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Braconid wasps are beneficial parasites. They can be 12 mm in length, and their body shape is short and stout. They have an ovipositor carried inside the body until it is needed to inject an egg into a host.
Braconids parasitize a broad range of hosts: caterpillars, flies, wasps, beetles, and aphids. After a female injects an egg into a host, the larva feeds slowly on that single host. By the time the host dies, the larva is fully grown. It pupates inside or near the dead host, sometimes in a silken cocoon, to emerge later as an adult wasp.
In the case of aphids, usually the aphid is disturbed by the attack but does not leave the plant. A parasitized aphid usually does not produce offspring but continues to feed until the parasite inside completely consumes it. The fully grown larva cements the dead aphid to the leaf surface and the aphid shell becomes parchment-like or black. An aphid killed in such a way is termed a mummy and is easy to recognize in a colony of live aphids.
When fully developed (about one week later), the adult wasp cuts a round hole in the mummy and emerges. The empty mummy, with its hole, remains on the leaf. The presence of mummies in a colony of aphids is a signal that many of the other healthy-looking aphids, may actually be parasitized and will die within days.
Braconids that parasitize caterpillars have a life cycle similar to that of the aphid parasites. A different pattern, however, is found among the Copidosoma species. A single egg is laid in the egg of the host. As the host goes through its various stages of development, the parasite egg divides and produces several individual larvae. When the host dies, the larvae pupate within it, to emerge later as adult wasps. In this way the female can produce many offspring even if she only finds one host.
Others take advantage of a large host by laying many eggs in one caterpillar. The larvae grow and feed, and when the host dies, parasite pupae can be found clustered in what is left of the host's cocoon.
