Walchia keoseima, Antonovskaia & Morand & Stekolnikov, 2024

Antonovskaia, Anastasia A., Morand, Serge & Stekolnikov, Alexandr A., 2024, New species and new records of chigger mites (Acariformes, Trombiculidae) from Cambodia, Zootaxa 5406 (2), pp. 343-358 : 351-352

Walchia keoseima sp. nov.

( Figs. 6A, B , 7 )

Diagnosis. SIF = 4B-N-3-2110.0000; fPp = N/N/NNN; fSc: PL> AL; fCx = 1.1.2; fSt = 2.2; Ip = 668–728; fD = 2H-6-8(9)-6(7)-4(5)-4(5)-2(3)-2(3)-0(1); DS = 34–38; V = 42–55; NDV = 78–89; leg claws equal; ventrofemorala III with one to three cilia. Standard measurements are in Table 3.

Description (larva). IDIOSOMA ( Figs. 6A, B , 7B, C, G, H ). Eyes 1+1; 34–38 dorsal idiosomal setae covered with long barbs, including two humeral setae; six setae in 1 st post-humeral row (C excluding humeral setae), 8–9 setae in 2 nd row (D), 6–7 setae in 3 rd row (E), distribution of setae by posterior rows unclear; 4 sternal setae; 42–55 ventral setae; total number of idiosomal setae excluding coxal and sternal 78–89.

GNATHOSOMA ( Figs. 7D–F ). Cheliceral blade with tricuspid cap; cheliceral base and palpal femur sparsely covered with puncta; gnathobase with moderate puncta and 1 pair of branched gnathocoxal (tritorostral) setae; galeal (deutorostral) seta nude; palpal claw with three prongs; setae on palpal femur, genu, and tibia nude; palpal tarsus with four branched setae and basal tarsala (ω).

SCUTUM ( Figs. 6A , 7A ). Pentagonal, longer than width, sparsely covered with puncta; posterior scutal margin tongue-shaped; ALs and PLs situated on scutal projections; SB situated far anterior to level of PLs, at equal distances from ALs and PLs; PL> AL; scutal setae barbed similarly to dorsal idiosomal setae; clavate sensilla moderately covered with setules.

LEGS ( Figs. 7I–K ).Anterior legs seven-segmented, middle and posterior six-segmented (with undivided femur). Legs with one pair of equally thick claws and thin claw-like empodium. Leg I: coxa with 1 non-specialized branched seta (1B); trochanter 1B; basifemur 1B; telofemur 5B; genu 4B, 2 genualae (σ), microgenuala (κ); tibia 6B, 2 tibialae (φ) in tandem, distal tibiala rod-like, striated, proximal tibiala setiform, microtibiala (κ) at level of distal tibiala; tarsus 22B, thin tarsala (ω) 22 long, microtarsala (famulus, ε) posterior to tarsala, subterminala (ζ), parasubterminala (z), pretarsala (ζ). Leg II: coxa 1B; trochanter 1B; femur 5B; genu 4B, genuala (σ); tibia 6B, 2 tibialae (φ) in tandem, distal tibiala rod-like, striated, proximal tibiala setiform; tarsus 16B, tarsala (ω) 13 long, microtarsala (famulus, ε) posterior to tarsala, pretarsala (ζ). Leg III: coxa 2B; trochanter 1B; femur 3B, ventrofemorala with three barbs; genu 3B, genuala (σ); tibia 6B; tarsus 15B.

Type material. Larval holotype ( ZIN 14325 , L-609) ex B. savilei No. C 0683, CAMBODIA, Mondulkiri Province, Keo Seima , 23 November 2009; six larval paratypes ( ZIN 14259 , 14267 , 14268 , 14313 , 14317 , 14318 ) with same data .

Etymology. The species epithet refers to the type locality, Keo Seima Wildlife Sanctuary.

Remarks. The new species is similar to Walchia fulleri Vercammen-Grandjean, 1971 and differs from the latter in having equal leg claws vs. one claw much thinner, almost filiform; different proportions of scutum (AW 32–36 vs. 26–28, and PW 39–44 vs. 44–46), and much longer legs (Ip = 668–728 vs. 533–578). The new species is also similar to Walchia naniparma ( Traub and Evans, 1957) by the similar shape of scutum and differs from it in having single eyes vs. paired, equal leg claws vs. one claw much thinner, larger scutum (AW 32–36 vs. 21 ± 1, PW 39–44 vs. 31 ± 2, SB 20–23 vs. 17 ± 1, and AP 32–36 vs. 29 ± 1) and longer scutal setae (AL 19–21 vs. 14 ± 2, and PL 27–29 vs. 16 ± 2).

Figures

FIGURE 6. Walchia keoseima sp. nov., holotype. A—anterior part of idiosoma, dorsal aspect; B—sternal area. Walchia lupella (Traub and Evans, 1957), specimen ZIN 9823. C—anterior part of idiosoma, dorsal aspect; D—sternal area. Scale bars: 100 µm.

FIGURE 7. Walchia keoseima sp. nov., holotype (A–C), paratype ZIN 14318 (D, E), paratype ZIN 14313 (F, I–K), paratype ZIN 14317 (G, H). (G). A—scutum (eyes not figured); B—preanal seta; C—humeral seta; D—palpal claw; E—ventral aspect of gnathosoma; F—dorsal aspect of gnathosoma; G—arrangement of ventral idiosomal setae; H—arrangement of dorsal idiosomal setae; I—leg I; J—leg II; K—leg III. Abbreviations: vf—ventrofemorala; other abbreviations as in Figures 2 and 3. Scale bars: 50 μm (A–C), 20 μm (D–F), 100 μm (G, H), 100 μm (I–K).