Bregmatothrips dimorphus (Priesner, 1919)

Thripinae, Thripidae, Terebrantia, Thysanoptera

Figures

Fig. 1: 8-segmented antenna, segments II-IV, terminal segments VI-VIII
Fig. 2: Head dorsal with ocellar triangle
Fig. 3: Pronotum
Fig. 4: Meso- and metanotum
Fig. 5: Meso- and metanotum craniale et caudale
Fig. 6: Fore wing, distal area of fore wing
Fig. 7: Fore wing, basal area with clavus
Fig. 8: Sternite VII
Fig. 9: Tergites VIII and IX

Bregmatothrips dimorphus is a grass feeding thrips. Female macropterous or micropterous; body color dark brown, with tarsi, apices of tibiae, and antennal segments III-V yellow; fore wings pale or very weakly shaded. Antennae 8-segmented; sense cone on segments III & IV simple (Fig. 1). Head longer than wide, projecting in front of eyes; 3 pairs of ocellar setae present, pair III anterolateral to ocellar triangle (Fig. 2). Pronotum with 2 pairs of elongate posteroangular setae (Fig. 3). Meso- and metafurca without spinula. Metanotal median area transverse lines with some irregular fusions; median setae close to anterior margin; campaniform sensilla absent (Fig. 4 and 5). Fore wing first vein with 2 setae on distal half; second vein with a complete row of 8-9 setae (Fig. 6). Mid and hind tarsi 2-segmented (Fig. 7). Tergites with median pair of campaniform sensilla close to posterior margin; continuous craspedum with margin of weakly and rounded lobes present on tergites II-VIII (Fig. 9); tergite X with complete dorsal longitudinal split; abdominal segment 10 shorter than segment 9. Sternites II-VII with 3 pairs of posteromarginal setae, VII with median setal pair arising at posterior margin (Fig. 8).
Male micropterous; wing lobe length shorter than thorax width; body dark brown, with prothorax, pterothorax and abdominal segment 1 yellow; sternites without glandular areas.

The genus Bregmatothrips Hood, 1912
This genus includes 9 species, all of which live on grasses in tropical and subtropical areas (Mound 2011). Species in this genus have the following common characters: head protruding considerably in front of the eyes, the antennae are 8-segmented and with simple sense cone on segments III and IV. The transverse metanotal sculpture with median setae at anterior margin, and the tergal craspedum comprising a series of small lobes, are typical of members of Bregmatothrips (Mound & Marullo 1996). Macropterous forms are dark brown whereas micropterous forms are bicolored brown and yellow (Stannard 1968).

The genus Bregmatothrips is commonly associated with the genera Limothrips and Chirothrips, and similar in general appearance to some other grass living thrips. However, most of the structural similarities are possibly related to sharing a similar habitat in the flowers of grasses. Bregmatothrips dimorphus can be distinguished from species of these genera in having antennal segments II and III more or less symmetric (species of the genus Chirothrips and Arorathrips mostly have antennal segment II with external margin strongly prolonged but III symmetric or slightly prolonged; Limothrips with antennal segment II more or less symmetric but III with external margin weakly prolonged), by the broadly rectangular pronotum with 2 pairs of posteroangular setae (Chirothrips and Arorathrips with a trapezoidal pronotum and 2 pairs of posteroangular setae; Limothrips with rectangular pronotum and 1 pair of posteroangular setae), and by the uniformly pale fore wings (other species with light brown fore wings). Limothrips cerealium differs from Bregmatothrips, Chirothrips and Arorathrips in having a pair of stout thorn-like setae on tergite X (in other species setae on tergite X are slender), no craspedum at posterior margin of tergites or sternites, but discal setae on sternites II-VII (other species with a craspedum at posterior margin of tergites and/or sternites, but without discal setae on sternites II-VII).

Life history
As with other thrips species the life cycle from egg to adult is dependent on temperature. The full cycle can take about 15 days (Lewis 1973) to over a month and adults may live for more than one month producing several generations in one year depending on seasonal weather.

Host plants
Forage grasses, (Poaceae).

Vector capacity
None identified, but possible mechanical distribution of phytopathogenic fungi and bacteria.

Damage and symptoms
-

Detection and control strategies
-

Biogeography

Mediterranean, Europe (Yugoslavia), Yemen, South Africa. Algeria (Sidi Ferruch, Tipasa), Mozambique, South Africa (Western Cape: Mossel Bay), Sudan.

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