Answer: Pediculus humanus
As pointed out by Hans, P. humanus has 2 ecotypes, which are referred to as head lice and body lice. Although they are very similar and have overlapping body features, they differ by only a single gene and can successfully interbreed to produce fertile off-spring. Here is an interesting review on human head and body lice which covers the taxonomy in greater detail:
Veracx and Raoult. Biology and genetics of human head and body lice. Trends in Parasitology, December 2012, Vol. 28, No. 12.
Enjoy, and Happy 2013!