|
Flies prove unlikely saviors, cup bubbles seek harmony
Q: I have a problem with stable flies in my house. On
Saturday, I cleaned house from top to bottom. On Sunday, I noticed 2 flies. On
Monday, 10 flies and on Tuesday, 30. I found cocoons when I rolled the carpet
back a few inches. The carpet is fairly clean, regularly vacuumed, and is about
one inch thick. The web sites I checked said stable flies nest in damp organic
material only. My two questions are — why would these flies infest my carpet?
What keeps the flies from laying their eggs on me and infesting my body?
(Leslie, Paris, Tennessee)
A:
You found fly pupae (cocoons) under your carpet — not maggots.
 Greenbottle fly [Leon Higley, Entomology Department,
University of Nebraska-Lincoln]
The Internet sites are correct. The adult female fly lays her
eggs in moist decaying animal and plant wastes. Likely choices are: excrement
mixed with straw, soil, silage, grain, soggy straw, compost, and grass
clippings. None of which sounds like a clean carpet. No self-respecting stable
fly would choose your carpet in which to lay her eggs. The eggs would probably
dry out and if maggots did hatch, they’d starve.
But that’s not what happened. The female picked a nice moist
site full of readily available food to lay her 100 to 150 eggs — in your stable
or yard. The eggs hatched within 2 to 5 days. The creamy-white maggots ate
voraciously, grew, and in 14 to 26 days became full-grown mature maggots. Then
they sought a cool, dry place to pupate — your carpet.
They can migrate up to 150 feet (46 m). So, they came inside
your cool house and found your dry carpet. A perfect place. The maggots,
shortened, hardened their skin, and darkened to chestnut brown pupae. After
anywhere from 3 days to 4 weeks (depending on temperature and humidity), they
emerged as adult flies. You saw 2, 10, and then 30 on the three successive days.
To answer your second question: be thankful they weren’t
blowflies. You have little to fear from stable flies since the females seek
decaying plant and animal wastes to lay their eggs in. Your body is safe — from
them. Blowflies are a different story. They lay eggs preferably in dead rotting
meat but they’ll happily use what’s available: open wounds, eye sockets, mouth
and body openings.
Actually, blowflies saved lives in World War I, in the days
before penicillin had been discovered. Battlefield doctors noticed that wounds
infested with maggots healed even more quickly than wounds the doctors had
treated immediately. The maggots ate infected pus-oozing flesh, which stopped
the infection from spreading. The wound could then heal. Doctors, recognizing
superior "technology", bred maggots in sterile conditions and put them in
pus-filled wounds, saving lives.
They still do it now! "Even today there are wound infections
in which maggots are superior to our newest antibiotics," says
John L. Foltz,
entomology professor at the University of Florida.
Further Reading:
University of
Florida: Stable fly (dog fly) control by P.G. Koehler
North
Dakota State University: Stable Flies by H.J. Meyer, R. Dean Christie, and Dean
K. McBride
University of Missouri Extension: Household flies by Richard M. Houseman
North Carolina State University: Insect development by John Meyer
University
of California, Irvine: Maggot therapy by Ronald A. Sherman
Q: Why do little bubbles form
along the bottom and the sides of a cup when carbonated drinks are poured into
it? (Crystal, Singapore, Singapore)
A:
Little bubbles form on cup surfaces because carbon dioxide bubbles out of
solution with the cola.
 Pink bubbly [Corel]
It happens like this when I drink a Coke:
The Coke in the can contains carbon dioxide (the carbonated
part of the drink) dissolved in liquid cola and a small pocket of gas at the top
of the can. The pressure inside the can is about twice that outside. Carbon
dioxide molecules bop back and forth — some leaving the Coke for the gas pocket
and others going from the pocket into the Coke, at the same rate — a condition
of equilibrium. Harmony reigns.
I pop the lid open. Almost all the gas in the pocket scrams
out and the pressure drops drastically. The harmony is disturbed. What to do?
Bubble out of solution!
So, masses of molecules zip out of the Coke at a much greater
rate than those that leave the vacated pocket. Furthermore, "they leave, not
individually, but together in bubbles," says
Craig Bohren,
meteorology professor emeritus at Pennsylvania State University.
But, wait. It’s not easy. Making bubbles takes energy. The
carbon dioxide has to make a bubble surface that separates the bubble gas from
the liquid Coke. But it doesn’t just happen.
So, the carbon dioxide hunts around for a tiny bubble. The
bubble already has surfaces so that part of the work is done. All the gas has to
do is to make the bubble larger — which is what it’s trying to do.
Where does the carbon dioxide find tiny microscopic bubbles?
You guessed it. Along the sides and bottom of the cup where nicks and pits trap
infinitesimal bits of air as bubbles.
That’s why bubbles form on cup surfaces — carbon dioxide is
escaping the
supersaturated Coke by enlarging preexisting tiny cup bubbles. Soon, the
bubbles grow big enough to notice.
Bubbles form also about any small grains dropped in Coke, says
Bohren. In fact, some people sprinkle salt into their beer — just to watch the
many bubbles form.
Further Reading:
Bohren, Craig F. Clouds in a Glass of Beer. New York:
John Wiley & Sons, Inc., 1987.
(Answered Sep. 3, 2004)
|
