Female macroptera. Body variable from yellow to brown, but widespread pest strain usually mainly dark yellow with brown areas medially on each tergite; antennal segments II & VI–VIII brown, III–V yellow with apices variably brown; legs mainly yellow washed with brown; fore wings pale with dark setae. Antennae 8-segmented, III–IV with forked sensorium, VIII longer than VII. Head wider than long; 3 pairs of ocellar setae present, pair III longer than distance between external margins of hind ocelli, arising on anterior margins of ocellar triangle; postocular setae pair I present, pair IV longer than distance between hind ocelli. Pronotum with 5 pairs of major setae; anteromarginal setae slightly shorter than anteroangulars, one pair of minor setae present medially between posteromarginal submedian setae. Metanotum with 2 pairs of setae at anterior margin, campaniform sensilla present. Fore wing with 2 complete rows of veinal setae. Tergites V–VIII with paired lateral ctenidia, ctenidia sometimes weakly developed on IV, on VIII anterolateral to spiracle; posteromarginal comb on VIII complete, with short slender microtrichia arising from triangular bases. Sternites III–VII without discal setae.
Male macroptera. Similar to female but smaller and paler; tergite VIII without marginal comb; IX with median pair of dorsal setae shorter than lateral pair, posterolateral setae stout in larger males; sternites III–VII with transverse pore plate.
Frankliniella species all have a pair of setae in front of the first ocellus, a complete row of setae on both veins of the forewing, and a pair of ctenidia on tergite VIII situated anterolateral to the spiracles. Most of the 180 described species are known only from the neotropics, but F. schultzei, F. occidentalis and F. williamsi have been widely introduced around the world (Kirk & Terry, 2003). F. occidentalis can usually be recognised by the pale forewings, long postocular setae, presence of metanotal campaniform sensilla, and the rather irregular comb on tergite VIII. However, this species is variable in size and colour, the dark brown form being more common at low temperatures, and the pale yellow form at higher temperatures, but the widespread pest strain is usually more constant in size and colour. Molecular studies have indicated that western flower thrips comprises two species that cannot be distinguished morphologically (Rugman-Jones et al., 2010).
Originally western USA, but now worldwide in temperate areas.
Locally abundant on cultivated plants across Australia.
Breeds and feeds on leaves and within flowers. Causes feeding damage on developing fruits.
This is a highly polyphagous pest, that is also an important vector of tospoviruses on many crops. However, it also feeds on leaf mites of which it can be a useful biocontrol agent.
Frankliniella occidentalis (Pergande)
Kirk, WDJ & Terry I. 2003. The spread of western flower thrips Frankliniella occidentalis Pergande. Agricultural and Forest Entomology 5: 301-310.
Hoddle MS, Mound LA & Paris D. 2008. Thrips of California. CD-Rom published by CBIT, Brisbane.