Life-style Aphidius ervi is originally a European species, but it has been widely introduced into North and South America and other regions in recent years as part of biological control programs for aphids on a variety of crops. Once a female finds an individual aphid or aphid colony, she will palpate the aphids with her antennae. If the aphid she is examining is of the correct size and has not already been parasitised, she rapidly curls her abdomen under her body and stabs the aphid with her ovipositor. This takes less than one second, but in this time the female checks the identity of the aphid with her ovipositor and lays an egg into it if she is satisfied. The egg soon hatches, and the resulting larva begins to feed within the aphid. Initially it will not kill the host, but as it grows it begins to feed on the vital organs so that the aphid dies. When fully grown, the Aphidius larva cuts a slit in the hollowed out shell of its host and attaches the carcass to the substrate with silk. As it spins more silk within the host skin, this gradually takes on a pale grey color and forms the characteristic ‘aphid mummy’. Within the mummy the larva pupates and after five to ten days an adult is ready to emerge. The adult cuts a circular trap door in the mummy, always on the upper surface at the back, and escapes through this to seek out new hosts. The life cycle of Aphidius ervi takes nearly 19 days at a temperature of 70°F.
