Hercinothrips femoralis (Reuter, 1891)

Panchaetothripinae, Thripidae, Terebrantia, Thysanoptera

Figures

Fig. 1: 8-segmented antenna, terminal segments V-VIII
Fig. 2: Head dorsal with ocellar triangle
Fig. 3: Pronotum
Fig. 4: Meso- and metanotum
Fig. 5: Meso- and metasternum
Fig. 6: Fore wing and fore wing distal region
Fig. 7: Sternite VII
Fig. 8: Tergites V and VI
Fig. 9: Tergite VIII
Fig. 10: Adult thrips feeding on a bean leaf (Phaseolus vulgaris)

Hercinothrips femoralis is a highly polyphagous leaf-feeding thrips which has been recorded as a pest on various crops including sugar beet, groundnut, and many glasshouse ornamentals. Both sexes fully winged. Body brown; head yellowish brown sub-medially, also abdominal segments 8-10; tarsi and tibiae yellow, also antennal segments I & III-V; antennal segments VI-VIII dark brown; fore wings largely dark brown, pale at apex and sub-basally, and with a submedian pale area which varies from small patch to a clear band, but always no longer than the pale apex of wing (Fig. 10). Antennae 8-segmented; segments III & IV with sense cone forked and short, scarcely extending beyond apex of segment, VIII more than twice as long as VII (Fig. 1). Head finely reticulate, cheeks slightly convex, sharply constricted to basal neck (Fig. 2). Pronotum finely reticulate; with several pairs of moderately long discal setae (Fig. 3). Mesonotum not divided medially. Metanotum without defined reticulate triangular area medially, median setae long (Fig. 4); metafurca elongate and Y-shaped (Fig. 5). Mid and hind tarsi 2-segmented. 1 pair of campaniform sensilla present. Fore wing first vein close or fused to costal vein; fore wing with complete row of setae on both longitudinal veins; costal cilia longer than setae, posteromarginal cilia wavy (Fig. 6). Tergites finely reticulate; median tergal setae minute; lateral fourth of tergites I-VIII with a posterolateral comb of short wedge-like teeth (Fig. 8); tergite VIII laterally with a posteromarginal comb of short and irregular teeth whose bases are fused (Fig. 9); tergite X not fully divided medially.
Male similar to female; with 3 pairs of spine-like setae and a posterior cluster of small tubercles on tergite IX; sternites III-VII with small transverse linear glandular area.

The genus Hercinothrips Bagnall, 1932
About 10 species recognised in this genus, all originally from Africa, a few are recorded as crop pests and are now widespread around the world. They can be distinguished from each other by differences in the color pattern of the body and the fore wings (Wilson 1975). Unlike the species of most Panchaetothripinae genera, the members of Hercinothrips have 2-segmented tarsi, and both veins of the fore wings bear complete rows of long setae. All of them have 8 antennal segments, antennal segments III and IV with forked sense cone, fore wings banded and with posterior fringe undulated.

Hercinothrips femoralis is similar to Hercinothrips bicinctus which has antennal segments VI-VIII yellow, fore wings with an extensive pale area medially, distinctly longer than the pale apex of wing, a weakly defined reticulate triangular area medially on metanotum. Antennal segments VI-VIII of Hercinothrips femoralis dark brown, fore wings with a short submedian pale area, when present, no longer than the pale apex of wing, and without triangular area medially on metanotum.
Unlike most Panchaetothripinae genera, members of Hercinothrips have 2-segmented tarsi (like in Monilothrips kempi and Panchaetothrips noxius), and complete rows of long setae on both veins of the fore wings (like in Monilothrips kempi and Selenothrips rubrocinctus). Monilothrips kempi differs from species of Hercinothrips in having no reticulate sculpture on head and pronotum except for the collar, no constriction posteriorly on head, no posteromarginal comb of microtrichia on tergite VIII, but having 2 pairs of elongated pronotal setae, and a distinct occipital ridge. Compared to Hercinothrips, Panchaetothrips noxius possesses a distinct occipital ridge, a pronotum without strong sculpture, fore wing first vein setal row is incomplete, the second setal row absent, costal setae on fore wing are about twice as long as wing width, all setae of fore wing are dark, and tergite X is elongate and tubular. In contrast to Hercinothrips, Selenothrips rubrocinctus has a pronotum with transverse striate sculpture, a dominant sculptured triangle medially on metanotum, uniformly dark brown fore wings, costal setae on fore wing which are about twice as long as wing width, and a complete comb of microtrichia on tergite VIII.

Life history
The egg, larva 1, larva 2, prepupa and pupa lasted for 7.5, 3.0, 3.5, 2.1 and 2.7, respectively. The developmental cycle, from oviposition to adult, takes 18.1 - 19.8 days under experimental conditions of 27°C (Laughlin 1971).

Host plants
Ornamentals like calla lily (Zantedeschia aethiopica), chrysanths, figs (Ficus spp.), and crops like banana, cotton, cowpea, cucumber, groundnut, maize, sugar beet, sugar cane, tomato.

Vector capacity
None identified, but possible mechanical distribution of phytopathogenic fungi and bacteria. The lesions caused by bean bacteriosis have been associated with its feeding punctures (Buchanan 1932).

Damage and symptoms
This species is polyphagous feeding primarily on the leaves of a high number of plant species. Sucking of both larvae and adults causes tissue damage and silvering. A smoky-red discoloration of bananas, occasionally leading to skin cracks, has been described as a typical symptom of Hercinothrips femoralis infestation (Lewis 1997).

Detection and control strategies
Hercinothrips femoralis susceptible to most pesticides and hence could be easily controlled with insecticide sprays (Scarpelli & Bosio 1999). However recent efforts are to develop environmentally safe management options. Foliar application of entomopathogenic nematodes, Steinernema feltiae and Heterodera bacteriophora at concentrations of 1000 IJ/ml was effective against both larvae and adults (Trdan et al. 2007).

Biogeography

Widespread in the tropics and subtropics (pantropical), also common in temperate areas in greenhouses. Kenya, Nigeria, Sierra Leone, Tanzania, Uganda.

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