Scolothrips sexmaculatus (Pergande)

Mound, Laurence A., 2011, Species recognition in the genus Scolothrips (Thysanoptera, Thripidae), predators of leaf-feeding mites, Zootaxa 2797, pp. 45-53 : 51-52

Scolothrips sexmaculatus (Pergande)

Thrips sexmaculata Pergande, 1891: 539

The Lectotype of sexmaculatus (in USNM) is mounted ventral side uppermost, and the chaetotaxy of the pronotum is not visible. The series used by Priesner (1950) to redefine this species (in SMF) comprises five poorly preserved females mounted irregularly in a row on one slide, but the pair of pronotal posteromesad discal setae is visible on two of these females. A sample of 22 reared females of sexmaculatus was obtained in November 2010, through the courtesy of Mark Hoddle, from a commercial supplier of biocontrol agents in California. These females included several individuals with the tergal colour pattern described for sexmaculatus by Priesner (1950), a pattern that can also be seen on the Lectotype designated by Stannard (1968). In this pattern, the entire median area of terga II–IV, including their posterior margins, is uniformly shaded but with no lateral darker spots ( Fig. 7 ). The shaded areas on terga V–VII of these females are more diffuse and incomplete medially. The metascutum is extensively shaded, and the metascutellum darker. This colour pattern distinguishes sexmaculatus clearly from rhagebianus – particularly if freshly collected specimens are examined.

Three New World species comprise the sexmaculatus species-group, but the significance of two of these, hoodi and pallidus , remains unclear. These three are distinguished by the presence and extent of shadings on the terga, and Hoddle et al. (2008) suggested that these colour differences might be due to environmental conditions during larval development, including temperature and the type of prey consumed. Specimens identified as hoodi (q.v.) have the body more extensively shaded, and the major setae slightly shorter (longest costal seta at fore wing subbasal band no more than 100 microns, but in sexmaculatus varying 115–130 microns). At present, hoodi cannot otherwise be distinguished from the darkest individuals in the series of 22 reared females from California mentioned above. The palest individuals amongst this series have the terga almost without any shading, but each of them has at least the metascutellum shaded, and the pronotum bears paired spots laterally. That is, none of these specimens are as pale as individuals labelled as pallidus in the Bailey collection (UCD). In all three members of the sexmaculatus species-group, also in the closely related rhagebianus , the sub-basal dark band on the fore wing does not extend fully to the anterior margin of the wing. In contrast, this dark band fully extends to the costal margin of the wing in all other species of Scolothrips , including the longicornis species-group (although tenuipennis has no dark bands).

Described from California, the “six-spotted thrips” has been widely recorded, but no specimens identifiable as sexmaculatus have been seen from Australia. All previously published records of this species from Australia ( Mound, 1996) are here considered to be based on misidentifications of the Old World species, rhagebianus .

Figures

FIGURES 1 – 8. Scolothrips species. (1) S. ochoa, pro, meso and metanota. Head and thorax 2 – 3 (arrow indicates position of posteromesad discal setae): (2) S. latipennis; (3) S. sexmaculatus. Antenna 4 – 5: (4) S. ochoa; (5) S. asura. (6) S. brevipilis (in Canada balsam). (7) S. sexmaculatus (in clove oil). (8) S. rhagebianus (in Hoyers mountant).