Paussus minutulus Nagel & Rasool

Abdel-Dayem, Mahmoud S., Elgharbawy, Ali A., Rasool, Iftekhar, Nagel, Peter & Aldhafer, Hathal M., 2019, The Carabidae (Coleoptera) of Shada Al-A'Ala Nature Reserve, Southwestern Saudi Arabia, with description of a new species of Paussinae, ZooKeys 812, pp. 93-131 : 112-116

Paussus minutulus Nagel & Rasool sp. n. Figs 4, 5, 6

Holotype (hereby designated).

Female; dry-mounted, glued on pinned pointed card; head with antennal clubs, left middle tibia with tarsus, left hind leg detached, and glued on to same card.

Original labels.

1. White, rectangular, black printed text and thin frame (verbatim, slash = line break): "KSA. Baha; / Shada Al-A’ Ala Nature Reserve; / 19°50.411'N, 41°18.686'E; / 1611 m; 2.IX.2015; PT.2; / Aldhafer, H., Fadl, H., Abdel-Dayem, M., / Elgharbawy, A., El Torkey, A., Soliman, A.". 2. White, rectangular, black handwriting: " Paussus sp. 3".

Added labels.

1. Red, rectangular, printed in black: "HOLOTYPUS/ Paussus minutulus / Nagel & Rasool, 2018". 2. White label, printed: “♀”.

Holotype repository.

King Saud University Museum of Arthropods (KSMA), Department of Plant Protection, College of Food and Agriculture Sciences, King Saud University, Riyadh, Saudi Arabia.

Type locality.

Arabian Peninsula, western Saudi Arabia, Baha Province, Upper Shada Mountain, Shada Al-A’ Ala Nature Reserve 19°50.411'N, 41°18.686'E), 1611 m, pitfall trap no. 2, emptied on 2 September 2015 after 48 hours of exposure. The place of exposure of pitfall trap no. 2 is dominated by the cactus pear Opuntia ficus -indica (L.) Mill. ( Cactaceae ). This "cactus zone" covers the area of the nature reserve above approximately 1500 m. It is an extensively cultivated area, also characterized by small-scale terraced fields (Fig. 4). More details are given in "Study area" above.

Etymology.

The specific epithet is the Latin adjective for very small, because it is the smallest known Arabian Paussus .

Diagnosis.

Paussus minutulus sp.n. is a small Paussus of the P. cucullatus group sensu lato and is most similar to P. abditus Nagel, 2018 (SA) and P. rougemontianus Lorenz, 1998 (Yemen). It is distinguished from both by the tumid antennal club with its posterior basal angle large, thick, and apically truncate. Further specific characters are as follows: antennal club with excavation ending far in front of apex; head with vertex produced, with two distinct pores at the top; collar of anterior pronotum low, with transverse edge rounded and with lateral projections absent; pronotal trichome well developed at both ends of transverse furrow; pygidium with lower (posterior) margin with dense fringe of hair; fore and middle legs robust, not compressed, hind femur dilated and flattened, hind tibiae little wider than thick; small, apically fringed setae present at several body parts, most obvious at antennomere 1 and all legs.

Description of female holotype specimen.

(Fig. 5) Standardized body length from tip of head to tip of elytra 3.4 mm (3.5 mm total body length from tip of head to tip of pygidium), width across mid-elytra 1.5 mm. Body castaneous, appendices little darker, ventral abdomen and anterior part of pronotum little lighter; compacted or reinforced marginal areas of head, antennal clubs and pronotum narrowly blackish. Surface smooth and shining, except forehead matt and antennomere 1 (scape) with dense and coarse, yet shallow punctuation. Pubescence of elytra inconspicuous, restricted mostly to apical and lateral parts (abraded in the middle?), of short and upright as well as recumbent, narrowly lanceolate setae; elytra additionally with very few, long, thin, upright setae on lateral part of disc and as series umbilicata; head, pronotum, pygidium and appendices with scattered, short, mostly appressed setae; these short setae have a multiple split (fringed) apex and are most obvious at antennomeres 1, femora and tibiae, yet absent at elytra; antennal clubs with the normal apical sensory field and with scattered upright or slightly curved medium setae. Head 1.3 times wider than long, frontal margin broadly truncated, slightly biconvex; in dorsal view head in front of eyes little narrowed apically, gena and eye of equal length; temples not projecting; head with vertex produced, with two distinct pores at the top; pores broadly marginate with orifice slightly sunk. Antennomere 1 devoid of distinctly marked longitudinal edges; antennal club excavate on its exterior (posterior) side, 1.5 times longer than wide (basal tooth disregarded), tumid; frontal margin distinctly emarginate near base, with one small and one tiny fenestriform pit; anterior basal angle of club acute, marked; posterior basal projection large, thick, apically truncate; hind (exterior) side of the club with excavation limited by broad dorsal and ventral borders, and ending far before apex; at posterior view dorsal and ventral margins of excavation swollen, undulate with 3 or 4 low tubercles, each with one to three subapical setae; club without distinct trichome near ventral base, just an indistinct assemblage of three slightly thicker setae. Mouthparts as shown in Figure 6, not dissected; ligula at ventral view with longitudinal carinula in the middle of the disc (not shown in Fig. 6); (antepenultimate) maxillary palpomere II at broadest view 1.5 times as long as wide with mesal margin almost straight; (terminal) labial palpomere III long, narrow, five times as long as wide, apically rounded; gula with width/length ratio at narrowest point 0.9 (for measurement see Robertson and Moore (2016). Pronotum approximately as long as wide (1.1 times wider), transversely bipartite, with large trichomes at both ends of furrow; anterior part little wider than head (1.2 times), low, with transverse dorsal edge of collar broadly rounded, slightly indented in the middle, not angulate, lateral angles obscure; posterior part narrowed towards base. Elytral pubescence of two types: a few, very scattered, thin, long, erect setae on lateral parts of the disc (in addition to the similarly looking hairs of the series umbilicornis), plus scattered, recumbent, narrowly lanceolate setae on lateral and apical parts of disc; lateral subapical folds ("flange of Coanda") normal, without peculiarities. Hind wings present. Pygidium with central disc almost even, with indistinct microsculpture, weakly shining; lower (anatomically posterior) margin explanate; pygidial trichome of dense fringe of long hair set semicircular along lower margin; ventral part of explanate margin set with one row of short, appressed setae. Legs robust, femora and tibiae of fore and middle legs not compressed, hind femur and tibia slightly compressed and dilated, the whole inner side of hind tibia with longitudinal shallow groove; pubescence of femora and tibiae of scattered, small, apically fringed setae; all tibiae without terminal spurs; terminal tarsomere of posterior tarsus as long as three preceding ones together; tarsomeres ventrally with few lateral setae, and glabrous in the middle. Inner side of hind femur subbasally with file of stridulatory organ; the file consists of multiple parallel fine grooves and is located at both the anterior and posterior parts of a longitudinal, short carinula.

Male.

Unknown.

Distribution.

The new species is only known from the holotype female specimen from the type locality at Shada Al-A’ Ala Nature Reserve.

Ecology.

This single specimen of Paussus was found in an area with low impact small-scale agriculture. The vegetation is characterized by dominant cactus pear. The altitude is ca 1610 m, the winters are cool and most of the 200 mm annual rainfall is concentrated between March and May (see details in chapter "Study area" above). The specimen of P. minutulus sp.n. was taken by a pitfall trap which also caught ants of the following taxa: Camponotus aegyptiacus Emery, 1915; Messor ebeninus Santschi, 1927; Monomorium jizane Collingwood & Agosti, 1996; Pheidole Westwood, 1839, sp.; Tetramorium simillimum Smith, 1851) and Tetramorium sericeiventre Emery, 1877. Members of all these genera are known as host of one or more species of Paussini ( Geiselhardt et al. 2007). Paussus minutulus sp.n. forms part of the Afrotropical P. cucullatus species group, of which several members are known to be associated with Pheidole sp., including the Arabian P. rougemontianus (see, for example, Luna de Carvalho 1989).

Remarks.

The new species is assigned to Paussus subgenus Hylotorus Dalman, 1823, according to the phylogenetically based classification of Robertson and Moore (2016) (see Nagel et al. 2017a). The description of P. minutulus sp.n. given above agrees generally well the diagnosis and characters used in the key provided by Robertson and Moore (2016) and their subgenus description. The labial palpomere III is longer and narrower than described as usual for the Subgenus Hylotorus , yet still within the range of variation of this character, and similar to P. abditus Nagel, 2018 in Abdel-Dayem et al. (2018). The lacinia was not dissected. The fringed setae are conspicuous, despite their tiny size. Sometimes, individuals of a few Paussus species were found to show the same type of setae with both split and unsplit apices. In these cases, the splitting is most probably an artifact caused by a treatment during or after collecting (use of certain chemicals in the killing bottle or relaxing chamber, for example). In P. minutulus sp.n. this particular shape is obviously an intrinsic character, because they are alike at all body parts where they occur.

Paussus minutulus sp.n. forms part of the P. cucullatus group sensu lato and is most similar to and possibly part of the same clade as P. abditus Nagel, 2018 in Abdel-Dayem et al. (2018) (SA) and P. rougemontianus Lorenz, 1998 (Yemen) (replacement name for Cochliopaussus rougemonti Luna de Carvalho, 1989). It differs from P. abditus by the slightly shorter pronotum, the less compressed and dilated hind leg, the absence of a distinct subbasal antennal trichome, the smaller extension of the excavation at the posterior antennal club, the large, thick, apically truncated posterior basal projection of the antennal club, the presence of fringed setae, and the clearly marked, distinct cephalic orifices.

It differs from P. rougemontianus by the slightly shorter pronotum, the less compressed and dilated hind leg, the absence of a distinct subbasal antennal trichome, the dorsal hind margin of the antennal club retracted, the presence of fringed setae, and, above all, the large, thick, apically truncated posterior basal projection of the antennal club in the new species. The new species differs from the little-known Ethiopian P. cyathiger Raffray, 1886, among others, by the long, thin peg-like posterior basal angle of the antennal club, and the longitudinal crescent margin at the external part of the cephalic pores of the latter (see Abdel-Dayem et al. 2018).

It is the smallest known Arabian Paussus and at the same time it is among the smallest Paussus at global scale (smallest measurements 3.3-3.5 mm total body length): Paussus (Subg. incertae sedis) exiguus Reichensperger, 1929, Sudan; P. (Anapaussus) asperulus Fairmaire, 1898, Madagascar; P. (Anapaussus) pipitzi Dohrn, 1884 [ssp. pictor Reichensperger, 1922, and possibly further subspecies], Madagascar and P. (Edaphopaussus) favieri Fairmaire, 1851, southwestern Europe and northwestern North Africa).

The Arabian Peninsula and adjacent regions harbour ten (with P. minutulus sp.n. included) species of Paussinae , all members of the genus Paussus Linnaeus, 1775 (see Nagel et al. 2017b; Abdel-Dayem et al. 2018). The following eight species have been recorded from the montane ecoregion of southwestern SA and Yemen (linked to the Eastern Afromontane Highlands Hotspot, see Mittermeier et al. 2004). The presence of all of them is in line with the zoogeographical affiliation of southwestern Arabian Peninsula to the Afrotropical Region: Paussus abditus Nagel, 2018 (END_SA); P. arabicus Raffray, 1886 (AFR_SAR); P. brittoni Reichensperger, 1957 (END_YE); P. cephalotes Raffray, 1886 (END_AR); P. cirenaicus Fiori, 1914 (PAL_SAR); P. minutulus Nagel & Rasool, sp.n. (END_SA); P. rougemontianus Lorenz, 1998 (END_YE) and P. thomsonii Reiche, 1860 (PAL_AFR_SAR).