By Dr. Lucas E. Roscoe, Research Scientist at the Canadian Forest Service (Natural Resources Canada)

Insects find their way around a forest using the same senses as humans and other animals do – sight, sound, touch and smell. Like other animals, they use their senses to find food, mates and shelter within a complex environment.

In the case of finding a prospective partner, insects will use their sense of smell to detect pheromones. Pheromones are an airborne scent that is unique and produced by members of the same species. They occur naturally and are species-specific, meaning that the spruce budworm pheromone only affects this insect.  In other words, one could compare pheromone molecules to keys, and the insect’s antenna to locks. Only when the right key finds the right lock does the pheromone molecule actually work. These unique pheromones allow insects to locate their own species, even when distances are great.

Why are pheromones important in research? Well, there’s a lot important information we can learn about an insect from its pheromones. We can tell how related it may be to another species by how similar or different their pheromones are. We can also replicate the pheromone and use it to manage the insect in question.

Some of you may also be aware of Budworm Tracker, our spruce budworm community science program. This program sees a large network of volunteers across Eastern Canada and Maine collecting moths for our research program throughout the flight season using a green plastic trap. While the most visible element to this trapping system is the trap itself, the key component really is the lure inside of it.

This lure contains a small amount of spruce budworm pheromone, which mimics the scent of a female spruce budworm. It acts as a beacon for males – when they detect it, they are attracted to the trap, and get caught. These moths are counted and this data helps researchers measure populations in areas where budworm populations are still low.

Pheromones can also be used in other scientific applications. When a female produces her pheromone, she is essentially a lighthouse in the middle of the fog. Males can detect her from far away, and can easily follow their senses to find this potential mate.

Mating disruption can be compared to placing millions of artificial lighthouses throughout the forest, all of which look and smell exactly like the female. The male budworm moths will spend all of their time moving from one lighthouse to another, eventually giving up on their quest to find a female. Because of this, the female will not be able to mate and lay her eggs. Fewer eggs means fewer caterpillars in the following season and fewer caterpillars means less feeding damage on needles, and fewer adult moths in the following generation!