicranial coronal suture. Frontal tubercles evident, antennal tubercles high, median tubercle low, almost rectangular. Occipital and frontal setae weakly capitate or, rarely, blunt. Antennae 6- or 5-segmented (initial 3rd and 4th segments fused in 1 specimen), with 1–4 (1.6–3.0) rounded secondary rhinaria in basal third of 3rd segment. Setae on antennae weakly capitate or, rarely, blunt; basal part of 6th antennal segment with 2–4 (2.7–4.0) setae, longest seta 0.67–0.93 (0.71–0.93) times as long as articular diameter of basal part of the segment. Rostrum reaching meso- or metathorax. Ultimate rostral segment elongated wedge-shaped, with slightly concave sides, 1.92–2.22 (2.12) times as long as its basal width. Legs long. Arms of mesosternal furca connected by more or less wide, weakly sclerotized stem. Peritremes on abdominal sternites I and II separated by a distance greater than diameter of peritreme. Setae on legs weakly capitate or blunt, on apices of tibia—pointed or finely pointed. Chaetotaxy of first tarsal segments 3,3,3. Second segment of hind tarsus 4.57 – 5.22 (4.78–5.22) times as long as its maximum width, with 5–8 (6.0–6.7) ventral and 2–4 (2.0–4.0) dorsal setae in addition to the three apical pairs. Siphunculi almost cylindrical, slightly widened in base, faintly narrowed to apex, imbricate, with flange. Subgenital plate oval. Setae on anal plate finely pointed. Cauda elongated, triangular, almost finger-shaped, with finely pointed setae.

Measurements of one specimen. Body—2487×1513, antennae—1586: III—448×33 (in the middle), IV—210, V—281, VI—164+283; hind femur—670, hind tibia—1172; siphunculus—301×43 (in the middle); cauda—288×180 (at base) ×154 (before base). For more biometric data see Table 3.

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Setae on head occipital length 23–30 23–33 (23–30) (26)

length / articular diameter of 3rd 0.90–1.14 0.86–1.44 antennal segment (0.92–1.12) (0.88–1.44) frontal length 28–38 30–33 (28–35) (31) length / articular diameter of 3rd 1.05–1.43 1.14–1.33 antennal segment (1.05–1.30) (1.22)

on 3rd number 8–17 11–15

antennal (11.0–12.5) (12.4)

segment length 16–25 18–23 (18–25) (19.8) length / articular diameter of 3rd antennal 0.62–0.95 0.64–1.00 segment (0.70–0.95) (0.64–1.00)

on hind femur length of dorsal 20–23 20–25 (22) (22)

length of ventral 18–33 23–30 (20–29) (26)

length of dorso-apical 18–23 18–23 (20) (20)

on hind tibia longest dorsal 38–66 43–56 (38–57) (48)

longest dorsal / mid-diameter of the hind tibia 0.65–0.84 0.82–0.92 (0.71–0.80) (0.88)

on abdominal dorsal length 15–20 17–25

tergite III (19) (22)

length / articular diameter of 3rd 0.67–0.80 0.67–1.11 antennal segment (0.74) (0.87) marginal length 20–25 20–28 (22) (22)

length / articular diameter of 3rd 0.73–1.05 0.73–1.22 antennal segment (0.76–1.03) (0.89) ventral length 29–38 35–43 (30–35) (39) length / articular diameter of 3rd 1.09–1.40 1.40–1.67 antennal segment (1.12–1.24) (1.52)

number on abdominal tergite VI between siphunculi 3–7 4–6

(3.5–4.0) (4.5)

on abdominal number 5–8 6–7

tergite VIII (6.0–8.0) (6.3) length 25–30 30–41 (28) (34)

length / articular diameter of 3rd antennal 0.95–1.20 1.09–1.78 segment (1.03–1.12) (1.33)

number on subgenital plate on anterior half 2–4 10–12 (2.0–4.0) (11.3) along the hind margin 7–12 15–23 (8.0–10.0) (19) ......continued on the next page Last antennal length of base 126–169 139–169

segment (136–169) (142–159) length of processus terminalis 218–304 379–430 (255–274) (379–426) length of processsus terminalis / length of base 1.72–2.06 2.24–3.04 (1.85) (2.65)

Ultimate number of accessory setae 7–10 6–9

rostral (7.0–8.4) (7.8)

segment length 121–142 126–134

(132) (131) length / head width across the compound eyes 0.25–0.29 0.28

(0.27)

length of 2nd segment of hind tarsus 0.85–1.06 0.87–0.94 (0.85–1.01) (0.91) length of base of last antennal segment 0.78–1.00 0.76–0.95 (0.78–0.98) (0.81–0.94)

Second length 136–152 134–152

segment of (136–152) (135–152)

hind tarsus length / head width across the compound eyes 0.26–0.35 –

(0.27–0.35)

length of base of last antennal segment 0.88–1.00 0.82–1.04 (0.88–0.98) (0.87–1.03) length/ width of siphunculus at half length 5.15–8.57 6.11–8.27 (6.10–8.14) (6.11–7.84) Biology. In the 1980–1990s, species of the genus Metopolophium were collected in pitfall traps in four localities of Wrangel Island (the middle course of the Mamontovaya River, the upper course of the Neizvestnaya River, Somnitel’nye Mountains, the upper course of the Khishchnikov River). They mainly were found in warm and dry habitats on south-facing slopes with tundra-steppe forbs-grass vegetation. In 2006 M. sabihae was collected in the two repeatedly studied areas and in the same habitats where specimens of this genus were collected earlier. Apart from the southern slopes with tundra-steppe vegetation, M. sabihae in both areas was found in dry and early snowmelt sandy-pebbly river flood plains with herb-shrub associations, where snow melts early. In these habitats, M. sabihae was collected not only in the mountainous region but also in the Southern Plain, in the river flood plains near the coast.

Comments. This species was described by Prior (1976) based on apterous and alate viviparous females, oviparous females and males from the coastal dunes of Great Britain (England, Scotland and Wales) and France (La Trinité sur Mer, Morbihan dept., Brittany). Aphids were collected from Festuca rubra L. and Vulpia membranacea (L.) Dumort. In laboratory experiments, the specimens of M. sabihae lived on different species of Poaceae, but Prior evidenced Festuca rubra as the most suitable host plant for this aphid species. Prior’s work with laboratory cultures indicates that British M. sabihae populations may often be anholocyclic, but some oviparous females and males were also produced indicating that a holocycle may also occur. On Wrangel Island, only fundatrices and oviparous females of this species were collected. The latter morph made it possible to identify the species: oviparous females were identified with the key from Blackman and Eastop (2014). After that, as far as this key permits to identify only apterous viviparous females, the morphometric data of oviparous females from Prior (1976) and specimens of this morph from Wrangel Island were compared. Fundatrix was not previously known. The presence of both morphs in the collected material indicated a holocyclic life cycle on Wrangel Island. Festuca rubra, the main host plant of Metopolophium sabihae in Great Britain, and another eight species of this plant genus are present on Wrangel Island and may be the aphid’s host plants in this area. The disjunct distribution of M. sabihae suggests that the population on Wrangel Island may be a relict in this Pleistocene refugium. The habitat preference of this species, occurring in the driest and warmest biotopes (Khruleva, 2009), also supports this conclusion. Taking into account the holocyclic life cycle of this species on Wrangel Island, we suggest that M. sabihae may be of Beringian origin.