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On Six Legs by Tom Turpin - Odors

 

Animals learn about the environment through their senses. These are touch, taste, sight, smell and hearing. The relative importance of each sense varies among animal species.

Which of the five basic senses is most important to the human animal is up for debate. If I had to vote, I would opt for sight. After all, without sight we couldn't do all of the purely human things, such as watch TV, stargaze, drive a car, peruse old photo albums or read a newspaper.

In the early 1900s, a newspaper editor named Arthur Brisbane wrote, "a picture speaks a thousand words." No doubt Brisbane was referring to the printed word in the newspaper, not the spoken word. Nonetheless, the comment underscores the role of sight in human lives.

Unlike humans, insects can't use the printed word to communicate. But both humans and insects can use sound to send messages. Sight also plays an important role in the lives of insects and humans. As do touch and smell.

Smell would seem to be the least important of the senses relative to the daily lives of humans. But in spite of this, research has shown that smell elicits human memories more quickly than the other senses. You never forget the odor of a food item that made you sick years ago! The smell of wood smoke might elicit memories of a family camping trip in the mountains when you were a youngster.

In general, odors are not associated with life or death situations for humans. However, we do find some odors pleasant, while others are downright repugnant. That is why perfumes and deodorizers do big business.

To insects, though, the sense of smell often plays an important role in the success of a species. One such chemical odor is called a pheromone. Pheromones are chemicals secreted by an animal that will influence other members of the same species. Because of this function, pheromones are sometimes called messenger chemicals.

In the world of insects, pheromones are often used to attract a mate. Here's how the system works. The female insect emits the pheromone and sometimes does a little wing waving, a process appropriately named calling. The pheromone disperses in the air away from the female, mostly in a downwind direction. A male of the species will detect the pheromone and follow it upwind to the source - the calling female.

Mating pheromones are complex, organic molecules that are specific to individual species. These chemicals can elicit a response at a very low concentration. Some males of the so-called giant silkworm moths, such as Promethea and Luna, have been shown to follow the plume of odor for as far as five miles to the female's location.

A keen naturalist, Indiana author Gene Stratton-Porter, whose works included "Freckles" and "Girl of the Limberlost," recognized that moths attracted mates using some volatile chemical. She recorded how a female moth in a screen cage attracted many males of the species during the course of a night.

Moths are the most widely recognized of the pheromone-producing insects. However, many orders of insects include species that use pheromones as mate attractants. Many beetle species, and even some cockroaches, produce pheromones.

Many of the insect pheromones have been chemically identified, and those of some pest insects have been synthesized. Entomologists use synthetic pheromones to determine the presence of a species in an area. It works by placing a lure with the pheromone on a sticky trap. Any insect attracted to the pheromone gets stuck to the trap. This seems like a nasty trick to pull on a male insect that is following a pheromone to find the love of his life!

In the insect world, the females are usually the pheromone producers. But in one widely recognized species of insect, the male emits a pheromone. That insect is the monarch butterfly. Hey, if you are a male monarch, you can wear perfume if you want!