One point of flexibility is the statistics. If you have a species that can naturally or technologically reproduce at high levels per individual, then you can have a really huge gap. If reproduction is more limited, the gap will be smaller.
Conversely, many animals use a "harem" structure where one male services many females, over and over. That can be anywhere from the ~2 dozen of a horse herd to the several hundred of a walrus herd.
One fun example in fiction is A Brother's Price, where the population is about 90% female.
From much farther back, I actually wrote about an insectoid species coming into sapience and thus starting to break away from the rigid caste system: Queen Choufa and the Rebel Drones.
Another point of flexibility is the caste structure. The more rigid it is, the more likely that fighting it becomes a plot point. The more flexible it is, though, the easier it is to play with diverse expressions across different characters.
A caste that's made up, like in India, is very different from one that's finely hardwired, like in social insects. In between you have things like naked mole-rats where if the queen dies, a worker female becomes a queen. This version is extremely useful in fiction because 1) a death is an effective form of tension, and 2) contextual fertility development is a way to avoid overpopulation, so it's well established and a plausible post-apocalyptic scenario. Some other species have not only contextual fertility but even contextual sex changes.
Thoughts
Frex, Honey bee colonies consist of a single queen, hundreds of male drones and 20,000 to 80,000 female worker bees. Queens have only one mating flight, but typically mate with several drones at that time.
Conversely, many animals use a "harem" structure where one male services many females, over and over. That can be anywhere from the ~2 dozen of a horse herd to the several hundred of a walrus herd.
One fun example in fiction is A Brother's Price, where the population is about 90% female.
I have a similar ration in Daughters of the Apocalypse.
From much farther back, I actually wrote about an insectoid species coming into sapience and thus starting to break away from the rigid caste system: Queen Choufa and the Rebel Drones.
Another point of flexibility is the caste structure. The more rigid it is, the more likely that fighting it becomes a plot point. The more flexible it is, though, the easier it is to play with diverse expressions across different characters.
A caste that's made up, like in India, is very different from one that's finely hardwired, like in social insects. In between you have things like naked mole-rats where if the queen dies, a worker female becomes a queen. This version is extremely useful in fiction because 1) a death is an effective form of tension, and 2) contextual fertility development is a way to avoid overpopulation, so it's well established and a plausible post-apocalyptic scenario. Some other species have not only contextual fertility but even contextual sex changes.