Spring 2005
Margined Soldier Beetle
Patrolling Our Prairies
There are soldiers marching through
our prairies and savannas, in old fields and along roadsides,
and even in our gardens. They may arrive in great numbers
and strike suddenly, but they present no threat.
These gentle warriors are the soldier
beetles, family Cantharidae, which number some
3,500 species worldwide. As many as 40 species may exist
in our area, according to Field Museum entomologist Jim
Louderman, who has personally collected about two dozen.
Many are small, black, and easy to overlook.
In May and June, however, an especially
striking member of the family appears. Chauliognathus
marginatus, the margined
soldier beetle, sports a beautiful uniform of orange
and black, along with an impressive pair of long, curving
antennae. With a maximum length of about a half inch (without
its antennae), it is larger and more colorful than many
of its cousins. Its orange wing-covers, outlined in black,
are indeed reminiscent of the soldiers’ uniforms of
past centuries. The beetles are also sometimes nicknamed
“leatherwings,” because these covers, unlike
the hard shells of most beetles, are soft and leathery.
In its two active life stages, the margined
soldier beetle leads an almost Jekyll-and-Hyde existence.
The larvae are carnivorous little predators, spending all
their time searching for, attacking, and devouring other
insects. Adults, on the other hand, spend their days prancing
about on flowers, feeding on sweet nectar and pollen to
build up their strength for the rigors of lovemaking and
reproduction.
Indeed, the soldier beetle must squeeze
a lot of living into its short, one-year lifespan. Adults
emerge in May and spend the next six to eight weeks flying
from flower to flower. Then they mate, and the females lay
eggs beneath a thin layer of earth. By the end of June,
their work done, the adults have all died. (Later in the
summer, however, look for adults of the similar goldenrod
soldier beetle, Chauliognathus pensylvanicus.)
The larvae hatch out in summer, looking
a little like small, wrinkly, black caterpillars. Patrolling
the damp ground and the stems and leaves of plants, they
feast on aphids, maggots, small caterpillars, and grasshopper
eggs.
In the fall, the larvae transform into
pupae, which spend the winter in the soil and under leaf
litter. They survive the cold by producing a sugar-based
antifreeze and entering into a state of diapause, the insect
version of hibernation. Once spring arrives, adults emerge
from the pupae, and the cycle begins anew.
But danger is also a part of their short,
sweet life. While soldier beetles have developed body toxins
that make them unpalatable to birds and small mammals, they
often fall victim to crab
spiders that lie in wait on the flowers they visit.
The lifeless shells of soldier beetles, their life fluids
sucked dry by spiders, cling to many a prairie wildflower,
bearing witness to this peril.
The margined soldier beetle does no
harm to crop plants, as it’s not much attracted to
grasses, grains, or leaves. If it should venture into your
backyard garden, greet it warmly. Its larvae prey on aphids
and other pests, while the adults provide an effective,
if inadvertent, pollinating service. Soldier beetles supply
similar beneficial services to the prairie communities in
which they live. They are equal-opportunity benefactors,
however, pollinating weedy invasives as often as they pollinate
native wildflowers.
So on your next jaunt through local
park or prairie, support our troops — keep an eye
out for the soldier beetles.
— Ron Trigg
Illustration by Peggy Macnamara, who
recently completed Illinois Insects and Spiders, a new book
from The University of Chicago Press. Visit our online
store to order. |
