Immature development of Eretmocerus mundus (Hymenoptera: Aphelinidae)

•Histology of Eretmocerus mundus larvae from hatching to pupation is studied.•All three instars have no peritrophic membrane or microvilli in the midgut.•Development is associated with a cellular capsule surrounding the larva.•Extensive salivary glands appear in all three instars.•The parasitoid does not consume its host completely.

The development from egg to pupation is followed for the wasp Eretmocerus mundus, parasitizing the whitefly Bemisia tabaci. We elucidate and describe structural details, histological developments and changes that the different parasitoid and host tissues have undergone during parasitism. These include the presence and apparent function of very large salivary glands, which probably produce substances that help to regulate the host's decomposition and parasitoid nutrition. Moreover, the gut of all instars is devoid of both peritrophic membrane and microvilli and, in the early instars, it has squamous rather than columnar epithelial cells. Differing from many other parasitoids, the E. mundus larva usually does not come into contact with the host tissues and does not devour the entire host during its development.The possible reasons for the developmental mechanisms, as well as the functions of the host capsule that envelopes the parasitoid, are discussed.