JUNE
2004

 

 

 

By
Tom Turpin
 
Professor of
Entomology
Purdue University

 

 

 

 

 

06-10-04

The Sounds of Insects Signal the Summer Season

It's the buzz of bees, the chirp of the cricket and even the hum of the mosquito. Add the songs of birds and the croak of a frog. Throw in a coyote's howl, a cow's moo or the bark of a dog, and what do you have? A summer chorus, that's what.

Yes, summer is a veritable smorgasbord of animal sounds. You can hear mammals and birds all year long. But insects and frogs are summer singers only. These creatures are cold-blooded and cannot function when temperatures dip much below 50 F. So, the summer thermometer readings are perfect for cold-blooded singers.

The animal sounds of summer all serve the same purpose. The sounds are produced to allow the singer to send a message. That message might attract individuals of the opposite sex or warn individuals of the same sex. A sound might also be used to attract members of the same species or warn or frighten individuals of different species.

Most insect sounds are produced by males to attract females. Singing cicadas are males just trying to impress the lady cicadas. The same is true for katydids. Don't let the name fool you; it is the male katydid that makes the noise.

How do insects produce sounds? Cicadas use the principle where a membrane is vibrated over a hollow cavity. Human musical instruments like this are called drums. Each male cicada has a tymbal, the membrane, on the first abdominal segment. The sound is produced by vibrating the membrane with a muscle.

Some insects use a violin approach. The process in insects is known as stridulation. Insect stridulators rub one surface over another to produce the sound. These insects include grasshoppers, katydids and crickets. Some grasshoppers rub back legs together. Most other stridulators rub wing surfaces on each other.

Stridulation is frequently used to attract a mate. However, the process is also used to warn other males. Crickets are very aggressive when it comes to territorial defense. That is why these insects are put in cages separated from other males. In such circumstances, the males will sing at each other. Such singing is considered pleasing to hear and is also a good luck omen to whoever hears it.

Some insects produce sound by wing vibration. This type of sound is generally a byproduct of flight. That is why bees buzz and mosquitoes hum. Each flying insect has a different wing beat frequency and each produces a different pitch sound. For instance, houseflies buzz in the key of F.

While we humans would just a soon not hear the hum of a female mosquito in our ear, the sound is very attractive to male mosquitoes. This is one of the rare instances where a sound produced by the female insect is used to lure the male for mating purposes. So enticing is that sound to males, they are attracted to a tuning fork vibrating in the same frequency as the wing beat of a female mosquito. There have also been reports of male mosquitoes congregating on the screen of a window where a squealing saw blade just happened to duplicate the attractive frequency.

This summer, when you hear all of the insect sounds, just stop and think that it is music to the female insects that hear it. Of course, you now know that all of that sweet talk will result in more insects next year. It gives new meaning to the old saying, "The birds and the bees!"

 

Writer: Tom Turpin
Editor: Olivia Maddox