Aphids often colonise the undersides of plant leaves where they are less visible to predators. In this photograph, you can see a number of lacewing larvae predating on an aphid colony gathered on the underside of a Lathyrus odoratus leaf.
Episyrphus balteatus, also known by its common name of marmalade hoverfly, laying eggs on a Sweet Pea tendril produced by one of the wigwam grown Sweet Pea plants, which were grown for my 2016 Sweet Pea Trial.
A closer look at an aphid colony present on the underside of an Lathyrus odoratus leaf. The white objects in the picture are the shed skins of the aphids, and the brown insects of varying sizes are lacewing larvae at differing stages of development.