The female beetle Ceratophyus hoffmanseggi buries dung, with the assistance of a male, to form a series of underground brood masses. An egg is laid in the soil near each mass. Beetles of either sex resist intruders in the entrance to their burrows by a head-to-head pushing contest, without injury to either opponent. The larva feeds within the brood mass forming an elongated cavity. This chamber is lined with a tube built from larval excrement. The larva does not immediately repair holes made in this tube, and can neither isolate itself from another larva introduced into the same chamber, nor maintain a closed chamber when it is placed in a free-standing brood ball.
A pair of beetles worked together to make a series of horizontal brood masses by packing dung into underground chambers. An egg was laid in the soil just beyond the tip of each mass. Resident beetles used their horns to resist intruders of either sex. During head-to-head pushing contests in the nest entrance-tunnel, a stable position was adopted where the horns of each opponent thrust harmlessly against the pronotum of the other. The larva prevented collapse of its chamber by building a rigid tube from accurately positioned faecal pellets. Defects in the larval chamber released no obvious repair behaviour and the larva was, therefore, not able to survive in a free-standing brood ball or in the presence of another larva in the same chamber.
It is a pleasure to thank Sr J. de Ferrer (8 Av. F. Franco, Algeciras) for his help and advice.