Agabus agulhas Bilton, Englund & Bergsten, 2020

Englund, William F., Njoroge, Laban, Bistroem, Olof, Miller, Kelly B., Bilton, David T. & Bergsten, Johannes, 2020, Taxonomic revision of the Afrotropical Agabus raffrayi species group with the description of four new species (Coleoptera, Dytiscidae), ZooKeys 963, pp. 45-79 : 45

publication ID	https://dx.doi.org/10.3897/zookeys.963.53470
publication LSID	lsid:zoobank.org:pub:9636C9F2-C6BD-4B34-BCC6-ED214C7B0D19
persistent identifier	https://treatment.plazi.org/id/FD6B9312-065E-4B96-9FDF-9B1C45EA8D69
taxon LSID	lsid:zoobank.org:act:FD6B9312-065E-4B96-9FDF-9B1C45EA8D69
treatment provided by	ZooKeys by Pensoft
scientific name	Agabus agulhas Bilton, Englund & Bergsten
status	sp. nov.

Treatment

Agabus agulhas Bilton, Englund & Bergsten sp. nov. Figures 1 View Figure 1 , 6G View Figure 6 , 8I View Figure 8 , 9F View Figure 9 , 11N View Figure 11 , 11R View Figure 11 , 12 View Figure 12 , 13 View Figure 13 , 14 View Figure 14

Type locality.

South Africa, Western Cape Province, Rooistrandveld, Bredasdorp, natural viei beside road to Die Dam at Ratelrivier 34°43'00.47"S, 19°41'53.81"E, 31 m.

Type material.

Holotype ♂ (AMG) labelled: "26/ix/2010 South Africa WC Rooistrandveld, Bredasdorp natural viei beside road to Die Dam @ Ratelrivier FW marsh with tussocks etc. D. T. Bilton leg.". Paratypes 3 ♂ 2 ♀ (AMG, CBP, NHRS, ZSM) labelled: "26/ix/2010 South Africa WC Rooistrandveld, Bredasdorp natural viei beside road to Die Dam @ Ratelrivier FW marsh with tussocks etc. D. T. Bilton leg.".

Diagnosis.

Very similar to A. austellus sp. nov. and A. riberae sp. nov., but distinguishable by the distinctly curved base of the aedeagal subapical tooth (compare Fig. 8I View Figure 8 with Fig. 8G, H View Figure 8 and see Fig. 6G View Figure 6 ), the scutellum being lighter than the elytra and its relatively narrow metasternal wing (see Table 1 View Table 1 and Fig. 12 View Figure 12 ).

Description.

Habitus as in Fig. 11N, R View Figure 11 .

Colour: Head black with weak rufous interocular spots and an anterior rufous area. Pronotum black with slightly rufous margins. Elytra blackish brown to black, with a lighter scutellum. Ventral surface black, testaceous lines on abdominal segments reduced or absent, hypomeron and epipleuron rufotestaceous to rufous. Legs rufopiceous to rufous. Antennae and palpi testacous.

Microreticulation : Relatively fine on both pronotum and elytra, and slightly more impressed in females. The microreticulation of the elytral disc is composed of a mix of small and larger, somewhat irregular meshes (Fig. 9F View Figure 9 ).

Structural features : Body length: 7.60-8.00 mm (see Table 1 View Table 1 ). Hypomeron marginally visible in strict lateral view, lateral bead of pronotum narrow and well defined. Metasternal wing very narrow, WC/WS> 3.6 in all specimens (see Table 1 View Table 1 and Fig. 12 View Figure 12 ). Pronotum broad, more than twice as broad as interocular distance (see Table 1 View Table 1 and Fig. 13 View Figure 13 ).

Legs: Protarsal claws very long,> 1.8 × as long as protarsomere 4 in all males (see Table 2 View Table 2 & Fig. 14 View Figure 14 ). Metatarsomeres short and broad; metatarsomere 2 <1.8 × as long as broad (see Table 2 View Table 2 ), metatarsomere 5 <3 × as long as broad in all specimens (see Table 2 View Table 2 ).

Male genitalia: Aedeagus without the prolonged section between subapical broadening and the apical and subapical teeth which is present in some species in the group. In ventral view the apex is asymmetrically curved. Base of subapical tooth distinctly curved basally (see Figs 8I View Figure 8 , 6G View Figure 6 ).

Female: Externally similar to males. Dorsal microreticulation slightly more impressed than in males.

Distribution.

Only known from the type locality, a lowland valley wetland at 31 m on the Agulhas Plain, Western Cape Province, Republic of South Africa (see Fig. 1 View Figure 1 ). The most southerly distributed Agabus species in the world.

Ecology.

Collected from the base of large tussocks in a valley wetland. Despite having largely lentic conditions, this is likely to experience some seepage flow, particularly following periods of high rainfall in winter and spring.

Etymology.

Named after the Agulhas Plain, on which the type locality is situated. The Agulhas Plain is itself named in reference to nearby Cape Agulhas (Portuguese - Cabo das Agulhas = Cape of Needles), the most southerly point on the African continent. As with other members of the species group, A. agulhas sp. nov. has sharp, needle-like, teeth at the aedeagal apex.

Comments.

COI sequence divergence between A. agulhas sp. nov. and A. austellus sp. nov. ranges from 3.9 to 4.7%; that between A. agulhas sp. nov. and A. riberae sp. nov. being 6.4% (I. Ribera, pers. comm.).