Clients sometimes tell me crazy ideas about how lice reproduce. Some think that they are like viruses, that you can get infected just by being in the same room as someone with head lice. Some think that head lice are hermaphrodites - that they have both male and female sexual organs and fertilize themselves. Not true.
Both a female louse and a male louse are required to produce a fertilized egg. So, why then can you get lots of head lice from just one bug on your head? Well, if the bug is a male, not much will happen. But if the bug is a fertilized female louse, watch out, because a little sperm goes a long way.
The female louse mates with the male louse just once and receives all the sperm she will ever need. She stores all the extra sperm in her body in a receptacle called a "spermatotheca". Then her eggs just get fertilized as she goes. Not very romantic, but it gets the job done. Bow chicka wow wow!