JohnInKansas makes great post concerning computers and electronics, but his knowledge of natural sciences is not so good.

From his description of the flea's life cycle, he does not know that there is a larval stage. In fact, the flea undergoes 'complete metamorphosis' which means there are four stages: egg, larva, pupa and adult.

The flea larva has three stages called 'instars' and sheds it's 'exoskeleton' between stages. The larva is the only stage that grows, although the adult flea will swell (and usually darken in color) after it's first 'blood meal'.

The pupal stage is the long-lasting one which is how the flea over-winters. It can survive here about a year. Other stages usually last 1-2 weeks. Adults (full-sized) are triggered to emerge by vibrations such as those caused by pets and humans walking. This results in the 'vacant house syndrome" where people move in and are soon innundated by adult fleas. They were in the pupal stage waiting for the sigal that potential hosts were present.

A growth regulator can be applied to prevent the larvae from molting, meaning that they are stuck (usually) in the first or second instar for a long period of time, eventually becoming 'spent', they die. Precor is one brand name for the hormone which is (usually) sprayed on carpets and baseboards the inside of the infested house.