13) If a colony with only one queen ant were to die, would she be replaced with another? Or does the colony die out. If she gets replaced, then are there always alates available to replace her at any time? Or are they only produced prior for the mating season, nuptial flight, and etc.? Is there any way of the colony knowing that the queen is about to expire, like some kind of special pheromone?
Mike, you've taken us on quite an adventure with your questions. It's been a fun learning experience for me to dig up the answers for the ones I didn't know about. If you have any more questions, or you'd like clarification about anything, feel free to ask.
As for the ability of ant colonies to replace their queens, this is a topic that comes up often.
For many temperate ant species with a single queen, the answer is that once the queen dies, the colony is a goner. The worker ants will not accept one of their sisters as a new queen, workers can not become a new queen themselves, nor can they raise a new queen like honey bees do. Some worker ants can produce eggs once the queen has died, but those eggs are unfertilized and will become males.
That said, there are a number of ant species that don't fit the norm. In species like the Argentine ant, Linepithema humile, colonies have many queens, and the males and queens mate right inside the nest. Having many queens allows the colonies to become large quickly. In fact, one problem with Argentine ants is that when they are introduced to places they have never been before, they form such large colonies that they can quickly overwhelm or drive out many native ants, even ants much bigger than themselves. Argentine ants proved to be hugely successful at spreading and are now found almost worldwide.
Another strategy is found in the ponerines that don't have a distinct, physically different queen. In those species, the egg-laying individual is called a gamergate. When one gamergate dies, the next high-ranking worker takes over laying eggs. Hoelldobler and Wilson discuss this in detail in their book, Superorganism.
Most ants colonies have distinct periods or seasons when the reproductives are produced, but that will vary from species to species and even somewhat from year to year, due to differences in environmental triggers, amount of food, age of the queen, etc.
Finally, the queen probably won't give off a specific signal that she is weak (it wouldn't be to her benefit), but there might be a decrease in the pheromone(s) she produces to attract the workers and keep them from producing eggs.
By the way, you might be interested to know that researchers recently synthesized the pheromone of the queen black garden ant and were able to show that it does suppress the ovaries and egg-laying ability of worker ants. See: University of Copenhagen (2010, July 14). Elusive ant queen pheromone tracked down. ScienceDaily. Retrieved July 24, 2010, from http://www.sciencedaily.com /releases/2010/06/100630101016.htm
For more information on ant queens, see a previous post answering questions about ant queen development.
If anyone has more information about this they'd like to share, please let us know.