After 7-18 days, flea larvae pupate. Not the latest dance fad, but the process by which they spin a protective cocoon around themselves and develop into adults.
 

Inside the cocoon, fleas are almost impervious to insecticides. In fact, about the only thing that will get them during this stage of their life cycle is a blowtorch (which is perhaps a bit extreme for most people!).
 

It takes between 5-14 days for fleas to develop inside the cocoon, after which they are triggered to hatch in response to vibration (being stepped on), or the carbon dioxide exhaled by a passing host. But in the absence of a trigger, they can survive inside the cocoon for up to nine months.
 

So, what does this mean for successful flea control?
 

1. There are no chemical sprays on the market today that will penetrate the pupal cocoon. So, if you have pupal fleas in the house, you will need to start your flea control programme and accept that it may be weeks before they hatch and can be completely eliminated from the house.
 

2. Once again, prevention is the best approach to flea control. If you treat your pet before it comes into contact with fleas, you won't end up with flea pupae around your home.