How long does a flea live? A fleas lifespan depends greatly upon the conditions when it's living. Oddly enough, a favorable lifespan is going to end up with a flea living a shorter lifespan. Sounds strange I know, but has less to do with how long you live and how much living you pack in that time. So, let's look at our little calender here. Let's see our, let's say our flea emerges from its pupae on the seventh of October, that flea has until the fourteenth of October to feed off of a host, your dog or your cat. He's got to have blood by the fourteenth from somebody. He's a little vampire, as you remember. If he doesn't eat by then, he's going to die. However, if he does eat by the fourteenth, it's all gravy after that. They can go a long time without eating again, in fact, up to a year if conditions are unfavorable. Again, like I said, it's not a matter of how long you live, but how much living you pack into it. If he keeps eating after the fourteenth, on a regular basis, on a regular host, his life cycle is going to be probably about a week, to two weeks after that. O.k, so on the twelfth, he needs to be start thinking about getting his funeral arrangements together. Again this is in optimum conditions, a flea in say freezing cold weather, or in a very cool area, is going to live a lot longer, because it's metabolism is going to be moving a lot slower, and he's not going to be feeding as often, and as much. So, in unfavorable conditions, a flea can live up to a year, but this is not good for the flea, and actually, he'd rather burn out fast, than burn out hard.