Only few ant species practice it. And some species will only mate in air.
About having more queens: I guess it is better to have more than one queen in nest when founding a colony. If one dies or is unsucessful you have "back up". Having more than one queen in nest doesn't necesery mean that the colony will grow faster. Lots of species where there are polygin queens only one lays eggs. Or more than one queen is tolerated but eventually all but one are killed. This varies from species to species. Just having more queens doesn't mean a bigger colony faster.





