Nice picture, huh? I like and encourage the reading of a variety of head lice fact sheets from a variety of research centres/universities. While the facts are usually (but not always) the same, they occasionally use different language that helps you understand an issue more clearly.
For example, here's an excerpt from the fact sheet from the Entomology Department of the College of Agricultural Sciences of Penn State University. It is regarding the viability of eggs that are not right near the scalp:
Most of the calls I receive come from people who want to know how to deal with this problem on their own. I am very happy to share all kinds of information about head lice and will do what I can to help you. You don't need a professional and every lice removal "expert" got that way just through experience, which my callers soon get. However, there are times that you might want an in-home visit.
You might want to call in a head lice professional when...