JAMES TRAGER
Invertebrates: the little things that run the world
–E.O. Wilson
P R A I R I E I N V E R T E B R AT E S
THE
CLEAN UP C
A VARIETY OF INSECT DECOMPOSERS ARE THE CU
When the life of one organism ends, the work
of insect decomposers begins. These insects
consume excrement or dead plants or animals,
and in the process help to recycle nutrients,
returning materials to the soil or atmosphere.
Some insect decomposers are general
omnivores that feed on a variety of decaying
organic matter—cockroaches, for example—
while others are more selective about the type
of dead material they consume.
14  Missouri Prairie Journal
Vol. 35 Nos. 3 & 4
Recyclers of Plants
The sheer quantity of the total mass of plant material found in
prairies is well beyond that of other prairie life, even beyond
the total mass of bison, the heavyweights of the prairie. While
much of this plant growth is consumed by herbivores, the
remaining grasses, wildflowers, and occasional shrub and tree
eventually die and become detritus. At this point, recyclers step
in to eat the dead plant material, a process that helps to return
nutrients and minerals to the soil and carbon dioxide and other
gasses to the atmosphere. Although bacteria are critical to the
decomposition process, without the preparation insects provide
by chewing, fragmenting, and passing detritus through their
digestive systems, bacteria cannot work quickly or efficiently.
Flies, beetles, cockroaches, caterpillars, and termites all
consume dead plant material, but termites in particular play a
large role in recycling plants. Termites are social insects. Their
colonies in the prairie region have thousands of individuals. Together the colony members—workers, reproductives,
soldiers—consume massive amounts of plant matter on the
surface and in the soil. Cellulose, a structural compound that is
JAMES TRAGER
MICHAEL JACOBS ST. LOUIS ZOO
At far left is a decomposer and
pollinator in one: According to Dr.
James Trager, entomologist and
MPF technical advisor, the adult
of this honeybee mimic, Eristalis
tenax, a fly native to Eurasia
but now naturalized in North
America, is a pollinator. Its larvae,
however, are decomposers. The
larvae—known as rat-tailed
maggots—feed on decaying matter in shallow, eutrophic water
or very moist soil, or sometimes
even carrion.
REW
Pictured in the center are termite
adult workers. While termites
are well known for decomposing
rotting logs in forests or wooden
elements of buildings, there are
two species on prairies that are
important recyclers of plants.
At far right are larvae of the
American burying beetle. The
adult beetles bury carrion of
small animals and lay eggs in
the burial chamber; when the
larvae hatch, the adults feed
them regurgitated carrion—a
parenting behavior uncommon in
the insect world.
By Jennifer Hopwood
S T O D I A N S O F T H E P R A I R I E.
abundant in plants, is indigestible for many animals. The guts
of termites, however, contain symbiotic bacteria and protozoa
that break down the compound and allow termites to digest
cellulose. Termites and other plant decomposers eat hundreds
of pounds of dead plants each year. While termites may be
most often associated with rotting logs in forests or wooden elements of buildings, there are two species that live on prairies.
Recyclers of Carrion
The bodies of animals provide nourishment to a variety of
insects, including blow flies, flesh flies, house flies, burying beetles, hide beetles, some hister and darkling beetles, and clothes
moths. Insects that dispose of dead animals play an invaluable
ecological role. Collagen, a protein abundant in mammals, and
keratin, found in hair and tissue of many animals, are indigestible compounds to most organisms, yet some insect decomposers can break down these compounds and utilize the released
amino acids.
As unappetizing as it may seem, the carcass of a dead animal is a hot commodity on the prairie. Carrion is not a predict-
able or abundant resource, so competition for it may be fierce.
Not only must carrion-feeding insects compete with each other
for the food, they also need to compete with larger scavengers
such as coyotes, crows, and vultures. As such, carrion-feeding
insects are often strong fliers and are remarkably sensitive to
odors.
Some species also employ other tactics to take advantage
of the ephemeral food source. Some flesh flies deposit larvae,
rather than eggs, in carrion, skipping a step in development
that might allow them a competitive edge over other flies that
must undergo the egg stage first. To get a jump on the competition, one group of blow flies lays its eggs in wounds of injured
animals, not even waiting for death. Burying beetles prevent
access by their competitors to the carrion by taking the body
and burying it. When they find a carcass, burying beetles tunnel underneath it until the carcass sinks deeply enough to be
covered by soil. Then the beetles, which may work as individual
pairs or cooperatively in small groups, lay eggs in the burial
chamber. When the eggs hatch, adults feed their young larvae regurgitated carrion until the larvae can feed off the body
Vol. 35 Nos. 3 & 4  Missouri Prairie Journal 15
Pictured here are two of the thousands of insect decomposers that recycle dung: from left are blow flies (on coyote scat) and a dung beetle. By
consuming dung, these decomposers carry out many important ecological functions, including releasing nitrogen back into the soil where it can
be absorbed by plants.
Ants as Decomposers
Ants are not decomposers in the same sense as detritivores. Their
contribution to decomposition is, however, significant given
that literally millions of ants can occur on a prairie. Many ants will
opportunistically grab up dead insects and other invertebrates
and carry them home to eat. They also may feed on carrion too
large to carry, scraping off edible bits and lapping up the more
liquid component to take to their colonies. They may also do
this with dung, especially that of insectivores and carnivores. A
number of them, such as the species in the picture below, also
gather dry plant fragments and build up the structure of their
mounds with them. The combination of the ants’ nitrogenous
waste and accumulated plant matter decomposes in the latrine
portions of their nests to locally enrich soil.
— Dr. James Trager, entomologist and MPF technical advisor
JAMES TRAGER
Jennifer Hopwood is a Senior Pollinator Conservation Specialist
with the Xerces Society for Invertebrate Conservation. She is based
in Nebraska and is an MPF member.
Formica pallidefulva individuals cooperating to carry home a charred
earthworm on a warm day after a prairie burn.
16  Missouri Prairie Journal
Vol. 35 Nos. 3 & 4
JAMES TRAGER
Recyclers of Dung
Animals excrete at least 40 percent of what they eat, and dung
feeders, which are mainly beetles and flies, consume that excrement. As with carrion, there is a great deal of competition for
excrement because it is an unpredictable resource. While some
adult beetles or flies may lay eggs directly in animal excrement
so their offspring can feed on it, others (mainly scarab beetles)
move it to a more secure and convenient location before laying
their eggs. Dung beetles will eat excrement from a variety of
animals, but many prefer dung from herbivores, such as cattle
and bison. Some beetles will dig burrows under the dung, and
pull dung down into the tunnels. Tumblebug dung beetles pat
dung into a ball and roll it away from the main dung mass to
their burrows where they later lay their eggs. As dung beetle
larvae munch away, they break down the dung and release
nitrogen back into the soil where it can be absorbed by plants.
Ball-rolling beetles have been fascinating people for ages; dung
beetles were sacred and symbolic to ancient Egyptians, for
example.
In prairies that are grazed by large mammal herbivores,
insect recyclers of dung also increase grazing indirectly by making grass and other prairie plants more palatable for cattle, elk,
and bison. They also decrease the exposure of livestock to biting
pest insects, which breed in moist places such as dung that has
not yet been broken down.
The ecological and economical value of dung beetles
became obvious soon after the introduction of cattle in the late
1880s to Australia, a continent with no native placental mammals. Although the native Australian dung beetles could process
the dung of marsupials such as kangaroos, they were unable to
fully break down cattle dung, which proceeded to accumulate
rapidly. In 1968, the government introduced species of dung
beetles accustomed to processing cattle dung, thereby saving
the burgeoning Australian cattle and dairy industry.
Death comes to all living things. The work of insect
decomposers helps bring forth life out of death.
JAMES TRAGER
themselves, and mother beetles remain with their progeny until
they are ready to pupate. Small carrion, such as dead insects
and earthworms, is effectively cleaned up and recycled by ants,
crickets, rove beetles, millipedes, and harvestmen, also known
as “daddy long-legs.”