Caliothrips impurus (Priesner, 1927)

Panchaetothripinae, Thripidae, Terebrantia, Thysanoptera

Figures

Fig. 1: 8-segmented antenna, segments III and IV with forked sense cone, terminal segments V-VIII
Fig. 2: Head dorsal with ocellar triangle
Fig. 3: Pronotum
Fig. 4: Meso- and metanotum
Fig. 5: Meso- and metasternum with lyre-shaped furca
Fig. 6: Fore- and hind wing, fore wing distal region
Fig. 7: Tergites IV-VI
Fig. 8: Tergite V, lateral region
Fig. 9: Tergite VIII
Fig. 10: Tergites IX and X

Caliothrips impurus causes damage in a range of crops, including seedling cotton, groundnut, and onion. Female macropterous; body dark brown; all tarsi and bases and apices of tibiae yellow; antennal segments dark brown, III-V yellow with apical half light brown (Fig. 1); fore wings brown, largely dark with small patches sub-basally and sub-apically, with extreme apex dark (Fig. 6). Antennae 8-segmented; segments III & IV with long forked sensorium (Fig. 1). Head not constricted at base (Fig. 2). Pronotum without long setae, with irregular longitudinal reticles and many markings within each reticle (Fig. 3). Metanotum irregularly reticulate, one pair of major setae near anterior margin (Fig. 4); metafurca elongate and lyre-shaped (Fig. 5), mid and hind tarsi elongate but 1-segmented. Fore wing first vein close to or fused to costal vein; fore wing second vein with about 5 setae; costal cilia shorter than costal setae (Fig. 6). Lateral sculpture on tergites broader polygonally reticulate and with markings in between (Fig. 7 and 8); tergite VIII with craspedum medially, tooth-like microtrichia laterally (Fig. 9); median split on X about half as long as tergite.
Male tergite IX with 3 pairs of stout setae medially; sternites III-VII with long, narrow transverse glandular areas.

The genus Caliothrips Daniel, 1904
The genus Caliothrips currently includes more than 20 species. Members of this genus are dark brown, head and pronotum with a heavy net-like sculpture and with internal markings inside each reticle. Head without neck and dorsal ridge. Fore wings banded (usually dark with pale areas) and antennae with 8 segments, and forked sense cone on antennal segments III & IV. Most of the species in this group are found living in grasses and legumes (Mound & Kibby 1998).

Caliothrips impurus is similar to Caliothrips fasciatus, both with tergites sculptured on lateral thirds comprising mainly polygonal reticulations and numerous internal wrinkles. Caliothrips impurus has a broader polygonally reticulate sculpture, whereas Caliothrips fasciatus has mainly angular oblique reticulations. Tergites of other Caliothrips species (Caliothrips graminicola, Caliothrips phaseoli and Caliothrips sudanensis) shows a transverse striation with or without internal markings on lateral thirds. Compared to Caliothrips sudanensis with pale extreme apex on fore wings, other species have a dark extreme apex. Caliothrips fasciatus is the only species with sculptured pronotum with mainly equiangular reticulations (other species with irregular longitudinal reticulations). In Caliothrips fasciatus and Caliothrips graminicola the forked sense cone on antennal segment IV scarcely extends beyond base of segment V, whereas in Caliothrips impurus, Caliothrips phaseoli and Caliothrips sudanensis the forked sense cone on antennal segment IV extends to a point at least a third to base of segment V.
Members of Caliothrips can be recognised by their reticulate sculpture that bears internal markings. Only Retithrips syriacus has also complex markings within each of the reticles, and fore wings bearing anteromarginally 3 curious blister-like callosities and minute setae. Compared to the closely related genera Hercinothrips and Selenothrips, the head of Caliothrips species is not constricted into a neck. Hercinothrips has 2-segmented tarsi (Caliothrips and Selenothrips with 1-segmented tarsi) and in Selenothrips the hind margin of tergite VIII has a complete comb of long teeth, the pronotum has a transverse striate sculpture and the metanotum a dominant sculptured triangle medially (in Caliothrips and Hercinothrips tergite VIII posteromarginal comb of microtrichia is only present laterally, pronotum with reticulate sculpture, and metanotum without dominant sculptured triangle medially).

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.

Host plants
Crops: alfalfa, beans (garden beans, hyacinth bean, Egyptian pea), berseem (Trifolium alexandrinum), cotton, groundnut, onion.

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

Damage and symptoms
-

Detection and control strategies
-

Biogeography

Africa. Egypt, Eritrea, Gambia (Yandum, Sapu), Kenya (Nyanza and Rift Valley provinces), Niger (Diadia, Madaoua), Nigeria (Lagos, Raba - Niger Province; Ibadan), Senegal (Fété Olé), Sudan (Khartoum, Mitaleib, Medani, Hag Abdalla, White and Blue Nile Province, Kassala Province, Fung Province), Zimbabwe (Nyanyadzi Irrigation Scheme - 25 miles north of Birchenough Bridge, Chipinga).

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