Symptoms include itching and irritation in the genital area. Since crabs live off of your blood, you may find bluish spots where the crabs have been feeding. Dark spots may also be visible on your skin or underwear. These spots are the crab feces and indicate a definite infestation. Additionally, you may be able to see genital crabs crawling around in your pubic hair or find nits (eggs) close to the bottom of the pubic hair shaft. It is also common to experience a slight fever and feel irritated and run down when you have a pubic lice infestation.