A species of moth that was determined to be new to
science was found at Great Smoky National Park. Drawing
courtesy of the National Park Service.
|
Bugs, spiders, creepy-crawlies—these words can make
your spine tingle. Slimy earthworms, dirty cockroaches,
black widow spiders with deathly bites—all creatures
folks often try to avoid. These animals, that can make the
hairs on your arms stand up, are actually invaluable members
of the earth's ecosystems. As disturbing as they are to
some of us, these creatures are responsible for sustaining
most life on this planet, directly or indirectly. They also
make up the largest group of living things, more numerous
than all other species of plants and animals combined—the
invertebrates
.
What are invertebrates?
Invertebrates are, simply enough, animals without backbones.
This group is very diverse and includes aquatic animals
like jellyfish and sponges as well as terrestrial animals
such as all insects, worms, and snails. Scientists continuously
attempt to count and describe all of the living species
on earth. So far, 1,110,000 arthropod
species alone have been described in science. Phylum Arthropoda
consists of insects,
arachnids,
crustaceans,
and many other groups. Some scientists believe that if we
are able to count all of the arthropods just in the tropical
rainforests, the number of species would swell to 10 million!
(source: Tree of Life Web
Project)
How do we know there are so many invertebrates?
Great Smoky Mountains National Park is trying to count
all of their arthropods along with all other living things
in an enormous project called the All
Taxa Biodiversity Inventory (ATBI).
This attempt to find and describe all species in the park
has revealed 3901 new
species to the park as of fall 2005 (check www.dlia.org
for the most recent numbers), some of which are entirely
new
species to science. Of the 3901 new species discovered
in the Park since the start of the ATBI, approximately 80%,
are invertebrates. Species new to science found in Great
Smoky Mountains National Park include 26 species of beetles,
32 species of flies, 39 species of spiders, and 72 new species
of moths and butterflies! Because there are few studies
involving this kind of blitz to learn all species, scientists
are able to hypothesize that most invertebrate species are
still left to be discovered and described.
The students in the photo are using an aspirator to
collect very small invertebrates they found using
a leaf litter sifter.
|
How do we find terrestrial invertebrates?
Terrestrial invertebrates are all around us, we just have
to think small. Aside from the gnats and no-see-ums that
fly around our faces on a hot, humid day or the worms we
use to lure fish, there are thousands of creatures working
their way through the soil, up the bark of trees, hiding
under rocks, or chewing their way into leaves. The tools
used by ATBI scientists to find invertebrates are primarily
their eyes and a hand lens. To collect invertebrates you
can look at or under anything found on the ground or on
plants. A fun and easy way to collect is with a leaf litter
sifter
(above). This handy tool allows us to shake critters out
of the fallen leaf layer on the forest floor into a container
that can then be searched. Anything moving can be sucked
out of the container using an aspirator
or picked out carefully with tweezers and identified or
placed into a specimen jar for later identification. A beat
sheet
is a tool used to catch insects shaken out of bushes or
tree branches. A Berlese Funnel
is a more technical tool which uses heat from a light source
to force insects out of leaf litter and down into a container
filled with alcohol or soapy water.
Why do we need to look at bugs?
The importance of terrestrial invertebrates is immeasurable.
Aside from products we can use like bees' honey and wax,
and silk from the silkworm, invertebrates play an imperative
role in natural ecosystems. For example, many plants would
not be able to grow and reproduce without bees, flies, and
other airborne insects. These are the primary carriers of
pollen from flower to flower. Relationships between plants
and their pollinators can be as specific as the one between
the monarch butterfly and the milkweed plant. Both species
are unable to survive without each other, in what is called
a symbiotic relationship.
Monarch butterfly larva feed on the milkweed plant and then
spread its pollen to other milkweed plants as an adult.
Soil invertebrates help decay materials and create the nutrient-rich
humus layer in soil necessary for plant growth. They also
serve as a food source for many birds and small mammals,
reptiles, and amphibians. Either way you look at it, invertebrates
play a major role in the cycle of life on this planet.
Balsam woolly adelgid destroys Frasier firs in the
high elevations at Great Smoky Mountain National Park.
Photo courtesy of the National Park Service.
|
Some species of invertebrates are detrimental to ecosystems.
In the Great Smoky Mountains we have lost large numbers
of some tree species due to infestation from exotic
species. Many of our older Frasier fir trees at high elevations
have been destroyed by the balsam
wooly adelgid and the young ones continue to be threatened.
This non-native insect was brought into the United States
on garden stock from Asia. It has no natural predator here
and in less than 60 years has drastically altered the appearance
and vegetation type of our high elevation environments.
The hemlock trees in the park are currently being attacked
by the hemlock
wooly adelgid. Cooperating research with the University
of Tennessee, has found a species of beetle, Pseudoscymnus
tsugae (Pt beetle) that feeds solely on the hemlock
wooly adelgid. Along with others treatments, we hope to
control the adelgid by establishing a self-sustainable beetle
population.
Monitoring invertebrate populations can tell us the health
of an ecosystem. We can determine water quality by looking
at the diversity of invertebrates and their larva in aquatic
environments (see the Hands on the Land water
quality study for more information). We can also monitor
the terrestrial invertebrate population to establish the
health of a forest or grassland. This is especially important
in areas threatened by air pollution or acid rain, such
as Great Smoky Mountains National Park. We are often afraid
of those things which we do not understand. By studying
the diversity of invertebrate life, we can determine which
critters are indicators of healthy or indicators of changing
environments. Creepy crawlies aren't so creepy and crawly
anymore, are they?
Resources
Websites
Classroom Information
Teacher's Guide: Instructor�s
guide to the terrestrial invertebrates website
Glossary: All
Taxa Biodiversity Inventory (ATBI), aquatic
animal, arachnid,
arthropod,
aspirator,
beat
sheet, berlese
funnel, crustacean,
exotic,
insect,
invertebrate,
leaf
litter sifter, symbiotic
relationship, terrestrial
animal
Teachers, learn about service learning opportunities and how to become a Take Pride in America School. 
