Thrips microchaetus Karny, 1920

Thripinae, Thripidae, Terebrantia, Thysanoptera

Figures

Fig. 1: 7-segmented antenna, segments III and IV with forked sense cone, terminal segments VI and VII
Fig. 2: Head dorsal with ocellar triangle
Fig. 3: Pronotum
Fig. 4: Meso- and metanotum
Fig. 5: Fore wing and fore wing distal region
Fig. 6: Pleurotergites II and III
Fig. 7: Tergites VIII and IX
Fig. 8: Tergites IX and XI
Fig. 9: Tergites VIII-XI (male)

Thrips microchaetus is a polyphagous flower thrips and sometimes associated with damage to roses. Both sexes fully winged. Body and legs yellow; antennal segments III-V (or IV & V) with apex brown, VI & VII brown; fore wings uniformly pale. Antennae 7-segmented; segments III & IV slightly constricted at apex with short forked sense cone (Fig. 1). Head as wide as long; with 2 pairs of ocellar setae, pair I absent, pair III arising outside ocellar triangle and lateral to fore ocellus (Fig. 2). Pronotum with transverse lines of sculpture and about 40 discal setae; with 2 pairs of long posteroangular setae; posterior margin with 3-4 pairs of setae; anterior margin with 3-5 pairs of setae (Fig. 3). Mesofurca with spinula. Metanotum with transverse lines at anterior, almost longitudinally striate on posterior half; median setae longer than lateral setae and arising behind anterior margin; campaniform sensilla present (Fig. 4). Mid and hind tarsi 2-segmented. Fore wing first vein with 3 setae on distal half; second vein with a complete row of 15-19 setae; clavus with 5 marginal setae, clavus terminal seta longer than subterminal seta (Fig. 5). Tergite II with 4 lateral marginal setae (Fig. 6); V-VIII with ctenidia present laterally, on VIII posteromedial to spiracles; posterior margin of VIII with complete comb of microtrichia that are small and irregular in length (Fig. 7 and 8); pleurotergites with 6-9 discal setae. Sternite II with 2 pairs of marginal setae, III-VII with 3 pairs, median marginal setae on VII arising in front of posterior margin; sternite II with about 5 discal setae, III-VII with 30 or more discal setae arranged irregularly.
Male similar to female in structure, but smaller, tergite IX with 4 stout setae (Fig. 9).

The genus Thrips L., 1758
There are nearly 300 species currently recognized in the genus Thrips making this genus one of the largest taxa within the order Thysanoptera. The genus was redefined progressively during the 1970's (see Mound et al. 1976), to include many species previously placed in Taeniothrips. The genus Thrips now includes a range of species, some with the antennae 7-segmented, others 8-segmented, and a few with the number of segments varying between 7 and 8. Similarly, some species have few setae on the fore wing first vein, whereas others have a complete row of setae on this vein. The species with a complete setal row on the first vein were placed from some taxonomists in the genera Isothrips or Isoneurothrips. However, all of the species in Thrips have the following character states: antennal segments III & IV with forked sense cone, absence of ocellar setae I, pronotum with 2 pairs of elongate posteroangular setae, paired ctenidia laterally on the tergites V-VIII, tergite VIII ctenidium arising posterior to the spiracle (in contrast to species of the genus Frankliniella). Other character states, such as number of antennal segments, number of setae on the fore wing veins, and number of discal setae on the abdominal sternites are variable between species (Mound & Masumoto 2005; Nakahara 1994; Palmer 1992). Identification keys are available for the species of this genus from many parts of the world. Of particular importance is the published key by Mound (2010) for members of the genus Thrips from Afro-tropical region as well as previous Lucid keys from Moritz et al. (2001, 2004, 2009).

Thrips microchaetus is very similar to some other Thrips species- like Thrips australis, Thrips subnudula and Thrips tenellus. Thrips microchaetus has sternites III-VII with at least 1 pair of discal setae and pleurotergites with discal setae (Thrips acaciae, Thrips brevisetosus, Thrips florum, Thrips gowdeyi, Thrips hawaiiensis and Thrips simplex, all of them have sternites III-VII with at least 1 pair of discal setae and pleurotergites without discal setae; Thrips orientalis and Thrips parvispinus, both have discal setae on sternites III-VI but not on sternite VII, and no discal setae on pleurotergites; Thrips nigropilosus, Thrips palmi, Thrips pusillus and Thrips tabaci, all of them have sternites and pleurotergites without discal setae).
Inside this group most of the species possess campaniform sensilla on metanotum (in Thrips tenellus absent), a fore wing first vein with a wide gap before distal group of setae (only Thrips australis with an almost complete setal row on fore wing first vein), pleurotergites without many rows of fine microtrichia (only in Thrips subnudula present), and sternites III-VI with 3 pairs of posteromarginal setae (except for Thrips subnudula with 5-7 pairs of posteromarginal setae). Thrips microchaetus as well as Thrips tenellus have ocellar setae III arising outside ocellar triangle and lateral to fore ocellus (in Thrips australis ocellar setae III arising on or just within anterior margins of ocellar trinagle; in Thrips subnudula ocellar setae III arising close together behind first ocellus within the triangle), the metanotal median area sculptured lines are transverse at anterior, but longitudinal and parallel on posterior half (in Thrips australis median area with mainly equiangular reticulation; Thrips subnudula with sculptured lines transverse at anterior, but forming equiangular or irregular longitudinal reticulations on posterior half), and both have a complete posteromarginal comb of microtrichia on tergite VIII (compared to Thrips australis and Thrips subnudula with tergite VIII posteromarginal comb absent medially). In structure, Thrips microchaetus is particularly similar to Thrips tenellus, but it lacks the dark median tergal markings and the dark tergal antecostal ridges of that species, the species has campaniform sensilla on metanotum, and the pleurotergites have 6 or more discal setae. Whereas Thrips tenellus has a brown median area and dark antecostal ridges on tergites II-VII, no campaniform sensilla on metanotum, and pleurotergites with only 3-5 discal setae.
Species of the genus Thrips are similar to species of Stenchaetothrips, Microcephalothrips abdominalis, Larothrips dentipes and Fulmekiola serrata because of tergites V-VIII bear a pair of ctenidia laterally, which placed on tergite VIII posteromedial to the spiracle, and all species have no ocellar setae I. In contrast to species with craspedum on tergites II-VII (Microcephalothrips abdominalis, Larothrips dentipes and Fulmekiola serrata), species of Thrips and Stenchaetothrips have no posteromarginal craspedum on tergites and sternites. Species of the genus Thrips as well as Fulmekiola serrata and species of Stenchaetothrips possess 2 pairs of elongate posteroangular setae (Microcephalothrips abdominalis with 2 pairs of moderately elongate pronotal setae and Larothrips dentipes without elongate setae). Compared to the species of Thrips, Microcephalothrips abdominalis, and Larothrips dentipes, which have ocellar setae II on head much shorter than or about as long as III, Fulmekiola serrata and species of Stenchaetothrips have ocellar setae II much longer than III, and sternites always without discal setae.

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. Adults may live for more than one month producing several generations in one year depending on seasons. With greenhouse temperatures the developmental time from egg to adult can decrease to about one week.

Host plants
On flowers of Lantana camara, Melia azadirach and rose.

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

Damage and symptoms
-

Detection and control strategies
-

Additional notes
-

Biogeography

Saharan, Arabia. Egypt, Kenya, Morocco, Sudan.

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