54 DISCOVERMAGAZINE.COM
Steyn gained a key insight
from The Afrikaans Children’s
Encyclopedia, perhaps while read-
ing it to his own children. He learned
that in parts of Africa, social spiders,
those that live together in colonies,
are intentionally brought into houses
to control ies and other pests. The
practice appears to have been used
irst by the Tsonga and the Zulu,
who even set up sticks in their homes
to make it easier for spiders to build
nests. The colonies, often the size of a
soccer ball, can easily be transported
from house to house.
Steyn wondered if this technique
could be used again.
In home kitchens and in hospitals,
Steyn suspended spider webs by a string
attached to a nail. They controlled
ies effectively. Steyn repeated the
experiment at the Plague Research
Laboratory in South Africa. The y
population declined by 60 percent in
three days in the lab’s animal house.
“In order to help protect humans
against y-borne diseases, it is sug-
gested that colonies of the social
spider be placed in public places like
markets, restaurants, milk barns,
public houses, hotel kitchens, as well
as in abattoirs and dairies, and espe-
cially in kitchens and latrines on all
possible premises,” Steyn wrote in a
paper published in 1959 in the South
African Medical Journal. “In cow-
sheds, they wou ld also help to i ncrease
milk production.”
He imagined houses illed with giant
balls of spiders, a world in which ies
and the diseases they transmitted
would become rare.But don’t spiders bite humans? Each
year, tens of thousands of “spider
bites” are reported around the world,
and the numbers seem to be increas-
ing. The truth is that spiders rarely
bite us, and nearly all of the reports
are actually infections due to resistant
Staphylococcus bacteria (MRSA), mis-
diagnosed by patients and doctors alike.
If you think you have a spider bite, ask
a doctor to test you for MRSA. Those
odds are much higher.
One reason why bites are rare is
that most spiders use their venomexclusively or nearly exclusively on
prey rather than for defense. For spi-
ders, it is nearly always easier to ee
than to ight.
One study even attempted to ind
out how many pokes it takes to get 43
individual black widow spiders to bite
artiicial ingers made out of congealed
Knox gelatin. After one poke, none
of them bit. Nor did any bite after 60
repeated pokes. Sixty percent of the
widows bit only after being pinched
between artiicial ingers three times
in a row, and even then, they released
venom only half the time. Those bites
would not have been problematic to a
human, just painful. Venom is costly to
spiders, and they don’t want to waste it
on you; they are saving it for mosqui-
toes and houseies.WASPS, FUNGUS TO THE RESCUE
Spiders aren’t the only creatures in your
home involved in pest control. Many
types of solitary wasps prey on speciic
cockroach species.
Their technique is far different from
that of spiders. By using their sense
of smell, the tiny insects, some only
a quarter-inch in size, locate cock-
roach eggs and commandeer them.
The mother wasp taps the egg cases
to make sure a roach is inside. Then,
she pierces the case with her oviposi-
tor, an organ used for egg laying, and
lays her own eggs inside. The wasps
hatch, devour the roach inside the egg
case and escape by drilling a hole out
to freedom.
In homes in Texas and Louisiana,
26 percent of American cockroach
egg cases were parasitized by the wasp
Aprostocetus hagenowii, and others
were parasitized by yet another wasp,
Evania appendigaster, according to
a study published in Environmental
Entomology.
Several researchers have attempted
to release parasitoid wasps into
homes to control roaches. All of
those attempts have been, in one way
or another, successful (though also
typically poorly documented). Just
know that if you ind in your houseHe imagined
houses filled
with giant balls
of spiders, a
world in which
flies and the
diseases they
transmitted would
become rare.