The entire lifespan of the whitefly is relatively short. The adult whitefly lifespan ranges from 6-55 days depending on a variety of factors including temperature, plant host, and species. 
The whitefly will go through six individual life stages within one month’s time depending on temperature, the egg, three distinct nymphal stages, the pupal stage, and finally the adult stage. 
The Egg Stage
Whiteflies deposit eggs on the underside of plant vegetation through the ovipositor. Though individually the eggs are almost non-detectable to the naked eye, the whitefly lays her eggs in circle groupings surrounding by their characteristic white, powdery film, making detection obvious.
Unfertilized eggs will become male, fertilized eggs will become female. Some whitefly species only reproduce females.
Development Timeline: 9-12 days depending on species and temperature
The Nymphal Stages
The nymphal stages begin once the egg hatches. The nymph will emerge during the first instar and move only a short distance to begin feeding. The nymph generally does not move during the subsequent instar stages to follow.
During the first three instar stages the nymph is less than .5mm in length, off-white to light green in color, and oval-shaped. 
First instar: 4-6 days depending on species and temperature
Second instar: 7-10 days depending on species and temperature
Third instar: 7-10 days depending on species and temperature
The fourth nymphal stage is referred to as the pupal stage during which time the nymph has grown more plump in appearance and has grown to .5-2mm in length. The pupal nymph begins to resemble the adult.
Though the fourth instar stage is referred to as the pupal stage, it is not a true pupa as it does not molt into a complete non-feeding, resting stage.
Development Timeline: 10-11 days depending on species and temperature
The adult emerges from a pupal case in a little over a week. The powdery, waxy, white film that covers the whitefly is produced and secreted through abdominal glands following emergence.  They may mate within hours of emergence and may lay eggs one to eight days after mating. 
Development Timeline: 5-40 days depending on species and temperature
 “About Whiteflies.” UA Whitefly – Home. N.p., n.d. Web. 25 May 2011. http://whiteflytax.biosci.arizona.edu/ipm/homegrnd/htms/48ghwfl.htm
 “Sweet Potato Whitefly.” University of Minnesota. N.p., n.d. Web. 25 May 2011. www.entomology.umn.edu/cues/inter/ inmine/Whitefsp.html