Neotrombidium folium, Shaw, 2025

Neotrombidium folium sp. nov.

Figs 24 View Figures 24, 25 –32 View Figure 32

Holotype.

SAMA J 25676 .

Type-locality.

Australia, 1 larva; South Australia, Cave 5 N-257 , Nullarbor Regional Reserve; 27 Nov. 2021 to 7 Mar. 2022; Steve Milner, Andrew Stempel, Matthew Shaw leg.; dark zone, on loose flakes and stones fallen from roof; sardine-baited propylene glycol-filled ramp trap, trap A; Bush Blitz 2021 Yalata; in folded wing under elytra of Brises sp.

Type-specimen.

Holotype larva, mounted on microslide in Hoyer’s medium. Original label: “ South Australia, Cave 5 N-257 / Nullarbor Regional Reserve / dark zone, on loose flakes & / stones fallen from roof, in / folded wing of Brises sp. / 27 Nov 2021 to 7 Mar 2022 / S. Milner, A. Stempel, M. Shaw / baited ramp trap A / Bush Blitz 2021 Yalata ” .

Description.

Dorsum: One engorged larva, idiosoma 713 L × 563 W (Fig. 24 View Figures 24, 25 ). The anterior section of the scutum expanded laterally, hyaline, leaf-like (Fig. 26 View Figure 26 ). Maximum width 93. AM setae 50 long. Sensilla moderately long 77, filiform, with short, distinct cilia along most of length. Dorsal setae in regular rows as 2.4. 6.6. 8.4. Standard measurements are given in Table 1 View Table 1 .

Gnathosoma: Short, broad, palp segments (Fig. 27 View Figure 27 ). Palp genu compact, length (16.9) similar to width (16.7). Hypostomal setae branched, 48 long. Gnathobase wall with fine punctuations on lateral edges. Palpal formula (fPp) is B. N. 3 N. 5 B 2 NS. Palp tibia with 3 setae, all nude, the dorsal seta (near tibial claw), a stout rod 8 long. Palp tarsus bearing 7 branched and 2 nude setae plus subterminala and tarsala. Palpal tibia spur bifid, with subequal broad and somewhat flattened tines, not claw-like, ventral tine broader and rounded.

Legs: Leg segmentation 7.6. 6, with femur I divided. Coxa I triangular in outline, internal width reduced and heel-like, external width produced (Fig. 28 View Figures 28, 29 ). Coxa I and III ornamented, irregularly foveolate (Figs 28 View Figures 28, 29 , 29 View Figures 28, 29 ). Coxa II with pitting only (Fig. 28 View Figures 28, 29 ). Coxa I and II setae positioned apically. Coxa II seta a curved pointed spur (27 µm, Fig. 28 View Figures 28, 29 ). Coxa III with seta positioned anterobasally. Coxa I and II separated by their own width in this engorged specimen. Many leg segments with internal ring-like thickening. All tarsal claws borne on stalk-like apices. All claws shaped as shallow curves, not strongly hooked or falcate.

Leg I: Tr (1 n) – bFe (2 n) – tFe [2 θ (proximodorsal 17, distodorsal 20), 5 n (3 d, 2 v)] – Ge [4 σ, (distodorsal 14, two proximodorsal 14, distoventral 21), 1 κ (thorn-like microgenuala 5), 5 n] – Ti [2 φ (proximodorsal 20, distodorsal 19), 7 n (including distodorsal mastiseta 39)] – Ta [1 ω (mid-dorsal 15), ca 18 n (including fine, mostly smooth mastiseta 33)].

Leg II: Tr (1 n) – Fe (2 θ, 6 n) – Ge (1 σ, 1 κ, 4 n) – Ti [2 φ, 7 n (including fine, mostly smooth mastiseta 45)] – Ta [1 ω, 1 ε (stout famulus, 4), 20 n].

Leg III: Tr (1 n) – Fe (2 θ, 6 n) – Ge (1 σ, 4 n) – Ti (1 φ, 6 n) – Ta (16 n).

Etymology.

Folium is Latin singular nominative for leaf and refers to the anterior section of the scutum. Gender: neuter, standing in apposition to the generic name (article 11.9.1.2., International Commission of Zoological Nomenclature, 1999).

Discussion.

This record is the first neotrombidiid from a troglophilic beetle, and the only known host for an Australian neotrombidiid. This specimen was found easily during a rapid search under the elytra of ca. 20 specimens of the many Brises sp. ( Tenebrionidae ) collected during cave pitfall trapping. It was loose in a fold of the wings – so its precise attachment site is unknown, and might be the wing itself, rather than dorsal cuticle. Two Neotrombidium species have been recorded from, and even attached to wings ( Lindquist and Vercammen-Grandjean 1971).

Apart from Monunguis parasitizing streblid flies, most host records for Neotrombidiidae are beetles inhabiting subcortical habitats, including species from families such as Cerambycidae , Cleridae , Elateridae , and Tenebrionidae . Two Neotrombidium species were attached to the tarsi of carabid beetles in Iran ( Noei et al. 2017).

Additional tenebrionid host records are the subcortical Alobates sp. ( Tenebrionidae ), parasitized by Neotrombidium tenebrione Lindquist and Vercammen-Grandjean, 1971 , from Washington, D. C., and by the highly similar Neotrombidium beeri Singer, 1971 a , from Kansas. Notably, Singer (1971 b) successfully reared N. beeri nymphs to adulthood by feeding with eggs of Tenebrio molitor .

Coxae I and II being well separated (Fig. 28 View Figures 28, 29 ) might initially argue against the placement of N. folium sp. nov. within Neotrombidium , given the emphasis on this character in early literature. However, in N. khanjanii Noei, Hasanvand, and Saboori (2017) , engorged specimens also exhibit well-separated coxae. For N. khanjanii and N. folium , separation might result from the synthesis of new cuticle during engorgement (cf. neosomy, Audy et al. 1972).

The expanded anterior region of the scutum of Neotrombidium folium appears unique. The form of the scutum highlights and extends the scutal variability known for the Trombidioidea . For Neotrombidiidae , scutal features to consider are to be AM setal insertions on an anterior projection, and in many cases the projection having a discernible posterior border, as a groove or suture, that marks the boundary between the projecting region and the remainder of the scutum, in various Neotrombidium spp and in Cruralonga milnerii sp. nov. (Fig. 5 View Figures 5, 6 ). The anterior projection in Leeuwenhoekiinae have AM setae inserted on the main part of scutum, not on the projection (nasus). I am not aware of Leeuwenhoekiinae where there is a line or groove delineating these two regions. These differences in form and position may not have been considered using homology criteria.

The distinctive characters of N. folium sp nov., viewed without a phylogenetic perspective, might be assumed to represent a generic novelty. Apparent taxonomic distance does not necessarily translate to robust systematic placement however. A straightforward count of branched setae on the legs closely matches those of Neotrombidium species, for instance the number of branched / normal seta on femora matches 7.6. 6 ( Lindquist and Vercammen-Grandjean 1971). The numerous sensory setae (e. g. leg I – III have genualae as 4.2. 1) while an increase compared to Neotrombidium , could even be autapomorphic features evolved as troglomorphic adaptations. If a new genus is proposed now, there is only a single, difficult, specimen which would become the type species. It would be more rewarding for researchers to use the leads provided here and study more material before embarking on further systematic revision.

The type locality of N. folium sp. nov. is a relatively simple cave of tiny volume and ca. 25 m across in its maximum dimension. Superficially, it seemed lifeless, dry and stony. We considered not placing traps at all. Yet remarkably two genera of Neotrombidiidae co-occur here. In addition to N. folium , the same ramp trap yielded two Cruralonga females ( SAMA J 25677 , J 25678). Candidates for postlarvae of N. folium remain uncollected.