Aphids

Aphids have a complicated life cycle and reproduction habits that make them extremely adaptable to their host plants and environments. When aphid eggs that have overwintered on their host plants hatch in the spring, they produce females without wings. These females and are capable of reproducing asexually, a process called parthenogenesis. Several asexual generations of aphids may be produced during a growing season.

When it becomes necessary to move to another plant, females with wings are produced and move to another host plant. As winter approaches, both males and females are produced and their fertilized eggs again overwinter until the next spring. Sometimes winged females that produce asexually also migrate to new hosts. A scanning electron micrograph (SEM) of a green peach aphid (Myzus persicae) on the leaf of a Marvel of Peru (Mirabilis jalapa). This aphid winters on peach trees and migrates to other plants for the summer. It is an economic pest when it infests crops such as potatoes. The aphid is also a carrier of plant viruses, which are transmitted when it inserts its stylet into the veins of a leaf in search of sugar-carrying cells. The tubes on the aphid's back are siphons for sending pheromone signals. ©Dr. Jeremy Burgess/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced with permission. The lack of wings among generations of aphids that have no need to migrate is seen as an adaptive advantage, since it helps keep them from being blown away in windy weather.