<p> The distribution of Eisenia rosea, the main host of P. rudis, is influenced mainly by soil moisture and bulk density. Cluster-fly larvae locate hosts by random locomotion through the soil pores, whereupon penetration is induced by a substance present in the worm slime. Penetration occurs mainly on the upper surface of the worm, with fewer penetrations occurring towards either end of the worm. Several species of earthworm, including some which do not normally act as hosts, were infected in the laboratory. </p> <p> The encystment, surface casting, burrowing and autotomising behaviour of E. rosea varies with soil moisture and bulk density. The penetration rate of P. rudis larvae into E. rosea is affected by this behaviour, as well as by the soil pore morphology. The success of maintenance of infected worms is also affected by the worm behaviour, which in turn depends on the soil conditions. </p> / Thesis / Doctor of Philosophy (PhD)