Euseius ovalis
Creators: name: Biswas, Shubhadeep
name: Karmakar, Krishna
Publisher: name: Zenodo
Year: 2025
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Arachnida
Mesostigmata
Phytoseiidae
Euseius
Euseius ovalis

description: Euseius ovalis (Evans, 1953)
(Figures 4a–g, 7a–h)
Typhlodromus ovalis Evans, 1953: 485.
Typhlodromus (Amblyseius) ovalis.— Chant, 1959: 68.
Amblyseius (Typhlodromalus) ovalis.— Muma, 1961: 288.
Amblyseius (Amblyseius) ovalis.— Ehara, 1966: 24.
Amblyseius (Euseius) ovalis.— Gupta, 1986: 92.
Euseius ovalis.— Chant & McMurtry, 2005: 215.
Diagnosis. Dorsal shield sparsely striated antero-laterally with marks of sigilla mostly on prodorsum and six pairs of solenostomes (gd1, gd2, gd4, gd6, gd8 and gd9); all dorsal setae smooth, short to medium in length, except setae j1 and Z5, which are long, seta Z5 longest and sword-like; setae r3 and R1 located on interscutal membrane; peritreme extending beyond the bases of setae z2; sternal shield smooth with three pairs of setae, posterior margin with a conspicuous, median, bifurcated lobe; ventrianal shield vase-shaped, with margin distinctly angulate anteriorly at position of seta ZV2, with three pairs of pre-anal setae and one pair of large crescentic pre-anal solenostomes (gv3) situated postero-laterad of seta JV2 and JV5 smooth; fixed digit of chelicera with four teeth clustered apically and movable digit unidentate; calyx of spermatheca elongate, tubular, wider proximally near atrium, major and minor duct distinct; leg IV with three smooth, pointed macrosetae on genu, tibia and basitarsus; genua II–III and tibia III each with a pointed macrosetae.
Redescription
Female (n = 7).
Idiosomal setal pattern 10A:9B/ JV -3: ZV.
Dorsum (Figures 4a, 7a–b). Dorsal shield sparsely striated antero-laterally, with marks of sigilla mostly on prodorsum, 396 (390–405) long, 302 (290–310) wide at level of seta s4 with prominent waist at level of seta R 1; with six pairs of solenostomes (gd1, gd2, gd4, gd6, gd8 and gd9); seventeen pairs of setae on the dorsal shield and two pairs of sublateral setae (r3, R 1) on the interscutal membrane: j1 36 (35–36), j3 19 (19–20), j4 8 (8–9), j5 8 (8– 9), j6 9 (9–10), J2 12 (12–13), J5 6 (6–7), z2 11 (11–12), z4 11 (11–12), z5 9 (9–10), Z1 12 (12–13), Z4 12 (12–13), Z5 54 (53–55), s4 17 (17–18), S2 16 (16–17), S4 15 (15–16), S5 12 (12–13), r3 12 (12–13), R 1 12 (12–13). All setae smooth, short to medium in length, except setae j1 and Z5 which are long, seta Z5 longest and sword-like.
Peritreme (Figures 4a, 7a). Extending to level crossing the bases of setae z2.
Venter (Figures 4b, 7d–e). All shields smooth. Sternal shield rectangular, 87 (86–89) long and 105 (101–106) wide, with three pairs of setae and two pairs of lyrifissures; posterior margin distinguishable with a conspicuous bifurcated median lobe; distances between ST1–ST1 62 (60–64), ST2–ST2 72 (71–74), ST3–ST3 80 (78–83), ST1– ST3 64 (61–66) and ST4 29 (28–31) on a metasternal plate. Genital shield broad at base, narrow at genital opening with anterior irregular circular flap having inconspicuous projection on either side, with one pair of setae ST5 30 (29–32) long; distance between ST5–ST5 91 (89–93). Ventrianal shield vase-shaped, with margin distinctly angulate anteriorly at position of seta ZV2, and wider laterally at level of anus; 124 (121–127) long, 58 (56–61) wide at the level of ZV2 and 90 (88–94) at level of anus, with three pairs of pre-anal setae: JV1 32 (31–34), JV2 27 (26–28), ZV2 22 (21–23). One pair of crescentic pre-anal solenostomes (gv3) situated postero-laterad of setae JV2, distant 23 (22–24) from each other. Seta ZV2 posted on anterolateral shield margin. Membrane surrounding ventrianal shield with four pairs of setae: ZV1 22 (21–23), ZV3 16 (15–16), JV4 15 (14–16) and JV5 34 (32–36). Two pairs of metapodal plates, anterior 12 (11–13) and posterior 23 (22–24) long located at level of seta ZV1.
Chelicera (Figures 4c, 7g). Fixed digit 30 (28–32) long with small four teeth clustered apically to a distinct pilus dentilis, movable digit 29 (27–30) long, unidentate.
Spermatheca (Figures 4d, 7h). Calyx 17 (16–18) long, tubular, elongated, wider proximally 5 (5–6) wide, near atrium. Atrium conspicuous, major and minor duct distinctly visible.
Legs (Figures 4e, 7f). Leg IV with three smooth, pointed, thick macrosetae: SgeIV 46 (44–50), StiIV 41 (38–42) and StaIV 60 (57–62). Leg II with single macroseta on genu: SgeII 21 (20–23) and leg III with two macrosetae: SgeIII 27 (25–28) and StiIII 28 (27–29). Chaetotactic formula of Ge II: 2 2/0, 2/0 1 and Ge III: 1 2/1, 2/0 1. Length of leg I 387 (383–393), leg II 301 (295–306), leg III 298 (292–303) and leg IV 390 (386–394).
Male (n = 6).
Dorsum. Dorsal shield 278 (275–280) long and 188 (185–193) wide, smooth with lateral lines on the whole dorsum, with five pairs of solenostomes (gd1, gd2, gd4, gd6, gd8 and gd9) and nineteen pairs of setae on the dorsal shield: j1 30 (28–32), j3 14 (13–15), j4 5 (5–6), j5 5 (5–6), j6 8 (8–9), J2 8 (7–9), J5 5 (4–6), z2 14 (13–16), z4 10 (10–11), z5 8 (8–9), Z1 8 (8–9), Z4 11 (10–13), Z5 48 (46–50), s4 15 (15–16), S2 10 (9–11), S4 12 (11–14), S5 12 (12–14), r3 9 (9–11), R 1 9 (9–10). All setae smooth, short to medium in length, except setae j1 and Z5 which are long, seta Z5 being the longest and sword-like.
Peritreme. Extending forward between setae z2 and j3.
Venter (Figure 4g). Sternigenital shield slightly reticulated, 126 (124–128) long and 76 (74–77) wide at level seta ST2, with five pairs of setae and two pairs of lyrifissures. Distances between ST1–ST5 91 (89–94), ST2–ST2 60 (58–62), ST5–ST5 36 (35–38). Ventrianal shield triangular 110 (108–112) long, 123 (122–125) wide at level of ZV2 setae and 70 (68–72) wide at level of anus; with three pairs of pre-anal setae, JV1 20 (19–22), JV2 20 (18–21) and ZV2 17 (16–18) arranged in a tangential line with one pair of large elliptical pre-anal solenostomes (gv3) distant 21 (20–23) from each other. Membrane surrounding ventrianal shield with one pair of setae JV5 22 (21–23) long, smooth.
Chelicera (Figures 4f, 7c). Fixed digit 20 (18–21) long with four small teeth clustered apically with a distinct pilus dentilis, movable digit 21 (20–22) long, unidentate. Spermatodactyl foot shaped, shaft 20 (20–21) long and foot 10 (10–11) long.
Legs. Legs IV with three smooth macrosetae pointed distally: SgeIV 32 (31–33), StiIV 30 (30–31), StaIV 46 (45–48). Chaetotactic formula of genu II and genu III are identical to the female. Lengths of leg I 348 (340–355), leg II 254 (245–263), leg III 257 (245–263) and leg IV 378 (360–388).
Material examined. 7 females (Acarol.lab/ BCKV /8928–8932/2023) on blackberry nightshade (Solanum nigrum L.: Solanaceae) at Conoor (11°20’49” N 76°47’40” E, 1550 m asl), 20 June 2023; 6 males (Acarol.lab/ BCKV /8933‒8938/2023) on guava (Psidium guajava L.: Myrtaceae) at Pitchandikulam Forest (11°59’39” N 79°49’24” E, 15 m asl), 29 May 2023, Tamil Nadu, India.
Distribution. World catalog: Demite et al., 2024; China: Fujian (Wu, 1981), Guangdong (Waite & Gerson, 1994); India: Arunachal Pradesh (Gupta, 1987), Bihar (Gupta, 1986), Karnataka (Narayanan et al., 1960), Kerala (Gupta, 1986), Maharashtra (Gupta, 1986), Manipur (Gupta, 1986), Meghalaya (Gupta, 1986), Pondicherry (Gupta, 1986), Punjab (Biswas et al., 2022), Tamil Nadu (Gupta, 1986), Tripura (Ray & Gupta, 1981), West Bengal (Karmakar & Gupta, 2011); Indonesia (Ehara, 2005); Japan (Ehara & Amano, 2002); Malaysia (Evans, 1953); Sri Lanka (Moraes et al., 2004). Oceania: Papua New Guinea (McMurtry & Moraes, 1985); New Zealand (Collyer, 1982). North America: Mexico (Chant, 1959).
Remarks
Euseius ovalis (Evans, 1953) was originally described based on female specimens from Kuala Lumpur, Malaysia by Evans (1953). In India, this species was first recorded by Narayanan et al. (1960) followed by Gupta (1977) from Andaman & Nicobar Islands. Inadequate information is provided for the number of solenostomes, cheliceral dentition, spermathecal shape, and leg macrosetae on legs II–III in the original description. In the present study, E. ovalis has been recorded from Tamil Nadu, West Bengal, Odisha, Andhra Pradesh, Karnataka, and other states. Measurements of the presently examined specimens are compared with the measurements of the holotype from original description (Evans, 1953) and that redescribed by Ehara (1967), Schicha (1977), Moraes et al. (2004), Liao et al. (2017) and Fang et al. (2019) mentioned in Table 4. Our specimens differ from original description by Evans (1953) by longer dorsal seta (j3 19–20 vs. 9–11), shorter dorsal seta (s4 17 –18 vs. 22) and longer leg IV macrosetae on genu (SgeIV 44–50 vs. 39). The present specimens differ from the specimens from Japan redescribed by Ehara (1967) by longer dorsal seta (j3 19–20 vs. 13), and longer leg IV macrosetae on genu (SgeIV 44–50 vs. 37). Again, the present Indian specimens differ from the Sri Lankan specimens redescribed by Moraes et al. (2004) by longer leg IV macrosetae on genu and tibia (SgeIV 44–50 vs. 34–35, StiIV 38–42 vs. 32–33). Our specimens differ from specimens from Taiwan redescribed by Liao et al. (2017) by longer dorsal seta (j3 19–20 vs. 8–12, J2 12–13 vs. 6–9, Z4 12–13 vs. 6–8), and longer caudoventral seta JV5 (32–36 vs. 21–30). And finally, the Indian specimens differ from those collected from Myanmar, redescribed by Fang et al. (2019) by longer caudoventral seta JV5 (32–36 vs. 25–29), and shorter calyx of spermatheca (16–18 vs. 21–24). However, we consider those differences to be due to climatic and geographical variation. The present specimens are very close to those illustrated by Ehara (1967), Schicha (1977), Liao et al. (2017) and Fang et al. (2019), but differ from the original description by Evans (1953).
Euseius ovalis (Evans, 1953) is widely distributed throughout West Bengal, Odisha, Andhra Pradesh, Tamil Nadu, and other eastern states where relative humidity is comparatively higher than central and northern states of India. This species is found to be associated with many agri-horticultural crops and weeds, infested with phytophagous mites. Nguyen & Shih (2012) established the biocontrol potential for mango spider mite Oligonychus mangiferus (Rahman & Sapra, 1940) on mango fruit orchards. This species was reported to be associated with Oligonychus spp. and Panonychus sp. colonies (Liao et al., 2017). E. ovalis was also found to be an efficient predator of poinsettia thrips Echinothrips americanus Morgan, an emerging pest of greenhouse ornamental crops (Ghasemzadeh et al., 2017).
description: Published as part of Biswas, Shubhadeep & Karmakar, Krishna, 2025, Three new species of Euseius (Mesostigmata: Phytoseiidae) from Tamil Nadu, India, with redescription of Euseius ovalis and key to the Indian species, pp. 281-308 in Zootaxa 5570 (2) on pages 295-302, DOI: 10.11646/zootaxa.5570.2.3, http://zenodo.org/record/14735062