The particulate basis of the resistance of a parasitoid to the defence reactions of its insect host.

Small, membrane-bound particles, about 130 nm in diameter, have been isolated from that region of the genital tract of the ichneumon Nemeritis known as the calyx. These particles have been shown to possess the ability to confer resistance to encapsulation by Ephestia, the natural host of Nemeritis, upon a surface which would otherwise be encapsulated.