The spider mites of the genus Eutetranychus Banks (Acari, Trombidiformes, Tetranychidae) from Saudi Arabia: two new species, a re-description, and a key to the world species

Abstract Two new species of the genus Eutetranychus Banks are described and illustrated based on adult females and males, E.spinosussp. n. from Indigoferaspinosa Forssk (Leguminosae), E.neotransversussp. n. from Juniperusprocera Hochst. ex Endl. (Cupressaceae), and E.palmatus Attiah, 1967 is redescribed from Washingtoniarobusta H. Wendl. (Arecaceae). Additionally, the intraspecific morphological variations within E.orientalis populations, collected from 28 various host plants and 80 different localities from six regions of Saudi Arabia from 2009 to 2017, are discussed and presented. The genus Eutetranychus is divided into two species groups based on the presence of one seta (orientalis group) or two setae (banksi group) on coxa II. In addition, seven Eutetranychus species are suggested as synonyms of E.orientalis (Klein, 1936) and E.papayensis Iqbal & Ali, 2008 is considered as species inquirenda. A key to all known species of the genus Eutetranychus is provided.


Introduction
The spider mites belonging to the genus Eutetranychus (Acari: Tetranychidae) mostly feed on shrub and tree leaves (Jeppson et al. 1975, Bolland et al. 1998) and make little webs on plant leaves (Saito 2010, Vacante 2010. Among Eutetranychus species, the Oriental red spider mite, E. orientalis (Klein) and African red spider mite, E. banksi (McGregor) have been recorded as major pests of citrus in many tropical and subtropical countries (Vacante 2010). Recently, E. palmatus Attiah was considered as a pest of date palms in Israel (Palevsky et al. 2010). Previously it has been reported from different palms (Arecaceae) from Egypt, Israel, Jordan, and Iran (Attiah 1967, Gerson et al. 1983, Kamali 1990, Ben-David et al. 2013.
The genus Eutetryanchus belongs to the tribe of Eurytetranychini Reck of the subfamily Tetranychinae. Banks (1917) considered Eutetranychus as subgenus of the Neotetranychus Trägårdh. Later, McGregor (1950) proposed Eutetranychus as valid and separated genus with type species Tetranychus banksi. Baker and Pritchard (1960) provided a key to the world with eight species of Eutetranychus. Later, only two regional keys of Eutetranychus species have been constructed from India and Africa including nine and 16 species, respectively (Nassar andGhai 1981, Meyer 1987). To date, Eutetranychus includes 34 nominal species, mostly reported from Africa and Asia (Migeon andDorkeld 2006-2017). Prior to this study, no diagnostic key to those world Eutetranychus species is available. Only four Eutetranychus species viz. E. africanus (Tucker), E. banksi, E. orientalis and E. palmatus have been reported from Saudi Arabia (SA) so far (Martin 1972, Alatawi 2011. The two species E. orientalis and E. banksi are widely distributed over the world and have been reported from approximately 223 and 84 various host plants, respectively (Bolland et al. 1998, Migeon and Dorkeld 2006-2017, Mattos and Feres 2009, Vacante 2010. Morphological variations in shape and length of dorsal setae, striation pattern between setae d1 and e1 and legs chaetotaxy have been reported in these two species (Baker and Pritchard 1960, Chaudhri et al. 1974, Meyer 1974, Meyer 1987, Khanjani et al. 2017. Because of such variations, some Eutetryanchus species have been synonymized with E. orientalis Pritchard 1960, Meyer 1987) and others with E. banksi Baker 1955, Bolland et al. 1998).
The aims of the present study were to explore Eutetranychus species from Saudi Arabia, to develop a key to the world species of this genus and to discuss the morphological intraspecific variations in E. orientalis populations collected from different hosts and localities from Saudi Arabia. In this study, two new species of Eutetranychus; E. spinosus sp. n. and E. neotransversus sp. n. are described and illustrated based on adult females and males (Figs 1−30). Also, E. palmatus is redescribed and illustrated based on adult female and male (Figs 31−46) because its original description was brief and incomplete from date palm trees in Egypt (Attiah 1967). Two previous recorded species, E. africanus and E. banksi, from SA were not found in this comprehensive collection. The intraspecific morphological variations within E. orientalis populations collected from 28 various host plants and 80 different localities in six regions of SA during 2009 to 2017, are discussed and presented (Figs 47A-H, 48, 49).

Materials and methods
Eutetranychus spider mites were collected from diverse host plants from different localities in six regions (Al-Ula, Madina, Nijran, Riyadh, Tabuk, and Taif ) of SA during 2009-2017. The mite specimens were collected by shaking the aerial parts of plants over a white piece of paper. The mites moving on paper were picked with camel hair brush and preserved in small vials containing 70% alcohol, then mounted in Hoyer's medium under a stereomicroscope (SZX10, Olympus, Tokyo, Japan). The specimens were examined and identified under a phase contrast microscope (BX51, Olympus®, Japan) using keys and available literature. Different mite body parts were pictured by using an auto-montage software system (Syncroscopy, Cambridge, UK) and then drawn with Adobe Illustrator (Adobe SystemInc., San Jose, CA, USA). All measurements are given in micrometers. The lengths of the legs were measured from the base of the trochanter to the tip of tarsus. The measurements are presented for the holotype followed by the range of paratypes in parenthesis. The morphological terminology used in this study follows that of Lindquist (1985). All collected specimens including type specimens of the new species have been deposited at King Saud University Museum of Arthropods (KSMA, Acarology section), Department of Plant Protection, College of Food and Agriculture Sciences, King Saud University, Riyadh, SA.

Species group banksi
Diagnosis. Coxa II with two setae.
Legs ( Immature stages. unknown. Etymology. The species name is derived from name of the host plant species, Indigofera spinosa, of which type specimens were collected. Remarks. Eutetranychus spinosus sp. n. belongs to the banksi species group. It closely resembles E. namibianus Meyer 1987 because both have same legs chaetotaxy (Table 1) and dorsal striae pattern. However, the new species differs from E. namibianus by all dorsal setae slender, much longer, mostly longer than the distance between their base  and the bases of next consecutive setae vs. all dorsal setae sub-spatulate, small, far behind the bases of next consecutive setae, setae c1 and e1 crossing the bases of next consecutive setae vs. reaching less than half distance to the bases of setae next in line and all hysterosomal setae set on strong tubercles vs. only some setae on opisthosoma set on tubercles in E. namibianus. The new species also resembles E. acaciae Miller 1966 because both have all dorsal setae slender, much longer, and mostly longer than the distance between their base and the bases of next consecutive setae. The new species can be separated from E. acaciae by setae f1 slightly more widely spaced as setae e1 vs. f1 two time more widely spaced as compare to e1, differences in legs chaetotaxy, genua I−IV with 5−5−4/3−3 vs. 3−3−1−1 and femora II & III with 6 & 2 vs. 4 & 3, respectively in E. acaciae.
The spermathecal sacculus terminally varied from rounded to slightly pointed in some specimens of this study ( Figures 48A, 49A). Also, the length of the spinneret on the palp tarsus varied from three to four times compared to its width. Similarly, Khanjani et al. (2017) reported that shape of spermathecal sacculus varied distally from rounded to pointed and that spinneret length also varied in E. orientalis. However, Meyer (1987) considered variations in shape of spermathecal sacculus (rounded or pointed distally) and length of spinneret (3 to 4 times as long as its width) as a method to differentiate E. fici Meyer from E. orientalis.
Eutetranychus fici Meyer, reported from Africa, was separated from E. orientalis by the slightly longer dorsocentral setae, shape of spermathecal sacculus, and length of palp spinneret (Table 2; Meyer 1987). The three species E. pruni, E. ricinus, and E. sanaae reported from Yemen were differentiated from E. orientalis by variation in the number of setae on femora I and IV, shapes of dorsal setae, and striation pattern between setae d1 and e1 (Smiley and Baker 1995). Eutetranychus phaseoli Nassar & Ghai, 1981 reported from India was separated from E. orientalis based on the difference in numbers of setae on femur I and distances between dorsal setae e1 and f1 (see also Table 2). The two species E. guangdongensis and E. xianensis, reported from China, were distinguished from E. orientalis and E. banksi, respectively, based only on differences in lengths of dorsal setae (Ma and Yuan 1982) (Table 2). However, the leg chaetotaxy of these two species were mentioned in the original descriptions as being similar in E. orientalis (Ma and Yuan 1982) (Table 2).
Because these seven species have been differentiated in their original descriptions by only one or more variable characters which have also been observed in E. orientalis populations (Chaudhri et al. 1974, Meyer 1987, Khanjani et al. 2017) as well as this study (see Table. 2), these seven Eutetranychus species (E. phaseoli, E. guangdongensis, E. xianensis, E. fici, E. pruni, E. ricinus, and E. sanaae) are suggested as synonyms of E. orientalis in this study.
Eutetranychus papayensis was described with coxae I−IV 2−2−2−2 (whereas they illustrate 2−2−1−1 setae) and three pairs of anal setae. Also, the empodium of this species were neither described nor illustrated. So, based on these characters together, E. papayensis can neither be placed in Eutetranychus nor even in other genera of the family Tetranychidae.The first author has informed us that type specimens of this species have been lost. Therefore, E. papayensis is considered as a species inquirenda.
After excluding those seven species which we suggest as synonyms and one species inquirenda, the genus Eutetranychus includes 28 species (including the new species described herein) and is divided into two species groups based on the number of setae (one or two) on coxae II: the species group orientalis has one seta on coxa II (12 species) and the species group banksi has two setae on coxa II (16 species). The number of setae on coxae II has been considered as a solid morphometric character founded to be strongly constant in all specimens of each Eutetranychus species (Pritchard and Baker 1955, Baker and Pritchard 1960, Chaudhri et al. 1974, Meyer 1974, 1987, Khanjani et al. 2017.