Bibliography: leaves 82-111. This thesis analyses the molecular composition of the surface components of the Endoparasitoid "Venturia canescens" using serological methods and specific sugar-binding lectins as diagnostic tools. The data reveals that the protective layer consists of at least two parts: a mucin-like glycoprotein and additional components from the wasp calyx fluid and the host hemolymph. The study suggests that the wasp larval cuticle is protected in a similar fashion to the egg chorion, except that the calyx-specific VLPs are probably replaced on the larval cuticle by host hemolymph proteins. The findings suggest that the mechanism of passive immune evasion could emerge during the evolution of the wasp-host interactions. The implication is that structurally conserved components may have similar functions in the parasitic and non parasitic species and could constitute a useful pre-adaptations for an endoparasitoid lifestyle.