Cellular immune reactions of larvae of Drosophila algonquin

The haemocytic reactions of larvae of Drosophila algonquin leading to encapsulation and melanization of eggs of the hymenopterous parasite Pseudeucoila bochei are characterized in part by the premature mass differentiation of plasmatocytes to lamellocytes. Normally this transformation of blood cells occurs at the time of pupation. The data suggest the haemocytes are stimulated to differentiate by chemotactic means. In susceptible host larvae the parasite appears activately to inhibit the immune reactions by blocking cellular differentiation.