The biology of a giant dung-beetle (Heliocopris dilloni) (Coleoptera: Scarabaeidae)

Heliocopris dilloni (Scarabaeinae) was studied in the Tsavo National Park, Kenya, between November 1972 and January 1974. Extensive variation in the structure of adult males is described. Heliocopris dilloni is extremely well adapted for survival in a semi-arid environment which is characterized by a fairly predictable bimodal rainfall pattern. Adult emergence takes place following heavy seasonal rainfall and breeding commences three weeks later. The adults excavate subterreanean chambers at depths between 30 and 120 cm. These cavities are partially filled with elephant dung, and up to seven eggs laid in soil- covered brood balls constructed from this material. The larva passes through three instars in two months reaching a final weight of 45 g. Adults emerge during the next seasonal rains. The depth of the chambers avoids desiccating conditions and may also reduce predation. It is suggested that the greatly reduced number of eggs laid compared with other beetles is related to reduced mortality of the developing insect.