Review of Anasillomos Londt, 1983 with the description of a new species (Insecta: Diptera: Asilidae)

Abstract The southern African assassin-fly genus Anasillomos Londt, 1983 is reviewed. A new species, Anasillomos juergeni sp. n., is described from the Namib desert and represents the second species in the genus. Descriptions/re-descriptions, photographs, and identification keys are provided to aid in the identification. Distribution, occurrence in biodiversity hotspots sensu Conservation International, and seasonal incidence are discussed.

This review was instigated by the collection of 10 specimens of Anasillomos at the Gobabeb Research and Training Centre (www.gobabebtrc.org) by the author in February 2012. Even though only a single male specimen was collected during this field trip, comparison with the original description and the illustrations of the male terminalia provided by Londt (1983) suggested that the new specimens belong to an undescribed species. Further study revealed that the new species is more widespread and that several specimens previously identified as Anasillomos chrysopos also belong to the new species.

Materials and methods
Morphological features were examined using a Zeiss SteREO Discovery.V12 stereo microscope. Wing length is measured from the tegula to the distal tip of the wing. The female genitalia and male terminalia were first excised and macerated in 10% potassium hydroxide (KOH) at 55°C followed by neutralization in acetic acid (CH COOH) and rinsing in distilled water (H O). They were temporarily stored in 75% ethanol (C H OH) for examination and illustration and eventually sealed in polyethylene vials containing 100% glycerine (C H O ) and attached to the specimen's pin.

Species descriptions and re-descriptions
Species descriptions are based on composites of all specimens and not exclusively on the holotype and are compiled from a character matrix of 205 features and 242 character states assembled with Lucid Builder (version 3.5) and eventually exported as naturallanguage descriptions. These species descriptions have been deposited in the Zenodo data depository and can be accessed in XML-format following the SDD (Structure of a b c d Figure 10.
Habitat photographs of Namib sand dunes at Gobabeb and Karoo near Grünau. Anasillomos juergeni sp. n. was collected at Gobabeb and Anasillomos chrysopos and Anasillomos juergeni sp. n. were collected near Grünau.

Specimen occurrence data
The following data on species occurrences are given (where available): country, state/ province, county, locality, geographic co-ordinates (formatted in both decimal and degrees minutes seconds latitude/longitude), elevation (in meters), date of collection (format: yyyymm-dd), habitat information, sampling protocol (if other than hand netting), collector, catalog number (a unique specimen number and any other identifying number), depository (institution and collection code), number of specimens, sex, life stage, name of person who identified the specimen, and any other previous identifications. Each specimen is listed with a unique specimen number (either an institutional catalog number or an AAM-XXXXXX number used by the author) that will allow the re-investigation as well as provide a unique Life Science Identifier (LSID). The occurrence of all species is illustrated in distribution maps plotted with SimpleMappr with all of those localities for which coordinates are available. Type localities are plotted with a square symbol while all other specimens are plotted with a circular symbol. The distribution map includes Biodiversity Hotspots sensu Conservation International. The specimen occurrence data are deposited as a Darwin Core Archive (DwC-A) in the Global Biodiversity Information Facility (GBIF) using the Integrated Publishing Toolkit (IPT) at the NMNH.

Photographs
Whole habitus photographs of pinned specimens were taken using a Visionary Digital Passport II system (base and StackShot only), an Olympus E-30 digital SLR, a 50 mm macro lens (equivalent to 100 mm focal length in 35 mm photography), and a 25 mm extension tube. The specimens were illuminated by a Falcon FLDM-i200 LED dome-light for even and soft light. Photographs of the female and male terminalia were taken on a Zeiss SteREO Discovery.V12 stereo microscope at 50x magnification and an attached Olympus PEN E-PL5 digital camera. The dissected terminalia were placed in 75% ethanol in a glass dish and illuminated by a Schott VisiLED light source utilizing mixed bright-field (dorsal), dark-field (lateral), and transillumination (ventral). Adobe DNG-format images were stacked using HeliconFocus software. All photographs have been deposited in Morph bank:: Biological Imaging. These images will be automatically harvested by the Encycloped ia of Life (EOL) and are available under the respective species page.

Keys
The dichotomous, interactive key has been build with Lucid Phoenix and the multi-access, matrix-based key with Lucid Builder and both have been deposited in the IdentifyLife archive, registered in Lucidcentral, and made available on the author's research web-site.

Institutions providing specimens
Institutions providing specimens are listed below, together with the abbreviations used in the text when citing depositories (institutionCode), a link to the record in the Global Registry of Biodiversity Repositories (GRBio), and the people who kindly assisted: NMNW -National Museum of Namibia, Windhoek, Khomas, Namibia (A. Kirk-Spriggs); NMSA -KwaZulu-Natal Museum, Pietermaritzburg, KwaZulu-Natal, South Africa (B. Muller, J. Londt); SAMC -Iziko South African Museum, Cape Town, Western Cape, South Africa (D. Lawson, S. van Noort); USNM -National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.

Data resources
Morphbank: image collection ID 851000.
Lucid Phoenix: illustrated, dichotomous identification key -asiloidflies.si.edu. Map of southern Africa with elevational relief and biodiversity hotspots (in grey) showing distribution of Anasillomos chrysopos (orange) and A. juergeni sp. n. (red). Possible A. juergeni sp. n. from Awasib in yellow (see Discussion). Type localities with square symbol. Map data available in Google Earth KML file and also through GBIF (data-set d61dc8a1-83f7-4905-8863-d19a5a89a0a4).

Diagnosis
Anasillomos has been included in the most recent key to Afrotropical Stenopogoninae sensu Papavero (1973) and Geller-Grimm (2004) with setose anatergites by Londt (2012). It can easily be distinguished from other southern African assassin-fly genera by the presence of strong macrosetae on the antepronotum, lateral postpronotum, and postpronotal lobes.

Taxon discussion
The phylogenetic studies on Asilidae based on both morphological (Dikow 2009a) and combined morphological and molecular data (Dikow 2009b) did not include representatives of Anasillomos and therefore the taxon cannot be directly placed in the phylogenetic classification proposed in Dikow (2009a). The external morphology suggests that Anasillomos belongs to the Stenopogoninae sensu Dikow (2009a) based on similarities to Daspletis Loew, 1859 and Microstylum Macquart, 1838 such as the male terminalia with a medio-distally projecting hypandrium (also known in other southern African genera though). These two genera have been included in Stenopogoninae: Enigmomorphini by Dikow (2009a). However, only the inclusion of Anasillomos specimens in a cladistic analysis can place this genus phylogenetically as overall similarity does not necessarily provide evidence as to the evolutionary relationships.

Description
Head: wider than high, black; vertex slightly depressed (less than 60°angle on median margin of compound eye); facial swelling extending over lower ¾ of face, white pubescent; mystax white macrosetose on ventral margin and light brown macrosetose elsewhere, extending over lower ¾ of face; 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, apubescent antero-medially, grey to golden pubescent otherwise, white setose and light brown macrosetose laterally; ocellar tubercle golden pubescent, light brown setose and macrosetose; vertex golden pubescent, asetose; median occipital sclerite (m ocp scl) with several light brown macrosetae; postocular (pocl) setae straight, light brown macrosetae; occiput dorso-medially golden pubescent and laterally grey pubescent, dorso-medially with V-shaped apubescent stripes, white setose.
Antenna: light brown, lightly grey pubescent; scape 2x as long as pedicel, short white and light brown setose dorsally and long light brown macrosetose ventrally; pedicel white and light brown setose distally; postpedicel cylindrical (same diameter throughout), 1.5x as long as scape and pedicel combined, sparsely white setose dorsodistally; stylus comprised of 1 element, asetose; apical seta-like sensory element situated apically on stylus.

Diagnosis
The species is distinguished from its congener by the dorso-medially white macrosetose anepisternum (in addition to white setae, Figs 2b, 3b), the distinct pubescence pattern on the lateral abdominal tergites (T2-5 with apubescent stripe from antero-lateral corner to postero-median margin, Fig. 3b), and the presence of long macrosetae on the tip of the pointed hypandrium (almost reaching tip of epandrium, Fig. 4b).

Distribution
Known from Botswana, Namibia, and South Africa and therefore widely distributed in southern Africa, but rarely collected (Fig. 11).

Taxon discussion
The type locality of A. chrysopos lies in eastern Botswana, far removed from the majority of specimens collected in western Namibia. There is little morphological variation within the species except for the setation color, which can vary from light brown to yellow.

Biodiversity hotspot
Not known to occur in any of the southern African biodiversity hotspots (Cape Floristic Region, Maputaland-Pondoland-Albany, or Succulent Karoo).

Description
Head: wider than high, black; vertex slightly depressed (less than 60°angle on median margin of compound eye); facial swelling extending over lower ¾ of face, white pubescent; mystax white macrosetose, extending over lower ¾ of face; 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, apubescent antero-medially, grey to golden pubescent otherwise, white setose and macrosetose laterally; ocellar tubercle golden pubescent, white setose and macrosetose; vertex golden pubescent, asetose; median occipital sclerite (m ocp scl) with several white macrosetae; postocular (pocl) setae straight, white macrosetose; occiput predominantly grey pubescent, dorso-medially with V-shaped apubescent stripes and medially with longitudinal light brown pubescent stripe, white setose.

Diagnosis
The species is distinguished from its congener by the dorso-posterior white setose anepisternum (not macrosetose, Figs 5b, 6b, 7b), the distinct median longitudinal dark grey pubescent stripe on the abdominal tergites (Figs 5a, 6a), the absence of a pubescence pattern on the lateral abdominal tergites (Figs 5b, 7b), the presence of a dorsal bipartite protuberance on the aedeagus tip (Fig. 8c), and the presence of only short macrosetae on the tip of the pointed hypandrium (Fig. 8b).

Etymology
The species is named after and dedicated to the memory of my late father, Jürgen Dikow, who has always been supportive of my entomological work and was excited to hear about every new species discovery I made.

Distribution
The species is so far only known from Namibia and in particular from the eastern edge of the Namib desert sand dunes (Gobabeb, Homeb, and Sesriem) as well as the Karoo in southern Namibia (near Grünau) (Fig. 11).

Biology
All recently collected specimens during field work at or near the Gobabeb Research and Training Center conducted in February 2012 were perching on sand. The majority of specimens were collected on the large sand dunes south of the station and Kuiseb river bed (Fig. 10a, b) while a few were encountered on the small dunes west of the Kuiseb river bed (Fig. 10c). The flies are very fast fliers and fly away even when one is several meters away. An attempt was made to photograph them in the field, but I was unable to get sufficiently close (see Fig. 10a with a fly in the center).
Four female specimens have been captured with prey at or near Gobabeb of which three were feeding on Bombyliidae (Diptera) and one on Ichneumonidae (Hymenoptera).

Biodiversity hotspot
Not known to occur in any of the southern African biodiversity hotspots (Cape Floristic Region, Maputaland-Pondoland-Albany, or Succulent Karoo).
Seasonal incidence of Anasillomos species. Numbers refer to specimens / collecting events in particular month. Note that the December records represent a single collecting event near Grünau where both species were collected sympatrically.

Habitat, sympatry, and a central Namibian locality
On first examination, the two Anasillomos species appear to be occurring in different habitats in that A. chrysopos lives in savanna and Karoo biomes whereas A. juergeni sp. n. occurs in the Namib desert (Fig. 11). However, both species occur sympatrically in the Karoo of southern Namibia near Grünau. A single collecting event resulted in the caption of four females (two of each species) in December 1999, which were mentioned in Dikow and Londt (2000), but not assigned to any species. Only with the collection of several specimens of both sexes of A. juergeni sp. n. at Gobabeb and the comparison with type material, it became clear that there are two species flying sympatrically near Grünau.
Unfortunately, specimens previously studied by Londt (1983) and Dikow and Londt (2000) from the National Museum of Namibia in Windhoek (NMNW) were not available for study in this project. I am confident that the four specimens from around Windhoek deposited in NMNW represent A. chrysopos because a single female specimen from Hakos Mountains (south-west of Windhoek) in a savanna habitat has been studied (USNMENT00995574). The identification of the sole specimen from Awasib (25°23'00"S 015°39'00"E) in the central Namib desert as A. chrysopos, however, is questionable. Awasib lies a few kilometers east of the Namib sand dunes and approximately 100 km SSW of Sesriem from where A. juergeni sp. n. has been recorded. The proximity of Awasib to the large sand dunes and the collection in November possibly suggest that this specimen represents A. juergeni sp. n. and was therefore misidentified in Londt (1983) and Dikow and Londt (2000). This locality is highlighted in Fig. 11 to provide a geographical reference and encourage future collecting along the eastern Namib desert transitioning into the savanna biome.
for skillfully illustrating the male holotype of A. juergeni sp. n. Thanks also to the peer reviewers for suggestions that enhanced the manuscript.