Scarabaeus (Pachysoma) denticollis (Péringuey, 1888)

Harrison, J. Du G., Scholtz, C. H. & Chown, S. L., 2003, A revision of the endemic south-western African dung beetle subgenus Scarabaeus (Pachysoma) MacLeay, including notes on other flightless Scarabaeini (Scarabaeidae: Scarabaeinae), Journal of Natural History 37 (3), pp. 305-355 : 342-344

Scarabaeus (Pachysoma) denticollis (Péringuey, 1888)

( figures 13 , 30 , 48, 69)

Pachysoma denticolle Péringuey, 1888: 93 ; Péringuey, 1902: 77; Gillet, 1911a: 6; Holm and Scholtz, 1979: 239. Lectotype: Walfish Bay, Namibia (1 3 SAMC).

Neopachysoma denticolle (Ferreira), 1953a: 37 ; Ferreira, 1961: 25; Ferreira, 1966: 60; Ferreira, 1969: 25; Zunino, 1977: 15; Holm and Scholtz, 1979: 239; Mostert and Holm, 1982: 277.

Neopachysoma penrithae Zunino, 1977: 15 ; Holm and Scholtz, 1979: 239. Holotype: Lüderitz, Namibia (1 ♀ SMWN).

Scarabaeus denticollis penrithae (Zunino) : Mostert and Holm, 1982: 277.

Diagnosis. Clypeus quadridentate, outer clypeal teeth smaller than medial teeth; genae finely serrated ( figure 30 ); protibia sexually dimorphic, protibial spurs bifid in males simple in females ( figure 48a, b); elytra orange to black, deeply striate, striae smooth to granular; metatarsal claw longer than last tarsal segment; male genitalia as in figure 69a, b.

Distribution, habitat and conservation. Restricted to the coastal and inland dunes of the central Namib ( figure 13 ), and conserved within the Namib-Naukluft Park. Holm (1970) suggests they prefer semi-stable sand and dune streets.

Comments on locality data. The Mata Mata locality (Kalahari Gemsbok National Park) is without doubt due to a labelling error. The Kuibis record also occurs out of the established distribution range for S. (P.) denticollis .

Morphological variation. Refer to comments on S. (P.) denticollis penrithae .

Biology. Scarabaeus (Pachysoma) denticollis feeds mainly on hare and Oryx dung which are dragged as single pellets to their preconstructed burrows. They are also reported to collect dead insects, mice and chameleon droppings and vegetable matter (grass blades, Monsonia sp. leaves etc.) ( Holm, 1970; Holm and Scholtz, 1979). Here the forage is picked up with the hind legs and held against the underside of the abdomen ( Holm and Scholtz, 1979), while the beetle runs on the front four legs.

Comments. Zunino’s (1977) description of Neopachysoma penrithae is based on two females from the southern Namib. Holm and Scholtz (1979) noted it was difficult to evaluate the characters proposed by Zunino due to the lack of material, but suggested three possibilities to account for the morphological differences: (1) the southern extreme of a cline; (2) a subspecies; (3) hybrids between S. (P.) denticollis and S. (P.) bennigseni . They however choose to synonymize S. penrithae with S. (P.) denticollis . Having examined 22 additional specimens of S. penrithae , from three localities, Mostert and Holm (1982) concluded it had become ‘fairly certain that S. penrithae Zunino is a subspecies of denticolle Péringuey , with a very limited distribution (parapatric with the typical form) in the triangle between Kolmanskop, Lüderitzbucht and Spencer Bay’ (see figure 4d ). Mostert and Holm (1982) also mention that ‘specimens collected on scattered dunes between Kolmanskop and Koichab pan were clearly intermediate between penrithae and denticolle in all the diagnostic characters given by Zunino (1977) ’. This suggests a cline rather than a distinct subspecies. Unfortunately, Mostert and Holm (1982) did not examine any black specimens from the north of S. (P.) denticollis distribution ( Walvis Bay), nor was S. (P.) denticollis penrithae included in their key.

Zunino (1977) used the following differences to separate S. (P.) denticollis from S. penrithae : (1) shape of the median clypeal teeth; (2) elytral sculpture; (3) coloration of elytra; (4) size of the epipleura and pseudo-epipleura. To assess the validity of retaining S. (P.) denticollis penrithae as a subspecies these characters were investigated in the 211 available specimens. The following was found: there is no consistent significant difference in the size or shape of the median clypeal teeth between the northern and southern populations of S. (P.) denticollis , the holotype of S. penrithae represents an individual where the outer two clypeal teeth are deflexed outwardly more than usual in southern specimens; granular elytral interstriae define the southern population more reliably than elytral colour. However, although most series of S. (P.) denticollis penrithae exhibit this character, it is variably expressed within and between the southern populations. For example, in the seven individuals from SE2615Ad4 (26 ° 26 ∞ S, 15 ° 26 ∞ E), elytral sculpture varies in expression and is not as marked as in the six individuals from 30 km N of Lüderitz (26 ° 22 ∞ S, 15 ° 07 ∞ E); both the northern ( Walvis Bay at 22 ° 58 ∞ S, 14 ° 30 ∞ E) and southern populations (Lüderitz at 26 ° 36 ∞ S, 15 ° 10 ∞ E) of S. (P.) denticollis have elytras that range in colour from completely black to a dark orange. The presence of black S. (P.) denticollis at both ends of the species distribution, but absent in the centre of its range, has not been reported previously (see Holm and Kirsten, 1979). Specimens with one black and one orange elytron further substantiate the variability of elytral colour. The disjunct occurrence of individuals with black elytra indicates that its use as a diagnostic character has no standing and should be avoided. Zunino (1977), however, used the black elytra of S. penrithae as a diagnostic feature for the species; the epipleura and pseudo-epipleura are broader in the southern populations, but do not constitute grounds for erecting a subspecies. The large female holotype has particularly wide elytra, and consequently large epipleura and pseudo-epipleura; while no substantial difference was found in the male genitalia between the northern and southern samples examined.

To retain S. (P.) denticollis penrithae as a subspecies would necessitate the description of two additional subspecies to account for the central Namib and northern Namib populations. S. penrithae represents the southern morphological variation within S. (P.) denticollis , which is no greater than that expressed in the central (small, always orange) and northern (medium sized, black to orange with smooth interstriae) populations. S. (P.) denticollis penrithae is thus regarded as synonymous with S. (P.) denticollis denticollis .

Types. Péringuey’s (1888) description of Pachysoma denticolle gives no range for size, and mentions a single locality (Walfish Bay) and collector (Mr P. Nightingale), which suggests he probably based his description on a single specimen (see Péringuey’s description of Pachysoma marginatum under S. (P.) striatus above for the opposite situation). However, Péringuey’s type label is on a male labelled ‘Ganab C.Wilmer’, while the Walfish specimen lacks a type label. This situation led Holm and Scholtz (1979) to designate the Walfish specimen as lectotype, although the Ganab specimen bears the type label.

Péringuey is renowned for inconsistently or not labelling type specimens (see Cochrane, 1995 for a discussion). Re-examination of all available evidence suggests that the lectotype (Walfish) designated by Holm and Scholtz (1979) is in fact the original holotype. Evidence for this includes the following: (1) of all potential type material examined, only the Walfish specimen is dated [‘Dec. (18)85’] before the publication date (1888) of the species. The Ganab specimen bearing the type labels is dated ‘2.(18)89’, which excludes it as a possible type; (2) Péringuey (1902) includes four diagrams (plate 7, figures 31–34 ) of Pachysoma aedeagi. P. denticolle , P. marginatum , P. hippocrates and P. aesculapius are illustrated, which comprise the only illustrations in Péringuey’s papers (1888, 1902, 1908) of Pachysoma genitalia. The only dissected Pachysoma aedeagi attributable to Péringuey in the SAMC collection (Péringuey Collection) includes only the above four species all labelled in his handwriting. These separately mounted genitalia were probably used for the above illustrations, but can they be matched to specimens?; (3) the potential type specimens include one male from Walfish Bay (1 3) and a pair from Ganab (1 ♀ 1 3). The only specimen previously dissected and lacking its genitalia is the Walfish Bay specimen (lectotype). Thus, the aedeagus labelled P. denticolle by Péringuey is probably from this Walfish specimen; (4) Péringuey (1902) in his ‘Catalogue of the Coleoptera of South Africa’ provides a new description for P. denticolle (the 1888 and 1902 descriptions are strikingly different). In which he mentions the female of P. denticolle for the first time, gives a range in body length (16–17 mm; width 11 mm) and records the distribution as Damaraland. The pair labelled Ganab, Damaraland was probably used for the second description, and possibly this is when Péringuey labelled the Ganab male as type.

This evidence substantiates the choice by Holm and Scholtz (1979) of the Walfish Bay Nightingale specimen as lectotype , but suggests that the Walfish Bay Nightingale specimen is probably the original holotype of Pachysoma denticolle . Short of submitting a query to the Zoological Commission , we retain the original lectotype designation, but designate the aedeagus as a paralectotype.

Type material examined (S 2 spec. [2], 1 ♀ 1 3, 1 3 diss.). NAMIBIA: LECTOTYPE 3, Pachysoma denticolle Péringuey designated by Holm and Scholtz 1979: Walfish B, (22.58S 14.30E), Dec. (18)85 (date hard to see) // Nightingale //, / Pachysoma denticolle, LP (written in black ink by Péringuey on faded white card) / Pachysoma denticolle Péringuey Lectotype, Holm and Scholtz, 1978, (1 3 SAMC); PARALECTOTYPE 3, Pachysoma denticolle Péringuey designated here: (aedeagus mounted with a brass minuten on white card) / Pachysoma denticolle LP (1 3 aedeagus SAMC). HOLOTYPE ♀, Neopachysoma penrithae Zunino : Lüderitz, SE 2615 Ca, 19 Oct 1970 / H5483 / Holotypus, Neopachysoma penrithae mihi, M. Zunino 1977 / (female genital slide labelled) Neopachysoma penrithae Zunino , Holotypus, (1 ♀ SMWN). Paratype: Suid. Namib / H2889, {1 ♀ MZTI}.

Additional material examined from Namibia (S209 specs [78], 85 ♀ 105 3, 8 3 diss., 19uns., 1p.) .

Figures

FIGS 10–13. Distribution of Scarabaeus (Pachysoma) species in Namibia. Questioned locality records or range extensions are shown by an open circle. (10) S. (P.) fitzsimonsi. (11) S. (P.) rotundigenus. (12) S. (P.) rodriguesi. (13) S. (P.) denticollis.

FIGS 18–35. (18–30) Head of Scarabaeus (Pachysoma) species in dorsal view: (18) S. (P.) aesculapius. (19) S. (P.) hippocrates. (20) S. (P.) glentoni. (21) S. (P.) endroedyi. (22) S. (P.) striatus. (23) S. (P.) gapiepinus. (24) S. (P.) bennigseni. (25) S. (P.) schinzi: (a) female, (b) male. (26) S. (P.) valeflorae: (a) female, (b) male. (27) S. (P.) fitzsimonsi. (28) S. (P.) rotundigenus. (29) S. (P.) rodriguesi. (30) S. (P.) denticollis. (31, 32) Head of flightless Scarabaeus (Scarabaeolus) species in dorsal view. (31) S. (Scarabaeolus) scholtzi. (32) S. (Scarabaeolus) silenus. (33–35) Head of flightless Scarabaeus (Scarabaeus) species in dorsal view. (33) S. (Scarabaeus) ritchiei. (34) S. (Scarabaeus) sevoistra. (35) S. (Scarabaeus) cancer.

FIGS 3–5. Distribution of Scarabaeus (Pachysoma) species in South Africa. Questioned locality records or range extensions are shown by an open circle. (3) S. (P.) aesculapius. (4) S. (P.) hippocrates. (5a) S. (P.) endroedyi and S. (P.) glentoni mapped at large scale to compare with S. (P.) hippocrates; (5b) S. (P.) endroedyi and S. (P.) glentoni mapped at small scale.