have ants in the/(one's) pants
1. To be unable to sit still, due to anxiety, excess energy, or impatience. The kids really have ants in the pants today, so I'm going to take them to the playground. A: "Why is Carrie pacing?" B: "She's waiting for her doctor to call, so she's had ants in her pants all day."
2. To be interested in or in pursuit of sexual activity. You've been single for awhile now—don't you have ants in the pants yet?