AUGUST
2004

 

 

 

By
Tom Turpin
 
Professor of
Entomology
Purdue University

 

 

 

 

 

08-26-04

In the Insect World, It's "Long Live the Queen"

Things change as fall approaches in temperate regions of the world. Days get shorter. Birds begin grouping for migration. Plants produce seeds. And sharp-eyed nature observers will notice changes in the insect world.

Some insects seem to have disappeared as the months of August and September roll around. Gone are the Japanese beetles that pestered gardeners. Gone are June bugs that crashed into lighted windows in the still of the night. Gone are the fireflies that twinkled over lawn and meadow.

Also gone are the periodical cicadas, the insect darlings of the media during the summer. The media frenzy over the emergence of Brood X of the periodical cicada was predicted by famed entomologist C. V. Riley in 1893. According to Riley, "We become accustomed to annually-recurring phenomena, and are interested in the periodical recurrences of any particular species of insect, our interest increases proportionately to the length of the period intervening between such periodical appearances."

While some insects have disappeared, others are more common. Butterflies jostle each other for sips of nectar at flower blossoms. Katydids, crickets and grasshoppers sing from meadow, tree and thicket. Yellow jackets, hornets and bumble bees seem to be everywhere. And cicadas are singing. Not the periodical cicadas but the dog-day type, the ones we hear every year.

The insect "changing of the guard" is just part of the ebb and flow of nature during the growing season. But, it brings up the age-old question of how long do insects live. The answer is, it just depends! It depends on the type of insect and whether or not the entire life or just the adult stage is considered.

As a general rule, insects have a very short life compared to other animals. Most adult insects live a matter of days. Many are victims of insect-eating predators or are killed by adverse weather. But, even if protected from the cruel world, the insect life is a short one.

The shortest natural life of an adult insect belongs to the mayfly. These insects are classified in the order Ephemeroptera, which literally means "for a day." An appropriate name for an insect that does not live as an adult for more than 24 hours. Even though the life of the mayfly is of short duration, it manages to find a mate and lay eggs during that time. In biology, that amounts to a successful life!

On the other end of the length-of-life scale for adult insects are the queens of social insects. These ant, bee and termite matrons live for years. Honey bee queens can live 4 or 5 years, and some ant queens have been shown to survive into their teens. Successful termite queens live decades, more than 50 years in the mound builders of Africa.

The length of life of the adult stage of insects can be somewhat misleading in a discussion of longevity of animals. In most animals, the immature stage is short compared to the potential length of life. The time as an immature is a fraction of the time spent as an adult. Humans, for instance, spend roughly one-fourth of their expected 80-year life span preparing for adulthood.

Compare that to most insects where immatures live longer than adults. The social insect queens are the exception. For example, white grubs feeding in the lawn may spend from 2 to 5 years in that stage. When they emerge as May beetles, their life expectancy is about a month. Even the Japanese beetles spend about 10 months as a grub. Japanese beetle adults will live less than a month.

This means that the highest percentage of an insect's life is spent as an immature. That would mean a lot of time for insect parents to worry about the younger generation. Except for one thing: The older generation is almost never around to see how the younger generation messes things up. In insects, not in humans!

 

Writer: Tom Turpin
Editor: Olivia Maddox