Releasing a few tens of thousands of these tiny wasps in the spring of 2003 in my front and back yards has made aphids a non-issue here both on my roses and my food crops ever since. The females lay their eggs inside adult aphids, then the babies hatch and eat their way out. Like mosquitoes, the females need a protein meal to lay eggs, but of pollen vs. blood, especially the pollen of umbillifers like dill, anise, cilantro or cumin. Year after year I have JUST enough aphids, generally on cow peas, to sustain a healthy population of lady bugs and lace wings to further control aphids. Growing roses here as a monoculture, and spraying pesticides, would eliminate this balance that effortlessly controls pests FOR me.