Chirothrips meridionalis Bagnall, 1927

Thripinae, Thripidae, Terebrantia, Thysanoptera

Figures

Fig. 1: 8-segmented antenna, terminal segments VI-VIII, segment III with simple and IV with forked sense cone
Fig. 2: Head dorsal with ocellar triangle
Fig. 3: Pronotum
Fig. 4: Pronotum
Fig. 5: Meso- and metanotum
Fig. 6: Meso- and metasternum
Fig. 7: Fore and hind wing
Fig. 8: Tergites III-V
Fig. 9: Tergites VII and VIII

Chirothrips meridionalis damages forage grasses and other Poaceae like maize. Female macropterous; body, antennae and legs brown, tarsi paler; fore wings light brown and weakly shaded. Antennae 8-segmented; segment II not strongly produced on outer margin, but drawn out into a sharply pointed angle, sense cone on segment III emergent and simple and on IV forked (Fig. 1). Head slightly prolonged in front of compound eyes; with 3 pairs of ocellar setae, pair III anterolateral to fore ocellus (Fig. 2). Pronotum trapezoidal (Fig. 3 and 4); with 2 pairs of elongate posteroangular setae. Meso- and metafurca with well-developed lateral flanges, but without median spinula (Fig. 6). Metanotum irregularly reticulate; median pair of setae subequal or shorter than lateral pair and arise at anterior margin; campaniform sensilla present (Fig. 5). Mid and hind tarsi 2-segmented; fore tibia not prolonged around fore tarsus. Fore wing pointed at apex; first vein with 2 or 3 setae on distal half; second vein with 5 or 6 setae. Tergites with weak lines of sculpture medially; posterior margin of tergites II-VIII with broadly rounded independent lobes fused at bases into continuous craspedum (Fig. 7 and 8); ovipositor moderately developed and bearing rows of teeth. Sternites with 3 pairs of marginal setae, median pair on VII arise in front of margin; posterior margins of sternites II-VI with craspedum of independent small pointed lobes, also laterally on VII.
Male macropterous and similar to female; sternites III-VII with circular glandular area.

The genus Chirothrips Haliday, 1836
Chirothrips currently includes about 45 to 50 species worldwide. Zur Strassen (1960) provided an identification key and catalogue of this genus for over 50 species, and Bhatti (1990) created six new genera for these species originally placed in the genus Chirothrips, and one of these, Arorathrips, is discussed in comparison to Chirothrips. Chirothrips appears to be a genus of Holarctic species, whereas Arorathrips is from the New World with a typical reduced mesothoracic endofurca. This genus has consistent characters that include small heads, short antennae with 8 segments, antennal segment II mostly expanded laterally (except in this key for Chirothrips guillarmodi), and a trapezoidal pronotum with 2 pairs of long posteroangular setae.

Chirothrips meridionalis can be distinguished from other species of the genus Chirothrips by the simple sense cone on antennal segment III and the forked sense cone on antennal segment IV (Chirothrips guillarmodi with forked sense cone on segments III and IV), and the antennal segment II is not strongly produced on outer margin, but drawn out into a sharply pointed angle. In contrast Chirothrips ah has a very slender and acute, slightly hook-shaped projection of the second antennal segment which bears a small sensorium at its apex, antennal segment II of Chirothrips frontalis and Chirothrips manicatus is asymmetric with prolonged external margin bearing an exactly terminal small seta at tip, in Chirothrips guillarmodi it is symmetric, and in Chirothrips pretorianus it is asymmetric with prolonged external margin bearing a apical sense area. Most of Chirothrips species with ocellar setae III arranged anterolateral to fore ocellus, and metanotal median setae are shorter than the lateral pair and arising behind anterior margin (except for Chirothrips ah with ocellar setae III on anterior margins of ocellar triangle and median metanotal setae which are distinctly longer than lateral metanotal setae and arising at anterior margin; Chirothrips guillarmodi and Chirothrips meridionalis with metanotal median setae arising at anterior margin). Chirothrips ah as well as Chirothrips meridionalis have tergites bearing broadly rounded independent lobes fused at bases into continuous craspedum (compared to Chirothrips guillarmodi with closely approximated but independent elongate lobes; Chirothrips frontalis with complete craspedum of unbroken border or flange; Chirothrips manicatus has a continuous craspedum with margin of weakly and rounded lobes; and Chirothrips pretorianus has a craspedum with independent small, triangular lobes). In Chirothrips ah as well as Chirothrips meridionalis posterior margin of sternites bears a craspedum of independent small pointed lobes (compared to Chirothrips guillarmodi with closely approximated but independent elongate lobes; Chirothrips manicatus with entire margin and a series of distinctive tubercles; Chirothrips pretorianus and Chirothrips frontalis without sternal craspedum). Moreover, the species has tergites II-VIII discal campaniform sensilla situated between the discal setae S1 and S2 or posteriorly (like in Chirothrips ah and Chirothrips guillarmodi); other species of the genus Chirothrips from East Africa have tergites II-VIII discal campaniform sensilla that placed in front of the discal setae S1 but somewhat farther apart than the setae.
Species of the genus Chirothrips are similar to Arorathrips mexicanus, but Arorathrips mexicanus has a greatly reduced mesothoracic furca (furcal pits widely separated), fore tibia prolonged at apex around the external margin of the first fore tarsal segment, and tergites II-V with transverse row of small tubercles along antecostal ridge. Whereas all species of the genus Chirothrips have furcal pits on mesosternum fused in the middle line, fore tibia not prolonged around fore tarsal segment, and the sculpture of antecostal ridge on tergites II-V is more or less elongated. Compared to described species of Chirothrips, Arorathrips mexicanus has the sternite VII median posteromarginal setae arising at margin, whereas in species of Chirothrips these setae arise in front of posterior margin.

Life history
As with other thrips species the life cycle from egg to adult is dependent on temperature. The full cycle can take less than a week to over a month and adults may live for more than one month producing several generations in one year depending on seasonal weather (Lewis 1973).

Host plants
Poaceae: forage grasses, maize.

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

Damage and symptoms
All species in this genus Chirothrips breeding in grass flowers, sometimes their larvae and especially pupae are transported around the world within commercial grass seed.

Detection and control strategies
-

Additional notes
The precise host-plant on which this species breeds is not clear, but like all members of the genus Chirothrips the females lay eggs in the young flowers of certain grasses. Each larva apparently feeds within, and subsequently pupates within a single floret.

Biogeography

South Europe (South France, Italy, Cyprus), Palestine, Yemen, India, North and South Africa, mediterranean. Algeria (Tipasa), Egypt, Morocco (Marrakech), Nigeria (Mokwa), South Africa (Gauteng: Pretoria - 4400 ft., Derdepoort; Limpopo: Ratomba - 21 miles east of Louis Trichardt 3150 ft., Mokopane - 4500 ft., Bela Bela - 4000 ft., Pretoria Salt Pan, Silverton; Mpumalanga: Sabie - Pilgrim's Rest District 4500 ft., Nelspruit - 2350 ft., Komatipoort - Baberton District 1000 ft.; North West).

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