Pheromones are another type of chemical that sends out signals. The key difference with pheromones is that those messages are sent outside the body as a way to communicate with others of the same species. (Keep in mind that they are fundamentally different than hormones since hormones act within the body, but their main purpose is the same: communication.)
Although lots of animals emit pheromones to communicate territory or reproductive behaviors, the most advanced pheromone system belongs to tiny honey bees. The most complex pheromone is the Queen Retinue Pheromone from queen bees.
Honey bees use pheromones to communicate all sorts of things: their attractiveness and desire to mate, their location, and the need to be on the defensive when there's an animal nearby.
Honey bee. If you aren't a queen bee, your life revolves around her.
Before we get into any details about these pheromones and the hierarchical and royal society of bees, let's go over honey bees 101, in case you somehow missed out on bee science. First, there are three different kinds of bees: queens, drones, and worker bees. The queen is supreme, and her main goal in life is to make babies. Heck, she lays nearly 2000 eggs in a day. (She basically does nothing else.) Drones are male bees whose sole purpose in life is to mate with a queen—whether it's his queen or one from another colony. Mating is so important that once they've done the deed, drones go belly up and die. The worker bees are sterile female bees that do all the work: cleaning the hive, making the honey, doting on the queen bee. What a life.
It's only when bees cover a larvae with a chemical called royal jelly that a queen is made. (So regal.) Unlike humans, these bees don't have to come from one royal family tree or another; they just need to get coated in that special jelly.
Once she's born, this virgin queen fights with any older queen bees to take over the hive. Most young queens die before she gets to become a mom. If she happens to survive, she'll fly around hoping to mate with about 15 different drone bees. It's the drone's sweet kiss of death, since they drop like flies once they've inseminated their queen.
The queen bee saves and stores all the sperm from this mating soiree since it's likely to be her last. She'll continue to lay fertilized eggs for the rest of her life. If she doesn't mate with enough drones and runs out of sperm, she'll lay unfertilized eggs that later become drones.
How do pheromones fit into this hierarchical society of honey bees? Queen bees actually produce a number of chemicals that are collectively known as Queen Retinue Pheromone (QRP). These chemicals are released from glands in her head and abdomen, and both attract mating drones and keep female worker bees sterile. That way she ensures that she's the only female able to make baby bees.
If you are chemically savvy, or just have a weird passion for chemical compound names, try some of the QRP chemicals on for size: 9-oxodec-(E)-2-enoic acid, 9-hydroxydec-(E)-2-enoic acid, methyl para-hydroxybenzoate, and 2-(4-hydroxy-3-methoxyphenyl)ethanol. Who knows? Maybe it'll show up on your next spelling test.
As long as the queen bee is healthy, life continues the same way: laying eggs day in and day out. But if her ovaries malfunction and aren't healthy anymore, she releases less QRP and the colony writes her off. They won't even hesitate at killing the royal bee once her baby-making capabilities have gone awry. The drones will mate with a new queen. Bee-making is serious business.
Another cool part about these queen bee pheromones is that they let her colony know how well she mated. Essentially, if she mated with many drones, her pheromones attract more bees than if she didn't have too many takers. If there are two queen bees in a colony, the more promiscuous one wins and gets all the attention.
There's no way to be quite sure, but this queen bee was probably pretty successful in that whole mating thing.