Members of this genus can be distinguished from other Thripinae by the lack of a comb of microtrichia on the posterior margin of tergite VIII, and the presence of a particularly long pair of setae arising in a unique position on the antecostal ridges of tergites III–VII (Figs 11, 13). Only one other genus shares these two character states, Apsilothrips Bhatti & de Borbon, 2008 from western Argentina (Mendoza and Jujuy). The single species placed in that genus could equally well be interpreted as an unusual species of Psilothrips, but is weakly distinguished by the presence of small cilia on the anterior margin of the fore wing and complete absence of sternal discal setae. In contrast, other Thripinae taxa in which the median tergal setae are unusually long have these setae arising just posterior to the antecostal ridge; they also usually have a comb on tergite VIII, and cilia present on the anterior margin of the fore wing. A generic definition of Psilothrips was provided by O’Neill (1960), but that failed to mention several important character states, including the number of ocellar setae, the presence of six prominently pigmented facets ventrally on each compound eye, and the presence of a prominent spinula on both the meso and metafurca. The number of ocellar setae is particularly important because of the failure of earlier workers to note the presence of ocellar setae pair I in front of the first ocellus, including O’Neill’s failure to illustrate these setae (see her Fig. 1/6). This led Bhatti (1967) to refer to an “additional” pair of anteocellar setae when describing P. indicus as a new species. This pair of setae is often very small, and is difficult to see due to the curvature of the head except when a specimen is very well cleared or the head crushed (Figs 1, 2).

Macropterous Thripinae. Antennae 8-segmented (Fig. 9), segment I with no dorso-apical setae, II with no long setae, sense cones on III–IV forked, III–VI with rows of microtrichia. Head transverse, with 3 pairs of ocellar setae, pair III near anterior margins of triangle (Figs 1, 2); maxillary palps 2-segmented; compound eyes with 6 pigmented facets (Fig. 2). Pronotum transverse (Figs 3, 4, 5, 6), weakly sculptured, discal setae small; with 4 pairs of posteromarginal setae, of which one posteroangular pair sometimes longer than other pairs. Meso- and metafurca with spinula. Mesonotal anterior campaniform sensilla absent, median pair of setae distant from posterior margin. Metanotal sculpture irregularly reticulate, median setae arise medially; no campaniform sensilla (Figs 6, 7, 8). Tarsi 2-segmented. Fore wing costa with setae but no cilia (Fig. 10); first vein with 3 widely spaced setae on distal half; second vein with continuous, widely spaced, row of setae; clavus with 4 veinal setae and one discal seta; posterior fringe straight. Tergites with weak transverse reticulation, posterolaterally these lines bear small microtrichia; II–VIII with setae S1 (median pair) elongate (Figs 11, 12, 13), on III–VII arising on antecostal ridge; V–VII with setae S2 unusually elongate, almost as long as S1; tergites without ctenidia, VIII with no posteromarginal comb; tergite IX with one pair of campaniform sensilla (Fig. 12), without discal microtrichia (except P. priesneri), X with no median split (Fig. 12); pleurotergites with or without discal setae; sternites III–VII with 3 pairs of marginal setae (lateral pair on VII sometimes absent), discal setae varying in number from zero to eight. Male with sternal pore plates present or absent.

Widespread in southern Mediterranean countries, from Morocco to Israel and Yemen, also in Iran from siris trees (Albizia sp., Fabaceae) in Khozestan Province (Alavi and Mohiseni 2002), this species is here interpreted to include records from India and central China. The type specimens of P. indicus, three females collected in Delhi on Ipomoea carnea (Convolvulaceae), are not available for study but are presumably in the “J.S. Bhatti Private collection” (Bhatti and de Borbon 2008). The proposed new synonymy is based on the original description, together with two females from Ningxia, China, collected from Lycium halimifolium (Solanaceae), 20.VII.1980, and identified as P. indicus by Han Yun-fa (in BMNH and SMF). These two females have been compared with females from Morocco, Egypt, Israel and Yemen. The colour, as described by Bhatti (1967) is distinctive, with abdominal tergites II–VII sharply paler posterolaterally, and the metanotal equiangular reticulations with few or no internal markings. This species, under the name of P. indicus, has been considered a pest on Chinese wolfberry (Lycium spp.) in China (Li et al. 2012).

Known only from the Canary Islands on Suaeda fruticosa, this species is unusually dark, and is the only member of the genus for which micropterous individuals are known. None of the available specimens are suitably cleared, but pleurotergal discal setae are not discernable. The tergal antecostal ridge is weaker in this species than among the other members of this genus, and the micropterae have the median tergal setae irregular in size and on some tergites arising posterior to the antecostal ridge.

As recognised by O’Neill (1960), the metanotal sculpture of this species is diagnostic (Fig. 6), and the major pronotal posteroangular setae are about 30 µm long. The species is recorded from Arizona, California, Idaho, Nevada, New Mexico, Texas, and Utah, and appears to be associated with Sarcobatus vermiculatus. In contrast to P. priesneri, the abdominal pleurotergites lack discal setae, and tergite IX lacks discal microtrichia.

The metanotal reticulation of this species, with extensive markings inside each reticle as illustrated by O’Neill (1960), is diagnostic for this species (Fig. 7). The pleurotergites bear several discal setae, and tergite IX has a distinctive transverse band of microtrichia (Fig. 12). This species has been recorded in western USA from Arizona, California, and Texas.

Body yellow to light brown, antennal segments I, III and IV pale, remaining segments shaded; head and pronotum with posterior margins weakly shaded; pterothorax light brown medially, including metascutellum; abdominal tergites I–VIII yellow laterally but with light brown patch medially; fore wings weakly shaded.

With the character states in the generic diagnosis; antennal segments slender (Fig. 9) with reduced microtrichia. Head weakly reticulate in basal third, ocellar setae III on anterior margins of ocellar triangle (Fig. 2).

Pronotum with irregular transverse sculpture lines; 4 pairs of posteromarginal setae, S1 and S3 longer than S2 and S4 (Fig. 5). Metanotum with equiangular reticulation on posterior half, median setae often asymmetric in position (Fig. 8). Fore wing relatively broad; first vein with two setae distally, second vein with about 11 setae (Fig. 10); apex with small sub-apical lobe bearing many long microtrichia ventrally. Abdominal tergites with transverse reticulation medially (Fig. 13), setae S2 slightly shorter than setae S1; tergites IV–VI with striate sculpture laterally bearing a few short microtrichia; sternites III–VII with about eight discal setae.

(holotype female; measurements in micrometer). Table 1.

Similar to female but paler. Tergite IX without any processes or stout setae; sternites apparently without pore plates.

(paratype male; measurements in micrometer). Table 1.

(slide-mounted). Holotype female, IRAN, Fars Province, Sarvestan, 100 km west of Shiraz, from leaves of Zygophyllum sp. (Zygophyllaceae), 17.IV.2014 (KM 1151) (in BMNH).

Paratypes: 7 females, taken with the holotype; 17 females, 6 males, 4 larvae, IRAN, Fars Province, Sarvestan, from leaves of Zygophyllum sp., 9.V.2014 (KM 1185) (in PPSU), 2 females, 1 male, 1 larva, IRAN, Fars Province, Sarvestan, from leaves of Zygophyllum sp. (in ANIC).

This species is named after the genus of plant from which it was collected.

This new species shares many character states with the North American species P. pardalotus. It differs in the form of the metanotal sculpture, longer major setae on the head and pronotum which are more prominently longitudinally grooved, shorter setae S2 on the abdominal tergites, and more slender antennae.

Figures 1–6. 

Psilothrips spp: Head (1) P. pardalotus; female (a: ocellar setae I) (2) P. zygophylli; paratype (a, b, c: ocellar setae I-III; d: pigmented facet). Pronotum (3) P. bimaculatus; female (a: no elongate posteroangular setae) (4) P. priesneri; female (a: no elongate posteroangular setae) (5) P. zygophylli; holotype (a: S1, b: S2, c: S3, d: S4). Pro, meso and metanotum (6) P. pardalotus; female (a: posteroangular setae, b: metanotal sculpture).

Figures 7–13. 

Metanotum (7) P. priesneri; female (a: metanotal sculpture) (8) P. zygophylli; paratype (a: metanotal sculpture; b, c: median setae). Antenna (segments II–VIII) (9) P. zygophylli; paratype. Forewing (10) P. zygophylli; paratype (a: setae). Abdominal tergites (11) P. pardalotus (V–VIII); female (a, b: median tergal setae) (12) P. priesneri (VIII–X); female (a, b: campaniform sensilla; c: tergite X without split) (13) P. zygophylli (VI–VIII); paratype (a, b: median tergal setae).