Aphid, or plant louse, small, soft-bodied insect that sucks plant sap. Aphids belong to order Hemiptera, suborder Homoptera, and may be red, pink, brown, yellow, green, purple or black. Aphids may be polymorphic with winged and wingless forms in the same species. Over 3900 species are known worldwide; over 600 in Canada.

Aphids appear to have originated about 280 million years ago. In Canada, a fossil aphid over 78 million years old has been found preserved in amber. Aphids can migrate great distances (up to 1300 km) and are very prolific.

Reproduction and Development

In autumn, fertilized females lay overwintering eggs. The following spring these eggs hatch into wingless females that reproduce asexually (without mating), giving birth to live female offspring (vivipary). Throughout the summer, several generations of unfertilized, daughter-producing females may occur. In late summer winged males and females are produced. These mate, producing fertilized, overwintering eggs. Often the asexual generations live on a different host plant from the sexually reproducing generation. In warm climates, aphids do not usually produce males, sexual females or eggs.

Interaction with Humans

Aphids are major insect pests which stunt or kill plants, cause plant galls, reduce yield and vigour, contaminate edible parts, and transmit plant viruses. They are controlled by climatic factors, land and water barriers, predaceous insects, fungus diseases, aphid-resistant plants, irrigation, modification of time of planting or harvest, and insecticides.