Chirothrips ah Girault, 1929

Thripinae, Thripidae, Terebrantia, Thysanoptera

Figures

Fig. 1: 8-segmented antenna, scape, pedicel and III. segment, segments III and IV with simple sense cone
Fig. 2: Head dorsal with ocellar triangle
Fig. 3: Pronotum
Fig. 4: Meso- and metanotum
Fig. 5: Fore wing and distal region of fore wing
Fig. 6: Tergites IV and V
Fig. 7: Sternites IV and V with glandular pore plates, male
Fig. 8: Tergite VIII
Fig. 9: Tergites IX-XI

Chirothrips ah damages forage grasses. Female macropterous; body, antennae and legs brown, tarsi paler; fore wings light brown and weakly shaded. Antennae 8-segmented; segment II with external margin hook-shaped with a small sensorium at apex, III & IV with stout simple sense cone (Fig. 1). Head small and scarcely prolonged in front of eyes; with 3 pairs of ocellar setae, pair III arise on anterior margins of ocellar triangle (Fig. 2). Pronotum trapezoidal; with 2 pairs of elongate posteroangular setae (Fig. 3). Meso- and metafurca with well-developed lateral flanges, but without median spinula. Metanotum irregularly reticulate; median pair of setae longer than lateral pair and arise at anterior margin; campaniform sensilla present (Fig. 4). 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 (Fig. 5). Tergites with weak lines of sculpture medially (Fig. 6); posterior margin of tergites II-VIII with broadly rounded independent lobes fused at bases into continuous craspedum (Fig. 8 and 9), often weakly developed craspedum; ovipositor moderately developed and bearing rows of teeth. Sternites with 3 pairs of marginal setae, median pair on VII scarcely 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; tergal sculpture stronger; sternites III-VII with large circular glandular area (Fig. 7).

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.

The species can be distinguished from other species of the genus Chirothrips by the very slender and acute, slightly hook-shaped projection of the second antennal segment which bears a small sensorium at its apex, the ocellar setae III on anterior margins of ocellar triangle (other species with ocellar setae III anterolateral to fore ocellus), and median metanotal setae which are distinctly longer than lateral metanotal setae and arising at anterior margin (other species with metanotal median setae shorter than the lateral pair and arising well behind anterior margin except for Chirothrips guillarmodi and Chirothrips meridionalis with metanotal median setae arising at anterior margin). In contrast, 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, in Chirothrips meridionalis it is not strongly produced on outer margin, but drawn out into a sharply pointed angle, and in Chirothrips pretorianus it is asymmetric with prolonged external margin bearing a apical sense area. 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 meridionalis and Chirothrips guillarmodi); other species of the genus Chirothrips have tergites II-VIII discal campaniform sensilla placed in front of the discal setae S1 (Chirothrips frontalis, Chirothrips manicatus, Chirothrips pretorianus), but somewhat farther apart than the setae S1.
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
Grasses (Poaceae), on the weed Deviľs whip, Achyranthes aspera.

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

Australia, Papua New Guinea, Fiji, New Caledonia, Africa. Ethiopia (Ambo), Kenya, South Africa (Gauteng: Pretoria - 4500 ft.; Limpopo: Tshakuma - 35 miles east of Louis Trichardt, Ratomba - 21 miles east of Louis Trichardt 3150 ft., Entabeni Forest Station - 4500 ft., 20 miles north of Pietersburg - 4100 ft., 15 miles north of Mokopane - 4500 ft., 5 miles west of Pienaarsrivier - 3700 ft.; Mpumalanga: 13 miles west of Pilgrim's Rest, 12 miles south of Sabie, Nelspruit - 2350 ft., Malelane - 1200 ft.; Piet Retief - 4170 ft.; North West; KwaZulu-Natal: St. Lucia Estuary, Newcastle - 4000 ft.; Western Cape: Knysna, Gordon's Bay, Fish Hoek, Worcester - 790 ft.), Zimbabwe (9 miles northwest of Mutare, 35 miles north of Melsetter - 4500 ft., 8 miles north of Chipinge, Chirinda Forest - Mount Selinda).

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Girault AA (1929). New pests from Australia VI. Published privately, Brisbane, 4 pp

Hartwig EK (1948). Six new species of South African Thysanoptera, with statistical analysis of measurements. Journal of the Entomological Society of Southern Africa. 11: 83-126

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Jenser G (1989). Data to the Thysanoptera fauna of Ethiopia. Acta Zoologica Academiae Scientiarum Hungaricae. 35 (3-4): 205-210

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

Minaei K & Mound LA (2010). Grass-flower thrips of the genus Chirothrips (Thysanoptera: Thripidae), with a key to species from Iran. Zootaxa. 2411: 33-43

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 & Palmer JM (1972). Grass-flower infesting thrips of the genus Chirothrips Haliday in Australia. Journal of the Australian Entomological Society. 11: 332-339

Nakahara S & Footit RG (2012). Review of Chirothrips and related genera (Thysanoptera: Thripidae) of the Americas, with descriptions of one new genus and four new species. Zootaxa 3251: 1-29

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zur Strassen R (1959). Studies in African Thysanoptera, 3 (With notes on oedimerous males in Terebrantia). Journal of the Entomological Society of Southern Africa. 22 (2): 436-464

zur Strassen R (1960). Key to and catalogue of the known species of Chirothrips Haliday, 1836 (Thysanoptera: Thripidae). Journal of the Entomological Society of Southern Africa. 23 (1): 144-176

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