Nuisance flies in your home - a butterfly
Timothy J. Gibb,
Why we are experiencing more nuisance (cluster
flies) in our homes this year may be due to what is called a
butterfly effect. You may have heard the example in chaos theory
that a nearly non-perceptible difference in the starting points
of two curves, so small that it is comparable to the effect of
a butterfly flapping its wings, over time can vastly change the
end points of the curves. In theory, even a butterfly wing beat
slightly changes the environment, which magnifies and ripples
into an ever-increasing effect on the environment ultimately
effecting an enormous difference. The specific example most often
quoted is as follows. “The flapping of a single
butterfly's wing today produces a tiny change in the state of the
atmosphere. Over a period of time, what the atmosphere actually
does diverges from what it would have done. So, in a month's time,
a tornado that would have devastated the Indonesian coast doesn't
happen. Or maybe one that wasn't going to happen, does”.
So how might this theoretical phenomenon relate to the pesky
cluster flies that are annoying us in our homes right now? Well,
this is how. Whatever meteorological event that caused the unprecedented
levels of precipitation this spring and summer also resulted in
very moist soils throughout much or Indiana that lasted for an
extended time. The wet soils, in turn, created conditions favorable
to the development of earthworms. The earthworms stayed in the
moist soils near the surface for much of the spring and summer.
Cluster flies lay their eggs in the soil and when the eggs hatch,
the larvae search for earthworms to parasitize. Because the earthworms
were so plentiful and accessible, the parasites too were very successful.
Over time, 3 generations of cluster flies parasitizing this large
population of earthworms also increased into populations that we
have not seen in a long time. Their abundance typically varies
from year to year in relation to the weather but this year it was
Cluster flies are named for their habit of clustering in large
numbers on outside walls of homes and buildings in the Fall time.
They eventually make their way through cracks in siding and window
casements and eventually into wall voids and attics during the
winter. They pass the winter in the adult (fly) stage and do not
feed or reproduce indoors. However, when temperatures get warm
on sunny days or when the furnace is on high, cluster flies become
active and buzz around the room even during the winter.
Flies buzzing around a room can be most effectively dispatched
with a fly swatter, rolled up newspaper or sucked up by a vacuum.
These are easy. The more difficult problem with cluster flies is
that fact that the majority of the populations is still hiding
deep in cracks, inside walls or under insulation, where they are
not exposed to chemical treatments or space sprays.
Preventing cluster flies from getting into the home in the fall
is the best solution. Seal cracks and openings around the outside
of the house, especially under the eaves, and around windows and
doors. Pyrethroid insecticides, applied as a preventative residual
treatment on the outside of the house in late fall, are recommended
when annual problems with attic flies persist. You may take consolation
in the fact that if the weather returns to normal next year we
may not have a concern.
And, of course, that all depends upon whether some butterfly beats
its wings in some remote area of the world or not.
Click image to enlarge
Photo of a cluster fly. Note the golden colored hairs on the thorax
that separate this fly from other household flies.