I have written several amateur evolutionary simulations, the most recent being a simulation of viral mutation and evolution. However, nothing I make is very accurate or even interesting. If you want to make a proper simulation, study the actual science on ants, and develop your simulation based on that. You don't have to get down and dirty with the specifics, but you do need to have a genotypic base that is similar enough to the genes of an ant's, and an environment with motivations that are comparable.

However, if you're just coding it for fun, just to get results and without any concern for realism, I suggest this: create an Ant class that has an array of integers or doubles which you will consider its genome. Go through the genome, and decide what each gene "means" (like size, color, speed, efficiency, sex, whether or not it has wings, whether or not it can mate, how long it lives, how much food it requires, etc.). In the constructor of the Ant class, give it all the attributes based on its genome. Then simply create a method for the life of the ant, telling it to do things like "random walk" or "sniff for pheremones" or "dig" or "find food". Make sure that each gene in your genome has a somewhat noticeable effect on the performance of the ant in each case. Finally, if the ant is able to reproduce, tell it to produce children that are the random combination of genes from each parent ant, with a slight chance of mutation.

Include also various classes representing environmental objects, preferrably a coordinate system,  along with ant-produced entities like pheremones and waste. The pheremones themselves could be a string of two or three integers, linked to the genomes of each ant. As the ants go about finding food, they could secrete a specific pheremone to whatever they are doing. If another ant has similar pheremone codes to the ant producing the pheremone, it should be able to respond appropriately to it.

If you have a structure basically like this, and run the simulation for a long enough time, you should at least see some evolutionary pattern occuring. It may not be even very interesting or much like ants at all, but you will definatley see a trend, and if you're lucky, the trend might be towards a stable, sociable ant population. In the case of my viral simulation, it almost always resulted in a single strain of virus which could not infect any cells and eventually died, and sometimes resulted in all of the cells being killed by the virus. So yes, unless your simulation closely fits reality, you probably will not get favorable results. In fact, you might be surprised and discover something totally new, and that's the joy of pure simulation.