Oxybelus lusitanicus Cross, 2020

Cross, Ian, 2020, Oxybelus lusitanicus spec. nov., a new Crabronid wasp species from Portugal, Zootaxa 4894 (2), pp. 292-296 : 292-295

Oxybelus lusitanicus Cross , spec. nov.

( Figs 1–5 )

Holotype. PORTUGAL: Carrapateira (Latitude 37.190, Longitude -8.902), 27.9.2016, m#1 (leg. I.C. Cross). Deposited in the NHMUK.

Paratypes. PORTUGAL: Carrapateira , 1.10.2014 to 7.10.2018, m#5, f#6 (leg. I.C. Cross); Rua Nova (Latitude 41.420, Longitude -7.957), 7.9.2019, f#1 (leg. I.C. Cross). f#1 deposited in the NHMUK with the remaining material retained in the private collection of the author .

Diagnosis. This species can be recognized by the following combination of characters: large size, mucron nonfoliaceous, femora mainly black and yellow, tegula yellow and bifid lamellae linked by a yellow band.

Description. FEMALE: Body length 8.0 to 9.5mm. Head: Entirely black. Frons, vertex and gena covered in short, pale pubescence, more or less erect in ocellar area. Hairs on frons more adpressed, downwardly-directed but parting and curving round scapal basin. Clypeus with median keel, between and just below antennal insertion. Keel low, rounded, bluntly-triangular prominence. Lower margin of clypeus gently convex and flanked by two, blunt, triangular teeth. Mandible pale yellow in the basal half, apically dark reddish-brown, becoming black at the tip. Antenna black with traces of dull, fuscous red, of variable extent and prominence, on the underside of antennal segments 6 to 12. Mesosoma: Entirely black, except yellow markings as follows: pronotal lobe and narrow band spanning width of the pronotal collar, spots on tegula and wing base (which are otherwise translucent), lamellae and a broad band occupying entire surface of the metanotum between them. Lamella bifid at tip. Mucron narrow, curved, tapering evenly to pointed tip, without truncation, emargination or notches at tip. Mucron black with a thin, translucent brown edge. Sculpture of mesonotum dense, coarse punctures. Intervals between punctures forming narrow, flattened, shining ridges approximately half a puncture width. Legs: All coxae and trochanters entirely black. Femora black in basal half and yellow distally, line separating them running diagonally. Zone of transition from black to yellow obscured by diffuse, ferruginous-orange region of variable extent. Ferruginous band most marked on front face of femur. On rear face band less marked, becoming progressively less prominent from hind femur to fore femur. Tibiae entirely yellow with diffuse, ferruginous-orange, longitudinal band below. Tarsi entirely ferruginous-orange. Strong tarsal comb on first tarsus, with 6 to 8 coarse, ferruginous-orange spines on outer face of basitarsus and one on each of three following tarsomeres. Each spine roughly twice as long as width of corresponding segment. Metasoma: All terga densely punctured, punctures slightly coarser on tergum 1. Area between punctures shining, less than a puncture width. Terga 1 to 5 marked by conspicuous, paired, yellow spots, widest at rear of tergum. Spots on terga 1 & 2 form rounded-triangular patches separated by roughly one third to a quarter of their width. On tergum 3, spots form wedge-shaped bands, barely separated or narrowly touching at midline. On terga 4 & 5, spots fuse to form broad bands that cover bulk of tergum apart from broad, black, inverted-triangular area along front edge of tergum. Pygidium entirely glossy-black, subtriangular, roughly two-thirds as wide at base as long. Upper surface marked by conspicuous rim, very slightly convex at sides and meeting at rounded tip. Pygidium has coarse, dense punctation with short, decumbent, very sparse bristles. Bristles pale, with hints of orange towards tip of pygidium. Sternites glossy-black with sparse, coarse punctation, most marked on second sternite. Very fine microsculpture between punctures, especially on second sternite. This only visible at high magnification (> 40x) and from certain angles. Sparse scattering of short, fine, decumbent pale bristles. Transition line between main body of sternite and depressed, marginal zone to rear, marked by few, slightly longer, more erect bristles. No dense fringe of hairs. Sternites entirely black apart from widely-spaced pair of triangular yellow patches at rear corners of second sternite and a pair of small yellow spots at edges of third sternite.

MALE: Body length 6.0 to 7.5mm. As female except in following respects. Head: Median keel of clypeus extended below, overhanging edge of clypeus in form of triangular tooth. Hollow underneath tooth with small median keel that rises a little towards rear to form small, secondary tooth (figure 3). Lower edge of clypeus at mid-point transverse or slightly concave. Tooth at lateral corner of clypeus more prominent than in female, rounded at tip rather than bluntly-triangular. Mandible entirely black, with slight hint of testaceous, reddish brown at apex. Mesosoma: Yellow band on pronotal collar narrows medially, the two halves only connected by a fine yellow line. Legs: Femora black and yellow, with no ferruginous-orange except a hint of orange-brown distally on rear of femur 3. Tibiae yellow with diffuse, black to dusky-brown, longitudinal streak on lower surface. Tarsi ferruginous-orange, except basitarsi which are mainly yellow. Tarsal comb weak, pale spines only a little longer than width of tarsomeres. Metasoma: Yellow spots on terga 1 to 5 all well separated. These form elongated ovals, apart from roundedtriangular spots on tergum 1. Pairs of small, triangular spines at rear corners of terga 3 to 6. Sternites similar in form to those of female but, in all males so far examined, entirely black with no trace of yellow.

Variation. A female specimen from Rua Nova in north Portugal has an almost totally black mandible, with dull yellow restricted to the very base. In this specimen the yellow band on the pronotal collar is reduced to two triangular spots; the ferruginous transitional zones on the femora are reduced to traces of ferruginous-orange, in the form of spots on the top of each femur; and only traces of the yellow patches on sternite 2, and no trace of those on sternite 3, remain.

On females generally, the ferruginous zone on each femur is variable. At its greatest extent, on the front face it can form a broad band reaching the base of the femur. At the other extreme, the band can be totally absent on the rear face of the fore femur.

Although the female antenna is generally black and fuscous, some specimens can have a thin line of yellow at the extreme rim of the distal end of the scape.

In some males there is a gap in the yellow band on the pronotal collar up to a quarter of its width.

Distribution. Until 2019 Oxybelus lusitanicus was found exclusively on coastal dunes at Carrapateira on the western coast of the Algarve, Portugal. Indeed it was at one time thought to be confined to this habitat. However, in 2019 a female was found on a rocky track in a steep-sided river valley in northern Portugal. This female differs from the southern ones in details of the extent of the pale markings (see variation above) but otherwise clearly belongs to the same species. Given the extent of its Portuguese distribution and the variation in habitats it can occupy, it is likely to occur more widely, including in Spain. For the moment though, it is a Portuguese endemic.

Biology. In common with most Oxybelus , little is known of its detailed biology. Oxybelus lusitanicus is a late summer/autumnal species with records spanning 7 th September to 9 th October. Both sexes visit flowers for nectar, with most recorded flower visits being to Helichrysum italicum (Roth) G. Don, 1830 (figure 4). This probably reflects the abundance of this particular flower in dune landscapes in the late summer rather than any particular preference. A male has also been recorded at Polygonum equisetiforme Smith, 1806 (figure 5). Males settle on bare sand in dune slacks, making brief sorties to investigate potential mates. Similar behaviour has been recorded in another Iberian species, Oxybelus lamellatus Olivier, 1812 ( Tormos et al. 2000).

Etymology. The epithet lusitanicus reflects the current known distribution which is restricted to Portugal, which corresponds roughly to the ancient Roman province of Lusitania.

Remarks. At 6.0 to 9.5mm Oxybelus lusitanicus is among the largest of the European fauna, matching species such as O. argentatus Curtis, 1833 and O. hastatus Fabricius, 1804 . Only O. lineatus (Fabricius, 1787) regularly exceeds it in size. The overall impression is of a large, slim, black and yellow species. The habitus of a typical female is illustrated in Figure 1 . The body is essentially glossy black marked by a bright, clear, strong yellow without white or creamy tints. The females are quite striking. In their large size, relatively slim build and unbroken yellow band uniting the lamellae, they have a surprising resemblance to some of the central European subspecies of O. argentatus , such as O. argentatus gerstaeckeri Verhoeff, 1948 . However, they can be instantly distinguished from that species by the bifid lamellae (figure 2) and the largely black and yellow mid and hind femora of O. lusitanicus , in contrast to the simple lamellae and largely ferruginous femora of O. argentatus .

In practice, and in the areas where O. lusitanicus has been found, it is more likely to be mistaken for a large, well-marked specimen of Oxybelus mucronatus (Fabricius, 1793) , alongside which it often flies. With experience, in the field it is possible to distinguish female lusitanicus from that species by their larger size (8.0 to 9.5mm compared with 6.5 to 7.5mm) and slimmer build. Males are more problematical. Firstly, because there is some overlap in size: 5.0 to 6.5mm for O. mucronatus , 6.0 to 7.5mm for O. lusitanicus . Secondly, because the difference in slimness is less apparent. Above all, O. mucronatus males are notoriously variable and the lightest specimens can be as yellow as O. lusitanicus —some even having a yellow band on the metanotum linking the lamellae.

Since size and build can be difficult to assess—especially in the absence of comparative material—for confirmation more critical characters need to be examined under the microscope. Following the key in Guichard (1993) both sexes will key out with the species pair Oxybelus mucronatus / O. dissectus Dahlbom, 1845 . More critical features to separate this trio in both sexes are given in the amended keys below.

Figures

FIGURES 1–5. 1: Oxybelus lusitanicus female habitus. 2: Metanotum showing broad yellow band and bifid lamella (arrowed). 3: Lateral view of male clypeal keel showing secondary tooth (arrowed). 4: Female nectaring on Helichrysum italicum. 5: Male nectaring on Polygonum equisetiforme.