Stenchaetothrips biformis

Stenchaetothrips biformis (Bagnall)

Female macroptera. Body uniformly brown (Fig. 19); antennal segments I–II dark, II paler at apex, III pale, IV slightly shaded, V–VII dark; all tibiae and tarsi pale, femur slightly shaded near base; fore wing uniformly shaded, clavus strongly shaded (Fig. 22). Head not convex in front; ocellar setal pair II longer than setal pair III; post-ocellar setal pair I variable, either both present or with one or both setae absent, when present longer than pair II and subequal to pair III, these setae usually as long as distance between hind ocelli. Pronotum with about 12 discal setae, median area smooth, posterior margin with a few weak transverse striations; posterior margin with 3–4 pairs of setae (Fig. 17), median pair variably long. Mesonotum without anterior campaniform sensilla. Metanotum with closely spaced striations, campaniform sensilla absent, median setae arising behind anterior margin but varying in position. Meso- and metafurca each without a spinula. Metasternum with about 14 discal setae. Abdominal tergites V–VIII with paired ctenidia; tergites I–VII posterior margin with a few tooth-like microtrichia laterally, VIII posterior margin with a complete comb of long slender microtrichia; submedian setae on VIII not extending beyond posterior margin; IX without anterior pair of campaniform sensilla. Sternites with irregular minute microtrichia on sculpture lines, sometimes with a few marginal microtrichia.

Male macroptera. Similar to female but smaller; sternites III–VII with a transverse pore plate, microtrichia more prominent on sternites and sternal posterior margins (Fig. 20).

Specimens studied. MALAYSIA, Selangor, UKM campus, 6 females, 1 male on grass near damp site, 14.ii.2012 (Ng, Y.F.) (CISUKM; ANIC).

Comments. This species, the rice thrips, is common in the state of Kedah, the primary rice production state in Peninsular Malaysia. It seems to be more abundant during the flowering season of paddy, but is usually considered a pest of seedling rice (Pathak & Khan 1994). Serious crop loss to this pest species has not been recorded in Malaysia. A few specimens, presumably vagrants, were recorded on Capsicum annuum in Peninsular Malaysia by Azidah (2011). Variation in the head chaetotaxy between populations of this species was discussed by Vierbergen (2004) and by Mound (2011).