[Pollinator] Follow that Fly

[Ladadams@aol.com]

Thanks to Roy Pea who sent us this article.


http://www.nytimes.com/2006/05/23/science/23observ.html?_r=1&oref=slogin





A dragonfly with a transmitter.


 




May 23, 2006
OBSERVATORY
Follow That Fly
By HENRY FOUNTAIN
You won't see them flying overhead in a V formation, honking away like 
miniature Canada geese, but some species of dragonflies do migrate. Not much is 
known about their journeys, however. After all, there's no way to track individual 
insects over long distances, is there? Well, yes, there is. A Princeton 
scientist and colleagues have done just that, attaching tiny radio transmitters to 
green darner dragonflies and following them using ground-based and airborne 
receivers. Their studies have revealed that dragonflies appear to act just like 
birds in deciding when to travel.
"They follow really simple rules," said Martin Wikelski, an ecologist at 
Princeton and the lead author of a paper on the subject in Biology Letters. "They 
just use temperature and wind."
Radio tracking has been used to follow larger animals. But transmitters have 
gotten much smaller, and Dr. Wikelski, who has worked with them for years, 
wanted to see if they could be used on insects.
He and his colleagues used a transmitter-battery package weighing about 
one-hundredth of an ounce ? about one-quarter of a dragonfly's weight ? and the 
insects are known to carry prey that weigh even more than that. The transmitters 
were attached to the thorax with false-eyelash adhesive and Super Glue.
"Everybody thought this was totally crazy," Dr. Wikelski said, and even his 
team had doubts. "We didn't really expect it to work well."
But of 14 green darners that were tagged in central New Jersey last fall, the 
scientists were able to track 13, following them by car or small plane and 
using signal strength to chart location.
The dragonflies headed south, generally, and were followed for about 35 
miles, on average, over six days. (The tiny batteries die after about 10 days.) 
Like birds, they had days when they traveled (about every third day) and others 
when they rested. And like birds, they flew only when the winds were relatively 
weak (less than about 15 miles an hour) and when temperatures fell over 
successive nights (a sign of a cold front with prevailing southerly winds).
What is still a mystery, Dr. Wikelski said, is why these insects migrate. 
Presumably it's to find better breeding grounds, but only more and longer 
tracking will determine that. "It's a question we can only really answer if we can 
follow individuals," he said.
Nocturnal, Without the Night
Light is one of the great forces of nature, the cycle of daytime and 
nighttime affecting the activities of countless plants and animals.
Take the oriental army worm caterpillar, Mythimna separata, which infests 
corn plants. During the day, the bugs hide underground or tucked behind a leaf 
where it joins the stalk. At night, they emerge and munch away on the plant. So 
the army worm is nocturnal, and it's a good thing, too: that helps it avoid 
being infested by a parasitic wasp, Cotesia kariyai, that is attracted to corn 
plants during the day.
There's only one problem. Researchers in Japan have discovered what makes the 
army worm nocturnal, and it's not light ? at least not directly.
Instead, Kaori Shiojiri of Kyoto University and colleagues reported last week 
in The Public Library of Science Biology, the caterpillar is responding to 
volatile chemicals produced by the corn plant. Those chemicals differ between 
day and night.
The researchers used a laboratory cage that exposed the caterpillars to the 
plant chemicals without exposing them to the plant directly. The cage had a 
food source on one side and a shelter on the other. When the caterpillars were 
exposed to the "daytime" plant chemicals they would hide, and when they were 
exposed to the "nighttime" chemicals they would feed. This behavior occurred 
regardless ? whether the caterpillars themselves were in light or dark.
The researchers point out that the behavior makes sense given the presence of 
a third party, the parasitic wasp. As the researchers put it, by feeding only 
at night, the caterpillar encounters "enemy-free space."
Effect Unknown
Triclocarban is an antibacterial compound that has been used in soaps, 
cosmetics and other personal care products for years. It and a related compound, 
triclosan (used in many toothpastes and in kitchen equipment like cutting boards) 
work by blocking the activity of an enzyme that bacteria need to make 
membranes.
About half a million to a million pounds of triclocarban are produced each 
year, and the chemical has been found in streams and in the water leaving sewage 
treatment plants. Now Johns Hopkins scientists have detected it in the sludge 
at a wastewater treatment plant. Since sludge is often spread on agricultural 
land, the finding means triclocarban may persist in the soil and accumulate 
in crops.
In a study to be published June 1 in the journal Environmental Science and 
Technology, Jochen Heidler, Amir Sapkota and Rolf U. Halden analyzed effluent 
and sludge from a large treatment plant that serves 1.3 million people. A 
special chromatography technique, developed by the researchers and used by Dr. 
Halden in the earlier stream study, was used to detect triclocarban.
The researchers found that roughly 97 percent of the compound was removed 
from the wastewater coming into the plant, and that most of it was soaked up by 
the particles in the sludge. Sewage sludge usually undergoes anaerobic 
digestion to break down organic compounds and create a safer, more stable waste 
product. But the researchers found that anaerobic digestion did nothing to break 
down triclocarban.
Little is known about the toxicity of triclocarban. And scientists don't know 
yet whether it is taken up by plants or remains bound to the sludge 
particles. But one concern is clear: an effective bactericide is being inadvertently 
spread on fields, with who-knows-what impact.
Better Luck This Time
The Japanese space agency's asteroid mission, Hayabusa, may have been 
something of a bust last year, but another project is functioning smoothly. Akari, as 
it is known, is an orbiting telescope designed to survey the sky in six 
infrared bands, to see stars and other objects that are obscured by gas and dust 
clouds in the visible part of the spectrum.
Launched in February, it has provided its first images in the past few weeks. 
The telescope, which is expected to operate for close to two years, will help 
scientists understand the formation and evolution of galaxies, stars and 
planets.

Laurie Davies Adams
Executive Director
Coevolution Institute
423 Washington St. 5th
San Francisco, CA 94111
415 362 1137
www.coevolution.org
www.nappc.org

Our future flies on the wings of pollinators.
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