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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!
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