You can accept that many of the insect
species around you are interesting, poorly
studied and more likely to help control
pests than to be them. Or you can go to war.
The modern way to wage such a ight
is with chemistry. But be warned: If
you decide on a chemical war, the bat-
tles are not evenly matched. Not even
close. To each round of new chemicals
we apply, the insects we attack respond
by evolving via natural selection. The
more aggressive the attack, the faster
the evolution. Insects evolve faster
than our ability to understand how
they have evolved, much less counter it.
It happens again and again, especially
among those pests we try hardest to
kill, such as the German cockroach
(Blattella germanica).
The pesticide chlordane was irst
used in homes in 1948. It was so toxic
to insects that it was thought to be
invincible. By 1951, however, German
cockroaches in Cor pus Christi, Texas,
were resistant to chlordane. In fact,
the roaches were a hundred times
more resistant to the pesticide than
laboratory strains of the bug were.
By 1966, some of the critters had also
evolved resistance to then-popular
pesticides such as malathion, diazi-
non and fenthion. Soon thereafter,
German cockroaches were discovered
that were fully resistant to DDT,which for a time was promoted by the
federal government for use on farms
and in households.
Each time chemists cooked up a new
pesticide, it was just a few years, or
sometimes just a few months, before
some population of the pests evolved
resistance. Sometimes, resistance to
an old pesticide conferred resistance
to a new one. In those cases, the battle
was over before it started. The roaches
spread and thrived.
Roaches aren’t the worst critters
in our homes, though. Yes, they can
carry pathogens, but your neighbors
or children carry more. Also, experts
haven’t yet documented any cases in
which someone has actually gotten
sick from a pathogen that a cockroach
spread, whereas people get sick every
day from pathogens spread by other
humans. The most serious problem
the bugs pose is that they are, in great
densities, a source of allergens. In
response to this real problem, and
the many perceived problems, we
have spent enormous resources trying
to kill them.
The German cockroach appears to
have made its way through Europe dur-
ing the Seven Years War (1756-1763),
a time when people were traversing
Europe with containers large enough to
hold quite a few cockroaches. Just who
transported them is unknown. Carl
Linnaeus, the father of modern taxon-
omy, asserted it was the Germans, but
he might have been biased. Linnaeus
was Swedish, and during the Seven
Years War, the Swedes fought several
battles with the Germanic Prussians.
Linnaeus thought that “German cock-
roach” was a itting moniker for a spe-
cies he didn’t like.Among the
species killed by
pesticides are
those that benefit
us, including
the natural
enemies of the
pests we are
trying to control.