Scirtothrips dorsalis Hood

Scirtothrips dorsalis Hood

[Figs 6, 7, 26, 27, 52, 59]

Scirtothrips dorsalis Hood, 1919: 90 ­91.

This is a highly polyphagous and widespread tropical insect. It is found from Pakistan to Japan and Taiwan, and south to the Solomon Islands and northern Australia, but no specimens have been seen from south of Brisbane. It is recorded as a pest on many different crops, from chillies and lotus plants to tea and strawberries. In life it is often recognisable from the dark wings contrasting with the pale body. Amongst the Scirtothrips recorded in Australia, the only one with microtrichia extending across the median area of the abdominal sternites is S. aurantii, and these can be distinguished by means of the key above.

Female macroptera. Colour: Body yellow with brown marking medially on tergites III – VII, sternites without brown markings but antecostal ridges on tergites and sternites dark brown; forewings usually strongly shaded but paler toward apex; antennal segment I pale, II shaded, III –VIII dark.

Structure: Head about twice as wide as long, postocular and ocellar region closely striate; ocellar setae pair III arise between the posterior ocelli, well behind tangent between their anterior margins; compound eyes with no ommatidia strongly pigmented; two pairs of post­ocellar setae as long as ocellar setae pair III. Pronotum closely striate, usually with 1 pair of anteromarginal setae, 10­12 discal setae; 4 pairs of posteromarginal setae, S 2 30 – 35 microns, clearly longer than S1. Metanotal sculpture variable, usually transversely arcuate anteriorly, with irregular longitudinal reticulations or striations posteriorly; median pair of setae far behind anterior margin. Forewing scale with 4 marginal setae; second vein with 2 setae; posteromarginal fringe cilia all straight. Tergites III­V with bases of median setae usually closer together than length of these setae; tergal microtrichial fields with 3 discal setae; VIII with discal microtrichia present anteromedially, posteromarginal comb complete; tergite IX with discal microtrichia present posteromedially. Sternites with microtrichia extending across median area on posterior half; median setae on sternite VII arising slightly in front of posterior margin.

Male macroptera. Similar to female in colour and sculpture, but smaller; aedeagus apparently with no armature.