Eretmocerus Penetration and Immature Development: A Novel Approach To Overcome Host Immunity

The mode of penetration of parasitoids belonging to the genus Eretmocerus into whitefly larvae and their immature development were examined. Examination included scanning electron microscopy and light microscopy of stained and unstained whole mounts and sections. The Eretmocerus larva pierces the venter of its host shortly after hatching, and subsequently enters the host through the same hole. The host reacts by forming a cellular capsule around the Eretmocerus larva. This capsule i s incomplete, with an opening in i ts ventral side opposite the penetration hole. The capsule remains intact during most of the second instar of the parasitoid. It then disintegrates, but its remnants are st i l l visible around the third instar. Whenever two Eretmocerus larvae penetrate, they are surrounded by two capsules. The capsule does not prevent parasitoid development, but it apparently precludes contact of cellular elements of the host’s blood with the developing parasitoid larva. Adaptive features of Eretmocerus larval biology include the early contact with the host’s internal medium that permits host regulation; and the delay of contact with the host’s blood cells that may preclude the need to confront host immunological systems.