Aphis verbasci Schrank, 1801

Kanturski, Mariusz, Wieczorek, Karina & Junkiert, Łukasz, 2014, Sexual morphs and biology of Aphis verbasci Schrank (Hemiptera: Aphididae), Zootaxa 3755 (5), pp. 485-490 : 485-490

Aphis verbasci Schrank, 1801 .

( Figs 1 , 2 , 3 )

Oviparous female ( Fig.1 a; Fig. 3 c,d; Table 1 )

Description of the oviparous female—color of live specimens dark green-olive slightly pulverulent, immatures being light green without wax. Legs dark yellowish-brown with darker knee area, end of tibiae and tarsi. Siphunculi and cauda black. Dorsal abdominal side of body without visible sclerotization ( Fig. 3 c,d). Colour of mounted specimen: pale brown. Head pale brown, thorax pale, antennae pale with brown segments I and II, also with light brown apices of segm. IV, V and base of segm. VI. Legs pale light-brown with darker knee area, ends of tibiae and tarsi. Siphunculi and cauda dark brown. Body egg-shaped or oval. Head with compound eyes and triommatidia. Head width 2.13–2.72 times length of antennae. Frons flat. Head chaetotaxy: 8 pairs of fine and pointed setae. Antennae ( Fig. 1 b) 6-segmented, 0.52–0.59 times body length. Surface of ant. segm III–VI imbricated. Ant. segm. III slightly narrower at base then at apex, almost as long as terminal process (VIb). Ant. segm. IV almost as long as ant. segm. V. Ant. segm. V slightly wider at apex with one small, rounded and ciliated rhinarium. Ant. segm. VI ( Fig. 1 c) longest. VIb 2.16–2.36 times base (VIa) with one rounded and ciliated rhinarium and 5–7 accessory rhinaria. Other antennal ratios: VI:III 1.44–1.76, V:III 0.64–0.75, IV:III 0.61–0.88. Antennal chaetotaxy: segm. I with 4–5 setae, segm. II with 3–4 setae, segm. III with 5–7 setae, segm. IV with 4–6 setae, segm. V with 4–5 setae. Ant. segm. VI with 3 basal, 3 apical and 2–3 subapical setae. Antennal setae pointed, 0.01–0.02 mm long; the longest antennal seta III 1.0 times basal articular diameter of this segment. Rostrum reaching end of hind coxae, apical segment of rostrum (ARS) long and pointed, with 4 primary and 4 accessory setae ( Fig. 1 d). ARS 0.80–1.00 times ant. segm. III and 1.81–2.00 times segment II of hind tarsus (HT II). Hind tibiae ( Fig. 1 e) slightly swollen in the middle with 25–35 circular or irregular pseudosensoriae situated in one row on anterior part of tibiae. First segment of hind tarsus very short with 2 setae ( Fig. 1 f). Abdomen without sclerites; only abd. segm. VII and VIII sclerotized on their entire surface. Abdominal reticulation in form of pentagons or hexagons ( Fig. 1 g). Dorsal setae very few, pale, capitate, 0.02–0.04 mm long. Abd. segm. V and VI with one pair of spinal setae, which can arising from small brown sclerites. Siphunculi ( Fig. 1 h) widest at base, without reticulation and flange, imbricated, 1.35 – 2.00 times cauda.Cauda tongue shaped with 9–10 pointed setae and short, pointed spinules ( Fig. 1 i). Subgenital plate very well developed, sclerotized with fine and pointed setae.

Wingless male. ( Fig. 2 a; Fig. 3 e,f; Table 1 )

Colour of live specimens dark green-olive slightly pulverulent. Legs dark yellowish-brown with darker knee area, end of tibiae and tarsi. Siphunculi, genitalia and cauda black. Dorsal abdominal side of body with dark sclerites ( Fig. 3 e,f). Colour of mounted specimen: head, thorax and antennae light brown. Legs light brown with darker ends of tibiae and tarsi. Siphunculi, cauda and genitalia dark brown. Body egg-shaped. Head with compound eyes and triommatidia. Head width 2.33–2.72 times length of antennae. Frons flat. Head chaetotaxy: 8 pairs of fine and pointed setae. Antennae 5-segmented ( Fig. 2 b), 0.69–0.72 body length. Surface of ant. segm III–V imbricated. Ant. segm. III almost as long as ant. segm. V, narrower at base than at apex with 20–36 rounded secondary rhinaria of variable size with sclerotic ring ( Fig. 2 c). Ant. segm. IV at least 2 times shorter than ant segm. III and V with 1 rounded and ciliated primary rhinarium and 3–5 secondary rhinaria, similar to those on ant. segm. III. Ant. segm. V with 1 rounded and ciliated primary rhinarium and 3–6 ciliated, accessory rhinaria ( Fig. 2 d). Vb 2.40–2.77 times Va; other antennal ratios: V:III 0.97–1.00, IV:III 0.32–0.41. Antennal chaetotaxy: segm. I with 5–6 setae, segm. II with 4–6 setae, segm. III with 8–12 setae, segm. IV with 3–6 setae, segm. V with 3 basal, 2–3 apical and 2–3 subapical setae. Antennal setae pointed, 0.01–0.02 mm long; the longest antennal seta III about 1.0 times basal articular diameter of this segment. Rostrum long, reaching abdominal segment V, ARS long and pointed, with 4 primary and 4 accessory setae ( Fig. 2 e). ARS 0.47–0.55 times ant. segm. III and 1.80–2.11 times HT II. First segment of hind tarsus with 3 setae ( Fig. 2 f). Abdomen with reticulation in form of pentagons and hexagons ( Fig. 2 g). Dorsal side of abdomen covered with variable sized sclerites in pleural and marginal position. On abd. segm. I–IV from these sclerites arising pleural and marginal setae. On abd. segm. V and VI there is also spinal sclerotization with 2 pairs of spinal setae. Dorsal setae pale, slightly capitate, 0.02–0.04 mm long. Abd. segm. VII and VIII completely sclerotized (cross bars). Siphunculi imbricated, widest at base and gradually narrowing toward apex without reticulation and flange ( Fig. 2 h). Cauda tongue shaped with 8 long and pointed setae and short and pointed spinules ( Fig. 2 i). Genitalia well developed, strongly sclerotized with lobate parameres with numerous setae. Basal part of phallus shortened, hooked-shaped with numerous setae ( Fig. 2 j).

Bionomic remarks. Numerous colonies of A. verbasci live always on the whole underside surface of the basal leaves of Verbascum spp., lying directly on the ground. During summer apterous viviparous females produce much honeydew and the colonies are visited by ants, especially Lasius niger . The bisexual generation begins to appear in October, with numerous oviparous females and less numerous males and for some time those two generations exist together ( Fig. 3 a). Ant attendance of sexuales in autumn was not observed. After copulation orange eggs are visible in the female's body ( Fig. 3 c) and the oviparae each lay 2–3 big, orange eggs on the lower surface of the leaf ( Fig. 3 d). Eggs are protected from the effects of winter under the dead leaves until spring.

Oviparous females of A. verbasci differ morphologically in comparison to parthenogenetic apterous viviparous females. They are characterized by longer and wider genital plate—a phenomenon which occurs also in other subfamilies of aphids e.g. in Lachninae ( Depa et al. 2013) or Chaitophorinae ( Wieczorek & Junkiert 2011), and also are slightly sclerotized on abdominal segments IV and V. Wingless males have 5-segmented antennae and well developed dorsal sclerotization, visible in life as well as in mounted specimens. In both sexual morphs siphunculi are straight, not curved like in apterous viviparous females. There are also considerable seasonal differences in coloration. The large, summer colonies of parthenogenetic females of A. verbasci are golden-yellow in colour, but in autumn they have much paler coloration from pale yellow to pale green ( Fig. 3 a,b). The bisexual generation on the other hand is slightly pulverulent and of a dark green-olive colour ( Fig. 3 c,e,f).

Figures

FIGURE 1. Aphis verbasci — oviparous female: (a) general feature, (b) antenna, (c) antennal segment VI, (d) apical segment of rostrum, (e) hind tibia, (f) hind tarsus, (g) dorsal abdominal reticulation, (h) siphunculus, (i) cauda.

FIGURE 2. Aphis verbasci — wingless male: (a) general feature, (b) antenna, (c) antennal segment III, (d) antennal segment V, (e) apical segment of rostrum, (f) hind tarsus, (g) dorsal abdominal reticulation, (h) siphunculus, (i) cauda, (j) genitalia.

FIGURE 3. Aphis verbasci from Verbascum phlomoides: (a) colony of apterous viviparous females and oviparous females ♀, (b) pale yellowish-green autumn apterous viviparous female, (c) oviparous females with visible eggs inside the bodies, (d) oviparous female with egg [●], (e, f) males ♂.

Tables

TABLE 1. Measurements of oviparous female (n = 7) and wingless male (n = 7) of Aphis verbasci from Verbascum phlomoides and Buddleja sp. (in mm). Two measurements refer to the range of measurements of each character for each morph.

Character	oviparous female	male
Length of body	1.06–2.20	1.25–1.40
Width of body	1.00–1.42	0.70–0.82
Head width across compound eyes	0.40–0.45	0.35–0.39
Length of antenna	0.94–1.19	0.91–1.01
Length of antennal segment III	0.20–0.26	0.34–0.38
segment IV	0.15–0.22	0.12–0.15
segment V	0.14–0.18	0.33–0.37
segment VIa (base)	0.10–0.13	0.09–0.10
segment VIb (processus terminalis)	0.23–0.29	0.24–0.27
Length of rostrum	0.70–0.74	0.62–0.69
Length of apical segment of rostrum	0.20–0.21	0.1
Length of hind femora	0.38–0.46	0.34–0.40
Length of hind tibiae	0.74–0.78	0.68–0.78
Length of hind tarsi segm. I	0.03–0.04	0.03–0.04
Length of hind tarsi segm. II	0.10–0.11	0.09–0.10
Length of siphunculi	0.22–0.30	0.17–0.21
Length of subgenital plate	0.16–0.20	–
Width of subgenital plate	0.31–0.34	–
Length of cauda	0.15–0.17	0.11–0.13