Tachinid fly Many flies of the family Tachinidae parasitize pest insects. Caterpillars, beetle larvae, and sawflies are preferred hosts. Tachinid eggs Tachinid flies generally lay their eggs on the outside of the host. The egg hatches and the larva penetrates inside the host where it consumes the body contents. These minute wasps attack insect eggs.
Moth eggs are common hosts.
They lay their eggs in the moth egg and the wasp larva develops instead of the caterpillar. There are many species of Trichogramma and some prefer one host over another. Many are available to purchase. Here you see an egg mass of healthy caterpillar eggs. No large picture These caterpillar eggs have been parasitized by Trichogramma .