Aphids - a major garden pest
Aphids are soft bodied insects which live on the sap of a wide number of plants. You will find them on the underside of leaves, and also clustering around buds and flowers. Aphids are generally greenish but can also be black, orange, or shades of brown. The green aphids typically found on roses are usually called "greenfly", and the fat black aphids often found on broad beans are called "blackfly".
Some Aphids have wings to fly in from outside and set up new Aphids colonies at any time. Aphids multiply extremely fast during warm weather by producing live young Aphids which already have the next Aphid generation developing inside them when they are born.