The little eggs stick to the base of your hair at the scalp, when they hatch out the egg stays in the same place and the bug goes where ever it wants. The further out the hair has grown the further out the egg casing will be, and they will all be on different levels of hair if you've had a bad case of them for a long time. Also, you can tell by how severe the infestation is. They all just don't jump on your head at once, they breed and live there for awhile. You have to wash everything in your house in scalding hot water and soap(bleach if possible), and you may have to get flea or lice foggers for your home(like bug bombs). I witnessed an extremely bad case of lice on a girl with thick curly red hair down to her butt, and you could tell she had them for a VERY VERY long time. Fortunately, no one she came in contact with got them...... I bet everybody living in her home had them though.