How do ants follow each other?

Question

I was observing ants in my house.They all were going in a straight line and also some of the ants were coming back through the the same line. I took some water and rubbed the line with my finger, then the ants were not able to follow each other. Looks like they were confused. My assumption is that they may had secreted some chemical . Am I right ? If yes, then which chemical is that and how it is secreted?

Answer 1

Here's an example from the Internet: There you can find out, for example, that the trail pheromone for Atta texana is me-4me-pyrrole-2-carboxylate, and what it’s structure looks like. 

I think each species has unique pheromones.

Answer 2

Yes, they lay down a chemical path which other ants can sense (smell). If you observe the first ant to travel a path to food, for example, you will see it touch the distill end of its abdomen to the surface repeatedly as it travels.