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aphid (representative specimen)

Features and Behaviors

Aphids are small, soft-bodied insects that feed on plant sap. The body has long antennae and is generally pear-shaped. Cornicles, structures protruding from two abdominal segments, are used to secrete a defensive fluid. Wings may or may not be present. When present, the hind wing is much smaller than the forewing. Wings are held vertically above the body when at rest. This insect is about one-eighth inch or less in length.

Aphids may be found throughout Illinois. They live on the stems, leaves and flowers of plants, sucking the plant sap for food. Aphids have a complex life cycle. They overwinter as eggs, then hatch in the spring into wingless females that reproduce parthenogenetically (without fertilization) and give birth to live young, which are also all females. They may produce two or more generations of these females before eventually a winged female generation appears that moves to a new food source. Again, these aphids reproduce parthenogenetically, producing more females. Late in the year, the winged adults return to the original food plant and produce males and females. The males and females mate, and the females lay eggs that overwinter. Aphids discharge honeydew from their anus. Honeydew is a clear liquid that contains excess sap ingested by the aphid, added sugars and waste products. Aphids may excrete so much honeydew that they make the plant they are feeding on and the ground around it sticky. Ants sometimes live in close association with aphids. They eat the honeydew produced by the aphids. They may even take aphid eggs to their nest in the fall of they year, store them in the nest during winter, take the newly hatched aphids to a food source in the spring and tend to them in the summer. Aphids may be pests of cultivated plants and may carry plant diseases.

Illinois Range


​Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hemiptera
Family: Aphididae

Illinois Status: common, native