Scirtothrips aff. dorsalis Hood

Mound, Laurence A. & Stiller, Michael, 2011, Species of the genus Scirtothrips from Africa (Thysanoptera, Thripidae), Zootaxa 2786, pp. 51-61 : 56-57

Scirtothrips aff. dorsalis Hood

( Figs 4–6 )

The species S. dorsalis was described by Hood (1919: 90) from 34 females collected from “castor and chillies” at Coimbatore, India. It is currently considered to be a widespread polyphagous pest across Asia, that more recently has been introduced to Florida and other countries around the Caribbean area, as well as Israel. In contrast, the first official record of dorsalis from South Africa ( Gilbert, 1986) is of a population that apparently remains restricted to the leaves of Ricinus , the castor oil plant. Molecular data suggest that this population is specifically different from some other populations around the world ( Rugman-Jones et al., 2006; Hoddle et al., 2008b). Specimens from Ricinus at Nelspruit, South Africa, were kindly collected by Dr Tim Grout in November, 2010 and sent to Canberra for slide-mounting. Females from this population do not have the microtrichial field on sternite VII extending fully across the postero-median area between marginal setal pair S1; in this they resemble females of S. aurantii ( Fig. 3 ). In contrast, sternite VII of females of dorsalis from all other available localities, including Australia, Asia, Israel, and the Caribbean, always bears several rows of microtrichia medially across the full width near the posterior margin ( Fig. 6 ). No differences have yet been detected between males from different populations. No molecular studies have been carried out on Indian specimens from Ricinus , despite this being one of the host plants from which it was described by Hood, and dorsalis has been reported as numerous on Ricinus in Delhi ( Mound & Palmer, 1981). The small structural difference on sternite VII indicated above, together with the molecular data, suggest that the South African population on Ricinus may be a distinct species from the widespread pest. However, the original material used by Hood to describe dorsalis needs to be re-examined, to decide if his specimens from “castor and chillies” can be distinguished, and to determine from which of these plants was collected the holotype that he selected (indicated only as the specimen measured).

Diagnosis. Body mainly yellow, terga and sterna with median area variably shaded and antecostal ridges usually dark medially; antennal segments V–VIII deeply shaded, III–IV slightly paler; fore wings variously shaded with apex paler. Ocellar setae III situated between mid-points of posterior ocelli ( Fig. 4 ); pronotum closely striate, posteromarginal setae 0.3–0.4 times as long as pronotum, S2 usually less than 2.0 times as long as S1; fore wing second vein with 2 setae, cilia straight; metanotum transversely striate on anterior half, irregular elongate reticulation on posterior half; tergum VIII with several rows of microtrichia anteromedially ( Fig. 5 ), IX with numerous microtrichia posteromedially; sterna IV–VI with microtrichia covering median area except on anterior third or half ( Fig. 6 ). Male tergite IX with no drepanae.

Figures

FIGURES 1 – 10. Scirtothrips species. S. aurantii 1 – 3: (1) Head & pronotum; (2) Terga VII – IX; (3) Sterna V – VII. S. dorsalis 4 – 6: (4) Head & pronotum; (5) Terga VII – IX; (6) Sterna V – VII. S. africanus 7 – 10: (7) Terga VI – IX; (8) Head; (9) Metanotum (of paratype); (10) Metanotum.