Spec, wouldn't you think I've read alot about this before I posted?? Allow me to prove you wrong. This quote is taken from
http://members.aol.com/Attic21/CreatureofDay/whip.html.
And the same info is all over the web, not just this site. Enjoy learning little cricket.
Andrew
Whiptail Lizards and Parthenogenesis (Virgin Birth)
In 15 of the Cnemidophorus species there are no males. They reproduce without fertilization, a process known as parthenogenesis of "virgin birth". Parthenogenesis is well known in lower animals, such as aphids,bees, and Daphnia but is rare in vertebrates. The offspring of parthenogenic lizards are clones, identical to the mother.
There are some advantages to a parthenogenic lifestyle:
All members of your species can lay eggs and reproduction is more efficient
Good mutations are passed on more efficiently in clones than in sexual species
You don't waste a lot of time and energy searching for a mate (this might not be true in this species, since the females do pair up)
One of the surprising things about unisexual whiptail reproduction is that a courtship ritual is still required even though there is only one sex. Unisexual whiptails pair up. In the courtship ritual one female takes the part of a male, while the other takes the role of a female. Later the 2 lizards switch roles. The switch is caused by hormones: estrogen promotes female behavior; progesterone stimulates male behavior. The mating ritual is required for survival of the species: without it few eggs are released (ovulation)