Thrips knoxi (Girault)

Mound, Laurence A. & Masumoto, Masami, 2005, The genus Thrips (Thysanoptera, Thripidae) in Australia, New Caledonia and New Zealand, Zootaxa 1020 (1), pp. 1-64 : 32

Thrips knoxi (Girault)

Idolimothrips knoxi Girault, 1927c: 2

Diagnosis: Female with body brown to light brown, legs yellow with light brown shadings; antennal segments I–III brownish yellow, IV–VIII brown; forewings pale at base then brown but paler medially then again a little darker at apex. Antennae 8 (or 7) ­segmented; VI usually with base of major sensorium exceptionally broad ( Fig. 45 ). Head slightly longer than wide; ocellar setae III arise just within or just outside ocellar triangle ( Fig. 44 ). Pronotum with transverse markings sometimes scarcely visible, discal setae varying in number from 10–24, external postero­angular setae scarcely 0.4 as long as inner pair ( Fig. 44 ). Metanotum longitudinally striate medially ( Fig. 47 ), median setae at anterior margin, campaniform sensilla absent. Forewing first vein with setal row complete with about 18 setae. Abdominal tergite II with 4 lateral margin setae; tergites with no sculpture medially; chaetotaxy of tergites VI–VII typical of Thrips , but VIII with ctenidia terminating anterior to setae S3 (Fig. 48), posteromarginal comb almost complete but irregular medially. Sternites and pleurotergites with no discal setae; sternite III usually with circular or transverse glandular area ( Fig. 46 ).

Male yellow, sternites III–VII with small circular glandular area.

Comments: There is considerable structural variation, both within and between samples in several characters. Most specimens have 8­segmented antennae, but several individuals have been studied with one or both antennae having only seven segments. The ocellar setae vary in position, from just inside the triangle to clearly outside. The metanotal striation seems to be related to body size, with the smallest individuals having the striae wider apart and irregular, and the largest individuals having the striae closely spaced. The glandular area on the third sternite of females varies from almost circular to more than five times as wide as long. None of this variation has been found to correlate with the different species of Lomandra from which samples have been taken, and the variants are thus treated here as conspecific. One series from Lomandra fibrata at Adelaide has the external pair of pronotal postero­angular setae more than 0.5 as long as the inner pair.

Breeding: This species occurs in large numbers in the inflorescences of several species of Lomandra in early summer, and it appears to be univoltine.

Distribution: An Australian endemic, this species has been taken at various sites in coastal forests between Adelaide and Brisbane.

Relationships: The ctenidia on abdominal tergite VIII terminate anterior to setae S3, close to the spiracle, and this species is therefore considered to be a member of the T. seti­ collis group of endemic Australian species. T. knoxi , however, is particularly unusual in two other character states: the sixth antennal segment usually (but not always) bears an enlarged “ Odontothrips ­like” sensorium, and the third abdominal sternite of females bears a glandular area of variable size.

Figures

FIGURES 38–47. Thrips species. T. imaginis 38–41: (38) Head & pronotum; (39) Sternites VI–VII; (40) Pleurotergites IV–VI; (41) Meso­metanota. T.safrus (42) Pleurotergites IV–VI. T. insignis (43) Meso­metanota. T. knoxi 44–48: (44) Head & pronotum; (45) antennal segments IV–VIII; (46) Sternites III–IV; (47) Meso­metanota; (48) tergites VII–VIII.