Euseius ovalis (Evans)

Fang, Xiao-Duan, Nguyen, Van-Liem, Ouyang, Ge-Cheng & Wu, Wei-Nan, 2020, Survey of phytoseiid mites (Acari: Mesostigmata, Phytoseiidae) in citrus orchards and a key for Amblyseiinae in Vietnam, Acarologia 60 (2), pp. 254-267 : 261-263

Euseius ovalis (Evans)

( Figs. 4 a – e )

Typhlodromus ovalis Evans 1953: 458 .

Typhlodromus (Amblyseius) ovalis, Chant 1959: 68 ; Narayanan, Kaur and Ghai 1960: 388. Amblyseius (Typhlodromalus) ovalis, Muma 1961 .

Amblyseius ovalis, Collyer 1964: 634 ; Gupta 1970: 98; Prasad 1974: 168; Wu 1980: 46; Ray and Gupta 1981: 279; Chen et al. 1984: 327.

Amblyseius (Amblyseius) ovalis, Ehara 1966: 24 .

Euseius ovalis, Gupta 1978: 335 ; Moraes et al. 1986: 49; Wu et al. 1997: 117; Wu et al. 2009: 235; Liao et al. 2017: 220 .

Amblyseius (Euseius) ovalis, Gupta 1985 ; Ehara and Amano 1998: 43.

Description — Female (n = 2)

Dorsum — Idiosomal setal pattern: 10A: 9B/JV-3: ZV. Dorsal shield ( Fig. 4a ) smooth, with anterolateral striated. Dorsal shield 359 (348–365) long and 238 (230–248) wide, distances between setae j1- J5 344 (331–353) and s4-s4 206 (198–213), shield nearly oval, constricted at level of R1. Setae r3 and R1 on soft membranous cuticle laterad dorsal shield, r3 at level of z4, R1 at level of shield incisions. All setae smooth, except Z5 slightly serrate. With six pairs of solenostomes on dorsal shield (gd1, gd2, gd4, gd6, gd8, gd9). Length of setae: j1 33 (30–35), j3 14 (13–15), j4 8 (7–9), j5 7 (5–8), j6 8 (7–8), J2 12 (10–13), J5 7 (5–8), z2 10 (9–11), z4 10 (8–12), z5 8 (7–9), Z1 11 (9–12), Z4 13 (11–14), Z5 56 (53–58), s4 14 (13–16), S2 14 (12–15), S4 14 (13–16), S5 12 (11–14), r3 13 (12–15), R1 10 (9–11).

Venter —(Fig. 4b). All ventral setae smooth. Sternal shield smooth, posterior margin not discernible in the examined specimens, 79 (78–81) wide, with three pairs of setae st1 33 (32–35), st2 29 (27–32), st3 30 (28–32), and two pairs of lyrifissures (pst1-pst2), distance between st1-st3 59 (57–60) and st2-st2 66 (65–68). Metasternal platelets drop-shaped, each with one metasternal seta, st4 27 (25–29) and one lyrifissure (pst3). Genital shield smooth, with one pair of thin genital setae st5 30 (29–31), distance between st5-st5 78 (76–80); one pair of associated poroids on soft cuticle near posterior corners of shield. Ventrianal shield smooth, nearly oval, 105 (102–109) long, 49 (47–52) wide at level of ZV2, 81 (79–83) wide at level of anus, three pairs of thin pre-anal setae, JV1 migrate next to JV2, JV1 29 (27–32), JV2 24 (23–26), ZV2 16 (14–19); Pa 15 (14–16), Pst 16 (15–17) long. Pre-anal pores crescentic, posteromedian to JV2, distance between pores 33 (31–34). Opisthogastric soft cuticle with four pairs of setae, ZV1 22 (20–23), ZV3 10 (8–11), JV4 13 (13–14), JV5 28 (27–30) long. All ventral setae thin, except JV5, thicker. Two pairs of metapodal platelets, primary platelets 22 (21–23) long, 5 (4–6) wide, secondary ones 13 (12–14) long, 2 (1–2) wide.

Peritremes — Peritremes extending anteriorly between j3 and z2.

Chelicerae — ( Fig. 4c ). Fixed digit 25 (24–27) long, with three teeth and pilus dentilis, movable digit 23 (21–24) long, unidentate.

Spermatheca — ( Fig. 4d ). Calyx of spermatheca 12 (10–13) long, base swollen, tubular, 3 (3–4) wide at inflated part, 1 (1–1) at distal part, atrium 1 1 (1–2) wide, small-knobbed, incorporated with calyx; major duct narrow, directly attached to calyx, without neck, and minor duct visible.

Legs — Genua formula for leg I 2 – 2/1, 2/1 – 2, leg II 2 – 2/0, 2/0 – 1, leg III 1 – 2/1, 2/0 – 1, leg IV 1 – 2/1, 2/1 – 0. Genua and tibia III each with one macroseta, Sge III 27 (25–28), tibia III 23 (21–24). Leg IV with three macrosetae on genu, tibia and basitarsus ( Fig. 4e ), Sge IV 36 (35–38), Sti IV 35 (33–36) and St IV 55 (52–57).

Material examined — 2 ♀♀, Cao Lanh district, Dong Thap Provine (accession no. DT-0532, DT-0560), on Citrus reticulata × sinensis, 13 IV 2018, Fang X.D. coll.

Previous records — Australia, China, Cook Islands, Fiji, Hawaii, India, Indonesia, Japan, Malaysia, Mauritius, Mexico, New Zealand, Papua New Guinea, Philippines, Sri Lanka.

Remarks — The calyx of the examined specimens is tubular, similar to illustration in Wu et al. (2009), but not distal flaring as illustration in Gupta (1986). Fixed digit of the examined specimens with three teeth is similar to illustration in Liao et al. (2017), but not only with one tooth as the original description ( Evans, 1953).

Euseius ovalis can be mass-reared on pollen and it is the dominant natural enemy in controlling Aceria litchi (Keifer) ( Wu et al. 1991) . This species also had potentiality in controlling Tetranychus kanzawai Kishida ( Shih et al. 1993) and Oligonychus mangiferus (Rahman and Sapra) ( Nguyen and Shih, 2010) . Liao et al. (2017) reported E. ovalis rarely located on the leaves with Tetranychus colonies and only located close to Oligonychus and Panonychus colonies.

The above three species are all found in citrus orchards in Vietnam, and they are associated with spider mites and small pests. Now, there are fifteen species reported in Vietnam in total. Nguyen et al. (2016) first reported eight phytoseiid mites were found in Ho Chi Minh city, including A. matinikus Schicha and Corpuz-Raros, 1992 , Graminaseius polisensis ( Schicha and Corpuz-Raros, 1992), Neoseiulus longispinosus ( Evans, 1952) , Paraphytoseius orientalis ( Narayanan, Kaur and Ghai, 1960) (synonym of Paraphytoseius multidentatus Swirski and Shechter according to Chant and McMurtry 2003, Kreiter et al. 2018), Scapulaseius asiaticus ( Evans, 1953) , Amblyseius tamatavensis Blommers, 1974 , Proprioseiulus dahonagnas ( Schicha and Corpuz-Raros, 1992) and an undetermined Typhlodromus sp. Furthermore, Paraphytoseius cracentis ( Corpuz and Rimando, 1966) , Neoseiulus californicus ( McGregor, 1954) , Proprioseiopsis lenis ( Corpuz and Rimando, 1966) , E. aizawai ( Ehara and Bhandhufalck, 1977) , E. ovalis ( Evans, 1953) and A. largoensis were reported to be found in the Red River Delta respectively ( Nguyen and De Clercq, 2018; Thuan et al. 2019; Nguyen, 2019a, 2019b; Nguyen and Dao 2019; Nguyen et al. 2019a, 2019b). In this paper, A. obtuserelus was first recorded in Vietnamese fauna. Fourteen identified species all belong to the subfamily Amblyseiinae . A key to the Vietnamese Amblyseiinae species is given as below.

Figures

Figure 4 Female of Euseius ovalis. a – Dorsal shield; b – Ventral idiosoma; c – Chelicera; d – Spermatheca; e – Leg IV, genu-basitarsus.