Leptotrombidium gracipalpe (Schluger, 1960)

(Figs. 6, 7)

Trombicula (Leptotrombidium) gracipalpis Schluger, 1960 (in Schluger et al. 1960b): 1793, fig. 3.

Leptotrombidium (Leptotrombidium) gracipalpe: Vercammen-Grandjean & Langston 1976: 520, pl. 137; Kudryashova 2004: 19; Chau et al. 2007: 48, fig. 20.

Leptotrombidium gracipalpe: Stekolnikov 2013: 80; 2021: 117.

Diagnosis. SIF = 7B-B-3-2111.0000; fsp = 7.7.7; fCx = 1.1.1; fSt = 2.2; fPp = N/B/BNN; fSc: PL> AM> AL; Ip = 574–643; fD = 2H-8-6-6-4(6)-4; DS = 30–32; V = 24–38; NDV = 56–68. Standard measurements of type series given in Table 3 .

Description (larva) (based on lectotype and 12 paralectotypes, fD recorded in four specimens). IDIOSOMA (Figs. 6A, 7B–G). Eyes 2 + 2; 30–32 barbed dorsal idiosomal setae, including one pair of humeral setae, with distribution by rows 2H-8-6-6-4(6)-4; 4 sternal setae; 24–38 ventral setae; NDV = 56–68.

GNATHOSOMA (Fig. 7H, I). Cheliceral blade with tricuspid cap; gnathobase covered with puncta and bears 1 pair of branched gnathocoxal (tritorostral) setae; cheliceral base covered with puncta; galeal (deutorostral) seta branched; palpal claw with 3 prongs; seta on palpal femur nude, seta on palpal genu branched, dorsal palpal tibial seta branched, lateral and ventral palpal tibial setae nude; palpal tarsus with 7 branched setae and tarsala (ω).

SCUTUM (Figs. 6, 7A). Rectangular, moderately covered with rather large puncta, greatly projected posterior to PL, posterior margin almost straight in middle part; AM posterior to level of AL, sensillary (trichobothrial) bases posterior to level of PL (P-PL – PSB = 1–5 µm); all scutal setae barbed similarly to dorsal idiosomal setae; PL> AM> AL; flagelliform sensilla (trichobothria) densely covered with small cilia in proximal half and with about 11 long branches in distal half.

LEGS (Fig. 7J–L). All 7-segmented, with 1 pair of claws and claw-like empodium. Leg I: coxa with 1 branched seta (1B); trochanter 1B; basifemur 1B; telofemur 5B; genu 4B, 2 genualae (σ), microgenuala (κ); tibia 8B, 2 tibialae (φ), microtibiala (κ); tarsus 22B, tarsala (ω), microtarsala (ε) distal to tarsala, subterminala (ζ), parasubterminala (z), pretarsala (ζ). Leg II: coxa 1B; trochanter 1B; basifemur 2B; telofemur 4B; genu 3B, genuala; tibia 6B, 2 tibialae (φ); tarsus 16B, tarsala (ω), microtarsala (ε) at level or slightly posterior to tarsala, pretarsala (ζ). Leg III: coxa 1B; trochanter 1B; basifemur 2B; telofemur 3B; genu 3B, genuala; tibia 6B, tibiala; tarsus 15B.

Distribution and hosts. This species was described from North Vietnam, Quang Ninh Province, ex Leopoldamys sabanus, Rattus tanezumi Temminck (= R. rattus tikos), and Tupaia belangeri chinensis (= T. glis modesta) (Schluger et al. 1960b).

Type material examined. Lectotype larva (ZMMU Tdt-3270, specimen 4, designated here) ex Tupaia belangeri chinensis (labeled as T. glis and T. ferruginea) No 29, VIETNAM: Quang Ninh Province, Ha Lam District, Ha Long (= Hon Gai), 1 February 1956, coll. I.M. Grochovskaja. Twelve paralectotypes larvae (ZMMU Tdt-3270, specimen 2; ZMMU Tdt-3271, specimens 3, 5; ZMMU Tdt-3272, specimen 2; ZMMU Tdt-3273, specimens 1, 3, 4, 5; ZMMU Tdt-3274, specimens 1, 4; ZMMU Tdt-3275, specimen 5; ZMMU Tdt-3266, specimen 6) with same data as lectotype.

Remarks. Leptotrombidium gracipalpe belongs to the orientale group, which includes, in total, 17 species (Stekolnikov 2013). This species is unique in its palpal formula fPp = N/B/BNN, i.e. the palpal genual seta is branched that is opposed to all other members of the group and to the overwhelming majority of other Leptotrombidium species.