Ryan, this is a good question. The answer is not that easy though. Different ant species can have different numbers of queens in their colonies. In the majority of ant species, a single female establishes a new colony on their own (only one queen). When we talk about ant colonies that have one queen we use the term "monogyny" (mono = single; gyn = female/queen), and when talking about ants with multiple queens we use the term "polygyny". Polygyny occurs when young queens get together in groups of young founding queens (primary polygyny). Still others return to the nest they were born into and join their mother and sisters in this already established colony to also lay eggs (secondary polygyny).
Also, a single queen can mate with one or more males before starting her colony. There are quite a variety of different colony structures that have been discovered in ants ranging from the "standard system" of one singly-mated queen per colony to colonies with multiple queens or queens that mated multiple times. A good overview of different colony structures can be found in Heinze (2008). In analogy to the terms monogyny and polygyny we refer to mating once as "monoandry" (mono = single; andr = male/mate) and mating several times as "polyandry". The queens of army ants and leaf-cutter ants show extreme cases of polyandry and mating with 20 males is not unusual for these ant species. Monoandry is often common in ant species that have multiple queens. So there seems to be a trade-off between queen number and matings per queen.
Sometimes the only way to know how many queens a species has in the nest is to dig up the entire colony to count them. With over 14,000 ant species there are many that have never had their nests studied, so for many species we still do not know how many queens are in a nest or how many times she has mated.
Heinze J (2008) The demise of the standard ant (Hymenoptera: Formicidae). Myrmecological News 11:9-20
- Steffi Kautz & the AskAnt Team