Trialeurodes ricini ( Misra )

Malumphy, Christopher, Walsh, Katherine, Suarez, Belen, Collins, Dominique W. & Boonham, Niel, 2009, Morphological and molecular identification of all developmental stages of four whitefly species (Hemiptera: Aleyrodidae) commonly intercepted in quarantine, Zootaxa 2118, pp. 1-29 : 15-17

Trialeurodes ricini ( Misra)

( Figs 25–35 )

T. ricini was originally described by Misra (1924) in the genus Aleyrodes , from specimens collected from Ricinus communis in India. It is broadly polyphagous, feeding on host plants belonging to 22 genera in 13 families ( Mound & Halsey, 1978). It occurs widely in Asia, Middle East, sub-Saharan Africa, Egypt and the Canary Islands. It is a pest of glasshouse and field crops in Egypt and is implicated in plant-pathogenic virus transmission.

Specimens measured

NIGERIA: (intercepted in UK), on Telfaria sp., 26.ii.2002, PHSI, CSL2020953 (1 second instar and 4 third instars), 23.iv.2002, PHSI, CSL2022136 (1 second and 2 third instars); on unspecified plant, 28.iii.2002, PHSI, CSL2021569 (2 adult males and 1 adult female). SPAIN: Gran Canaria, Margazan, on Ricinus communis , 9.i.2003, C. Malumphy, KV85 TR 1-KV85 TR 11 (20 eggs, 10 first, 7 second and 10 third instars, and 7 adult males and 8 adult females). Cultured under licence at CSL, Phaseolus vulgaris , 6.iii.03, KV85 TR 28-KV85 TR 31 (10 eggs, 10 first, 10 second and 1 third instar).

OVUM ( Fig. 25 )

Habitus. Cream coloured when first laid, becoming pale yellow. Red eyes and yellow fat bodies of the first instar clearly visible prior to hatching. Scattered, or in small groups, occasionally in small irregular rows, on the under surface of the foliage. Eggs may be laid at very high densities, particularly on the young, unexpanded leaves of Ricinus communis . As the leaves rapidly expand the eggs become more widely distributed before hatching. Elliptical, slightly narrower anteriorly. The chorion is smooth and shiny with little wax evident although the surrounding leaf may be dusted with powdery wax by the adult female forming a circular patch. Each egg is firmly attached to the leaf surface by a long, slender peduncle extending from the base of the egg, inserted into the leaf. The peduncle bends so the eggs usually lie at an acute angle to the leaf surface. After hatching, the egg completely collapses, is translucent and very difficult to detect. Length 228 microns (184–256 microns), width 129 microns (94–152 microns), 1.78 times longer than wide (1.30–2.17). Peduncle length 43 microns (37–52 microns), width is 9 microns (8–13 microns).

FIRST-INSTAR LARVA ( Fig. 26 )

Habitus. Scale-like, pale translucent yellow, becoming darker as they mature. Reddish eye spots, two yellow abdominal mycetomes and abdominal segmentation visible. A wide, bluish, translucent wax fringe develops around the margin. They usually settle to feed within a few mms from their eggs.

Margin. Outline ovoid, lozenge-shaped; length 301 microns (272–332 microns) width 169 microns (144–198 microns), 1.79 (1.65–1.83) times longer than wide. With 17 pairs of well-developed setae: 14MS length 48 microns (40–53 microns); CS length 109 microns (100–116); ratio CS/14MS = 2.32 (2.08–2.60). Margin relatively smooth or very finely crenulate in parts, and not differentiated at thoracic and abdominal tracheal openings.

Dorsum. Chaetotaxy comprises paired ASS, length 24 microns (20–28 microns); CeS, 4 microns (2–4 microns); 1 AS, 3 microns (2–4 microns); and 8 AS, 4 microns (2–5 microns). The 8 AS may be close to the anterior corners of the vasiform orifice or displaced antero-laterad. All of the setae have large bases. Cephalic tubercles well developed, oval to sub-rectangular. One pair of clear pores present subdorsally on the third abdominal segment. Vasiform orifice sub-oval to almost rectangle, closed behind, length 25 microns (24–28 microns). The lingula is spatulate with two terminal setae, the distal portion is spiculate, and it is half-covered by the operculum. The operculum is quadrate with the posterior margin spiculate.

Ven t er. Legs well developed. Mid and hind coxae and tibio-tarsi with long spine-like setae. Claw digitules long. Antennae long and slender, length 85 microns (64–92 microns). Abdominal setae bases correspond approximately with the anterior margin of vasiform orifice. Cuticle fine, diaphanous.

SECOND-INSTAR LARVA ( Fig. 27 )

Habitus. Distribution similar to first instars. Scale-like, similar in appearance to first instar but larger and more transparent.

Margin. Outline ovoid, widest across mesothoracic legs; length 383 microns (344–432 microns), width 229 microns (188–344 microns), 1.79 times longer than wide (1.20–1.84). Marginal setae fine, acute. AMS minute and often very difficult to detect, length 5 microns (4–5 microns); PMS 13 microns (10–16 microns); CS length 38 microns (32–46 microns). Ratio CS/PMS = 2.94 (2.25–3.67). Margin evenly crenulated, not modified at thoracic opening and smooth at abdominal tracheal openings.

Dorsum. Chaetotaxy comprises paired CeS, length 3 microns (2–5 microns); 1 AS, length 3 microns (2–4 microns); and 8 AS, length 6 microns (3–8 microns). Approximately 4 pairs of close-set geminate pore/ porettes distributed longitudinally from the mesothorax to rear of abdomen as shown in Fig. 27 . Abdominal segmentation rather faintly marked, medially and submedially. Abdominal segment VII reduced medially, pockets marked. Vasiform orifice sub oval to rectangular, closed behind, length 33 microns (26–36 microns), inset from posterior margin by less than its own length, just over half occupied by the operculum with only part of lingula head visible. Lingula head spinulose with pair of stout setae.

Ve n t e r. Legs roughly triangular, each with a subcircular apical pad. Antennae small and slender, laterad, length 27 microns (24–32 microns). Abdominal setae placed mid vasiform orifice. Cuticle fine, diaphanous.

THIRD-INSTAR LARVA ( Fig. 28 )

Habitus. Distribution similar to first instars. Larger and darker yellow than first and second instars.

Margin. Outline ovoid, widest across metathoracic legs; length 525 microns (464–588 microns), width 329 microns (268–380 microns), 1.60 times longer than wide (1.52–1.81). AMS undetectable. PMS fine, acute length 16 microns (12–22 microns). CS length 49 microns (42–56 microns). Ratio CS/PMS length = 3.25 (2.36–4.67). Margin distinctly and evenly crenulated, not modified at thoracic and abdominal tracheal openings.

Dorsum. Chaetotaxy comprises paired CeS, length 7 microns (6–10 microns); 1 AS setae, length 6 microns (4–8 microns); and 8 AS setae, length 10 microns (8–12 microns). Approximately 8 pairs of close-set geminate pore/porettes distributed longitudinally from the head to rear of abdomen as shown in Fig. 28 . Abdominal segmentation rather faintly marked, medially and submedially. Abdominal segment VII reduced medially, pockets distinct. Vasiform orifice cordate to rectangular, closed behind, length 42 microns (40–48 microns), inset from posterior margin by about its own length, just over half occupied by the operculum with only part of lingula head visible. Lingula head lobed, spinulose with pair of stout setae.

Ven t er. Legs roughly triangular, each with a subcircular apical pad. Antennae small and slender, mesad but apex strongly curved back on itself; length 22 microns (18–26 microns). Abdominal setae placed anterior to vasiform orifice. Cuticle fine, diaphanous.

FOURTH-INSTAR LARVA ( Figs 29–30 )

Described and illustrated by Martin (1987, 1999) and Martin et al. (2000).

ADULT ( Figs 31–35 )

Body yellow, wings hyaline, covered with sparse, powdery wax. Antennae 7-segmented. Antennal segment II about half as long as antennal segment III; antennal segment III about as long as segments IV–VII combined; segments IV–VII subequal. Segment III with one sensorium located on the proximal portion, and three sensoria (a cone and two rhinarial-types) close together on the distal portion. Segment IV with a sensorial cone; segment V with a distal rhinarial-type sensorial; segment VI with a subapical sensorial cone, and segment VII with two sensorial cones and a rhinorial sensorium, and terminating in a narrow conical sensorium. Upper eye composed of 47 ommatidia, each 7.6 (7.0–8.9) microns in diameter; lower compound eye composed of about 36 ommatidia, each 11.5 (10.4–12.8) microns in diameter, arranged in interconnected groups of 6 pigmented ommatidia surrounding a clear, smaller ommatidium. Upper and lower eyes connected by three, sometimes two, ommatidia. Metatibial combs consisting of 14 setae, all tibial brushes consisting of 2–4 adjacent setae. Male claspers paired, with about 10 long setae. Aedeagus ventral base spiculate; distal portion parallel sided or slightly tapered, gently curved upwards, terminating in a fine 'nipple-like' tip which may extend outwards. Male collar and female gonapophysis and supragenital plate pigmented. Female cement gland not sinuous, without bands and with a large disc shaped-head.

Figures

FIGURES 25 – 30. Trialeurodes ricini. 25, ovum on Ricinus communis from Gran Canaria; 26, first instar on R. communis from Gran Canaria; 27, second instar on R. communis from Gran Canaria; 28, third instar on R. communis from Gran Canaria; 29 – 30, fourth instar on Telfairia sp. from Nigeria showing variation in submarginal tubercles.

FIGURES 31 – 38. Trialeurodes spp. 31, T. ricini, diagrammatic representation of left compound eye of adult female; T. ricini, 32, upper and lower compound eyes linked by two to four ommatidia; T. ricini, 33, male antenna; T. ricini, 34, aedeagus; T. ricini, 35, female cement gland; 36, T. vaporariorum, ovum on Euphorbia pulcherrima from Italy; 37, T. vaporariorum, first instar on E. pulcherrima from the UK; 38, T. vaporariorum, second instar on E. pulcherrima from Italy.