Walchia dismina (Schluger, Grochovskaja, Ngu, Hoe and Tung, 1960)

Antonovskaia, Anastasia A. & Stekolnikov, Alexandr A., 2021, Redescriptions of ten chigger mite species (Acariformes: Trombiculidae) from Vietnam, Zootaxa 4969 (1), pp. 1-53 : 15-19

Walchia dismina (Schluger, Grochovskaja, Ngu, Hoe and Tung, 1960)

( Figs. 8A, B , 9–11 )

Gahrliepia (Walchia) dismina Schluger, Grochovskaja, Ngu, Hoe and Tung, 1960c: 468 , figs. 31–38.

Gahrliepia (Walchia) dismina: Lakshana 1973: 24 ; Chau et al. 2007: 168, fig. 83.

Walchia (Walchia) dismina: Vercammen-Grandjean 1968: 112 .

Walchia dismina: Kudryashova 2004: 45 ; Chaisiri et al. 2016: 335.

Diagnosis. SIF = 4B-N-2-2110.0000; fsp = 7.6.6; fCx = 1.1.2; fSt = 2.2; fPp = N/N/NNN; fSc: PL> AL; Ip = 688– 739; fD = 2H-6-[6-2]-6-[4-2]-4-5; DS = 32–39; V = 44–51; NDV = 77–90. Eyes absent. Standard measurements of type series given in Table 4 .

Description (larva) [based on lectotype and 6 paralectotypes]. IDIOSOMA ( Figs. 8A, B , 9 ). Eyes absent; 32–39 dorsal idiosomal setae covered with long barbs, including one pair of humeral setae; 4 sternal setae; 44–51 ventral setae; NDV = 77–90.

GNATHOSOMA ( Fig. 10D, E ). Cheliceral blade with tricuspid cap; cheliceral base with sparse puncta; gnathobase with sparse puncta and 1 pair of branched setae; galeala nude; palpal claw with 2 prongs; setae on palpal femur, genu, and tibia nude; palpal tarsus with 4 branched setae and tarsala.

SCUTUM ( Fig. 8A ). Pentagonal, longer than width, with angulate posterior margin, moderately covered with small puncta, with 1 pair of ALs and 1 pair of PLs; PLs longer ALs; sensilla claviform, covered with spikes; sensillum bases situated at equal distances from levels of ALs and PLs.

LEGS ( Fig. 10A–C ). All with 1 pair of claws and claw-like empodium. Leg I: 7-segmented, coxa with 1 branched seta (1B); trochanter 1B; basifemur 1B; telofemur 5B; genu 4B, 2 genualae, microgenuala; tibia 8B, 2 tibialae, microtibiala; tarsus 22B, tarsala, microtarsala proximal to tarsala, subterminala, parasubterminala, pretarsala. Leg II: 6-segmented, coxa 1B; trochanter 1B; femur 6B; genu 3B, genuala; tibia 6B, 2 tibialae; tarsus 16B, tarsala, microtarsala far proximal to tarsala, pretarsala. Leg III: 6-segmented, coxa 2B; trochanter 1B; femur 4B, nude ventral femorala; genu 3B, genuala; tibia 6B; tarsus 14B.

Hosts. Rattus sp. ( Schluger et al. 1960c), Leopoldamys sabanus (Thomas, 1887) (= Rattus sabanus ), Mus cervicolor Hodgson, 1845 ( Rodentia : Muridae ), Rattus tanezumi (= R. sladeni (Anderson, 1879)) , Bandicota indica , Maxomys surifer , Menetes berdmorei , Niviventer niviventer , Rattus rattus , Tupaia glis ( Lakshana 1973) , Mus cookii Ryley, 1914 , Rattus losea (Swinhoe, 1871) ( Rodentia : Muridae ) ( Chaisiri et al. 2016).

Distribution. Thailand ( Lakshana 1973; Chaisiri et al. 2016), Vietnam.

Type material examined ( Fig. 11 ). Lectotype (here designated): larva ZMMU Tdt-3252 (specimen 1) ex Rattus sp. No 542, Vietnam, Nghe An Province, Phu Quy , 8 September 1956, coll. I.M. Grochovskaja. Paralectotypes: two larvae, ZMMU Tdt-3252 (specimens 2, 3), same collection data as for lectotype ; two larvae, ZMMU Tdt-3254 (specimen 1), ZMMU Tdt-3255 (specimen 2), ex Rattus sp. No 542, Vietnam, Nghe An Province, Phu Quy , 9 September 1956, coll. I.M. Grochovskaja ; two larvae, ZMMU Tdt-3258 (specimens 3, 4), ex Rattus sp. No 595, Vietnam, Nghe An Province, Phu Quy , 13 September 1956, coll. I.M. Grochovskaja.

Remarks. According to the original description, W. dismina is similar to W. kritochaeta Traub and Evans, 1957 and differs from it by longer legs and by the presence of two setae on leg coxa III (fCx = 1.1.2 vs. 1.1.1) ( Schluger et al. 1960c). The latter difference is reliable, but the former one is unclear, as the lengths of legs were absent in the original description of W. kritochaeta ( Traub & Evans 1957) . However, we found the following additional differences between these species. Walchia dismina has 2-pronged palpal claw, equal leg claws, and has no eyes, while W. kritochaeta has 3-pronged palpal claw, unequal leg claws (one claw is very thin, like the empodium), and one pair of eyes.

Walchia dismina is also similar in the size and shape of scutum to W. isonychia Nadchatram and Traub, 1964 , but differs in the presence of two setae on leg coxa III (vs. one seta), a 2-pronged palpal claw (vs. 3-pronged), and by the absence of eyes (vs. eyes 1 + 1).

Specimen No. 4 on the slide ZMMU Tdt-3254, specimens Nos 1, 3, 4, and 5 on the slide ZMMU Tdt-3255, specimens Nos 2 and 5 on the slide ZMMU Tdt-3258 belong to Walchia chinensis (Chen and Hsu, 1955) . Specimen No. 2 on the slide ZMMU Tdt-3254 presumably belongs to Walchia disparunguis (Oudemans, 1929) .

Figures

FIGURE 8. Walchia dismina (Schluger, Grochovskaja, Ngu, Hoe and Tung, 1960), paralectotype ZMMU Tdt-3252 (specimen 2). A, dorsal aspect of idiosoma; B, ventral aspect of idiosoma. Cheladonta neda Schluger, Grochovskaja, Ngu, Hoe and Tung, 1960, additional material ZMMU XM14.63k1 (specimen 11). C, dorsal aspect of body; D, ventral aspect of body. Scale bars: 100 μm.

FIGURE 9. Walchia dismina (Schluger, Grochovskaja, Ngu, Hoe and Tung, 1960), lectotype. A, arrangement of dorsal idiosomal setae; B, arrangement of ventral idiosomal setae; C, dorsal idiosomal seta of 1st row; D, preanal seta. Scale bars: 100 μm (A, B), 20 μm (C, D).

FIGURE 10. Walchia dismina (Schluger, Grochovskaja, Ngu, Hoe and Tung, 1960). A, leg I (trochanter–tarsus) of lectotype; B, leg II (trochanter–tarsus) of paralectotype ZMMU Tdt-3252 (specimen 2); C, leg III (trochanter–tarsus) of lectotype; D, dorsal aspect of gnathosoma of lectotype; E, ventral aspect of gnathosoma of lectotype. Scale bars: 50 μm (A–C), 20 μm (D, E).

FIGURE 11. Type specimens of Walchia dismina (Schluger, Grochovskaja, Ngu, Hoe and Tung, 1960) on slides.

Tables

TABLE 4. Standard measurements (µm) and numbers of setae of Walchia dismina (n = 7).

	Range	Mean	Lectotype
AW	30–34	32	30
PW	40–44	41	41
SB	21–24	23	22
ASB	19–24	21	23
PSB	35–41	37	35
SD	55–65	59	59
P-PL	18–24	21	19
AP	34–38	35	38
AL	19–23	21	21
PL	28–30	29	30
H	27–31	29	27
D min	24–29	27	29
D max	33–38	36	36
V min	17–21	18	20
V max	28–33	30	29
pa	240–263	252	253
pm	207–218	211	208
pp	241–258	251	254
Ip	688–739	715	715
DS	32–39	35	37
V	44–51	47	46
NDV	77–90	83	83