Acnephalomyia platygaster ( Loew, 1858 )

Blee, Tayler, Cabrero, Allan & Dikow, Torsten, 2025, Namib Desert Asiloidea (Diptera) 1. A review of the assassin-fly genus Acnephalomyia Londt, 2010 (Asilidae) with the description of a new species, African Invertebrates 66 (2), pp. 251-271 : 251-271

Acnephalomyia platygaster ( Loew, 1858)

Figs 9 , 10 , 11 B

Links.

ZooBank https://zoobank.org/ 3B30C903-65C3-4305-9FBB-D5389298A469.

GBIF https://www.gbif.org/species/12026579.

original description online https://www.biodiversitylibrary.org/page/15959408.

Plazi TreatmentBank https://treatment.plazi.org/id/ FA455017-FFFC-AD61-FEBC-7445490FFDA0.

Type locality.

Namibia: Erongo: Swakop (= Swakop riverbed) ( 22°41'09"S, 014°31'51"E, updated more precise coordinates).

Material examined.

Holotype. Namibia – Erongo • 1 ♂ Swakop (= Swakop riverbed) ; [ 22°41'09"S, 014°31'51"E]; 1854; Wahlberg, J. leg.; NHRS -GULI-000111153 ; NHRS .

Other material. Namibia – Karas • 1 ♀ Aus, outskirts overlooking town ; [ 26°39'57"S, 016°15'34"E]; 30 Aug 1983; Stuckenberg, Brian, Londt, Jason leg.; rocky area, shrubs; NMSA -DIP 108897 ; NMSA .

Diagnosis.

The species is distinguished from congeners by the yellowish to light brown setose scutum, the postero-dorsally white setose katepisternum, the presence of dorso-ventrally flattened setae on legs and abdomen, the strong, light brown macrosetae on the postpronotal lobe and the presence of strong, short, yellowish marginal macrosetae on the abdominal tergites.

Distribution, biodiversity hotspots, endemism, seasonal imago flight activity and biology.

A widespread but less commonly collected species occurring from Swakopmund in Namibia in the north to southern South Africa (see Londt (2010): fig. 67) with the majority of records from southern Namibia ( Karas Region) and north-western South Africa ( Northern Cape Province). A rarely collected species in the southern Namib Desert known only from two specimens from two collecting events (Table 2 ). The species is known to occur in the Cape Floristic Region and Succulent Karoo biodiversity hotspots (see Londt (2010): fig. 67), but also occurs outside of these hotspots. The species is not endemic to a particular environment or country. Adult flies are active in spring (August) in the southern Namib Desert (Table 3 ). Nothing is known of the biology.

Remarks.

The exact locality and collection details of the holotype are unknown, but Brinck (1955, p. 31) provides an overview of J. A. Wahlberg’s collecting in the Swakop riverbed in May 1854 and July – October 1854. All Acnephalomyia specimens from the southern Namib Desert have been collected in the spring only (see Table 2 ) so it seems more plausible that the holotype was collected between August and October 1854. From that, it is also apparent that the species was collected in the western Namib as Wahlberg used Rooibank ( 27 km SE of Walvis Bay on the coast, Fig. 1 ) as his base (and the species is not a more inland species in the Swakop riverbed between Swakopmund and Otjimbingwe, which Wahlberg travelled in May 1854).

Londt (2010) cites a specimen from Gobabeb belonging to Acnephalomyia platygaster . The study of this specimen deposited in the South African National Collection of Insects ( SANC, Namibia – Erongo • 1 ♀ Gobabeb; 23°33'37"S, 015°02'26"E; Feb 1984; Marsh, B. leg.; feeding on flowers of female Welwitschia ) revealed that it belongs to the genus Sisyrnodytes and can, at present, not be identified further (see Londt (2009), interestingly this specimen together with another one in the NMNW are the only known specimens of Sisyrnodytes from Gobabeb to date). This specimen was originally identified as Acnephalum platygaster by Jason Londt in 1984 and subsequently received another ID label as Acnephalomyia platygaster by Londt in 2009. The holotype of A. platygaster is, therefore, the northernmost record for this species and no other specimens have been collected in and around Swakopmund / Swakop riverbed / Walvis Bay since 1854.

Figures

Figure 1. Maps of west-central Namibia with satellite imagery, major road network, major towns, watercourses (blue stippled to indicate non-permanent water flow) and biodiversity hotspots (sensu Conservation International in grey) introducing the southern Namib Desert as the study area. A. View of the Namib Sand Sea (light orange) between Swakopmund in the north and Lüderitz in the south. Note the grey area representing the northern reaches of the Succulent Karoo biodiversity hotspot; B. Selected protected areas (Namib-Naukluft NP, NamibRand NR, Kulala Wilderness Reserve) highlighted. Blue circle = Gobabeb Namib Research Institute.

Figure 9. Acnephalomyia platygaster. A. ♂ holotype (NHRS - GULI- 000111153), dorsal; B. Same, lateral; C. Same, head anterior. Scale bar: 10 mm. Photographs by NHRS staff.

Figure 10. Acnephalomyia platygaster. A. ♂ (NMSA - DIP 108887, images at FigShare https://doi.org/10.25573/data.30142279), dorsal; B. Same, lateral; C. Same, head anterior; D. ♀ (NMSA - DIP 108898, FigShare https://doi.org/10.25573/data.30142294), head anterior; E. Same, dorsal; F. Same, lateral. Scale bars: 5 mm. Both specimens collected outside study area (Namibia – Karas • 1 ♀ 1 ♂ Karasburg, 50 km NW, in Karasberg mountains; [27 ° 36 ' 29 " S, 018 ° 40 ' 29 " E]; 28 Aug.; 1983; Londt, Jason, Stuckenberg, Brian leg.; NMSA).

Figure 11. Distribution of Acnephalomyia species in the southern Namib Desert. A. Acnephalomyia andrenoides, red circles, A. metallicoindica sp. nov., purple circles; B. A. eremia, red circles, A. platygaster, purple circles. White outline = type locality. Occurrence data available at GBIF (dataset https://www.gbif.org/dataset/aef90774-efd0-4629-80ce-85bc4cbe24e8, DOI 10.15468/2bbawn).