Thrips subnudula (Karny, 1926)

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: Meso- and metanotum
Fig. 6: Fore wing and fore wing distal region
Fig. 7: Pleurotergites II and III
Fig. 8: Sternites VI and VII
Fig. 9: Tergites VI-VIII

Thrips subnudula is a polyphagous flower-dwelling thrips, often on amaranth and mango. Both sexes fully winged. Body and legs yellow; antennal segments III-V brown distally, 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 small and arising close together behind first ocellus within the triangle (Fig. 2). Pronotum with numerous small discal setae; 2 pairs of moderately elongate posteroangular setae; posterior margin with 4-5 pairs of setae; anterior margin with 4-6 pairs of setae (Fig. 3). Mesofurca with spinula. Metanotum with transverse lines at anterior and irregular longitudinal or equiangular reticulations medially on posterior half; median setae small and arising well behind anterior margin; campaniform sensilla present (Fig. 4 and 5). Mid and hind tarsi 2-segmented. Fore wing first vein with 3 setae on distal half; second vein with a complete row of about 15 setae; clavus with 5-7 marginal setae, clavus terminal seta longer than subterminal seta (Fig. 6). Tergite II with 3 lateral marginal setae; V-VIII with ctenidia present laterally, on VIII posteromedial to spiracles; posterior margin of VIII with comb broadly interrupted medially and with a few small microtrichia laterally (Fig. 9); pleurotergites with many rows of fine microtrichia and 4-8 discal setae (Fig. 7). Sternite II with 4 pairs of marginal setae, III-VI with 6-7 pairs, VII with 3-4 pairs of marginal setae; median marginal setae on VII arising at posterior margin (Fig. 8); sternite II with 2-6 discal setae, III-VI with 14-25 discal setae in an irregularly single row, VII with 20-30 discal setae in a double row.
Male similar to female in structure, but smaller; tergite VIII posteromarginal comb complete but irregular, microtrichia indistinct; tergite IX setae S1 and S2 almost equal in length, S2 displaced laterally, S1 much closer to each other than to S2; sternites III-VII each with a narrow, transverse glandular area.

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 and 2009).

Thrips subnudula is very similar to some other Thrips species - like Thrips australis, Thrips microchaetus and Thrips tenellus. Thrips subnudula 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 Thrips subnudula is the only species that has ocellar setae III on head arising close together behind first ocellus within the triangle (in Thrips australis ocellar setae III arising on or just within anterior margins of ocellar trinagle; in Thrips microchaetus and Thrips tenellus ocellar setae III arising outside ocellar triangle and lateral to fore ocellus), many rows of fine microtrichia on pleurotergites (in other three species absent), and sternites III-VI with 5-7 pairs of posteromarginal setae (other three species with 3 pairs of posteromarginal setae). Most of the species have campaniform sensilla on metanotum (in Thrips tenellus absent), and 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). Compared to Thrips subnudula with metanotal median area sculptured lines transverse at anterior, but forming equiangular or irregular longitudinall reticulations on posterior half, Thrips australis has the metanotal sculpture with mainly equiangular reticulation, and in Thrips microchaetus and Thrips tenellus these are transverse at anterior, but longitudinal and parallel on posterior half. In Thrips subnudula as well as Thrips australis tergite VIII posteromarginal comb is absent medially (compared to Thrips microchaetus and Thrips tenellus with complete posteromarginal comb of microtrichia on tergite VIII). The species differs from most other Thrips-species by the number of marginal setae on fore wing clavus, because only three species have more than 5 marginal setae on fore wing clavus: Thrips australis with 6, Thrips subnudula with 5-7, and Thrips acaciae with 5-8 marginal setae. The remaining have always 5 marginal setae on clavus. Outside this group, also Thrips acaciae, Thrips gowdeyi, Thrips simplex and Thrips tabaci have pleurotergites covered in rows of fine microtrichia.
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 on head. 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 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.

Host plants
Polyphagous, often on amaranth, beans (common bean, hyacinth bean, soybean), mango, tamarind.

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

Damage and symptoms
-

Detection and control strategies
-

Biogeography

Pakistan, India, Bali, Philippines, Australia, Africa. Nigeria, Uganda.

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