The female wasp lays a single egg in each aphid. The larva will hatch inside the aphid and feed on it. The larva pupates with the aphid body, spinning a cacoon which causes the body to bloat and it becomes a golden-brown colour. At this stage the aphids are referred to as “mummies”.
A single female can lay around 300 eggs in her lifetime. It takes about 14 days from egg to adult in ideal temperatures.