University of Delaware
Office of Public Relations
The Messenger
Vol. 5, No. 3/1996
Research shows beneficial insects, environment suffer from electric traps

     Who would have thought the black lights of the '60s would
come back in the '90s, designed to beckon not flower children but
     Electric insect traps, complete with black lights and
electric grids, have been marketed to consumers who want to keep
their summer evenings free of biting flies, notably mosquitoes.
     The sound of a bug "frying" when hitting the electric trap
may be a satisfying one to a consumer, but it sets Doug Tallamy's
nerves on edge. The UD entomologist says the problem is not just
a false sense of security for consumers-the electric traps do
little to reduce the biting-fly population, he says- but the
impact that the traps have on beneficial insects.
     Tallamy says it's not news to entomologists that most
species of mosquitoes don't respond to black lights and that
certain mosquitoes only bite during the day, anyway. So, what is
getting fried in those traps? Tallamy enlisted the aid of Newark
High School student Tim Frick to find out.
     Over the summer of 1994, the two collected and identified
the kill from electric traps at six sites in suburban Newark,
Del. The results, Tallamy says, disturbed his environmental
sensibilities and  should disturb those of others, as well.
     Only 31 of the nearly 14,000 electrocuted insects were
biting flies. That's less than a quarter of one percent. Species
from more than 104 nontarget insect families were destroyed.
Almost half of these were aquatic insects-caddisflies and midges.
To the untrained eye, midges look like mosquitoes. But, to a
trained entomologist and a balanced ecosystem, there is a big
     "Midges don't feed on mammalian blood or spread disease,"
Tallamy says, "and, they are an important part of the aquatic
food chain as larvae. Diminishing their population has an effect
on other populations, including the frogs and fish that feed on
them. As adults, the midges also are an important food item for
nesting birds.
     "The manufacturers claim their products kill insects and
they do. Many of the electrocuted insects look like mosquitoes-an
undesirable insect-but they are not mosquitoes," Tallamy says.
     "The heavy toll on nontarget insects and the near absence of
biting flies in catches suggests that electric insect traps are
worthless for biting-fly reduction," Tallamy says, "and probably
are counterproductive to consumers and the larger ecosystem."
                                 -Claire McCabe, Delaware '85M