1999 Ford Taurus Trunk Leak

My Taurus has about 120,000 miles and it has been a great car. I notice that there is a leak in the truck somewhere. I checked the weather stripping and everything seams to be good. No tears no holes. The spear tire was sitting in the water. The plug for the hole under the tire is still in good shape also. I was wondering if you could help me with that. it leaks only when it rains. Also Today I found out that there were tiny ants under the weather stripping of the front 2 doors . What could cause that also. Thanks for your time
Seth