Tiny barbarians at the gate
By NED ROZELL
April 29, 2009
Mosquitoes and black flies, now stirring after a long winter,
have probably helped assure that most of Alaska remains unpopulated,
says an expert on the creatures.
"I've spent a lot of time in the far north-in Canada, Siberia,
and Alaska," said Peter Adler, a professor of entomology
at Clemson University. "You can go down rivers for a month
or two at a time and see no humans. Why is that? What's keeping
An Alaska black fly.
Some Alaska black flies, such as this one, are orange rather
Photo by Mateus Pepinelli.
Headnet season is almost
here in Alaska.
Photo by Ned Rozell.
The magnified head
of a larval black fly. Black fly larvae attach to rocks in streams
and use a pair of "labral fans" for filtering food
from the water.
Photo by Mateus Pepinelli.
"There are two main features that might play a role-bitterly
cold winters and biting flies."
Adler is interested in the latter element, so much so that he
waded through streams in western Alaska and far-east Russia a
few years ago, finding and describing the black flies and mosquitoes
of the regions. He undertook the expedition because he was curious,
and because no one had cataloged in detail the biting flies of
the former land mass known as Beringia, now cleaved in two by
the Bering Strait.
Armed with his field kit, which consists of rubber boots, a 10x
hand lens, a vial containing a preservative solution of alcohol
and acetic acid, and a set of jeweler's forceps used to pluck
black fly larvae from rocks, Adler combed the waterways of western
Alaska and far-east Russia.
He and Doug Currie of the University
of Toronto rented a car in Nome, drove every road they could,
and stopped at streams to take samples of black flies. They also
flew into the upper Kisaralik River, a tributary of the Kuskokwim
River, and floated out, gathering larvae along the way. They
also explored the Anadyr River in Russia, plucking samples with
forceps and using finely woven dip nets in slower waters.
After a close-up look at each species of black fly, Adler could
tell if the female's claw had a thumb-like lobe, which is used
to clutch feathers when cutting a bird for a blood meal, or a
curved talon that is used by flies to feed on mammal blood. Adler
found that almost a quarter of the black flies lacked scissor-like,
serrated mouthparts and had no need for blood, having acquired
all their nutrition as larvae in the water. Two species had simplified
their lives further by producing no males; instead females reproduce
by virgin birth (parthenogenesis).
Adler also found evidence of the Cold War as it applied to black
flies and mosquitoes. In several instances, Russian scientists
and American scientists working on opposite sides of Bering Strait
had each given the same insect different names.
"We found that more than half of the black flies are shared
(between the Russia and Alaska sides of the Bering Strait),"
Adler said. "And 70 percent of the mosquito species are
Those findings didn't surprise Adler, as the land bridge existed
in the area until about 11,000 years ago, and the 62-mile barrier
between Wales, Alaska and Uelen, Russia is not too far a distance
for a biting fly to cover, given a sufficient wind. He thinks
such pests as the striped black fly, Simulium vittatum, a current
resident of North America, could easily cross over to Russia,
and the same applies to species hovering at the western edge
"Some are poised there, ready to make that leap across the
Bering Strait," Adler said.
Genetic evidence also tells him that several species of black
fly have found their way to the Seward Peninsula from farther
"If it continues to warm, then species from more southerly
climes will keep working northward," he said. "At some
point in the future, you would expect western Alaska to have
many more (species of black flies and mosquitoes)."
Those biting flies will have plenty of company. Adler cited other
scientists who have measured more than 600,000 black fly larvae
in about three square feet of streambed, and more than 12 million
adult mosquitoes hovering above one unfortunate acre of northern
This column is provided
as a public service by the Geophysical Institute,
University of Alaska Fairbanks, in cooperation with the UAF research
Ned Rozell [email@example.com]
is a science writer at the institute.
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