Aphids are also known as plant lice, they destroy plants by sucking the juices out. Most aphids have soft bodies, which may be green, black, brown, pink or almost colourless. Aphids are distributed worldwide, but are most common in temperate zones. They can migrate great distances, mainly through passive dispersal by riding on winds.
On various plants and trees.
Ladybugs mostly, and Praying mantis eat aphids, so it's good to have these insects in your garden if you have aphids. Some ants drink the sweet dew that comes out of aphids, and will frequently guard them from the predators of aphids.