As if having a flea infestation and finding a hoard of flea eggs or larvae is not bad enough, there lies the pupa, also known as the pupae, stage of flea development. This stage is the third in the life cycle of a flea, and the last before the flea becomes a fully grown little "vampire."
Did you know?
Flea pupae amount for about 10% of the total population of fleas at any given time.
In this stage, the flea forms a cocoon around itself, similar to a moth or butterfly, only much smaller. They are hard to locate with the naked eye, since each flea larva uses things found locally to form the cocoon. Yes, they produce a type of silk like butterflies do, but that is only a part of what makes up each cocoon. Lint, hair (both human and pet varieties), carpet fibers and even dust can all be used as cocoon-building material. This helps the flea pupae blend in with the environment around them -- kind of clever, in a disturbing sort of way.
If you do happen to find a flea pupa and have the chance to magnify it, you will see that it looks like a lumpy, crusty little thing. There is no better way to describe it. While butterfly and moth cocoons can be as beautiful as the fully emerged creatures themselves, flea pupa are the complete opposite. Their cocoons are not smooth, and look more like a abstract geometric figures, with pointy angles sticking out all over.
The worst thing about a flea pupa is that the cocoon is virtually impenetrable. They do not stay on your pet during this stage, choosing your carpeting, furniture and other high-pet-traffic areas instead. During the average lifespan of a flea, they remain in the pupae stage for between five to ten days. However, if nothing triggers them to hatch, they can stay cocooned (and alive) for up to nine months.
While they are encased in their cocoons, nothing can kill them. Flea sprays and whole-house foggers only coat the outside of the cocoon, and cannot get inside of it. If you vacuum up the pupae and do not clean your vacuum well, the cocoons (and therefore the fleas) will live inside of it until they hatches. This is why, if you are trying to rid your house of fleas, you need to keep vacuuming and spraying your house.