This is a very large group of parasitic insects, accounting for about half of the known species of British Hymenoptera. There are over 2,000 known British species and dramatically vary in size from very small to very large, including a number of wingless species. Adults can be usually found in the Summer on flowers, especially Apiaceae species and can be seen searching around on herbage for potential hosts. Ichneumons are not usually confined to one specific host, although they do generally keep to their own particular group of hosts. The Ichneumonidae play an important part in controlling insect numbers, the majority of Ichneumons parasitise Lepidoptera (a few species even prey on spiders) and are responsible for controlling huge numbers of insect pests. The species can be recognised by the long antennae. There are two families Ichneumonidae and the Braconidae, they differ mainly in their venation. The female with the aid of her slender ovipositor inserts her eggs into the host’s body. Some species merely lay their eggs on the outside, from there, the larvae may make their own way inside by beginning to feed on the outside of the host’s body. The length of the ovipositor allows the female (Some species, the ovipositor is longer than the female's body) to inject her eggs into hidden hosts such as leaf-rolling or stem-boring caterpillars. The Ichneumons may over winter as grubs, in a host larvae or pupae and can also pupae in their own cocoons. Some species overwinter as adults, these are mainly mated females that do this; as most males normally die in the autumn.
