Head Lice continue to show impressive abilities to develop resistance to pesticides that are used to eradicate them.  The cardinal survival tool of a successful parasite is the ability to adapt quickly to changing environments.  We could say that Head Lice have so far mastered this ability to adapt to new pesticide formulations that are being used on them.  The adaptability of Head Lice is one explanation for why Head Lice are doing so well in 2014 and appear to be increasing in numbers and geographical distribution in North America