Thortus michauxi, Leschen & Chen & Harmer, 2024

Thortus michauxi sp. nov.

( Figs 13 View Fig , 19B View Fig )

Type material. HOLOTYPE: ♁ ( NZAC), labelled: ‘ Ewing I. Auckland Is. 9 Feb 73 D. S. Horning // ex mat of thick moss on prostrate trunk of Olearia lyalli // NZ Arthropod Collection Private Bag 92170 Auckland New Zealand NZAC04235028 About NZAC .’ PARATYPES (80; AMNZ, BPMN, NZAC, OMNZ). AUCKLAND ISLANDS (AU): 2,Adams Island, 20 Jan - 4 Feb 2011, tussock and megaherbs, in flat albatross nestling area, G. Elliott, K.J. Walker, 50°54.158′S, 166°0.262′E, AMNZ 85286, AMNZ 85287;1,Adams Island, 19 Jan - 3 Feb 2011, southern rata forest coastal, sooty shearwater colony, G. Elliott, K.J. Walker, 50°51.905′S,166°22.117′, AMNZ 85292; 1 ( OMNZ), Adams Island, 2-7 Dec 1996, G.H. Sherley, B. Patrick, [50°50.248′S, 165°55.342′E]; 1, Adams Island, Fairchilds Garden, 20 Jan 1966, litter, G. Kuschel, 50°50.248′S, 165°55.342′E, NZAC 04235277; 2, Adams Island, Fairchilds Garden, 22 Mar 2006, megaherb leaf litter, R. Leschen, E. Edwards, 50°50.248′S, 165°55.342′E, NZAC 03019027, NZAC 03021584; 1, Adams Island,Magnetic Point, 28 Nov - 14 Dec 1996, herbfield, G.H. Sherley, [50°50.248′S, 165°55.342′E], NZAC 04235197; 21, Adams Island, Magnetic Cove Station, 28 Jan 1966, litter, G. Kuschel, [50°51.645′S, 166°5.302′E], NZAC 04231310, NZAC 04235064, NZAC 04235068, NZAC 04235112, NZAC 04235158, NZAC 04235160, NZAC 04235161, NZAC 04235163, NZAC 04235210, NZAC 04235238, NZAC 04235239, NZAC 04235245, NZAC 04235265, NZAC 04235299, NZAC 04235305, NZAC 04235313, NZAC 04235314, NZAC 04272528, NZAC 04272540, NZAC 04272541, NZAC 04272542; 1, Carnley Harbour, E Tagua Bay, 4 Feb 1973, litter, J.S. Dugdale, [50°48.633′S, 166°3.933′E], NZAC 04235268; 7, Auckland Islands, Disappointment Island, 15 Feb 1975, plants,D.S.Horning, [50°36.45′S, 165°58.283′E], NZAC 04235186, NZAC 04235212, NZAC 04235221 NZAC 04235224, NZAC 04235228, NZAC 04235310, NZAC 04235318; 18, Ewing Island, 9 Feb 1973, in bark of live Olearia lyalli, D.S. Horning , [50°31.711′S, 166°18.215′E], NZAC 04235032, NZAC 04235039, NZAC 04235040, NZAC 04235055, NZAC 04235061, NZAC 04235067, NZAC 04235070, NZAC 04235071, NZAC 04235149, NZAC 04235162, NZAC 04235164, NZAC 04235167, NZAC 04235170, NZAC 04235247, NZAC 04235289, NZAC 04235290, NZAC 04235295, NZAC 04235319; 13 (same as holotype), Ewing Island, 9 Feb 1973, ex mat of thick moss on prostrate trunk of Olearia layallii, D.S. Horning , [50°31.713′S, 166°18.229′E], NZAC 04235028, NZAC 04235031, NZAC 04235083, NZAC 04235084, NZAC 04235101, NZAC 04235162, NZAC 04235180, NZAC 04235183, NZAC 04235195, NZAC 04235200, NZAC 04235219, NZAC 04235256, NZAC 04235272, NZAC 04235275; 4, Ewing Island, 7 Feb 1973, in rotting bark of live Olearia lyallii, D.S.Horning ,[50°31.713′S, 166°18.229′E], NZAC 04235037, NZAC 04235077, NZAC 04235298, NZAC 04235317; 3, Ewing Island, 9 Feb 1973, leaf litter in Olearia layallii forest in drainage, D.S. Horning, [50°31.713′S, 166°18.229′E], NZAC 04235065, NZAC 04235132, NZAC 04235276; 1, Ewing Island, 9 Feb 1973, Stillbocarpus polaris,

Olearia layalli litter, D.S. Horning, [50°31.713′S, 166°18.229′E], NZAC 04235114; 1 ( BPMN), Ewing Island, Port Ross, 1 Jan 1963, moss on tree trunk, K.A.J. Wise, [50°31.733′S, 166°18.033′E]; 1, Fleming Plateau, 9 Feb 1973, swards, J.S. Dugdale, [50°47.383′S, 165°56.833′E], NZAC 04235230; 1, Mount D′ urville, 4 Jan 1973, mats, J. Farrell, [50°49.9′S, 166°10.333′E], NZAC 04235216; 1, Waterfall Inlet, 26 Mar 2006, litter along stream margins, R. Leschen, E. Edwards, 50°48.977′S, 166°12.042′E, NZAC 04235209.

Diagnosis. The Auckland Islands endemic Thortus michauxi sp. nov. is distinguished from all other Thortus species by having a large body with a weak supra-antennal ridge which lacks a rim and abdominal ventrite 1 lacking postcoxal lines. It is also the only species of the genus with males that have a dense brush of tenent setae on tarsomeres 1–3 on the pro- and mesolegs and the aedeagus with a well-formed basal plate in the distipenis.

Description. Length 2.10–2.50 mm. Colour of body dark to light reddish-brown, mouthparts, legs, and distal parts of the antennae often lighter. Body surface semiglabrous, microsculpture strigulate over all surfaces, but weaker or absent from elytra. Dorsal setae golden, sparse, dual, consisting of very short decumbent and erect setae, and longer suberect to erect setae. Ventral surfaces with more dense and shorter erect setae of variable lengths; finely to shallowly punctate, central disc of metaventrite with punctures larger and more impressed than those of prosternum, punctation of abdominal ventrites 1 to 4 less impressed than metaventrite, and on ventrite 5 denser, and with a well-defined patch of posteriorly-directed setae. Head lengthened with relatively long gena, about 2 times as long as antennomere 1; frons relatively wide and parallel-sided between antenna, width about equal to length of antennomere 1; supra-antennal ridges without a well- -developed rim and bead; vertex with regular punctation and not delimited anteriorly by a transverse crenulate line or distinctly glabrous areas; punctation of gula and sides of the head similar, distinct and ovate. Eye consisting of 12–16 facets. Antennomere 2 cylindrical, wider than long, antennomere 3 subconical, longer and as wide as 2 and longer and slightly wider than 4, proportions of antennomeres 4–8 same, antennomere 4 shorter than 3, antennomere 9 wider than 8 and narrower than 10 and 11, antennomere 10 transverse and scarcely wider than 11, antennomere 11 longer than 10, shorter than 9 and 10 combined. Pronotum quadrate, pronotal length/width ratio ~1.00, shape widest at middle; anterior margin weakly sinuate; anterior angles obtuse lateral edges subparallel in basal half and gradually converging anteriorly; pronotal disc with punctures regular and uniform, widely separated by a distance between punctures up to 3–6 times their diameter; median impression absent; transversely depressed at basal 1/5; basomedial macropuncture present, ovoid and well-delineated by extensions of the posterior bead; posterolateral angles subacute and not projecting posteriorly; posterior margin evenly and weakly convex, scutellar lobe absent. Prosternal process with well-developed lateral marginal beads, without longitudinal depression medially, process not expanded apically behind procoxae, apex rounded, width subequal that of procoxa and 0.49 times as long as prosternum; procoxal cavity with weak anterolateral notch. Scutellary shield ovoid, 1.4 times as wide as long. Elytra about 1.68 times as long as combined widths, about 1.25 times as wide as width of pronotum, about 2.08 times as long as length of pronotum; setation dual, consisting of very short decumbent or erect setae, and longer suberect to erect setae; humeral plica absent; parasutural stria present in apical 1/3, with interspace asetose; punctation similar to pronotum, but less uniform, and separated by a distance of 1–4 times their diameter. Metaventrital process with anterior margin weakly curved, marginal bead connected at middle. Tarsi moderately slender, 5-5- 5 in female, 5-5- 4 in male, male pro- and mesotarsomeres 1–3 with dense tenent setae; mesotarsomeres 1–3 of subequal lengths with 1 slightly shorter than 2, 3 and 4 which are equal, mesotarsomere 5 equal to tarsomeres 1–4 combined. First abdominal ventrite without postcoxal lines; intercoxal process subacute. Aedeagus with very short parameres broadly fused to phallobase at their bases, separated at the apex, length about 2.25 times as long as wide; apices asetose, lacking membranous extensions; basipenis about 5.17 times as long as distipenis; distipenis about 1.38 times as long as wide, lateral lobes moderately separated, basal plate present; internal sac with a pair of short slender endophallites.

Etymology. A high school teacher dedicated to understanding Earth history and conservation of birds, Bernard Michaux, friend and colleague of the first author, is honoured with the specific epithet.

Distribution. Offshore Island: Auckland I. (AU) ( Fig. 21 View Fig ).

Remarks. Like many species of edaphic subantarctic beetles, T. michauxi sp. nov. does not appear to be a microhabitat specialist ( CARLTON & LESCHEN 2001). It has been collected in leaf litter, under bark, and in moss.