By Pat Kelley, ACE
In the amazing world of nature, several unique species of insects and spiders actually produce or respond to the pheromones of other insects for their own benefit. This intriguing phenomenon has developed over evolutionary time within certain species that share the same living environment. Insect species that exploit the pheromones of other species are doing so because it gives them an advantage to survive. Let’s look at some examples nature has provided.
Bolas spiders of the family aranidae are not even true insects, but they produce the sex pheromone of Pyralid moths. The clever spiders attract their moth prey right to
them without even having to move. Bolas spiders are incredibly adept at swinging a sticky silk blob at the end of a line of silk (bolas). When the male moths approach the pheromone scent, the spiders maneuver their bolas and rope-in the unsuspecting
moth for a juicy feast. (Note: The term “bolas” comes from the age-old hunting tool used mainly in South America that incorporates two heavy weights connected by a long rope. The bolas is thrown and it entangles the feet of its large prey and brings it to the ground until the hunter can approach).
A Bolas Spider draws in a male moth with the female moth pheromone and captures it.
Butterfly larvae of the family Lycaenidae produce a substance that mimics the
pheromone of ants that they share a home with. As the vulnerable butterfly larvae feed on edible plant leaves, approaching ants would typically look at the larva as an easy meal. Instead, the larvae produce a pheromone odor that mimics the attending ants in the colony while at the same time offering up a liquid food substance from their glands. While competing ant species look at the larvae as “dinner”, the home colony views the larvae as a food source and a “brother.” The butterfly larvae even have a second line of defense in their pheromone pocket. If they are attacked by an outside ant colony, the larvae produce an alarm pheromone that mimics the alarm pheromone of the home ant colony. The home colony will respond and fight the other attacking ants to the death while protecting the sly and deceitful butterfly larvae.
Photo: GREGORY G. and MARY BETH DIMIJIAN
Lycaenid moth larvae produce an ant brood pheromone that makes the ants think it is one of them.
The Pine Engraver beetle, ips pini, is a common bark beetle and important pest of
pine trees in the Great Lakes region of North America. When a male pine engraver
beetle discovers a suitable pine tree to attack, he emits an aggregation pheromone that attracts other male and female engraver beetles to that tree. Large numbers of pine engravers will gather on that single tree to mate, lay eggs and begin a new generation of engraver beetles.
The checkered beetle, thanasimus dubius, is a specialist predator that feeds exclusively on the insects within trees killed by bark beetles. Checkered beetles are much larger than bark beetles and they have voracious appetites. They have been said to eat several times their own weight in a single day. Checkered beetles have
become so specialized in the Great Lakes region that they are strongly attracted to the aggregation pheromone that pine engraver males emit. These predators pick
up the pheromone scent of the bark beetles and will fly to the tree and immediately begin feeding on the pine engravers.
Photo: BILL BARR
Adult Checkered beetle attacking a Pine Engraver beetle.
These are just a few of the examples that nature gives us in the amazing world of pheromones. The next time you find yourself placing a moth pheromone lure
into a sticky trap, remember that you’re not too much different than the clever bolas spider drawing in her prey!