Thrips florum Schmutz, 1913

Thripinae, Thripidae, Terebrantia, Thysanoptera

Figures

Fig. 1: 7-segmented antenna, segments III and IV with forked sense cone, segments III-VII
Fig. 2: Head dorsal with ocellar triangle
Fig. 3: Pronotum
Fig. 4: Meso- and metanotum
Fig. 5: Fore wing and fore wing basal region
Fig. 6: Tergites V and VI
Fig. 7: Sternites VI and VII
Fig. 8: Tergites VIII-X

Thrips florum is a strict flower-dwelling species which can attack various crops such as banana, citrus, coffee, mango, and ornamental plants like gladiolus, gardenia and rose. Both sexes fully winged. Body color brown; legs yellowish; antennal segment III yellow; fore wings brown with base paler. Antennae 7-segmented (sometimes with 8 segments); segments III & IV slightly constricted at apex and with short forked sense cone, segment VII short (Fig. 1). Head wider than long; with 2 pairs of ocellar setae, pair I absent, pair III stout and arising just outside anterior margins of ocellar triangle; postocular setae pairs I & III shorter than ocellar setae pair III, pair II minute and much smaller than half length of setae I (Fig. 2). Pronotum with 2 pairs of long posteroangular setae; posterior margin with 3 pairs of setae; anterior margin with 4-5 pairs of setae (Fig. 3). Mesonotum without lines of sculpture around campaniform sensilla near anterior margin; mesofurca with spinula. Metanotum with lines of sculpture transverse at anterior, and longitudinally on posterior half; median setae longer than lateral setae and arising at 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 about 14 closely set setae; clavus with 5 marginal setae and 1 discal seta, clavus subterminal seta longer than the terminal seta (Fig. 5). Tergite II with 4 lateral marginal setae; tergites V-VIII with ctenidia present laterally (Fig. 6), on VIII posteromedial to spiracles; posterior margin of VIII with comb complete medially but microtrichia small and irregular and sometimes arising in groups (Fig. 8); pleurotergites without discal setae. Sternite II with 2 pairs of marginal setae, III-VII with 3 pairs, the median pair on VII arising in front of posterior margin; sternite II with 1-4 discal setae, III-VII with discal setae varying in number from 6-14 in a regular transverse row (Fig. 7).
Male similar to female in structure, but smaller and paler; tergite VIII with no marginal comb; tergite IX with median S1 setae longer than S2 and arising closer to S2 than to each other; sternites III-VII with transverse glandular area anterior to row of about 8 discal setae.

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 florum is very similar to some other Thrips species - like Thrips acaciae, Thrips brevisetosus, Thrips gowdeyi, Thrips hawaiiensis and Thrips simplex. Thrips florum has sternites III-VII with at least 1 pair of discal setae and pleurotergites without discal setae (Thrips australis, Thrips microchaetus, Thrips subnudula and Thrips tenellus, all of them have sternites III-VII with at least 1 pair of discal setae and pleurotergites with discal setae; Thrips orientalis and Thrips parvispinus with discal setae on sternites III-VI but not on sternite VII, and without 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 almost all species have the ocellar setae III on head arising on anterior margin of, or in front of, ocellar triangle, and the fore wing first vein with less than 5, mostly 3, setae on distal half (only Thrips simplex with ocellar setae III arising within ocellar triangle anterior to tangent of anterior margin of hind ocelli, and fore wing first vein with 6-10 setae on distal half). Most of them exhibit campaniform sensilla on metanotum (except for Thrips gowdeyi and Thrips simplex without metanotal campaniform sensilla), and 2 pairs of elongate pronotal posteroangular setae (except for Thrips brevisetosus without elongate pronotal setae). In Thrips florum as well as Thrips hawaiiensis metanotal median setae arise at anterior margin (compared to Thrips acaciae, Thrips brevisetosus, Thrips gowdeyi and Thrips simplex with median setae arise behind anterior margin). Like Thrips hawaiiensis, the species has 7- or 8-segmented antennae (in Thrips acaciae and Thrips brevisetosus antennae are 7-segmented; in Thrips gowdeyi and Thrips simplex antennae are 8-segmented). Compared to Thrips acaciae and Thrips brevisetosus with mainly equiangular reticulation on metanotal median area, in other species the metanotal median area exhibit transverse sculptured lines at anterior, but longitudinal or equiangular reticulations on posterior half (Thrips gowdeyi and Thrips simplex), longitudinal and parallel sculptured lines on posterior half (Thrips florum), or longitudinal and parallel sculptured lines or equiangular reticulations on posterior half (Thrips hawaiiensis). Furthermore, Thrips florum has pleurotergites not covered in microtrichia (in Thrips brevisetosus and Thrips hawaiiensis; in Thrips acaciae, Thrips gowdeyi and Thrips simplex pleurotergites are covered in rows of fine microtrichia, situated on widely spaced lines of reticulation). Thrips florum is very similar to Thrips hawaiiensis, but postocular setae II are minute and much smaller than half length of setae I, the mesonotum has no lines of sculpture close to anterior pair of campaniform sensilla, and in most individuals the terminal seta of fore wing clavus is shorter than subterminal seta. Whereas Thrips hawaiiensis has the postocular setae II about half as long as setae I, a mesonotum with lines of sculpture around the anterior pair of campaniform sensilla, and fore wing clavus with terminal seta longer than subterminal seta.
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 is 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 have 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. Development period from egg to adult female for Thrips florum reared on gardenia flowers ranged from 17 days at 20°C to 11 days at 24°C (Hollingsworth, 2003).

Host plants
Polyphagous.
Crops: banana, citrus, coffee, Gardenia, gladiolus, mango, potato, red gram, rose.
Weeds: Lantana camera.

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

Damage and symptoms
Breeding in flowers of a wide range of plants and causes direct damage by puncturing flowers and fruits. The species causes considerable damage in the bud condition, with the result that the flowers become smaller, the petals shrink and show feeding scars (Ananthakrishnan 1971).

Detection and control strategies
Cavendish group, Plantain group and Monthan are susceptible to thrips attack (Molina et al. 2004). Debudding/deflowering of the male flowers after fruit set and covering fruit bunches with polythene sheets in banana can protect the crop from Thrips hawaiiensis, Thrips florum and Chaetanaphothrips.

Biogeography

Throughout the Oriental and Pacific Regions. Kenya, Nigeria (Ibadan), Sierra Leone, Uganda.

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