Euseius madrasi Karmakar & Biswas, 2025

Euseius madrasi Karmakar & Biswas sp. nov.

( Figures 2a–e View FIGURE 2 , 6a–e View FIGURE 6 )

Diagnosis. Dorsal shield strongly reticulated with marks of sigilla mostly on prodorsum and five pairs of solenostomes (gd2, gd5, gd6, gd8 and gd9); all dorsal setae smooth, short to medium in length, with pointed tip, except setae S2, blunt; setae j3 and s4 subequal, and seta Z5, longest, setae r3 and R1 located on interscutal membrane; peritreme extending anterior to the bases of seta j3; sternal shield sparsely striated, with three pairs of setae and posterior margin constricted laterally near setae ST3 with an inconspicuous median lobe; ventrianal shield pitcher-shaped, with anterior margin angulate at ZV2 level, lateral margin slightly indented and wider at level of anus, with three pairs of pre-anal setae and one pair of large elliptical pre-anal solenostomes (gv3) situated posteriad to setae JV2 and JV5 smooth; fixed digit of chelicera with five teeth clustered anteriorly and movable digit unidentate; calyx of spermatheca proximally narrowed, medially wider and distally flared towards vesicle; atrium wide, nodular, submerged within proximal part of calyx; leg IV with three blunt and hyaline macrosetae each on genu, tibia and basitarsus; genu II and III each with a pointed macrosetae.

Description

Female (n = 6).

Idiosomal setal pattern 10A:9B/ JV -3: ZV.

Dorsum ( Figures 2a View FIGURE 2 , 6a–b View FIGURE 6 ). Dorsal shield strongly reticulated medially, and striated laterally forming elongated cells, with marks of sigilla mostly on prodorsum, 382 (375–388) long, 260 (258–270) wide at level of s4 seta and 262 (257–267) wide at level of S2, with irregular waist at level of seta R1; with five pairs of solenostomes (gd2, gd5, gd6, gd8 and gd9); seventeen pairs of setae on the dorsal shield and two pairs of sublateral setae (r3, R1) on the interscutal membrane: j1 38 (36–39), j3 42 (40–44), j4 14 (12–14), j5 14 (13–15), j6 17 (15–17), J2 18 (16–18), J5 6 (5–6), z2 29 (27–30), z4 29 (27–30), z5 16 (15–17), Z1 19 (18–20), Z4 23 (20–23), Z5 68 (66–69), s4 41 (39–42), S2 30 (28–31), S4 29 (27–30), S5 33 (30–33), r3 16 (15–17), R1 18 (16–18). All setae smooth, short to medium in length, with pointed tip, except setae S2, blunt; seta j3 and s4 subequal and seta Z5 the longest.

Peritreme ( Figures 2a View FIGURE 2 , 6a View FIGURE 6 ). Extending anterior to the bases of seta j3.

Venter ( Figures 2b View FIGURE 2 , 6d View FIGURE 6 ). Sternal shield sparsely striated, rectangular, 81 (79–83) long and 100 (96–105) wide, with three pairs of setae and two pairs of lyrifissures; posterior margin constricted laterally near setae st3 with an inconspicuous median lobe-like projection; distances between ST1–ST1 67 (65–69), ST2–ST2 73 (70–75), ST3–ST3 77 (74–79), ST1–ST3 61 (58–63). Seta ST4 26 (24–26) on an inconspicuous metasternal plate. Genital shield broad at base and rounded posteriorly, narrower at genital opening with anterior irregular circular flap, with one pair of setae ST5 28 (26–29) long; distance between ST5–ST5 84 (82–85). Ventrianal shield pitcher-shaped, with anterior margin angulate at ZV2, lateral margin widely wider at level of anus; 102 (100–107) long, 45 (43–46) wide at the level of ZV2 and 88 (86–90) at the anus level, with three pairs of pre-anal setae: JV1 26 (23–26), JV2 31 (29–31), ZV2 29 (27–30). One pair of large elliptical pre-anal solenostomes (gv3) situated posteriad to setae JV2, distant 22 (20–24) from each other. Setae ZV2 located near the anterior shield margin. Membrane surrounding ventrianal shield with four pairs of setae: ZV1 25 (22–25), ZV3 15 (14–16), JV4 14 (14–16), and JV5 39 (36–40). One pair of metapodal plates, 25 (24–27) long at the level of the base of the genital shield.

Chelicera ( Figure 2c View FIGURE 2 ). Fixed digit 31 (30–33) long with five small teeth clustered anteriorly to a distinct pilus dentilis; movable digit 28 (26–29) long, unidentate.

Spermatheca ( Figures 2d View FIGURE 2 , 6e View FIGURE 6 ). Calyx 13 (13–14) long, proximally narrowed, medially wider, distally flared towards vesicle. Atrium wide, nodular, submerged within proximal part of calyx. Major and minor duct wide, distinctly visible.

Legs ( Figures 2e View FIGURE 2 , 6c View FIGURE 6 ). Leg IV with three blunt and hyaline macrosetae on genu, tibia and basitarsus. Length of macrosetae: SgeIV 42 (41–44), StiIV 35 (32–36) and StaIV 49 (46–50). Leg II–III each with single macroseta on genu: SgeII 25 (25–26) and SgeIII 31 (31–34). Chaetotactic formula of Ge II: 1 2/0, 2/0 2 and Ge III: 1 2/1, 2/0 1. Length of leg I: 375 (368–381), leg II 266 (262–269), leg III 281 (276–284), and leg IV 383 (376–388).

Male. Unknown.

Type material. HOLOTYPE: Female (Acarol.lab/BCKV/8915/2023) deposited in the NZC, Zoological Survey of India, Kolkata, on Madagascar periwinkle ( Catharanthus roseus (L.) G.Don: Apocynaceae ) at Tholkappia Poonga (13°01’08” N 80°15’58” E, 6 m asl), 12 May 2023; GoogleMaps PARATYPES: 5 females (Acarol.lab/ BCKV /8918‒8922/2023) on oleander ( Nerium oleander L.: Apocynaceae ) at Guindy National Park (13°00’12” N 80°13’52” E, 8 m asl), 20 May 2023, Chennai, Tamil Nadu, India. GoogleMaps

Etymology. The specific name madrasi refers to Madras, the earlier name of Tamil Nadu state of India from where the specimens were collected.

Differential diagnosis. The new species Euseius madrasi is distinct among all the species in by genus with the following combination of characters: strongly reticulated dorsal shield with five pairs of solenostomes (gd2, gd5, gd6, gd8 and gd9); all dorsal setae shorter, pointed, except seta S2, blunt; setae j3 and s4 subequal; setae r3 and R1 on interscutal membrane; peritreme extending anterior to bases of j3; posterior margin of sternal shield constricted laterally near setae ST3 with an inconspicuous median lobe; pitcher-shaped ventrianal shield, with anterior margin angulate at ZV2 level, with one pair of pre-anal solenostomes (gv3) posteriad of JV2; movable digit of chelicerae unidentate; calyx of spermatheca proximally narrowed and medially wider; wide atrium submerged within calyx; leg IV with three blunt and hyaline macrosetae each on genu (SgeIV 41–44), tibia (StiIV 32–36) and basitarsus (StaIV 46–50).

The new species is close to E. astrictus Karmakar & Bhowmik, 2018 ; E. finlandicus ( Oudemans, 1915) ; E. rubicolus Van der Merwe & Ryke, 1964 ; and E. sativum Karmakar & Gupta, 2014 ; by sharing characters like reticulated dorsal shield with distinct irregular waist at level of seta R1; sublateral setae r3 and R1 on interscutal membrane; teeth in the fixed digit of chelicerae clustered apically and peritreme not extending beyond seta j3. However, the new species E. madrasi clearly differs from E. astrictus by shorter leg IV macrosetae on tibia and basitarsus (StiIV 32–36 vs. 44, StaIV 46–50 vs. 65); and calyx of spermatheca not constricted throughout its length (calyx of spermatheca constricted throughout in E. astrictus ). The new species E. madrasi differs from E. finlandicus by longer opisthosomal seta Z5 (66–69 vs. 51–52); peritreme extended anterior to the bases of seta j3 (peritreme extended up to seta z 4 in E. finlandicus ); and tip of leg IV macrosetae blunt and hyaline (leg IV macrosetae pointed and not hyaline in E. finlandicus ). Again, the new species E. madrasi differs from E. rubicolus by longer dorsal setae (z2 27–30 vs. 13–14, Z5 66–69 vs. 52–55, S2 28 –31 vs. 19–20); and calyx of spermatheca short and not trumpet shaped (calyx of spermatheca long 13–14 vs. 30 and trumpet shaped in E. rubicolus ). Also, the new species E. madrasi differs from E. sativum by smooth dorsal setae s4, S4 and S5 (weakly serrated dorsal setae s4, S4 and S 5 in E. sativum ); tip of leg IV macrosetae blunt and hyaline (leg IV macrosetae gently spatulate in E. sativum ); calyx of spermatheca not tubular (calyx of spermatheca tubular in E. sativum ); and anterior margin of ventrianal shield uniform (anterior margin of ventrianal shield deeply indented in E. sativum ). These comparisons are summarised in Table 2 View TABLE 2 .