Aphids only feed on living plants and trees. They mostly focus on younger plants, like a budding flower or a new tree stem. Many types of aphids live on only one type of vegetation (for the most part), many times the type of plant they feed on is in the species name. Some vegetation this includes are cabbage, peaches, beans, and apples. In general, however, most attacks on crops are done by aphids who eat more than one type of plant sap. Like any other animal, aphids poop after they eat, and aphids poop a lot. They can excrete their entire body weight once every two hours. Their poop is unlike ours, they excrete honeydew, a substance not unlike sap. It is a sugar-rich, sticky, and opaque liquid.
In the fall, male and female aphids mate and the fertilized females lay eggs on a plant host that will survive the harsh winter. The aphids that hatch from these eggs in the spring are all females. The aphids continue to reproduce in the spring and summer, but this time without males. The females that hatched in the spring are already pregnant with live genetic clones of themselves. The clones they’re pregnant with are also pregnant with their clones (often with wings to prevent overpopulation). This means that one hatched female is pregnant with two generations of offspring. This is called telescopic development and it means that aphids make babies extremely fast (which is good considering their short life cycle of a week to a month).
Aphids may be small but they have prey, plants. Aphids are considered pests to many gardeners of both crops and ornamental plants. Aphids can easily pass disease from a diseased plant to a healthy one in just a few seconds (especially the winged generation). The viruses they pass can’t be cured so the plants have a decline in yield. Some fungi create a barrier on aphid honeydew and create sooty mold which can block photosynthesis and it’s hard to remove from glass. The mold often falls on vehicles parked underneath trees. Their sucking can also cause shriveled leaves, leaf loss, and metabolic imbalance. Their predators include lady beetles and parasitic wasps. Luckily, aphid honeydew attracts insects that feed on it. Ants often defend aphid colonies from predators for honeydew in return. This is an example of a mutually symbiotic relationship.
Even though aphids may be the occasional pest, they have a lot of good functions. They feed many insects including ants and yellowjackets, and some species of bees like making honey from it. The honey that’s produced is called honeydew honey and it is sold at high prices in areas of Europe and Asia. Aphid poop may not sound appetising, but honeydew has more nutritional benefits than normal floral honey including higher antioxidant and antibacterial levels. Aphids may be the occasional pest, but they're interesting and generally helpful creatures.