Answer: Crab lice, (Phthirus pubis or Pthirus pubis).
Anon points out that "Pthirus" is correct rather than "Phthirus;" however the only reference I could find on this was Wikipedia. The CDC DPDx Web page uses "Phthirus" as does many publications on PubMed. Does anyone have a different reference for me on the correct spelling?
Another interesting comment that came up on this post was how this little arthropod may be at risk of extinction due to the widespread practice of genital hair shaving. I've heard this several times now from a variety of popular media sources, but haven't seen any published studies on this phenomenon. Also, we seem to still get a good number of these cases in my lab. Does anyone know of any studies to back this up? It's definitely an interesting hypothesis!
Thanks for all of the interesting comments, as always.