The Ants and the Bees

I find eusocial insect fascinating. The way they work together and appear to have a “hive mind” (when really they are quite simple creatures when you look closely) enthralled me as a kid. There’s so many things I want to talk about in relation to them but right now I’ll just focus on their unique genetic and familial situation. Also, to simplify I’ll be talking about ants in particular. Keep in mind, not all ant species work this way but what I’m about to explain goes for most of your typical ant species.

Sex and Caste Determination

I’m sure you’re familiar with how biological sex typically works in mammals. Females have two X chromosomes while males have an X and a Y. No matter what, each mammal has two sets of DNA. One comes from the mother and one from the father.

Ants break all these rules completely. They are what we call haplodiploidy. When a queen lays eggs, some are fertilized. These have DNA from a father so they have two chromosomes. We call them diploid. Some eggs are not fertilized and only get one chromosome from the queen. These are haploid. Unlike unfertilized bird and reptile eggs, these will still develop and hatch. All fertilized (diploid) eggs will hatch into female larvae while the unfertilized (haploid) eggs are male.

All males grow up to be male alates or drones. Their only purpose is to one day leave the colony to try and mate with a female alate, after which they die. They do not help with any activities in the nest and so are kinda just a drain on colony resources. Most females grow up to become workers. They are the ones who get things done: finding food, caring for young and the queen, cleaning the nest, and occasionally defending the nest. Some females grow into specialized worker roles such as majors or soldiers but for my purposes, I’ll just lump them in with the other workers. No matter their role, all these worker females are infertile¹.

If the colony is doing particularly well, they’ll have plenty of extra food to feed the larvae. Some female larvae get fed so much that it triggers a change in their hormones,² and they start to develop functioning ovaries. These larvae grow bigger than their sisters and eventually become female alates. Like the males, they do no work and will eventually leave the colony to mate. Many of them will not succeed or get eaten or killed somehow. The few who find a mate and survive long enough to find a safe place to dig a hole in the ground will try to start a new colony and become a queen.

Familial Relations

Some interesting things come up when you think about how related ants in a colony are to each other. For us mammals, we are always 50%³ related to our parents, siblings, and children because we get half our genes from our mother and half from our father. Queen ants are 50% related to all their children. Nothing too crazy there. But what about the workers?

You might be tempted to say that they should be the same since they get half of their genes from their mother and half from their father. That’s true, but remember that all males are haploid; they only have one set of genes. You and your siblings have an equal chance of inheriting either chromosome from your father but ant fathers only have one chromosome to give. So while the workers are 50% related to the queen, they are actually 75% relate to each other since they are guaranteed to have at least one full chromosome in common.

If we believe Richard Dawkin’s idea of the selfish gene, where animals tend to act to the benefit of those most closely related to them, then all workers would favor their sisters over their queen! This logic also extends to the female alates. The workers would favor them equally to themselves since they share 75% relatedness.

Now here’s something even more interesting… what about those male alates? They don’t get a chromosome from a father. They don’t have a father at all! Male ants have no father and cannot have sons! Wild! Anyway, what does this do to relatedness? Well since they only get one chromosome from the queen, and they have an equal chance of getting either of her chromosomes, the average relatedness between a female and male sibling is only 25%!

Conclusion

So to sum up: The queen is equally related to all her children so she cares about them all equally. The females of the colony care most about their sisters, then the queen, and they care about the males the least. The males would care mostly about the queen and other males, but they honestly don’t do much so can be disregarded for this next part. So the queen shouldn’t care much about if she’s laying male or female eggs since she’s equally related to all of them. As long as she’s having children she’s happy. But the workers would prefer to have more sisters than brothers. To be precise they would prefer to have 3 sisters for every 1 brother to line up with the 75% and 25% relatedness. Wouldn’t it be nifty for them to find a way to change the likelihood of an egg being fertilized? I mean, it’s not like the queen would mind. And wouldn’t you know it, that happens to be the exact ratio that we find in real ant colonies. 75% female, 25% male. Wow!

To be honest, the worker ants probably aren’t doing anything intentionally to make this happen. They might not be doing anything at all! I just made some observations in my research and tried to make some fun connections between information. It’s much more likely that this 3:1 split just happens to be optimal for colony maintenance. Cause you don’t want too many of those lazy male alates sitting around and eating all the food! And again, I want to emphasize that there is a TON of variety in ant species! Everything I’ve talked about here applies to most of them but there are plenty of exceptions. For example, there’s one species that doesn’t have a queen at all! All the females can lay eggs, and they sometimes fight to determine who gets that privilege in the colony. There are also species where the queens mate multiple times before starting a colony, in which case the females are less related to each other! And there’s even species where multiple queens exist in the same colony!

There’s so much to talk about with eusocial insects, but I’ll leave it at that for now.