Chirothrips frontalis Williams, 1914

Thripinae, Thripidae, Terebrantia, Thysanoptera

Figures

Fig. 1: 8-segmented antenna, terminal segments V-VIII, antennal segments III and IV with simple sense cone
Fig. 2: Head dorsal with ocellar triangle
Fig. 3: Pronotum
Fig. 4: Meso- and metanotum, micropterous male
Fig. 5: Meso- and metanotum
Fig. 6: Fore wing, distal region of fore wing
Fig. 7: Sternites VI and VII
Fig. 8: Tergites IV and V
Fig. 9: Tergites VII and VIII, male
Fig. 10: Tergites IX-XI

Chirothrips frontalis damages forage grasses belonging to Poaceae and other forage crops like alfalfa. Female macropterous; body, antennae and legs brown; tarsi paler and antennal segment III distinctly lighter; fore wings light brown and weakly shaded. Antennae 8-segmented; segment II asymmetric with prolonged external margin bearing an exactly terminal small seta at tip, III & IV with stout simple sense cone (Fig. 1). Head small and distinctly prolonged in front of eyes; with 3 pairs of ocellar setae, pair III anterolateral to fore ocellus (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 shorter than lateral pair and arise behind anterior margin; campaniform sensilla present (Fig. 4 and 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 (Fig. 6). Tergites with weak lines of sculpture medially; posterior margins with a complete craspedum of unbroken border or flange; ovipositor moderately developed and bearing rows of teeth (Fig. 8-10). Sternites with 3 pairs of marginal setae, median pair on VII scarcely in front of margin; posterior margins without craspedum (Fig. 7).
Male micropterous (Fig. 4) and bicolored (head and thorax yellow, abdomen blackish brown; antennal segments I-IV yellow, V-VIII gray); small circular glandular area usually present on sternites III-VI, rarely also on VII.

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.

This species can be distinguished from other species of the genus Chirothrips by the distinct prolongation of the head in front of the eyes that is longer than in any other species of Chirothrips from East Africa. Chirothrips manicatus as well as Chirothrips frontalis have a asymmetric antennal segment II with prolonged external margin bearing an exactly terminal small seta at tip. Whereas 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, in Chirothrips guillarmodi antennal segment II 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 sens-area. Chirothrips frontalis and most of Chirothrips species with ocellar setae III arranged anterolateral to fore ocellus, and metanotal median setae 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). In Chirothrips frontalis tergites with complete craspedum of unbroken border or flange at the posterior margin (compared to Chirothrips ah and Chirothrips meridionalis with broadly rounded independent lobes fused at bases into continuous craspedum; Chirothrips guillarmodi with closely approximated but independent elongate lobes; Chirothrips manicatus has a continuous craspedum with margin of weakly and rounded lobes; and Chirothrips pretorianus with craspedum with independent small, triangular lobes). Chirothrips pretorianus as well as Chirothrips frontalis posterior margin of sternites without craspedum (compared to Chirothrips ah and Chirothrips meridionalis with craspedum of independent small pointed lobes; Chirothrips manicatus with entire margin and a series of distinctive tubercles; Chirothrips guillarmodi with closely approximated but independent elongate lobes). Moreover, the species has tergites II-VIII discal campaniform sensilla situated in front of the discal setae S1 but somewhat farther apart than the setae (as well as Chirothrips pretorianus and Chirothrips manicatus). Whereas Chirothrips ah, Chirothrips guillarmodi and Chirothrips meridionalis have tergites II-VIII discal campaniform sensilla placed between the discal setae S1 and S2 or posteriorly.
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: alfalfa, forage grasses (Themeda triandra - red oat grass).

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 America, East and South Africa. Kenya (Chala), Lesotho (Mamathes), South Africa (Gauteng: Pretoria; Eastern Cape: Somerset East, Grahamstown; Western Cape: Koekenaap).

Andre F (1941). Two new species of Chirothrips Haliday with notes on Chirothrips frontalis Williams. Annals of the Entomological Society of America. 34 (2): 451-457

Bhatti JS (1990). On some genera related to Chirothrips (Insecta: Terebrantia: Thripidae). Zoology (Journal of Pure and Applied Zoology). 2 (4): 193-200

Hood JD (1953). Two new species of Chirothrips new to Africa (Thysanoptera, Thripidae). Revue de Zoologie et Botanique Africaines. 47 (1/2): 108-119

Jacot-Guillarmod CF (1937). Ten new species of Thysanoptera and a catalogue of the known South African forms. Publications of the University of Pretoria, Serie 2, Natural Science. 3: 1-63

John O (1922). A new genus and two new species on Thysanoptera from British East Africa. Annuaire du Musée Zoologique de ľAcadémie Impériale des Sciences de Saint Pétersbourg. 23: 345-351

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

Moulton D (1936). Thysanoptera from Africa. Annals and Magazine of Natural History, Zoology, Botany and Geology. (Serie 10) 17: 493-509

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

Williams CB (1914). A new species of Chirothrips (Thysanoptera) from South America. Entomologist. 47: 51-53

zur Strassen R (1958). Studies in African Thysanoptera, 1. Journal of the Entomological Society of Southern Africa. 21 (2): 333-353

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