Red flour beetles on wheat kernels. Image courtesy
Department of Agriculture Western Australia, Entomology Branch,
How the Beetle Gets Its Shell
By Erin Peabody
August 31, 2005
Even in an age of Gore-Tex and other
high-tech wearable fibers, there may be no better coat for withstanding the
elements and protecting a body than that belonging to an insect.
Durable, yet flexible and lightweight, the sturdy shell encasing most
insects has undoubtedly helped ensure their evolutionary success and great
abundance. And now, scientists with the Agricultural Research Service (ARS) and their colleagues have discovered
which of a beetle's genes are responsible for crafting this impressive coat.
Beeman, an entomologist in ARS'
Marketing and Production Research Center in Manhattan, Kan.--with help from
retired ARS researcher
Kramer and researchers at nearby Kansas
State University--learned that just three genes orchestrate the complex
One gene cues production of the beetle's outer cuticle, called the
exoskeleton, while another prompts an enzyme to start building the cuticle that
lines the insect's gut. A third finishes the job, telling the fresh outer
skeleton to harden into a protective armor, guarding the insect against injury,
infection and desiccation.
The findings, some of which were published in a recent issue of the Proceedings of the National Academy of
Sciences, could spur development of new, nonchemical forms of insect
To serve as their model, the researchers chose a well-studied insect, the
red flour beetle (Tribolium castaneum). This rust-colored beetle is
known in the grain industry for its costly invasions of stored cereals and
Beeman had already amassed extensive genetic information about the insect.
His genetic maps of the beetle and other colleagues' findings, in combination
with recently released genome sequencing information, laid the necessary
groundwork for the recent study.
Using a technique called RNA interference, the researchers "knocked
out" certain candidate genes to determine which were involved in
synthesizing the chitinous material that makes up insect shells.
They knew they'd identified one of the key genes when, after deactivating
it, the cuticle in the research beetles stayed white and soft. It didn't tan
and harden the way it normally would.
ARS is the U.S. Department of
Agriculture's chief scientific research agency.