Kids Ask Dr. Bug about the curious things found in the garden

What are pheromones?

Pheromones are the chemicals insects and other animals use to communicate with each other. Pheromones help insects attract and find mates, find food, warn others of their species, as well as many other uses that affect insect behavior and physiology. I’ll share a few examples.

Female Luna moths release a pheromone at night to attract a mate. The male Luna moth has feathery antennae that can pick up the females pheromone up to six miles away! Japanese beetles use an aggregation pheromone to attract other Japanese beetles to a good food source. And, beneficial predatory wasps may pick up on pheromones given off by their prey which can help them find their prey.

Do ants and bees have the same kinds of pheromones and why do they have them?

Eusocial species, such as ants, honey bees, and paper wasps use pheromones in many ways. The colony uses pheromones to recognize their nestmates versus those who do not belong in their nest. This way they can warn nestmates of a potential invader and to recruit help in protecting against invaders. This is important because with thousands of insects in a colony, this would be an easy meal for predators if they were able to get in undetected. Even though these insects use similar pheromones for similar purposes, each species’ and colony’s pheromones are different.

Another pheromone used by ants involves laying down a trail when they leave the nest in search of food. As each ant travels, they drop some pheromone on the trail. If it is a really good food source, and many ants travel on the trail, the pheromone trail becomes strong. A trail that doesn’t lead to a good food source will not be very strong and will be abandoned.

If the queen bee dies, what do you do? A new queen wouldn’t have the right pheromone, would she?

If the queen bee dies in a honey bee hive, the pheromones she produced will cease. Queen bees produce multiple pheromones, each with various purposes. One pheromone keeps the hive calm and keeps the bees from swarming, and another pheromone keeps the other female bees in the hive from laying eggs. So, if a new queen isn’t developed or brought in quickly (within a week or two), worker bees will start laying eggs that are not fertilized, the bees will be restless, and the hive will eventually die off.

If there are new eggs in the hive when the queen dies, the worker bees will start “queen cells” to rear up a new queen. Queens are made by feeding the young bee a special diet. If all goes well, in 16 days, a new queen emerges and can restore order in the hive.

In managed hives, beekeepers regularly check their hives to be sure they are “queen-right” meaning that the queen is healthy. If the queen is missing, they will bring in a new queen. Since she will not “smell” right to the other bees in the hive, she will be put in the hive in a little protective cage with a candy plug blocking the exit. As she and the other bees eat the plug, her pheromone will spread through the hive. By the time she gets out of the cage, the other bees will be used to her pheromone and will allow her to become the hive’s queen.

Do people use pheromones to manage pest insects?

Yes! Pheromones are used by humans to manage pests in a few ways. If we can discover the pheromone that attracts a particular pest, scientists can create a synthetic chemical that is the same as the one the insect makes. Then that chemical can be added to a lure. The lure may be put in a sticky trap to capture pests. This kind of trap can be used to capture pest, or the trap can be used to monitor when pests are around so that other management methods can be used. Another way pheromones are used is to fill the air with the pheromone so that the insects can’t find what they are looking for. This method is often used as a mating disruption, where the mating pheromone is spread, and the males are unable to find the females so they can’t mate and create more pests.

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Dr. Tamra Reall (@MUExtBugNGarden) is a horticulture specialist for MU Extension –Urban West Region. For free, research-based gardening tips, call 816-833-TREE (8733), email mggkc.hotline@gmail.com, or visit extension.missouri.edu. The University of Missouri is an equal opportunity/access/affirmative action/pro-disabled and veteran employer.