Tuberocephalus tsengi (Tao), 2020

Blackman, Roger L., Brightwell, Robert, Dransfield, Robert D. & Brown, Paul A., 2020, Tuberocephalus tsengi (Tao, 1963) STAT. REV. (Hemiptera: Aphididae), an East Asian Artemisia - feeding aphid species introduced to Britain, Zootaxa 4743 (1), pp. 144-150 : 144-147

Tuberocephalus tsengi (Tao)

= Myzus tsengi Tao, 1963

= Tuberocephalus sasakii (Matsumura) [partim]: Eastop & Hille Ris Lambers, 1976; Remaudière & Remaudière, 1997; Su, Jiang & Qiao 2010.

= Tuberocephalus sasakii (Matsumura) : Noordam, 2004.

Apterous viviparous female (alienicola). (figs 1, 2a,d,e,g). Colour in life: yellowish green with dark red eyes, black tips to antennae, legs and siphunculi, and a pale cauda (fig. 1).

Morphology (for measurements see Table 1 ): Body oval (fig. 2a). Head spiculose, antennal tubercles well developed, with rugose thumb-like, rounded processes about as long as their basal widths, projecting inwards and forwards and bearing thick hairs that are about as long as the basal diameter of the antennal segment III and have blunt or slightly expanded apices (fig. 2e). Inner sides of antennal segment I are swollen and rugose but not projecting forward beyond base of antennal segment II, and having hairs that are generally much smaller than those on the antennal tubercles.Antennae 6-segmented, with heavy imbrication, about 0.5–0.6 of body length.Antennal segment VI with a relatively short processus terminalis, about twice the length of the base of the segment. Eyes large with well-developed ocular tubercles. Rostrum about one quarter of body length, with last segment (R IV+V) narrowly wedge-shaped, straight-sided, more than 1.4 × longer than hind tarsus segment II, and bearing 2–3 small accessory hairs. First tarsal segments with 3 hairs. Dorsal integument sinuously corrugated (fig. 2d), with short, mostly blunt hairs; those on anterior abdomen maximally 8–10 µm long, the hairs on abdominal tergite 8 being 17–20 µm long. Siphunculi with coarse, scaly imbrication and a large flange (fig. 2g), 1.85–2.46 × longer than the cauda which is digitiform, tapering, and bears 4–7 hairs.

Alate viviparous female (fig 2c; based on 2 specimens). Colour in life unknown, but presumably head, thorax, dorsal sclerites, siphunculi and cauda are brown-black; legs also dark except for basal parts of femora and central parts of tibiae.

Morphology (for measurements see Table 2 ): Antennal tubercles much lower than in aptera, converging apically. First antennal segment much thicker than second with inner side gibbous and rugose. Antennae 6-segmented; basal segments of flagellum heavily imbricated, with small rounded secondary rhinaria distributed III 21–37, IV 6–12, V 0. Processus terminalis c.2.2 × longer than base of sixth segment (only measurable on one antenna). Forewings with twice-branched media. Dorsal abdomen with marginal sclerites and broad transverse sclerites on tergites 2–7, those on at least 3–5 partially fused to form a large irregularly margined central patch. Siphunculi 2.1–2.5 × longer than cauda.

Material examined. Type material: CHINA, Sichuan Prov., Chengtu, C.C. Tao leg., 29.iii.1937: 9 apterae and 1 alata on Artemisia sp. (on 2 slides mixed with Capitophorus formosartemisiae ). [These bear the original label identifying them as Myzus tsengi , and have the collection locality and date agreeing with the original description ( Tao, 1963), so they clearly constitute the type series ( ICZN Article 72.4.1.1). In accordance with Article 74.7, we have designated one aptera as a lectotype (arrowed on slide). This material is in the insect collection of the Taiwan Agricultural Research Institute.]

Other material of T. tsengi : ENGLAND, Sussex, Rye Harbour, R. Dransfield leg., 13.v.2018, 7 apterae on Artemisia vulgaris (1708) ; INDONESIA, Java, Tosari, D. Noordam leg., 14.vi.1976, 4 apterae amd 1 alata on Artemisia vulgaris ( BM 1984-340); WEST MALAYSIA, Pahang, Cameron Highlands near Brinchang, J.H. Martin leg., 13.ii.1985, 4 apterae on Artemisia ? vulgaris ( JHM 4475); WEST MALAYSIA, same locality and collector, 27.x.2011, 9 apterae on Artemisia ? vulgaris ( JHM 8564).

Material of T. sasakii : JAPAN, Osaka, R. Takahashi leg., 18.viii.1958, 3 apterae on Artemisia sp. ( BM 1961- 762); JAPAN, same locality and collector, vi.1957, 6 apterae on Artemisia sp. ( BM 1984-340); JAPAN, Tochigi Pref., Nasu, M. Miyazaki leg., 12.viii.1969, 3 apterae on Artemisia princeps ( MM 2661 and BM 1982-492); JA- PAN, Yamaguchi University, S. Hamasaki leg., 7–20.vi.1980, 3 apterae reared on Artemisia princeps , transferred to Prunus lannesiana (113/81); INDIA, West Bengal, Kalimpong, A.N. Basu leg., 20.i.1966, 3 apterae on Artemisia vulgaris ( BM 1984-340).

Diagnosis. There are a number of significant differences between apterous viviparae (alienicolae) of T. tsengi and those of T. sasakii (figs 2a,b). The antennal tubercles of T. sasakii project further forward than those of T. tsengi , and antennal segment I has a corresponding forward projection beyond base of antennal segment II, bearing thick hairs that are almost as long as those on the antennal tubercles (fig. 2f). The eyes of T. sasakii are reduced, and the ocular tubercles are not evident. The dorsal integument of T. sasakii is only slightly wrinkled. The siphunculi of T. sasakii have a less scaly, more spinulose imbrication, and a smaller flange (fig 2h). Morphometric characters are compared for specimens from several different countries in Table 1 , where it can be seen that the specimens collected in England agree closely in all respects with the type material of T. tsengi from China. Apterae of T. sasakii from Artemisia have 5-segmented antennae in all specimens in the BMNH collection; this species is reported in the literature to have 5- or 6-segmented antennae, perhaps because of the confusion with T. tsengi , which consistently has apterae with 6-segmented antennae. Apterae of T. sasakii are mostly smaller than those of T. tsengi , have relatively longer antennae compared to body length, and higher ranges of the ratios of antennal processus terminalis to base of last antennal segment and siphuncular length to caudal length. The last rostral segment (R IV+V) of T. sasakii is shorter than that of T. tsengi , and the ratio of the length of R IV+V to the second segment of the hind tarsus is less in T. sasakii , with no overlap.

There are also differences in the appearance in life and the feeding habit of the two species. Apterae of T. sasakii on Artemisia are whitish with a flattened body and feed adpressed to the undersides of mature leaves ( Sorin & Remaudière 1998), whereas the apterae of T.tsengi collected in England were green with conspicuously dark-tipped siphunculi, as reported by both Tao (1963) and Noordam (2004), and colonised young growth.

Only two alatae of T. tsengi were available and these both have an extensive dark dorsal abdominal sclerite, as illustrated by Noordam (2004, fig. 306, as sasakii ). Alatae of T. sasakii from Artemisia were not available for comparison, those in the BMNH collection all being spring migrants from galls on Prunus , and these have only marginal sclerites. However, according to Monzen (1929), alatae of T. sasakii from Artemisia in Japan (gynoparae) are also without any extensive dorsal sclerotisation.

In the keys to apterae on Artemisia provided by Blackman & Eastop (2006), T. tsengi runs to couplet 48 of Key C, which can be amended as follows:

48 ANT 5- or 6-segmented, 0.50–0.85 × BL, with PT/BASE 1.67–2.8. Dorsal cuticle wrinkled or smooth, not nodulose. Frontal projections thumb-like, 0.04–0.06 mm long, less than twice their diameter....................................…. 48a

- ANT 4-, 5- or 6-segmented, 0.3–0.4 × BL, with PT/BASE 1.3–1.8. Dorsal abdominal cuticle markedly nodulose. Frontal projections finger-like, 0.08–0.1 mm long, 3 or more times longer than their diameter........... …. Tuberocephalus artemisiae

48a R IV+V 1.0–1.3 × HT II. ANT 5-segmented, 0.65–0.85 × BL, with PT/BASE 2.1–2.8. Inner sides of ANT I projecting forward and bearing long thick hairs like those on frons. SIPH 2.18–3.83 × cauda, with a moderate apical flange.................................................................................................. Tuberocephalus sasakii

- R IV+V 1.4–1.9 × HT II. ANT 6-segmented, 0.50–0.65 × BL, with PT/BASE 1.67–2.33. Inner sides of ANT I not projecting forward and bearing much smaller hairs than those on frons. SIPH 1.85–2.46 × cauda, with a large apical flange............................................................................................. Tuberocephalus tsengi

[An updated version of this key is available online ( Blackman & Eastop, 2019).]