Hey John,
Each of the many aphid species has its own life cycle. One feature most species share is that they are incredibly prolific. Wingless adult female aphids can produce 50 to 100 offspring. A newly born aphid becomes a reproducing adult within about a week and then can and then can produce up to 5 offspring per day for up to 30 days! Reproduction is accomplished without the help of male aphids, in a process known as parthenogenesis.
In spring an egg hatches, producing a wingless female aphid who soon begins parthenogenetically producing new wingless females. Generation after generation of wingless females survive one another until hot weather comes or maybe the plant on which they are living dies and then suddenly some of the females grow wings and fly off.
They come in many colors and shapes. This new generation of female winged aphid very well may at this time find a plant host of a completely different species from that on which their spring generations have developed. For instance, Green Peach Aphids overwinter as eggs on peach and related trees but in spring they move to various weeds and agricultural crops, and then still later they move to potato crops, only in the fall returning to peach and related trees.
Typically late in the year when it's time to move back to the plant species on which the aphid overwinters, finally some aphids develop into males as well as females. Sexual reproduction then takes place and when the mated females return to the winter plant-host they lay fertilized eggs. Then next spring the females hatch from the eggs and the cycle begins again, with no males in sight.
