Crabs: a.k.a pubic lice/head lice are transmitted by contact with an infected person. Skin irritation and itching are the most common symptoms. Detecting them is done by visual inspection. Crabs or crab eggs, known as "nits" can be located on hair shafts. They are usually found in either the scalp or pubic hair. Occasionally, they will be found in chest or underarm hair.

If you would like to learn more about crabs, contact these sights:

http://www.stdservices.on.net/std/crabs/

http://www.hsph.harvard.edu/headlice.html

http://www.ces.ncsu.edu/depts/ent/notes/Urban/lice/pubic.htm