Sitobion (Metobion) graminearum ( Mordvilko, 1919 )

Stekolshchikov, Andrey V., 2011, Redescription and lectotype designation of Sitobion (Metobion) graminearum (Mordvilko) (Hemiptera: Aphididae), Zootaxa 2888, pp. 31-38 : 32-37

Sitobion (Metobion) graminearum ( Mordvilko, 1919)

( Figs. 1–8 , 9–14 ; Tabl. 1 )

Material. Lectotype: oviparous viviparous female, No. 10139, slide No 85, specimen No 2 (lower specimen), „ Macros[iphum], 23 Sept [ember] 1913, Razdel’naya, AM[ordvilko]“. Paralectotypes: 4 oviparous females and 2 male on 3 slides, same data as for lectotype. Additional materials: 6 apterous viviparous females, 2 intermediate between apterous viviparous and oviparous females and 3 oviparous females on 6 slides " Sitobion (Metobion) graminearum ( Mordvilko, 1919) , No 10140/381, 9.IX.2006, Novosibirsk Prov., Novosibirsk Distr., environs of vill. Zherebtsovo, on upper side of leaves, Calamagrostis epigejos (L.) Roth., coll. Gavrilyuk A.V.".

None of the five oviparous females available on the original Mordvilko slides resemble the individual represented by Mordvilko in the figure in the description of Acyrthosiphon (Metopolophium) graminearum (figure 107, page 292). Mordvilko (1919) also gave morphometric data for two oviparous females that do not coincide with measurements of available material. It is necessary to assume that the part of the material used at the description has been irrevocably lost. For this reason we choose as a lectotype the most intact specimen.

Description. Apterous viviparous female. Body spindle-shaped, widest in the middle of the abdomen (III–IV segments), 1.8–2.1 (2.0) times as long as wide. Light green or pink in life, with dark antennae. Cleared specimens with brown apices of 3rd–4th antennal segments, bases of 4th–5th antennal segment, more or less gradually darkening to the apex 5th antennal segment, 6th antennal segment, processus terminalis gradually brightening to the apex and with brown apices of siphunculi. Head, antennal segments 1st–4th, rostrum, legs, sclerites at bases of coxae, siphunculi, subgenital and anal plates light-brown, cauda very light-brown. Abdominal dorsum not sclerotized, light, membranous except very light-brown peritremes. Surface of head wrinkled, of dorsal side of thorax and abdominal tergites I–VI faintly wrinkled, sometimes nodulose, of abdominal tergite VII with sparse and short rows of spinules, which on tergite VIII are smoothed-out and partially fused to form scales; surface of ventral side of thorax wrinkled or with sparse short rows of spinules, of ventral side of abdomen with rows of small spinules sometimes forming strongly stretched cells. Setae on dorsal surface of thorax and abdomen sparse, short, rodshaped, blunt or weakly capitate, longest dorsal and marginal setae on abdominal tergite III 12–18 (12–17) and 18– 25 (20) μm long, 0.27–0.38 (0.27–0.35) and 0.36–0.54 (0.42) times as long as articular diameter of 3rd antennal segment, respectively; setae on ventral surface of thorax and abdomen relatively long, longest ventral seta on abdominal tergite III 48 –63 (55) μm long, 1.00–1.28 (1.13) times as long as articular diameter of 3rd antennal segment; abdominal segment III with 9–15 (12.7) dorsal and marginal setae; tergite VI with 5–8 (7.2) setae between siphunculi; tergite VIII with 5–14 (9.6) setae, 20–33 (26) μm long, 0.41–0.68 (0.54) times as long as articular diameter of 3rd antennal segment. Small flat marginal tubercles always present on prothorax (1 individual of 6 with 1 tubercle), frequently present on abdominal tergite III, and sometimes present on abdominal tergites IV and V; sum of marginal tubercles on abdominal tergites I–VII—0–4 (2.5). Spinal tubercles absent. Head with distinct traces of epicranial coronal suture. Frontal tubercles moderately developed, antennal tubercles relatively high, divergent, median tubercle not high but distinct, almost semicircular, coarsely wrinkled; ratio of depth of frontal sinus to the width between antennal bases 0.21–0.22. Occipital and frontal setae short, rod-shaped, blunt or weakly capitate, longest occipital and frontal setae 17–23 (21) and 25–41 (31) μm long, 0.38–0.47 (0.43) and 0.50–0.84 (0.65) times as long as articular diameter of 3rd antennal segment, respectively. Antennae 6-segmented, 1st and 2nd antennal segments weakly wrinkled, almost smooth, 3rd antennal segment smooth, only apex of the segment with rare weakly marked scale, 4th–6th segments with scales. 3rd antennal segment with 1–4 (2.2) secondary rhinaria near base of segment. Secondary rhinaria are rounded or oval, small (with internal diameter 10–20 μm), weakly projecting, with external diameter 4.0–8.3 times as long as high. Antennae with short, rod-shaped, blunt or weakly capitate setae; 1st antennal segment with 7–10 (8.4–9.0) setae 25–28 (26) μm long; 3rd antennal segment with 29–32 (30.6) setae 12–18 (12–17) μm long, 0.27–0.38 (0.27–0.36) times as long as articular diameter of 3rd antennal segment; base of 6th antennal segment with 2–4 (2.9) setae, 0.50–0.70 (0.58) times as long as articular diameter of basal part of the segment. Rostrum short, reaching only anterior margin of mesothorax. Ultimate rostral segment wedge-shaped, almost cordiform, 1.19–1.36 (1.27) times as long as its basal width, with 3–4 (3.0–4.0) accessory setae. Legs long, hind femora and hind tibiae 0.29–0.35 (0.30) and 0.49–0.60 (0.53) times as long as body length, respectively. Setae on legs short, rod-shaped, blunt or weakly capitate, on apices of tibia pointed; ventral seta on hind trochanter 0.50–0.70 (0.58) times as long as basal diameter of hind femur; longest dorsal, ventral and dorsoapical setae on hind femur 18–25 (22), 30–38 (35) and 20–28 (23) μm long, respectively; longest dorsal seta on hind tibia 43–53 (49) μm long, 0.72–1.02 (0.86) times as long as the mid-diameter of the latter. Chaetotaxy of first tarsal segments 3, 3, 3. Second segment of hind tarsus 5.46–6.17 (5.74) times as long as its maximum width and 0.98–1.17 (1.06) times as long as base of 6th antennal segment, with 3 pair of apical setae, 3–4 (3.8) ventral, 2 lateral and 1–3 (2.0) dorsal setae. Siphunculi relatively long, with distinct, but not conspicuous flange, with conical base, gradually tapering towards apex with growing imbrication apicad, and with 1–2 rows of polygonal cells forming by large scales at apex; sometimes rows of polygonal cells very weakly developed and consist of several isolated large scales. Siphunculi 4.05–5.12 (4.64) times as long as their basal width, 0.17–0.21 (0.19) times as long as body length and 0.72–0.84 (0.79) times as long as length of 3rd antennal segment. Subgenital plate oval, with 3– 4 (3.2) long pointed setae on anterior half and 11–13 (12.3) short, rod-shaped, blunt or weakly capitate setae along the hind margin. Setae on anal plate finely pointed. Cauda tongue-shaped with the rounded apex and easy narrowing in first third, 1.95–2.31 (2.16–2.29) times as long as its basal width, with 13–19 (13.0–16.7) long, pointed or finely pointed setae.

Alatae viviparous female (after Heikinheimo, 1990). Colour in life unknown. Cleared specimen with pale abdomen, gradually darkening from base to apex of antennae, slightly darker towards apices of siphunculi and pale cauda. Abdominal dorsum not sclerotized, light, smooth. Longest setae on abdominal tergite III 20 μm long, tergites VIII with 7 setae, longest seta 35 μm long. 3rd antennal with indistinct, 4th–6th segments with distinct imbrications. 3rd antennal segment with 11–13 secondary rhinaria arranged in a row, which reaches 68% of length of segment. First antennal segment with 9–10 setae; longest seta on 3rd antennal segment 18 μm long, 0.40 times as long as articular diameter of 3rd antennal segment. Ultimate rostral segment with 3 accessory setae. Siphunculi with 3–4 rows of polygonal cells at apex varying in shape and size. Siphunculi 0.16 times as long as body length and 0.60 times as long as length of 3rd antennal segment. Cauda with 16 setae.

Intermediate between apterous viviparous and oviparous females. Very similar to apterous viviparous females, but hind tibia with 22–25 (23.5) pheromone plates. Abdominal tergite VIII with 4–5 setae. First antennal segment with setae 25–35 (30) μm long; 3rd antennal segment with 25–34 (29.0) setae 18–20 (19) μm long, 0.37– 0.42 (0.40) times as long as articular diameter of 3rd antennal segment. Siphunculi 5.00–6.70 (5.62) times as long as their basal width. Subgenital plate with 13–15 setae along the hind margin.

Male. Body elongated spindle-shaped, 2.8–3.3 (3.1) times as long as its width. Greenish yellow with brown head, prothorax and central part of mesothorax. Cleared specimens with brown head, prothorax, central part of mesothorax, antennae (except for base of 3rd antennal segment), apices of femora and tibia, tarsi, siphunculi, band, spots and marginal sclerites on abdominal segments II–VI; with light brown base of 3rd antennal segment and cauda. Abdominal dorsum with brown reticular pattern on abdominal tergites II–V consist of partially fused short band and spots and with large brown marginal sclerites on abdominal segments II–VI. Longest dorsal, marginal and ventral setae on abdominal tergite III 23–25 (24), 25 and 41–43 (42) μm long, 0.71, 0.71 and 1.14 times as long as articular diameter of 3rd antennal segment respectively; tergite VIII with 5–6 (5.5) setae, 38 μm long, 1.07 times as long as articular diameter of 3rd antennal segment. Small flat marginal tubercles present on prothorax and one of male with one tubercle on IV and V abdominal segment. Ratio of depth of frontal sinus to the width between antennal bases 0.16–0.21. Longest occipital and frontal setae 25 and 20–30 (25) μm long, 0.71 and 0.42–0.86 (0.64) times as long as articular diameter of 3rd antennal segment, respectively. Third antennal segment with 30–37 (34.0) secondary rhinaria arranged more or less in a row, which reaches almost the whole of length of segment, 4th segment with 8–10 (9.0) and 5th segment with 13–16 (14.7) secondary rhinaria. First antennal segment with 6–7 (6.7) setae; longest seta on 3rd antennal segment 35–48 (42) μm long, 0.42–0.57 (0.49) times as long as articular diameter of 3rd antennal segment. Ultimate rostral segment 1.39–1.43 (1.41) times as long as its basal width, with 4–5 accessory setae. Hind femora and hind tibiae 0.37–0.45 (0.40) and 0.66–0.74 (0.70) times as long as body length, respectively. Longest dorsal and dorso-apical setae on hind femur 25–28 (27) and 18–20 (19) μm long, respectively; longest dorsal seta on hind tibia 41–43 (41) μm long, 1.00–1.03 (1.01) times as long as the mid-diameter of the latter. Second segment of hind tarsus 6.00–6.27 (6.15) times as long as its maximum width. Siphunculi 4.50– 6.35 (5.23) times as long as their basal width, 0.16–0.19 (0.18) times as long as body length and 0.46–0.49 (0.48) times as long as length of 3rd antennal segment. Cauda with distinct narrowing in first third, 1.44–1.91 (1.67) times as long as its basal width.

Oviparous female. Body 1.9–2.4 (2.0–2.2) times as long as its width. Yellow-green or greenish-yellowy, antennae, siphunculi and cauda yellow-green. Longest dorsal, marginal and ventral setae on abdominal tergite III 15–19 (17–18), 15–23 (19–20) and 46–56 (47–52) μm long, 0.29–0.45 (0.33–0.44), 0.32–0.62 (0.37–0.49) and 0.98–1.25 (1.02–1.18) times as long as articular diameter of 3rd antennal segment, respectively. Sum of marginal tubercles on abdominal tergites I–VII—0–5 (3.4). Ratio of depth of frontal sinus to the width between antennal bases 0.17–0.23. Longest occipital and frontal setae 18–25 (21) and 25–40 (30–34) μm long, 0.38–0.62 (0.39–0.53) and 0.49–0.97 (0.58–0.82) times as long as articular diameter of 3rd antennal segment, respectively. First antennal segment with setae 23–35 (29) μm long; 3rd antennal segment with 19–33 (26.0–27.5) setae 13–22 (18) μm long, 0.28–0.55 (0.34–0.43) times as long as articular diameter of 3rd antennal segment. Legs long, hind femora and hind tibiae 0.26–0.36 (0.27–0.32) and 0.46–0.57 (0.48–0.53) times as long as body length, respectively. Ventral seta on hind trochanter 0.39–0.67 (0.50–0.54) times as long as basal diameter of hind femur; longest dorsal seta on hind tibia 43–51 (46–48) μm long, 0.45–0.72 (0.50–0.66) times as long as the mid-diameter of the latter. Second segment of hind tarsus 4.74–5.50 (5.09–5.43) times as long as its maximum width and 0.90–1.08 (0.97–1.02) times as long as base of 6th antennal segment. Siphunculi 4.40–7.00 (4.82–5.37) times as long as their basal width and 0.74–0.97 (0.78–0.88) times as long as length of 3rd antennal segment. Subgenital plate oval, with 11–19 (12.5– 18.3) setae on anterior half and 20–26 (22.5–26.0) setae along the hind margin. Cauda 1.64–2.16 (1.70–2.07) times as long as its basal width, with 15–21 (17.7–18.4) setae. Hind tibia with 387–627 (415.3–530.5) rounded pheromone plates.

Measurements of lectotype. Body—3619 x1695, antennae—3702: III—837 x46, IV—670, V—564, VI— 177+1120; hind femur—1020, hind tibia—1878; siphunculus—731 x73; cauda—517x243 (at base) x 195 (before base).

Distribution. Sweden: Värmland; Finland: Ahvenanmaa ( Heie, 1994), Nylandia; Czech Republic; Russia: north–west of European part (near St. Petersburg), Western Siberia (near Novosibirsk),? Ukraine.

Biology. Holocyclic and monoecious, living on leaves of graminaceous plants, including Phalaris arundinacea , Calamagrostis epigejos and possibly Arrhenatherum elatius . Oviparous females occur in south of Western Siberia in the beginning of September (9th of September) and oviparous females and males occur in north–west of European part of Russia at the end of September (23th of September).

Discussion. Heie (1994) (p. 194) stated that his description of the apterous viviparous female of this species was “after Ossiannilsson, 1969, one specimen”, and gave the number of caudal setae as 8. He then wrote (p. 195): “ Heikinheimo (1990) determined an alate viviparous female, caught in a wind net trap, to this species. The number of caudal hairs is remarkably different from that found in the apterous female by Ossiannilsson, so it is possible that these two specimens are not conspecific after all, or the intraspecific variation with regard to this character is extremely large.” But Ossiannilsson (1969) stated in his work that the cauda of the apterous viviparous female had 13 setae.

Eastop & Blackman (2005) indicated that Acyrthosiphon calvulum Ossiannilsson, 1958 on the basis of the reticulation of the siphunculi and probable association with Gramineae , that this species belongs in the Sitobion (Metobion) group. Thus the subgenus Metobion now includes six species— Sitobion (Metobion) graminearum ( Mordvilko, 1919) (type species), S. (M.) beiquei ( Hille Ris Lambers, 1960) , S. (M.) brevirostre ( Heikinheimo, 1978) , S. (M.) calvulum (Ossiannilsson, 1958) and S. (M.) scoticum ( Stroyan, 1969) . Most species of the subgenus are known only from a few specimens and are studied insufficiently, but they are distinguished tentatively by the following key:

1 Processus terminalis less than 3.1 times as long as base of 6th antennal segment. Ultimate segment of rostrum with 3 or more secondary setae. Body length less than 2.5 mm. Life cycle very short, only fundatrices, oviparous females and apterous males present................................................................ S. (M.) calvulum (Ossiannilsson, 1958)

- Processus terminalis more than 3.1 times as long as base of 6th antennal segment, but if less than 3.1 then ultimate segment of rostrum with 2 secondary setae. Body length 1.7–4.2 mm ...................................................... 2

2 Body length less than 3 mm. Processus terminalis 2.1–5.0 times as long as base of 6th antennal segment. Cauda with 5–12 setae. 3rd antennal segment of apterous morphs with 6–17 secondary rhinaria............ S. (M.) scoticum ( Stroyan, 1969)

- Body length more than 3 mm. Processus terminalis 3.7–7.8 times as long as base of 6th antennal segment. Cauda with 9–21 setae. 3rd antennal segment of apterous morphs with 1–13 secondary rhinaria...................................... 3

3 Processus terminalis 3.7–3.9 times as long as base of 6th antennal segment. Cauda with less than 10 setae. 3rd antennal segment of apterous morphs with 11–13 secondary rhinaria........................ S. (M.) brevirostre ( Heikinheimo, 1978)

- Processus terminalis 4.3–7.8 times as long as base of 6th antennal segment. Cauda with more than 10 setae. 3rd antennal segment of apterous morphs with 1–6 secondary rhinaria......................................................... 4

4 Processus terminalis 4.3–5.5 times as long as base of 6th antennal segment, 0.9–1.1 times as long as 3rd antennal segment. 3rd antennal segment of apterous morphs with 2–6 secondary rhinaria.............. S. (M.) beiquei ( Hille Ris Lambers, 1960)

- Processus terminalis 5.5–7.8 times as long as base of 6th antennal segment, 1.1–1.5 times as long as 3rd antennal segment. 3rd antennal segment of apterous morph with 1–4 secondary rhinaria................. S. (M.) graminearum ( Mordvilko, 1919)

graminearum ( Mordvilko, 1919) .

Figures

FIGURES 1 – 8. Sitobion (Metobion) graminearum, apterous viviparous female. 1, body; 2, frons; 3, antennae; 4, base of 3 rd antennal segment; 5, ultimate segment of rostrum, 6, hind tarsus; 7, siphunculus; 8, cauda.

FIGURES 9 – 14. Sitobion (Metobion) graminearum, male and oviparous female. 9, abdomen of male; 10, hind tibia of oviparous female; 11, siphunculus of male; 12 siphunculus of oviparous female; 13, cauda of male; 14, cauda of oviparous female.