Thrips nigropilosus Uzel, 1895

Thripinae, Thripidae, Terebrantia, Thysanoptera

Figures

Fig. 1: 7-segmented antenna, pedicel and 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: Pronotum and pterothorax
Fig. 6: Fore wing and fore wing basal region
Fig. 7: Tergites I-III
Fig. 8: Tergites VIII and IX
Fig. 9: Tergites IX-XI

Thrips nigropilosus is a common leaf feeding species and causes damage on chrysanthemum, lettuce, flax, and wheat. Female macropterous or micropterous (with wings shorter than width of thorax). Body color mainly yellow, with black setae and abdominal tergites shaded medially; antennal segments III-VII dark brown, II lighter, I white; fore wings pale with dark setae. Antennae 7-segmented; segments III & IV constricted at apex and with forked sense cone; segment VII slender (Fig. 1). Head wider than long; with 2 pairs of ocellar setae, pair I absent, pair III about as long as side of ocellar triangle and arising lateral to fore ocellus; alternating short and long postocular setae, setae I & III of equal length, setae II minute (Fig. 2). Pronotum with 2 pairs of posteroangular setae; posterior margin with 3 pairs of setae; anterior margin with 4-5 pairs of setae; 3 pairs of discal setae larger than remaining discal setae - 2 near anterior margin and 1 near lateral margins (Fig. 3). Mesofurca with spinula. Metanotum median area with sculptured lines transverse at anterior, but with irregular and large reticulations on posterior half; median setae longer than lateral setae and arising behind anterior margin; campaniform sensilla absent (Fig. 4 and 5). Mid and hind tarsi 2-segmented. Fore wing first vein usually with 1-3 setae on distal half; second vein with a complete row of about 10 setae; clavus with 5 marginal setae, clavus terminal seta longer than subterminal seta (Fig. 6). Tergites with 2 or more transverse lines of sculpture between median pair of setae; tergite II with 3 lateral marginal setae (Fig. 7); II-VIII with median setal pair at least half as long as median length of tergite; tergites VI-VIII (rarely V) with ctenidia present laterally, on VIII posteromedial to spiracles; posterior margin of VIII with complete comb of long and slender microtrichia (Fig. 8 and 9); 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 margin; sternites without discal setae.
Male micropterous; similar to female but smaller; tergite VIII comb with long microtrichia medially; sternites III-VII with a 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 nigropilosus is very similar to some other Thrips species - like Thrips palmi, Thrips pusillus and Thrips tabaci. Thrips nigropilosus has sternites and pleurotergites without 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 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 is the only species inside the afore-mentioned group and one of few members of the genus Thrips that produce short-winged adults. Furthermore, this species has alternating short and long postocular setae on head (absent in other three species), the median setae of tergites II-VIII are unusually long and at least half as long as median length of tergite (other three species with median setal pair no more than 0.3 as long as median tergite length), and tergites with two or more transverse lines of sculpture extending medially across the tergites (other species with one or without sculptured lines between median pair of setae). Inside this group most of the species have no campaniform sensilla on metanotum (except for Thrips palmi with campaniform sensilla), metanotal median setae that are longer than lateral setae (except for Thrips tabaci with shorter median setae), 1-3 distal setae on fore wing first vein (only Thrips tabaci with 2-6, usually 4, distal setae), 3 lateral marginal setae on tergite II (only Thrips palmi with 4 setae), and pleurotergites without many rows of fine microtrichia (present in Thrips tabaci). Thrips nigropilosus as well as Thrips tabaci have the metanotal median area sculptured lines transverse at anterior, but forming equiangular or irregular longitudinal and large reticulations on posterior half (in Thrips palmi and Thrips pusillus sculptured lines transverse at anterior, but longitudinal and mostly parallel on posterior half).
Species of the 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 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 approximately two months 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. The adult longevity ranged from 1 - 21 days depending on temperature and the ratio of male to female was 2:11 (Anyango 1992).

Host plants
Polyphagous.
Crops: aubergine, chrysanthemum, cucurbit, flax, lettuce, pyrethrum, onion, tomato, wheat, and various Asteraceae.

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

Damage and symptoms
Breeding on young leaves as well as in flowers. The species attacks flower and developing floral buds of pyrethrum causing shrinkage, distortion and/or death, leaves silvered and have necrotic dry patches (Bullock 1963; Smith & Hanson 1991).

Detection and control strategies
-

Additional notes
Males are always short winged, but females are more commonly long winged under long day lengths and short winged under short day lengths (Nakao 1993). At high population densities, short-winged females predominate and are smaller than long-winged females (Nakao 1995). The species is known to undergo reproductive diapauses and brachepterous forms of females are induced due to short day length and moderate or low temperature conditions. Significant inter-population variation exisits for induction of brachepterous forms with photoperiod (Nakao 2011).

Biogeography

Widespread around the world, particularly in temperate areas: Africa, Asia, Australia, New Zealand, Europe, North America. Egypt (Dokki), Kenya, Tanzania.

Anyango JJ (1992). The life-history of chrysanthemum thrips, Thrips nigropilosus Uzel (Thripidae, Thysanoptera) and an evaluation of the effects of temperature on its life-cycle. Insect Science and its Application. 13 (1): 41-44

Beach AM (1896). Contribution to a knowledge of the Thripidae of Iowa. Proceedings of the Iowa Academy of Sciences. 3: 214-227

Braman SK & Beshear RJ (1994). Seasonality of predaceous plant bugs (Heteroptera, Miridae) and phytophagous thrips (Thysanoptera, Thripidae) as influenced by host-plant phenology of native Azaleas (Ericales, Ericaceae). Environmental Entomology. 23 (3): 712-718

Bullock JA (1963). Thysanoptera associated with pyrethrum, and the control of Thrips tabaci Lind. Tropical Agriculture. 40: 329-335

Bullock JA (1965). The assessment of populations of Thrips nigropilosus Uzel on pyrethrum. Annals of Applied Biology. 55 (1): 1-12

Lewis T (1973). Thrips: their biology, ecology and economic importance. Academic Press Inc., London Ltd., 349 pp

Lewis T (1997). Thrips as crop pests. CAB International, Wallingford, 740 pp

Moritz G (2006). Thripse. Pflanzensaftsaugende Insekten, Bd. 1, (1. Auflage). Westarp, Hohenwarsleben, 384 pp. ISBN-13: 978 3 89432 891 7

Moritz G, Morris DC & Mound LA (2001). ThripsID - Pest thrips of the world. ACIAR and CSIRO Publishing Collingwood, Victoria, Australia, CDROM ISBN 1 86320 296 X

Moritz G, Mound LA, Morris DC & Goldarazena A (2004). Pest thrips of the world - an identification and information system using molecular and microscopical methods. Centre for Biological Information Technology, University of Queensland, Australia, CDROM ISBN 1 86499 781 8

Moritz G, O'Donnell C & Parrella M (2009). Pest thrips of North America. Centre for Biological Information Technology, University of Queensland, Australia, CDROM ISBN-13: 978 1 86499 940 2

Mound LA (2005). Thysanoptera: Diversity and interactions. Annual Review of Entomology. 50: 247-269

Mound LA (2010). Species of the genus Thrips (Thysanoptera, Thripidae) from the Afro-tropical Region. Zootaxa. 2423: 1-24

Mound LA & Kibby G (1998). Thysanoptera: An identification guide, (2nd edition). CAB International, Wallingford and New York, 70 pp

Mound LA & Masumoto M (2005). The genus Thrips (Thysanoptera, Thripidae) in Australia, New Caledonia and New Zealand. Zootaxa. 1020: 1-64

Mound LA, Morison GD, Pitkin BR & Palmer JM (1976). Thysanoptera. Handbooks for the identification of British insects, Vol. 1, Part 11. Royal Entomological Society of London, London, 79 pp

Nakahara S (1994). The genus Thrips Linnaeus (Thysanoptera: Thripidae) of the New World. Technical Bulletin, USDA, Agricultural Research Service. 1822: 1-183

Nakao S (1993). Effects of temperature and photoperiod on wing form determination and reproduction of Thrips nigropilosus Uzel (Thysanoptera, Thripidae). Applied Entomology and Zoology. 28 (4): 463-472

Nakao S (1994). Effects of food type on wing form determination and development in female Thrips nigropilosus Uzel (Thysanoptera, Thripidae). Applied Entomology and Zoology. 29 (2): 273-278

Nakao S (1994). Photothermal control of wing form and reproductive diapause in female Thrips nigropilosus Uzel (Thysanoptera, Thripidae). Japanese Journal of Applied Entomology and Zoology. 38 (3): 183-189

Nakao S (1995). Effect of high-density rearing on the incidence of brachypterae in female Thrips nigropilosus Uzel (Thysanoptera, Thripidae). Applied Entomology and Zoology. 30 (1): 249-251

Nakao S (1997). Overwintering and seasonal changes in wing form composition of Thrips nigropilosus Uzel (Thysanoptera: Thripidae) in Kyoto, Japan. Applied Entomology and Zoology. 32 (1): 49-55

Nakao S (2011). Geographical variation of photoperiodic wing form determination and genetic background of reproductive diapause in arrhenotokous populations of Thrips nigropilosus Uzel (Thysanoptera: Thripidae) in Japan. Applied Entomology and Zoology 46 (1): 111-116

Nakao S & Yabu S (1998). Ethological and chemical discrimination between thelytokous and arrhenotokous Thrips nigropilosus Uzel, with discussion of taxonomy. Japanese Journal of Applied Entomology and Zoology. 42 (2): 77-83

Nickle DA (2006). A review of the species of Thrips Linnaeus, 1758 (Thysanoptera: Thripidae) from Africa, Europe, and the Mediterranean region. Proceedings of the Entomological Society of Washington. 108 (2): 443-466

Nickle DA (2008). Commonly intercepted thrips at U.S. ports-of-entry from Africa, Europe, and the Mediterranean. III. The genus Thrips Linnaeus, 1758 (Thysanoptera: Thripidae). Proceedings of the Entomological Society of Washington. 110 (1): 165-185

Palmer JM (1990). Identification of the common thrips of Tropical Africa (Thysanoptera, Insecta). Tropical Pest Management. 36 (1): 27-49

Palmer JM (1992). Thrips (Thysanoptera) from Pakistan to the Pacific: a review. Bulletin of the British Museum (Natural History), Entomology. 61 (1): 1-76

Palmer JM, Mound LA & du Heaume GJ (1989). 2. Thysanoptera, 73 pp. In Betts CR [ed.], CIE Guides to insects of importance to man. CAB International, Wallingford, Oxon, UK

Priesner H (1920). Beitrag zur Kenntnis der Thysanopteren Oberösterreichs. Jahresbericht des Museum Francisco-Carolinum. 78: 50-63

Priesner H (1922). Neue Rasenthripse aus Oesterreich. Konowia. 1: 87-96

Priesner H (1938). Contributions towards a knowledge of the Thysanoptera of Egypt, XI. Bulletin de la Société Royale Entomologique ďEgypte. 21: 208-222

Smith LM & Hanson PM (1991). Yield reduction in pyrethrum caused by Thrips nigropilosus Uzel (Thysanoptera, Thripidae). Tropical Agriculture. 68: 235-238

Stannard LJ (1968) The thrips, or Thysanoptera, of Illinois. Illinois Natural History Survey Bulletin. 29 (4): 214-552

Uzel H (1895). Monographie der Ordnung Thysanoptera. Uzel, Königrätz, 473 pp

Walker KM & Michaux B (1989). The chrysanthemum thrips, Thrips nigropilosus UZEL (Terebrantia: Thysanoptera), on Scoth thistle, Cirsium vulgare (Savis) Ten. (Compositae: Cynarea) in New Zealand. New Zealand Entomologist. 12 (1): 17-19

zur Strassen R (1996). Neue Daten zur Systematik und Verbreitung einiger west-paläarktischer Terebrantia-Arten (Thysanoptera). Entomologische Nachrichten und Berichte. 40 (2): 111-118