Aphids are very small common insects. They have tiny, sharp, pointed mouths which they stick into the skin of tender stems and new-growth leaves of specific plants. Once an aphid's mouth is stuck in place on a plant, the aphid will stay there for many days.

Aphids live off the sap of their host plant. Aphids produce a sweet byproduct called honeydew. Some types of ants like the sweet honeydew and, when they find an aphid colony, they will stay around protecting their aphids from other insect predators.

The process of an ant taking honeydew from an aphid is called "milking." The ant does not kill the aphid.

There are well over 1,000 different kinds of aphids in North America. Aphids can both lay eggs and give live birth to their offspring. Sometimes aphid colonies like the one I found on a non-native quince bush can number into the thousands of individuals.