Chirothrips manicatus

Minaei, Kambiz & Mound, Laurence, 2010, Grass-flower thrips of the genus Chirothrips (Thysanoptera: Thripidae), with a key to species from Iran, Zootaxa 2411, pp. 33-43 : 40-41

Chirothrips manicatus species-group

This group includes some of the most common grass thrips of Europe and western Asia. Four species are discussed here, each of which is characterised in the key to European Terebrantia by zur Strassen (2003a). These four species are:

Thrips ( Chirothrips ) manicata Haliday, 1836: 444.

Chirothrips pallidicornis Priesner, 1925: 312 .

Chirothrips ammophilae Bagnall, 1927b: 564

Chirothrips africanus Priesner, 1932: 46

The distribution of each of these four nominal species is as follows:

C. manicatus is a European species that has been distributed widely in temperate areas around the world, presumably in grass seeds. It has been reported from various parts of Iran ( Bhatti et al., 2009). Adults vary considerably in body size, and have been swept from many different grass species. However, there is little reliable information on which species of Poaceae are used for development.

C. pallidicornis is reported from several European countries, between Poland and Sicily (zur Strassen, 2003a), and also from Iran ( Bhatti et al., 2009). The available evidence suggests that it shares the same host species as C. manicatus .

C. africanus is reported from a range of grass species in many warmer parts of the world (Mediterranean, Egypt, Sudan, United Arab Emirates, India, Taiwan; see zur Strassen & Harten, 2008). In Iran, it was reported by Alavi (2000) from Golestan Province.

C. ammophilae is not reported from Iran, but was described from southern France on Ammophila arenaria , and is otherwise reported only from Spain (zur Strassen, 2003a).

The most recent taxonomic treatment of these species (zur Strassen, 2003a) uses the following character states to distinguish africanus ( Fig. 3 ) and pallidicornis ( Fig. 8 ) from ammophilae and manicatus ( Figs 10, 11 ):

1. Head prolongation in front of eyes scarcely 7 microns (contrast: 3–16 microns);

2. Ocellar region with 4 ante-ocellar setae (contrast: usually 6 such setae);

3. Antennal segment II outer margin almost straight (contrast: curved).

All three of these differences are dependent to a variable extent on the precision with which a specimen has been slide-mounted. The first is undoubtedly related to body size, and is also affected by slight differences in the horizontality of a slide-mounted specimen. The antero-lateral pair of ocellar setae is frequently difficult to see, and its presence also seems to be related to body size. The shape of the external margin of the second antennal segment is particularly difficult to evaluate, due to variation in body size and the precise orientation of the segment in slide mounted specimens ( Figs 10, 11 ). Despite these problems, specimens from warmer parts of the world seem to be smaller, with the head prolongation consistently shorter, and antennal segment III smaller and thus with a straighter inner margin; it is to these that the name africanus is given. Whether this represents a different species from, or merely a size variant of, manicatus is a point that merits experimental investigation and statistical analysis of suitably acquired data. The form referred to as pallidicornis is distinguished from africanus by zur Strassen (2003a) because the distance between the pair of dorsal setae on the fourth antennal segment is 11–13 microns rather than 4–6 microns. Despite this, there is no biological evidence that pallidicornis is more than a small form of manicatus .

Of the other two species in this group, ammophilae was formally synonymised with manicatus by Mound (1968), but is distinguished by zur Strassen (2003a) on the following character states:

1. Head prolongation in front of eyes 11–16 microns (contrast: 3–12 microns);

2. Antennal segment VII longer than VIII (contrast: shorter than VIII);

3. Ovipositor length 235–265 microns (contrast: 140–230 microns);

4. Sternites IV–V marginal craspedum not lobed (contrast: lobed).

Considering these differences, it is relevant to mention that the flowering spike of Ammophila is about 10– 16 mm long, whereas that of Dactylis , a common host of manicatus , is only 5–9 mm long. Adults developing in the larger spikes can be expected to grow larger. The first three character states listed are likely to be a function of body size, and the presence and size of small tubercles (not lobes) on the posterior margins of the sternites in females of manicatus is too variable within populations for distinguishing between species ( Fig. 17 ). Currently there appears to be no good biological nor morphological evidence that ammophilae represents a distinct species.

Diagnosis: Body colour brown, tarsi yellow to yellowish brown, forewing and clavus shaded. Head weakly produced in front of eyes ( Figs 10, 11 ); vertex with three pairs of setae, ocellar setae anterolateral to fore ocellus. Antennal segment II external margin usually concave, apex acute with terminal seta; sensoria on segments III–IV simple; antennal segment I without transverse ridge on dorsal surface. Tergal campaniform sensilla anterior to median setae; posterior margins of tergites I–VIII with continuous craspedum with margin of rounded lobes (Fig. 20); sternites II–V posterior margins with row of tubercles ( Fig. 17 ), also laterally on VI but not on VII. Male apterous, smaller than female; tergal craspeda with margin straight.

Figures

FIGURES 1 – 6 Chirothrips species. (1) adults emerged from pupae within grass seeds. Chirothrips heads 2 – 6: (2) aculeatus; (3) africanus; (4) ah; (5) atricorpus; (6) meridionalis.

FIGURES 7 – 11. Chirothrips heads. (7) kurdistanus. (8) pallidicornis. (9) molestus. (10) manicatus [A. C. T.]. (11) manicatus [England].

FIGURES 12 – 19. Chirothrips and Limothrips species. (12) Limothrips cerealium, meta pre-episternum arrowed. (13) C. meridionalis pteronota. (14) C. ah meta pre-episternum arrowed. (15) C. manicatus meta pre-episternum arrowed [Victoria]. Abdominal sternites: (16) C. meridionalis IV – V; (17) C. manicatus III – IV [A. C. T.]; (18) C. hamatus IV – V; (19) C. ah VI.