The Namib Desert beetle, Onymacris plana developed a behavioural fever when given injection of highly purified lipopolysaccharide isolated from E. coli. The beetles sought a higher preferred temperature in a thermal gradient after injection of the pyrogen than they had previously chosen. The elevation of thermal preference was observed within 1 h after injection and remained elevated for at least 12 h. The peak amplitude was 1.5°C, about 5 h after injection of lipopolysaccharide doses of around 250 mg. kg⁻¹. This is the second report of febrogenesis in an insect and the first using a highly purified lipopolysaccharide pyrogen. Keywords: Behavioural fever, thermal biology, arthropod fever, thermal preference, purified lipopolysaccharide.