Acnephalomyia metallicoindica, Blee & Cabrero & Dikow, 2025

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

publication ID	https://doi.org/10.3897/afrinvertebr.66.153047
publication LSID	lsid:zoobank.org:pub:E1816FD5-584F-429C-AE13-CD0BCF699B5C
DOI	https://doi.org/10.5281/zenodo.17494777
persistent identifier	https://treatment.plazi.org/id/B906D667-A508-5E70-9F26-220BBA1BEF71
treatment provided by	African Invertebrates by Pensoft
scientific name	Acnephalomyia metallicoindica
status	sp. nov.

Treatment

Acnephalomyia metallicoindica sp. nov

Figs 7 View Figure 7 , 8 View Figure 8 , 11 A View Figure 11

Type locality.

Namibia: Erongo: Namib-Naukluft National Park, Hope Mine wash ( 23°34'05"S, 015°16'39"E).

Description.

Head: wider than high, black; vertex slightly depressed (less than 60 ° angle on median margin of compound eye); facial swelling indistinct, but extending over entire face, whitish-silver pubescent; mystax yellowish-white macrosetose ventrally and para-medially, long white setose laterally (no setae medially), extending over lower ¾ of face, long, reaching beyond tip of proboscis; ommatidia of different size, at least some median ommatidia distinctly larger; postgena posterior margin simple, smooth; frons (at level of antennal insertion) more or less parallel-sided, whitish-silver pubescent, laterally asetose; ocellar tubercle apubescent, white setose; vertex apubescent, predominantly asetose, yellowish-white macrosetose at base of ocellar tubercle; median occipital sclerite (m ocp scl) asetose; postocular (pocl) setae straight, yellowish macrosetae; occiput lightly grey pubescent, predominantly asetose, ventrally long white setose; compound eye posterior margin (in lateral view) straight or slightly curved throughout.

Proboscis and maxillary palpus: proboscis straight, black; postmentum plate-like, straight, median groove only in distal part, white setose ventrally; prementum circular, with dorso-median flange, asetose; labella reduced, fused to prementum entirely, occupying from 1 / 3 to 1 / 2 length of proboscis, apically rounded, yellowish setose; maxillary palpus dark brown, one-segmented, long white setose distally, cylindrical; stipites fused entirely medially, apubescent, long white setose, laterally with 2 white macrosetae.

Antenna: dark brown, lightly grey pubescent; scape dark brown, apubescent, approximately as long as pedicel, 3 yellowish macrosetae ventrally, long, reaching at least centre of postpedicel; pedicel dark brown, lightly grey pubescent, long yellowish macrosetose ventrally, shorter white setose dorsally; postpedicel cylindrical (same diameter throughout), 1.5 x as long as scape and pedicel combined, brown to dark brown, lightly grey pubescent, asetose; stylus comprised of 2 elements, element 1 dark brown, element 2 dark brown, stylus 0.3 x as long as postpedicel, asetose; apical seta-like sensory element situated apically in cavity on stylus, hyaline.

Thorax: black, bluish metallic; prosternum grey pubescent, separated from pro-episternum, square to rectangular in shape (straight dorsally); pro-episternum grey pubescent, long white setose; cervical sclerite long yellowish-white setose; antepronotum grey pubescent, short yellowish setose and long yellowish macrosetose; postpronotum predominantly apubescent, grey pubescent anteriorly and laterally, short yellowish-white setose, long yellowish-white macrosetose laterally; postpronotal lobe grey pubescent, short white setose, 1–3 long yellowish-white macrosetae; pleuron predominantly apubescent, greyish-silver pubescent anteriorly and dorsally; pro-epimeron grey pubescent, long white setose anteriorly; anepisternum grey pubescent anteriorly and dorsally, apubescent otherwise, short white setose dorsally, single long yellow macroseta postero-medially, supero-posteriorly asetose; anterior basalare asetose, posterior basalare asetose; anepimeron antero-dorsally grey pubescent, asetose; katepisternum apubescent, asetose; katepimeron apubescent, asetose; katatergite yellowish-grey pubescent, long yellowish macrosetose; meron + metanepisternum predominantly apubescent, yellowish-grey pubescent posteriorly, asetose; metakatepisternum grey pubescent, asetose; metepimeron yellowish-grey pubescent, apubescent ventrally, asetose; anatergite white pubescent, asetose; scutum whitish-grey pubescent, apubescent stripes paramedially (not reaching scutellum), apubescent areas pre- and postsuturally laterally, scutum setation: sparsely white setose only in pubescent areas, setae with small sockets, 2 yellowish npl setae, 2–3 yellowish spa setae, 1 yellow pal setae, dc setae long white pre- and postsuturally, macrosetae absent, acr setae few long white presuturally, median posterior scutum (between dc setae) sparse long white setose, setae directed posteriorly; scutellum apubescent, ds sctl setae absent, ap sctl setae present, 7–8 long yellow macrosetae; postmetacoxal area entirely membranous.

Leg: black, apubescent, all setae circular in cross section; pro coxa black, greyish-silver pubescent, white setose and yellowish macrosetose; pro trochanter black, apubescent, white setose; pro femur black, short brown setose, longer white setose ventrally, 1 yellowish macroseta postero-distally; pro tibia black, short white setose, yellowish macrosetose: 4 in 1 antero-dorsal row, 3 in 1 dorsal row, 5 in 1 posterior row, 3 in 1 postero-ventral row, distal tip with 3–4 long yellowish and 2 long brown macrosetae; mes coxa black, greyish-silver pubescent, yellowish macrosetose; mes trochanter dark brown, apubescent, short white setose; mes femur black, short brown setose, longer white setose ventrally, yellowish macrosetose: 1 antero-distally, 1 dorso-distally, 1 postero-distally; mes tibia black, short white setose, yellowish macrosetose: 4 in 1 anterior row, 4 in 1 dorsal row, 4 in 1 antero-ventral row, 3 in 1 postero-ventral row, distal tip with 2 long yellowish and 4 long brown macrosetae; met coxa black, grey pubescent, white setose, 1 long yellowish macroseta laterally, anteriorly without any protuberance; met trochanter black, apubescent, white setose, 1 yellowish macroseta, cylindrical, medially without any protuberance; met femur black, short white setose, longer yellowish setose ventrally, yellowish macrosetose: 3–4 in 1 anterior row, 2 dorso-distally; met tibia black, straight, short white setose, yellowish macrosetose: 3 in 1 anterior row, 4 in 1 antero-ventral row, 4 in 1 dorsal row, distal tip with 5 long dark brown and 1 long yellowish macrosetae; proximal pro and mes tarsomere as long as following 2 tarsomeres combined, proximal met tarsomere longer than 2 following tarsomeres combined, proximal met tarsomere as wide as following tarsomeres; pro tarsomeres 1–5 short brown setose, tarsomeres 1–4 long dark-brown macrosetose laterally and dorso-laterally; mes tarsomeres 1–5 short brown setose, tarsomeres 1–4 long dark-brown macrosetose laterally and dorso-laterally; met tarsomeres 1–5 short brown setose, tarsomeres 1–4 long dark-brown macrosetose laterally and dorso-laterally; pulvilli small, 1 / 3 length of claw; claw fairly straight throughout, pointed; empodium setiform, approximately 1 / 2 length of claw.

Wing: 3.8–4.2 mm, hyaline, without microtrichia; C terminating at CuA and CuP, anterior wing margin in males straight; R 2 + 3 distally relatively straight, r 1 open; R 4 terminating anterior to wing apex, relatively straight, stump vein (R 3) absent; r 4 open, R 4 and R 5 diverging from each other; R 5 terminating posterior to wing apex; r 5 open; M 1 terminating posterior to wing apex; cell d closed by base of M 2 and m – m, M 2 and m – m not aligned, r – m situated in distal half; m 3 open; cu a closed at C (non-petiolate); alula well-developed; microtrichia on posterior wing margin arranged in a single plane.

Abdomen: shape compressed, T 2–3 distinctly transversely rectangular (length to width ratio> 1: 3), dark brown to black (bluish metallic touch), tergites smooth, setae with small sockets only; T 1 sparsely short white setose medially, laterally long yellowish setose, 4–5 long yellow macrosetae postero-laterally, apubescent, entirely sclerotised medially, dorsal surface smooth, without protuberances; T 2–8 entirely sclerotised, black to dark brown (bluish metallic touch), segments laterally and posteriorly narrowly brown, apubescent, sparsely short white setose, longer white setose antero-laterally on T 2, marginal macrosetae absent on T 2–7, medial macrosetae absent on T 2–7; S 1–8 black to dark brown, lightly grey pubescent anteriorly, sparsely short white setose.

Female (Fig. 8 B – D View Figure 8 ): T 7 and S 7 without modifications, ovipositor comprised of 8 th and following segments, T 6–8 apubescent, setation directed dorsally; postero-paramedian T 8 pores absent; T 8 with internal rectangular apodeme (entirely fused to T) anteriorly, S 8 plate-like, slightly emarginate medio-distally; T 9 and T 10 partly fused, T 10 divided into 2 heavily sclerotised acanthophorite plates, with 5 dark brown acanthophorite spines per plate; cerci simple and flat, long yellowish setose; 3 spermathecae, all equally large, reaching posterior end of segment 6; common spermathecal duct short, not extending beyond tip of genital fork (S 9, furca), individual spermathecal ducts short; ejection apparatus not observable; spermathecal reservoirs formed by more or less expanded ducts, weakly sclerotised; genital fork (S 9, furca) formed by single, inverted V-shaped sclerite, median sclerite (at posterior tip) absent, anterior apodeme absent.

Male (Fig. 8 A View Figure 8 ): T 1 – T 8 entire, S 1 – S 2 reduced, S 3 – S 7 entire, S 8 reduced or lost; hypopygium dark brown, not rotated, directed posteriorly; epandrium divided medially into 2 halves, joined proximally; hypandrium well-developed, triangular, posterior margin with long postero-median projection, distinctly separated from epandrium by gonocoxite, not fused to gonocoxite; gonocoxite entirely free from epandrium; gonostylus present, positioned distally on gonocoxite; subepandrial sclerite asetose, ventrally smooth (without protuberances), laterally straight (without protuberances), distal margin simple, straight margin; cerci fused medially; phallus long, tip at tip of gonocoxite and gonostyli, 1 phallic prong, tip pointed, without any protuberance.

Material examined.

Holotype. Namibia – Erongo • 1 ♀ Namib-Naukluft National Park, Hope Mine wash ; 23°34'05"S, 015°16'39"E; 589 m a. s. l.; 24 Sep 2019; collected a. m. (9: 00 – noon); Dikow, Torsten, Cabrero, Allan leg.; dry, open wash, perching on sand, USNMENT 01519441 ; NMNW GoogleMaps .

Paratypes. Namibia – Erongo • 4 ♀ 1 ♂ Namib-Naukluft National Park, Hope Mine wash ; 23°34'05"S, 015°16'39"E; 589 m a. s. l.; 24 Sep 2019; collected a. m. (9: 00 – noon); Dikow, Torsten, Cabrero, Allan leg.; dry, open wash, perching on sand, USNMENT 01519440 , USNMENT 01519442 , USNMENT 01519443 , USNMENT 01519446 , USNMENT 01519447 , Paratype; USNM GoogleMaps • 1 ♀ near Vogelfederberg ; [ 23°03'17"S, 014°59'21"E]; 13 Nov 1986; Kleinjan, C. leg.; gravel plains, NMSA -DIP 007177 , Paratype Acnephalomyia iota Londt, 2010 ; NMSA GoogleMaps • 1 ♀ Namib-Naukluft National Park, Ganab ; 23°05'46"S, 015°31'04"E; 971 m a. s. l.; 22 Oct 2024; collected a. m. (9: 00 – noon); Dikow, Torsten, Cabrero, Allan leg.; gravel plains with adjacent wash, perching on ground, USNMENT 02018420 , Paratype; NMNW GoogleMaps .

Diagnosis.

The species is distinguished from congeners by the predominantly apubescent thorax and abdomen, the metallic bluish-black cuticle, the absence of dorso-ventrally flattened setae on legs and abdomen, the small size (wing length 3.8–4.2 mm) and the restricted distribution on the gravel plains of the Namib Desert. From Acnephalomyia iota in particular, it is distinguished by the few, thin setae on pubescent stripes on the scutum ( A. iota entire scutum covered with short setae) and the absence of stump vein R 3 at base of R 4 ( A. iota with short stump vein).

Etymology.

Latin metallicus = metallic, indicum = indigo. The specific epithet, treated as feminine, refers to the metallic blue colour of this species.

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

Known only from three localities on or near the Namib Desert gravel plains in the northern parts of the southern Namib Desert (Fig. 11 A View Figure 11 ). A rarely collected species known only from eight specimens from three collecting events (Table 2 View Table 2 ). The species is not known to occur in any currently recognised biodiversity hotspot, but is endemic to the Namib Desert and likely the gravel plains in particular. Adult flies are active in spring (September and October) (Table 3 View Table 3 ). Nothing is known of the biology.

Remarks.

When the newly-collected specimens of A. metallicoindica sp. nov. were compared to photographs of the holotype of A. iota , kindly provided by Kirstin Williams ( NMSA), it was discovered that they belong to an undescribed species and that the paratype female of A. iota from near Vogelfederberg (Fig. 11 A View Figure 11 ) also belongs to this new Namib species. A. iota was described, based on three specimens – two males from near Nieuwouldtville and Brandkop in the Northern Cape Province of South Africa and the female from near Vogelfederberg in Namibia. The two Northern Cape localities are only 5 km apart, whereas the distance to the Vogelfederberg is approximately 1,000 km. Londt (2010) mentioned several features distinguishing this female from the two males. However, because of the possibility of sexual dimorphism within A. iota, Londt refrained from describing two distinct species. We can provide evidence (see diagnosis) that there is no sexual dimorphism in A. metallicoindica sp. nov. and that the Namib Desert species is distinct from A. iota , which is now restricted to a small area in the central Northern Cape Province. The known collecting localities of A. metallicoindica sp. nov. on the Namib Desert gravel plains (Fig. 4 D – F View Figure 4 ) are also quite distinct from Fynbos vegetation north-east of Nieuwouldtville, South Africa. Amongst the eight known specimens of A. metallicoindica sp. nov. is only a single male specimen. We refrained from dissecting the male terminalia to preserve the integrity of this unique specimen, but provide a high-magnification photo of the lateral aspect of the tip of the abdomen (Fig. 8 A View Figure 8 ) even though these are retracted significantly under tergite 6 in Acnephalomyia .