Ngaliadessus humphreysi, Watts & Villastrigo & Langille & Bradford & Humphreys & Balke & Stringer & Austin, 2023

Watts, Christopher H. S., Villastrigo, Adrian, Langille, Barbara L., Bradford, Tessa M., Humphreys, William F., Balke, Michael, Stringer, Steven J. B. Cooper Danielle N. & Austin, Andrew D., 2023, Phylogenetic placement and description of Ngaliadessus humphreysi gen. et sp. nov., Watts & Villastrigo (Coleoptera: Dytiscidae), a subterranean diving beetle from the Ngalia Basin in central Australia, Austral Entomology 62 (3), pp. 300-309 : 303-306

Ngaliadessus humphreysi sp. nov., Watts & Villastrigo

(Figures 3-4)

https://zoobank.org/ urn:lsid:zoobank.org:act:3BD0F3CF-3D60-4B5A-A822-E4952C5F2E80

Type locality: Australia, Northern Territory, Sullivans Well – Napperby Station . (22.73614 S, 132.46104 E) .

Material examined

Holotype

Female (Museum and Art Gallery of the Northern Territory, MAGNT I011303 ), Sullivans Well, Napperby Station 16/9/2015, collected by S. Cooper, W. Humphreys, and D. Stringer.

Paratype

1 female, partial, consisting of head capsule, abdomen and elytra, lacking appendages, mounted on same microscope slide as holotype MAGNT I011303 . Two DNA samples ( BES18753.1 and BES18753.2 ), stored at the South Australian Museum , represent female specimens that were morphologically identical to the holotype MAGNT I011303 . Specimen BES18753.1 was used for the exon capture analyses to generate mitochondrial genome data (accession numbers are available in Table S 1) .

Description

The description below is based on female specimens only as no males were available.

Adult female

Size, colour and habitus

Habitus as in Figure 3. Length 2.7 mm; relatively flat, moderately constricted at junction of pronotum and elytra; elongate, elytra almost parallel-sided; uniformly testaceous; hindwings absent.

Head

Narrower than elytra, shiny, smooth, reticulation virtually absent, punctures sparse, very small; widening from apex to about middle, then roundly angled to almost parallel sided; lacking setae, eye remnant absent other than very small crease. Antenna relatively short, relatively stout antennomeres 3–10 weakly widening towards apex on anterior edge, antennomeres broadening slightly towards apex, of approximately similar lengths except for antennomere 11 which is noticeably longer than antennomere 10. Each antennomere, except antennomer 1 with some very small setae on anterior side apically, antennomeres 5–10 slightly expanded on anterior apical corner. Maxillary palpus elongate, palpomere 4 as long as palpomeres 1–3 combined.

Pronotum

A little narrower than elytra; anterolateral angles projecting strongly forwards, projection about half length of rest of pronotum, posterior angles bluntly rounded, overlaying head somewhat; surface smooth, reticulation obsolete, punctures very weak, sparse, some weak but relatively long setae at sides; without stria.

Elytra

Not fused; sides slightly widening in middle, smooth, very weakly reticulate, very sparsely covered with small punctures; epipleuron weakly differentiated from rest of elytron, thin, weakly expanded close to front of elytra.

Ventral surface

Prosternal process very narrow between procoxae, then rapidly widening before smoothly narrowing to near apex where it sharply narrows to point, reaching mesothorax, sides subparallel, apex rounded. Metathorax relatively narrow, metaventral wings short. Metacoxal plates broad, pear-shaped, large, shiny, virtually nonreticulate. Sutural line between ventrites 1 and 2 complete, ventrites 3–5 mobile, sparsely covered with small punctures.

Legs

Protibia narrowly club-shaped, row of very short setae along inner edge, 5–6 setae along both inner and outer edges and a group of strong spines at apex, protarsus 5-segmented, tarsomeres weakly expanded, apices not strongly bifid, tarsomere 1 about 2 as long as broad, tarsomere 2 as wide as tarsomere 1, about half its length, tarsomere 3 slightly longer than tarsomere 1 deeply bifid, tarsomere 4 about length of tarsomere 3, narrower, moderately curved, claws curved relatively short, tarsomeres with some short setae on inner angles; profemur stout, elongate. Mesotrochanter small, oval; mesofemur relative thin, elongate boat-shaped with some weak spines near base and along basal half of anterior edge; mesotibia shorter than mesofemur, club-shaped with number of stout spines towards apex and along anterior edge; mesotarsi much weaker than protarsi, tarsomere 1 1.5 longer than wide, tarsomeres 2 and 3 similar, about half as long as tarsomere 4, smaller than tarsomere 3, tarsomere 5 elongate, weakly curved almost 3 length of tarsomere 1. Metatrochanter relatively large, elongate oval, apex bluntly pointed; metafemur relatively narrow, broadest in middle, lacking spines, with 4 long setae along dorsal edge; metatibia curved, widening towards apex, with field of long stiff setae close to apex on inner angle otherwise without spines or setae; metatarsus elongate, with swimming hairs, tarsomere 1 longest, tarsomeres 2 and 3 shorter, equal length, tarsomeres 4 and 5 similar length, slightly shorter than tarsomere 3, tarsomeres 1 and 2 in combination slightly shorter than others, claws very weak. Spermatheca with elongate, triangular spine (Figure 3).

Larvae

Two specimens, slide mounted, same data as holotype, one complete other only head capsule. By size and lack of egg busters we judge both to be second instar ( SAMA 25-039823 ; SAMA 25-039824 ).

Colour and habitus

Body uniformly very pale, unpigmented. Head capsule, abdominal segment 8 and urogomphi as in Figure 4.

Head capsule

Longer than broad, with small lamellae clypeales; without stemmata (Figure 4a–c). Maximum width just posterior to where eyes would be, with slight neck constriction; nasal elongate, rounded apically, sinuate laterally; dorsal surface with some setae on margin near apex; margin of ventral surface from apex to near antennae with band of lamellae clypeales of varying sizes and some patches of small lamellae clypeales in middle near apex, two longer setae near base of antennae. Antenna elongate with four antennomeres, shorter than head; antennomere 1 short, relatively broad; antennomeres 2 and 3 approximately similar in length; antennomere 4 short, elongate, pointed. Mandible broad basically, distal half projecting inwards and upwards, apex sharp, mandibular channel present. Maxillary palpus elongate, relatively thin, composed of three palpomeres; palpi 2 and 3 subequal in length. Epidysal suture weak in specimens. Legs long, thin, tarsi moderately long thin, sparce setae on hind margins, without swimming hairs.

Abdomen

Abdominal segment eight longest, completely sclerotised, setae only on margins, siphon short, subconical with one set of ABC pores ( Michat et al. 2012) (only one very small pore was detected). Most of second segment of both urogomphi missing from specimens; first segment moderately long, little less than twice length of abdominal segment 8, with three long setae on shaft and two long setae at end (Figure 4d).

Etymology

Named after William Humphreys in recognition of the outstanding research he conducted in the subterranean biology field for more than three decades, and his numerous field trips to discover, collect and describe, in partnership with Chris Watts and other colleagues, the majority of stygobiotic dytiscid species currently known in Australia. The specific name is a noun in the genitive case.