A review of the Attagenus (Coleoptera: Dermestidae) species from South Africa and an image-based key to identification

The Dermestidae is a relatively poorly studied family of insects but with a high rate of species discovery. The South African region is particularly rich in Attagenus spp. many of which are distinctively patterned. This study provides an updated list of Attagenus spp. in South Africa with a complete literature review and an image-based identification key to the Attagenus species within South Africa. Images of most species are provided. With the rise in significance of citizen science recording schemes, this study facilitates image-based identification and encourages both entomologists and citizen scientists to further contribute to the understanding of this beautiful Coleopteran family.


INTRODUCTION
Dermestidae (Insecta: Coleoptera), the skin, hide, and carpet beetle family, is a moderately speciose group comprising about 1900 species globally (Háva 2023).The family includes 60 genera.The number of species in the genus Attagenus Latreille, 1802 has grown by 47% in the last 50 years from 170 spp.(Mroczkowski 1968) to over 250 spp. in 2021 (Háva 2023).Given the rate at which new species are being described and the very small number of people contributing to their taxonomy, it is likely that there remain many more species yet to be discovered.Associated with this high rate of discovery is an almost continual reassessment of the taxonomy of the genus (Háva 2023).Recently, several Attagenus species have been moved to Lanorus Zhou et al., 2022 Lanorus is comparatively small (23 species); most species remain as Attagenus.Mroczkowski (1968) maintained that two zoogeographical regions were rich in Attagenus: the Palaearctic and the African regions (Ficetola et al. 2017) (African region is contained within the Ethiopian region referred to by Mroczkowski (1968)).The Palaearctic species are better known and currently about 75 Attagenus spp.have been described from this region.The wider African region (including the Saudi peninsular) has been less well studied.Even so, about 170 species have been described from the African region (NB some species occur in both the Palaearctic and African regions).A list of the Attagenus species in South Africa was published by Herrmann and Háva (2020), but no literature was linked to each species to facilitate the assessment of the authenticity of each entry.
Hermand and Holloway (2020) carried out a morphological examination of A. rufiventris Pic, 1927, a species known from South Africa.In their study, Hermand and Holloway (2020) noted that among the South African species of Attagenus, A. rufiventris was very easy to recognize using the elytral colour pattern.Many of the South African Attagenus species are attractively coloured.The identification of colourful taxa, such as Lepidoptera and Odonata, is achieved using colour patterns, exclusively.Identification guides to Dermestidae are scarce but include Peacock (1993) and Háva (2011).Both rely on the use of dichotomous keys using morphological characters even though in many instances the colour and pattern of the species in question is distinctive.There is a great deal of colour pattern variation among species of Attagenus.One possible reason why few people are working on Dermestidae is that there are insufficient guides to identification facilitating entry to the group delivered in a manner that might inspire students of Coleoptera to dig deeper into aspects of Dermestidae taxonomy, ecology, and distribution.
The current study has two objectives: • to present an updated list of Attagenus spp. of South Africa with a complete literature review, and • to produce a simple image-based identification guide and accompanying key to the Attagenus species of South Africa focusing solely on dorsal colour patterns.

METhODS
The list of South African Attagenus species produced by Herrmann and Háva (2020) was used as a starting point and revised using Háva (2022Háva ( , 2023)).Háva (2023) was used as a guide to current taxonomy.After this process, an extensive literature search was carried out to establish the original source relating to each record and additional references relating to Attagenus in South Africa.
A dichotomous key was generated based entirely on dorsal colour pattern.Colour patterns of South African Attagenus species were obtained from Herrmann (2023) and Háva (2016).To ensure high-quality images of Attagenus colour patterns, illustrations were created using acrylic paint on high-density 200 g cartilage paper.The limbs, head, and antennae were excluded from the illustrations to emphasise elytral pattern and colour variation.Illustrations were imaged using an Olympus TG4.Body length (BL) (front margin of pronotum to apices of elytra) was included for each species in the key.BL values were obtained from Herrmann (2023) unless otherwise stated.Distribution data were from Háva (2023).

RESULTS
Forty-four species of Attagenus are recorded from South Africa (Table 1).No original source evidence supporting the occurrence of A. brunneus Faldermann, 1835, which has a wide global distribution (Háva 2023), could be found.Species affiliated with supporting literature are listed in bold.
Table 2 presents a dichotomous key with species differentiation based on dorsal colour pattern and supplemented with BL where available.Using this approach, two-thirds (30/44) of the species of Attagenus found in South Africa can be differentiated comfortably (Figures 1-6).A smaller number might require further investigation to be sure of identification, hence a number of these species are omitted but listed at the end of the key.
Attagenus brunneus has been listed as a species of South Africa (Herrmann and Háva 2020), however, no original record could be found to support this.A recommendation to remove A. brunneus from the list could be made due to the lack of records supporting the presence of this species in South Africa.Duff (2018) states that a species should be included in a national list if a self-sustaining population exists in the region.With no evidence or records to suggest a population existing in this manner, it is recommended by Holloway (2020a) and Holloway et al. (2019) to exclude such species from national checklists.
A significant issue hindering progress in our understanding of various aspects of Dermestidae is the lack of identification guides.Only two guides exist, Peacock (1993) and Háva (2011), both of which deal with species across very limited geographical ranges (national).Herrmann (2023) displays many images of different species of Dermestidae online but by no means all species.Strangely, little effort has been invested in identification guides (excluding the list by Herrmann 2023, which represents a huge effort).Attagenus species are often colourful.Insect orders and families possessing intricate colour patterns, such as Lepidoptera, are identified based on their colour patterns.Keys to most families of Coleoptera rely principally on qualitative characters.Such characters used to differentiate among species are reliable and entirely consistent but often require the use of stereo microscopes to inspect these characters.Modern guides to Lepidoptera rely almost entirely on colour patterns, and most species can be quickly and easily differentiated.Some genera are more difficult and contain species of similar appearance, such as fritillaries (Nymphalidae Rafinesque, 1815) and skippers (Hesperiidae Latreille, 1809).It is well known that insect colour patterns vary depending on seasonal developmental conditions.This has been demonstrated in Lepidoptera (Nylin 1989;Holloway et al. 1993;Holloway and Brakefield 1995;Kemp and Jones 2001;Karl et al. 2009), as well as Diptera (Marriott and Holloway, 1998;Ottenheim et al. 1999;Mielczarek et al. 2016) and Coleoptera (Holloway et al. 1995;Pajni and Airi 2017).Many entomologists would argue that this variation demonstrates the problem with using quantitative characters such as areas of coloured patches and instead seek immutable qualitative characters for identification purposes.These issues do not appear to be recognised as difficulties by students of Lepidoptera (especially for daytime flying butterflies and moths) and new guides continue to be produced based on colour patterns.Some Dermestidae genera show great inter-specific colour pattern variation as illustrated by the images in Herrmann (2023).Some Dermestidae groups are indeed colourful but difficult to differentiate, for example, the Anthrenus pimpinellae complex of species (Kadej et al. 2007;Kadej and Háva 2011;Holloway 2019Holloway , 2020bHolloway , 2021;;Holloway and Bakaloudis 2020;Holloway et al. 2020aHolloway et al. , b, 2021)), but certain other genera contain species that are straightforward to recognize.The Attagenus species of South Africa largely fall into the latter category.As illustrated here, most species are quite distinctive.Some are trickier to differentiate, such as species in the A. capensis group, but a student of Dermestidae having used the key and established that a species from the A. capensis group has been found could consult the material referred to here for more detailed descriptions.
The Dermestidae is a relatively small family of beetles with about 1900 known species (Háva 2023).People find the group attractive judging by the number of images of different Dermestidae species found on citizen science recording sites.For example, there are hundreds of records of different Attagenus species from South Africa on iNaturalist (2023).It ought to be a popular group with more people working on various aspects of the family, although many entomologists have a loathing for Dermestidae because of the destructive activities of one species: Anthrenus verbasci Linnaeus, 1767.Currently, a small number of workers are generating many small manuscripts largely focussing on faunistics and the reporting of specimens held in public and private entomological collections.If more Dermestid species identification resources were available, it might be possible to encourage more students to work on the family in a collaborative manner to enrich our understanding of the life history, ecology, and taxonomy of this beautiful family of Coleoptera.

Table 1 .
Species of Attagenus believed to occur in South Africa.Sources of records for each species, where known, are provided.Records associated with supporting literature are in bold.

Table 2 .
Dichotomous key for South African Attagenus spp.based on dorsal pattern variation.