STAGES IN THE DEVELOPMENT OF TWO INSECT VIRUSES

Abstract

Stages in the development of viruses of two Hymenopterous insects, Diprion hercyniae (Htg.) and Neodiprion americanus banksianae Roh., are shown in electron micrographs of thin sections. Following swelling of the nuclei and nucleoli and coagulation of the chromatin, rod-shaped virus particles appear chiefly on the exposed surfaces of the chromatin. The chromatin of D. hercyniae often coagulates into separate lumps that suggest small polyhedra. These first produce rod-shaped particles on their exposed surfaces and later transform into recognizable polyhedra. The chromatin of N. a. banksianae is more uniformly dispersed, and polyhedra arise as thickenings within the chromatin. In the latter insect, virus particles are frequently observed within the developing polyhedra, suggesting that polyhedra are formed by the accumulation of protein around groups of virus particles. Both polyhedra and free virus particles are larger and denser in the nuclear sap than in the chromatin. Their formation continues in remnants of chromatin in nuclei otherwise filled with large polyhedra. An incidental observation is that the nuclear membranes of some nuclei are pitted with small holes.