Female macroptera. Body dark brown, head and tergites IX–X darkest; antecostal ridges on tergites III–VIII dark across full width of segments, on sternites III–VII shaded full width of segments; fore wings uniformly light brown; antennal segments brown, I and III–VIII paler than head. Head with vertex bearing closely spaced and transversely anastomosing striae, but ocellar region without sculpture lines; bases of ocellar setae pair III arising within ocellar triangle, separated approximately by the length of these setae, arising anterior to tangent between anterior margins of posterior ocelli; two pairs of post-ocular setae. Pronotum with transverse striae closely spaced but irregular; posteromarginal setae S2 variable but no more than 1.5 times as long as S1, S3 subequal to S1. Metanotum transversely reticulate anteriorly, equiangular medially, but longitudinally reticulate on posterior half, median setae posterior to margin. Fore wing scale with 3–5 marginal setae; first vein with 10 –14 setae; second vein 2–4 setae; posteromarginal fringe cilia mainly straight but wavy near base of wing. Tergites III–IV median setae short, distance between bases at least 1.25 times their length; tergal microtrichial fields with 3 discal setae; VIII with no discal microtrichia medially, posteromarginal comb complete; tergite IX with discal microtrichia on posterior half. Sternites III–VI usually with 4 pairs of posteromarginal setae; microtrichial fields reduced to 5 or 6 rows of microtrichia anterolaterally.
Male not known.
The genus Scirtothrips comprises over 100 described species worldwide, with 21 species known from Australia most of which are endemics to this continent. These species all have the lateral thirds of the abdominal tergites covered in closely spaced rows of fine microtrichia, and in many species the sternites also bear similar microtrichia. The antennae are 8-segmented, except inS. casuarinae and S. solus, both forewing veins have an irregular and incomplete setal row, and a median spinula is present on both the meso and metafurca. S, quadriseta is related to S. kirrhos and S. moneres, but has short pronotal posteromarginal setae. Moreover, many of the available specimens are remarkable in having four pairs of posteromarginal setae on the sternites, a character state that otherwise has been seen only in a few individuals of S. tenor.
Known only from Australia.
Presumably feeding and breeding on young phyllodes.
Acacia aneura, A. brachystachia (Mimosaceae).
Scirtothrips quadriseta Hoddle & Mound
Hoddle MS & Mound LA. 2003. The genus Scirtothrips in Australia (Insecta, Thysanoptera, Thripidae). Zootaxa 268: 1-40. http://www.mapress.com/zootaxa/2003f/zt00268.pdf