Sericothrips sativus Hartwig, 1952

Sericothripinae, Thripidae, Terebrantia, Thysanoptera

Figures

Fig. 1: 8-segmented antenna, terminal segments V-VIII, segments III and IV with forked sense cone
Fig. 2: Head and pronotum
Fig. 3: Head dorsal with ocellar triangle
Fig. 4: Pronotum
Fig. 5: Meso- and metanotum
Fig. 6: Meso- and metasternal furca
Fig. 7: Meso- and metasternum
Fig. 8: Meso- and metanotum with brachypterous wings
Fig. 9: Tergites I-V
Fig. 10: Tergites V-VII
Fig. 11: Tergites VII-XI

Sericothrips sativus causes damage on leaves of forage plants alfalfa and red clover (Fabaceae). Female macropterous or micropterous. Body bicolored; brown with abdominal segments 3-6 yellow, also pronotum with pronotal blotch and posterior of head; fore femora, apices of tibiae and tarsi yellow, also antennal segments I-III; fore wings grey brown with sub-basal pale band. Antennae 8-segmented; segments III & IV with sense cone forked, VI with base of sense cone slightly elongate (Fig. 1). Head wider than long; postocular region with weakly transverse reticulation; ocellar triangle finely reticulate; 3 pairs of ocellar setae, pair III arise on anterior margins of ocellar triangle; 3 pairs of postocular setae, median pair long (Fig. 2 and 3). Pronotum, including pale pronotal blotch, uniformly fine and closely transverse striate; 1 pair of moderately long setae near posterior angles (Fig. 4). Meso- and metafurca with stout median spinula; meso- and metanotum sculpture mainly transverse striate. Metanotum with median setae arise well behind anterior margin or medially; without campaniform sensilla; metasternum with a transverse line along anterior margin; metascutellum with bands of microtrichia medially (Fig. 5). Mid- and hind tarsi 2-segmented. Fore wing first vein distinct from costal vein and with continuous row of setae; second vein without or with 1 seta near apex (Fig. 8). Tergites I-VIII uniformly and densely covered with microtrichia, with complete posteromarginal comb of long and irregular microtrichia, and with median pair of setae similarly placed and of equal size; median setal pair of tergites II-VII shorter than distance between their bases (Fig. 9-11). Sternites without discal setae but fully covered with rows of microtrichia; sternites III-VII with lobed posteromarginal craspedum bearing long microtrichia between the marginal setae; sternite VII posteromarginal setae S1 arising in front of margin. Micropterous female with wing lobe shorter than width of thorax.
Male micropterous; similar to female, but tergite VII yellow.

The genus Sericothrips Haliday, 1836
Sericothrips comprises 9 species, 8 of these holarctic, Sericothrips sativus from South Africa. It is a member of the subfamily Sericothripinae, closely related to the genus Neohydatothrips and Hydatothrips. These thrips all have numerous closely spaced rows of microtrichia on the lateral thirds of the tergites, fore wings with a complete row of setae on the first vein whereas on the second vein there are 0 or only 2 setae. Most of them have a remarkably elongate base to the sense cone on the sixth antennal segment and a distinctive colored and/or sculptured area on the pronotum, the pronotal blotch. Bhatti (1973) has given identification keys to distinguish the various genera involved. All of the species of Sericothrips have the tergites completely covered with microtrichia, also medially, and with a complete posteromarginal comb of long microtrichia, and the metasternum has a transverse line along anterior margin.

Sericothrips sativus is closely related to Hydatothrips adolfifriderici and Neohydatothrips samayunkur. Compared to these both species, Sericothrips sativus has a pale pronotal blotch, and the metanotal median area sculptured lines are transverse striate. In Hydatothrips adolfifriderici the dark pronotal blotch is not emarginate posteriorly, and metanotal median area sculptured lines are transverse at anterior, but forming irregular longitudinal reticulations on posterior half. In Neohydatothrips samayunkur the dark pronotal blotch is deeply emarginate posteriorly, and metanotal median area sculptured lines are also transverse at anterior, but longitudinal and parallel on posterior half. Sericothrips sativus as well as Neohydatothrips samayunkur have the metasternum anterior margin almost transverse, whereas in Hydatothrips adolfifriderici the metasternum has an anterior margin deeply U-shaped with median V-shaped apodem. Furthermore, Sericothrips sativus differs from both related species by the metascutellum covered with bands of microtrichia medially, tergites I-VIII completely covered with microtrichia, and have a complete posteromarginal comb of microtrichia, the tergal median setae are similarly placed and of equal size, and the median setal pair is shorter than distance between their bases. Whereas Hydatothrips adolfifriderici as well as Neohydatothrips samayunkur have no microtrichia on metascutellum, dense microtrichia on tergites I-VIII only on lateral thirds and median area smooth or with sparse microtrichia, tergites I-VI posteromarginal comb of microtrichia is present laterally but incomplete medially, median setae are short on tergites I-IV and longer on V-VIII, median setal pair longer than distance between their bases.

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. With greenhouse temperatures the developmental time from egg to adult can decrease to about one week.

Host plants
Fabaceae: alfalfa, red clover (Trifolium pratense).

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

Damage and symptoms
-

Detection and control strategies
-

Additional notes
Feeding and breeding on leaves.

Biogeography

South Africa (Gauteng: Pretoria; Free State: Glen; Northern Cape: Kimberley, Douglas, Sutherland).

Bhatti JS (1973). A preliminary revision of Sericothrips Haliday, sensu lat., and related genera, with a revised concept of the tribe Sericothripini (Thysanoptera: Thripidae). Oriental Insects. 7 (3): 403-449

Hartwig EK (1952). Taxonomic studies of South African Thysanoptera, including genitalia, statistics and a revision of Trybom's types. Entomology Memoirs. 2 (11): 340-499

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

zur Strassen R (1960). Catalogue of the known species of South African Thysanoptera. Journal of the Entomological Society of Southern Africa. 23 (2): 321-367