Absence of endothermy in flightless dung beetles from southern Africa

Endothermy in insects is normally associated with flight but has been observed during strictly terrestrial activity in beetles (Bartholomew & Casey 1977a, b). A study by Bartholomew & Heinrich (1978) in Kenya showed that dung beetles are conspicuously endothermic during flight, ball making and ball rolling, and sometimes while walking. Endothermy during terrestrial activity is probably advantageous when competing for fresh dung: this was clearly demonstrated in Scarabaeus laevistriatus, a large, nocturnal species which is involved in intense competition for elephant dung (Heinrich & Bartholomew 1979). Some interesting flightless dung beetles (Coleoptera: Scarabaeinae) occur in southern Africa. Ten flightless species of the genus Scarabaeus (formerly assigned to the separate genus Pachysoma) occur along the west coast between the Cape and the Namib Desert (Mostert & Holm 1982). The unrelated genus Circe/lium is endemic to South Africa and consists of a single species, Circellium bacchus, once widely distributed but now abundant only in the Addo Elephant Park. Body temperatures of this large, diurnal, ball-rolling dung beetle were measured in the present study to find whether they are maintained at elevated levels as in the winged dung beetles already studied. Observations were made in the field at Addo Elephant Park on 27 and 28 January 1981, when the beetles were active after rain. Body masses were measured to the nearest 0,1 g with Pesola spring balances. Body temperatures were measured with calibrated copperconstantan thermocouples threaded through 22-gauge hypodermic needles and connected to a Bailey BAT 4 thermometer. Beetles were captured with gloved hands and body temperatures measured within 5 s of capture, to the nearest 0,1 0c. For meta thoracic temperatures (Tmth) the thermocouple was inserted to a depth of 5 mm between the coxae of the second and third pairs of 323