Leptotrombidium monstrosum (Schluger, 1960)

Stekolnikov, Alexandr A. & Antonovskaia, Anastasia A., 2021, Re-descriptions of eight chigger mite species (Acariformes: Trombiculidae) of the Leptotrombidium generic complex from Vietnam, Zootaxa 5057 (3), pp. 329-363 : 349-353

Leptotrombidium monstrosum (Schluger, 1960)

( Figs. 14–16 )

Trombicula (Leptotrombidium) monstrosa Schluger, 1960 (in Schluger et al. 1960b): 1798, fig. 6.

Leptotrombidium (Leptotrombidium) monstrosa: Traub & Lakshana 1966: 282 .

Leptotrombidium (Leptotrombidium) monstrosum: Lakshana 1973: 8 ; Vercammen-Grandjean & Langston 1976: 569, pl. 155; Kudryashova 2004: 27; Chau et al. 2007: 54, fig. 23.

Leptotrombidium monstrosum: Stekolnikov 2013: 47 ; 2021: 123.

Diagnosis. SIF = 7B-B-3-2111.0000; fsp = 7.7.7; fCx = 1.1.1; fSt = 2.2; fPp = N/N/BNB; fSc: AM ≥ PL> AL; Ip = 708–784; fD = 2H-8-6-6-4-2-2; DS = 30; V = 30–33; NDV = 60–63. Standard measurements of type series given in Table 6 .

Description (larva) (based on lectotype and 21 paralectotypes, fD recorded in three specimens). IDIOSOMA ( Figs. 14A , 15B–G ). Eyes 2 + 2; 30 barbed dorsal idiosomal setae, including one pair of humeral setae, arranged 2H-8-6-6-4-2-2; 4 sternal setae; 30–33 ventral setae; NDV = 60–63.

GNATHOSOMA ( Fig. 16A–E ). Cheliceral blade with tricuspid cap; gnathobase covered with puncta and bears 1 pair of branched gnathocoxal (tritorostral) setae; cheliceral base covered with puncta, palpal femur with few puncta; galeal (deutorostral) seta branched; palpal claw with 3 prongs; setae on palpal femur and genu nude, dorsal palpal tibial seta branched, lateral palpal tibial seta nude; ventral palpal tibial seta branched; palpal tarsus with 7 branched setae and tarsala (ω).

SCUTUM ( Figs. 14 , 15A ). Rectangular, moderately covered with rather large puncta, projected posterior to PL, posterior margin slightly concave in middle part; AM posterior to level of AL, sensillary (trichobothrial) bases at level of PL or slightly anterior (P-PL – PSB = –4–1 µm); all scutal setae barbed similarly to dorsal idiosomal setae; AM ≥ PL> AL; flagelliform sensilla (trichobothria) with about 8 branches in distal part.

LEGS ( Fig. 16F–H ).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) 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 sabanus ) and Tupaia belangeri chinensis [= T. glis modesta ; = T. hongaiensis (nomen nudum)] ( Schluger et al. 1960b). Later on, it was recorded in Thailand ( Lakshana 1973) from Menetes berdmorei . Vercammen-Grandjean & Langston (1976) added also Leopoldamys edwardsi (Thomas) [= R. grochovskiae (nomen nudum)] to the list of hosts based on examination of syntypes. Chau et al. (2007) also reported this species from Atherurus macrourus (L.), Callosciurus erythraeus (Pallas) , Dremomys rufigenis , Rattus andamanensis (Blyth) (= R. koratensis ), Tamiops rodolphii (Milne-Edwards) , Hylomys suillus , Paradoxurus hermaphroditus , and birds Gallus gallus domesticus (L.) and Francolinus pintadeanus (Scopoli) , probably, from Vietnam.

Type material examined. Lectotype larva ( ZMMU Tdt-3250, specimen 1, designated here) ex L. edwardsi [labeled as Rattus sp. and R. grochovskii (nomen nudum)] No 45, VIETNAM: Quang Ninh Province, Ha Lam District, Ha Long (= Hon Gai), 6 February 1956, coll. I.M. Grochovskaja. Twelve paralectotypes larvae ( ZMMU Tdt-3244, specimens 1–5; ZMMU Tdt-3245, specimens 1, 2, 4, 6; ZMMU Tdt-3246, specimens 1, 4, 5) ex Tupaia belangeri chinensis [labeled as T. glis and T. hongaiensis (nomen nudum)] No 42, 3 February 1956, other data same as for lectotype; one paralectotype larva ( ZMMU Tdt-3248, specimen 4) ex L. edwardsi [labeled as Rattus sp. and R. grochovskii (nomen nudum)] No 40, 3 February 1956, other data same as for lectotype; one paralectotype larva ( ZMMU Tdt-3249, specimen 1) ex L. edwardsi [labeled as Rattus sp. and R. grochovskii (nomen nudum)] No 44, other data same as for lectotype; five paralectotypes larvae ( ZMMU Tdt-3250, specimens 2, 3, 5, 6, 7) with same data as lectotype; two paralectotypes larvae ( ZMMU Tdt-3268, specimens 1, 2) ex Tupaia belangeri (labeled as T. glis and T. ferruginea ) No 29, 1 February 1956, other data same.

Remarks. This species is a member of the scanloni group ( Stekolnikov 2013), which includes three species.

Leptotrombidium monstrosum differs from L. scanloni Traub and Lakshana, 1966 in having the ventral palpal tibial seta branched (fPp = N/N/BNB vs. N/N/BNN); sensillary bases situated at the level of PL or slightly anterior to them vs. posterior; and larger scutum (AW 67–73, PW 78–89, and AP 26–30 vs. 62–66, 73–78, and 23–25, respectively). Leptotrombidium monstrosum differs from L. hanseni Traub and Lakshana, 1966 in having a slightly lesser number of idiosomal setae (DS 30, V 30–33, and NDV 60–63 vs. 34, 34, and 68, respectively); fD = 2H-8-6-6-4-2-2 vs. 2H-8-6-6-6-4-2; and shorter legs (Ip 708–784 vs. 847). Taxonomical significance of these rather slight differences is unclear, since no data on the variation of NDV and Ip are available for L. hanseni . Probably, the latter species should be synonymized with L. monstrosum , but this suggestion needs a verification based on a larger material.

Traub & Lakshana (1966) stated that L. hanseni differs from L. monstrosum , in addition to the difference by fD, also by a smaller scutum (PW 84, SB 36, and AP 25 vs. 100, 45, and 33, respectively), but our measurements of L. monstrosum do not support that observation ( Table 6). The source of the values provided by Traub & Lakshana as measurements of L. monstrosum is unclear. These data do not coincide with those in the original description ( Schluger et al. 1960b), and these authors did not mention the examination of any material on L. monstrosum .

Figures

FIGURE 14. Leptotrombidium monstrosum (Schluger, 1960). A, dorsal aspect of idiosoma of lectotype (right sensillum lost); B, scutum of paralectotype ZMMU Tdt-3250, specimen 2 (left sensillum detached). Scale bars: 50 μm.

FIGURE 15. Leptotrombidium monstrosum (Schluger, 1960). A, scutum of lectotype (right sensillum lost); B, humeral seta (C antero-marginal) of lectotype; C, dorsal idiosomal seta of lectotype; D, postanal seta of lectotype; E, preanal seta of lectotype; F, arrangement of dorsal idiosomal setae in paralectotype ZMMU Tdt-3244, specimen 1; G, ventral aspect of idiosoma in paralectotype ZMMU Tdt-3244, specimen 1. Abbreviations as in Fig. 2. Scale bars: 50 μm (A–E), 100 μm (F, G).

FIGURE 16. Leptotrombidium monstrosum (Schluger, 1960). A, ventral aspect of gnathosoma of lectotype (cheliceral blade lost); B, dorsal aspect of gnathosoma of lectotype (palpal claw broken); C, cheliceral blade; D, palpal claw; E, palpal claw (other side); F, leg I (trochanter–tarsus) of paralectotype ZMMU Tdt-3250, specimen 2; G, leg II (trochanter–tarsus) of paralectotype ZMMU Tdt-3250, specimen 2; H, leg III (trochanter–tarsus) of paralectotype ZMMU Tdt-3250, specimen 2 (one claw and empodium lost). Abbreviations as in Fig. 2. Scale bars: 50 μm (A–E), 50 μm (F–H).