Scarabaeus (Scarabaeolus) silenus ( Gray, 1832 )

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 : 346-347

Scarabaeus (Scarabaeolus) silenus ( Gray, 1832)

( figures 15 , 32 , 50, 71)

Mnematium silenus Gray, 1832: 40 ; Felsche, 1907: 275; Balthasar, 1935: 27; Balthasar, 1963: 141; Ferreira, 1969: 28.

Mnematidium silenus (Gray) : Reitter 1894: 183.

Scarabaeus rotundipennus Holdhaus, 1919: 54 .

Mnematium rotundipenne (Holdhaus) : Balthasar, 1935: 28; Balthasar, 1963: 141; Ferreira, 1969: 28.

Pachysoma rotundipenne (Holdhaus) : Holm and Scholtz, 1979: 226.

Pachysoma silenus (Gray) : Holm and Scholtz, 1979: 227.

Scarabaeus (Scarabaeolus) silenus (Gray) : Mostert and Holm, 1982: 277.

Diagnosis. Clypeus quadridentate, teeth pointed and almost equal in size, separated by equal gap, genal anterior apex produced into distinct tooth ( figure 32 ); protibia quadridentate, serrations between and proximal to teeth, proximal serrations’ coarse; spurs simple, males with inner edge of protibia serrated ( figure 50); Sub-elytral rim present, small elytral rim, striae very faint, humeral callus absent; metatarsal claws about half length of last tarsal segment; mesocoxae semi-contiguous (> 1.5 mm), with prominent depression between mesocoxae, anterior to which is prominent mesosternal ridge; male genitalia simple ( figure 71a, b).

Distribution. Recorded from the Sinai Peninsula, Aleppo in Syria, Anah and Baghdad in Iraq to Saudi Arabia ( figure 15 ). Probably associated with the Tigris and Euphrates Rivers in Iraq, which extend into Syria as the Al Furat River.

Morphology. The vestigeal second mesotibial spur, which places this species in the subgenus Scarabaeolus , is very hard to see. Some specimens of S. (Scarabaeolus) silenus examined had lost (open socket visible) their vestigeal spur, the spur is however present in the species. No difference was found between S. silenus (distribution centred on the Sinai Peninsula and Saudi Arabia) and its synonym S. rotundipenne (distribution centred on Iraq and Syria).

Biology. Unknown. The mouthpart morphology appears intermediate between that of wet dung feeding Scarabaeus and dry dung feeding Pachysoma , which suggests a mixed diet of both wet and dry food.

Comments. The inclusion of this species in the subgenus Scarabaeolus (sensu Balthasar, 1965; Mostert and Holm, 1982), requires further investigation.

Types. Balthasar (1963) was unable to locate the holotype. Mostert and Holm (1982) examined the holotype, which is housed in the SMTD collection.

Type material examined (1uns. spec.). SYNTYPE: ARABIA: Silenus Ol. * Arab. Ol. (written on to faded yellow card) / 8889 / (1uns. ZMHB) .

Additional material examined from Egypt and Iraq (S8uns. specs).

Figures

FIGS 14–17. Distribution of flightless Scarabaeus (Scarabaeolus) and Scarabaeus (Scarabaeus) species in Africa, the Middle East and Madagascar. (14) S. (Scarabaeolus) scholtzi in Somalia. (15) S. (Scarabaeolus) silenus in Sinai, Syria, and Iraq. (16) S. (Scarabaeus) ritchiei in Libya. (17) S. (Scarabaeus) sevoistra in Madagascar. See figure 2 for distribution of S. (Scarabaeus) cancer in Angola.

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.