By Anthony DeBartolo

CHICAGO (Hyde Park Media) Try to recall those two houseflies
you saw hanging around during the first really warm days of April.

Though entomologists, and anyone else who happens to speak Latin,
would call them Musca domestica, let`s call them Fran and Fred.

Further, imagine they were the only flies in existence, so when their
four eyes` 16,000 facets first met, it`s understandable why their 10
hearts beat as quickly as Buddy Rich did in his prime.

Instinctively, Fred likely mounted Fran, with her blessing, somewhere
on the ground. Copulation, say entomologists, apparently never takes
place in the air, though more than one male has been seen attempting a
hijack.

After a split-second of fly foreplay--caressing her head with his
forelegs, to which she responds by extending her genitalia to
his--they mate, anywhere from a few seconds to a couple minutes before
Fred buzzes off.

Within a week, Fran will lay the average 120 eggs in whatever rich,
warm organic matter she finds--since houseflies, unlike the iridescent
green bottle flies you`ll find around outdoor garbage cans, aren`t big
meat eaters, horse manure is ideal.

During the next 12 days, her eggs will undergo the complex
metamorphous passage to larvae, then maggots, then pupae, finally emerging
as fully-grown, 1/4-inch adults. There are no baby houseflies; any
smaller ones you see were underfed as maggots or are another species.

Two weeks later, when Fran and Fred have reached the golden days of
their typical one-month lifespan, they`ll be grandparents several thousand
times over.

By the end of August, if all their descendants were to survive the
summer, you`d think twice about that Labor Day picnic. Depending upon
which statisticians` fly facts you choose to believe, the planet would be
covered to a depth of 23 to 47 feet.

Fortunately for us, says Bernard Greenberg, professor of biological
sciences at the University of Illinois at Chicago and an
internationally recognized authority on flies, these real good reasons for window screens don`t get to realize anything near their potential:

* The fly`s natural enemies--birds, reptiles and certain other
insects, not to mention those Venus flytraps that show up at your grocer`s
every spring --eat their fair share.

* And unless there`s sufficient food, warmth and moisture throughout
the eggs` development, those maggots don`t have a chance.

* Because they`re tropical animals, temperatures also greatly affect
an adult`s life--and with it, if not their ability to reproduce, at least
the likelihood of getting around to date.

At 53 degress they`re airborne; at 48 degress, they`re reduced to a
crawl; at 44 degrees, they`re virtually comatose; and at a few degrees
below freezing, it`s death within hours.

If it climbs much past 102 degrees, heat paralysis sets in; at 116
degrees, death comes almost as swiftly as with a swatter. It`s the low
90s in which these critters thrive.

And they`ve been thriving for a while now, ``at least 20 or 25 million
years,`` says Greenberg. Even so, after all that time, they haven`t
gotten any better looking.

Their diminutive size (coming about 100,000 to the pound) and aversion
to being petted doesn`t give us much of a chance for a really good
look at them or many of the other approximate 87,000 species in the diptera order, that grouping of all two-winged insects.

It took Al Hedison in the 1958 horror film ``The Fly`` to show us
what beasts they really are. Playing yet another scientist who got
carried away exploring the mysteries of life, he accidentally swapped heads with the title star. Not a pretty sight.

Mouse-gray and loaded with short stubby hairs (as are the fly`s other
two body parts, thorax and abdomen), the head can rotate nearly full
circle and is dominated by two colossal purplish-brown eyes, each made
up of 4,000 six-sided lenses, all of which work independently.

While they see all colors except red, Greenberg says, flies are rarely
guided by their fragmented sight alone. They rely on two short, thick
antennae set between the eyes to detect air movement (an approaching
swatter, for instance) and smell food.

(They will, by the way, eat just about anything liquid or easily
liquefied, though they have a decided preference for hot meals, and a
special need for sugar and protein.)

At the head`s base is the mouth, the proboscis, a retractable
funnel-like device nearly as long, and just as unsightly, as the head
itself. From our standpoint, its most endearing quality is that it can be used
only as a vacuum. Houseflies don`t bite.

(Stable flies--resembling the housefly in size and color--do. They`re
the ones, Greenberg says, ``that attack your ankles at the beach,``
and both sexes are out for blood.)

The worst offender, however, is the female horse fly. (Males are
harmless.) Three times the gentle Musca`s size, her pointed proboscis
can pierce leather and draw up to 100 cubic centimeters of blood on a good
day.)

As any reasonably coordinated 10-year-old can tell you, the housefly isn`t terribly swift, despite the fact that those wings beat 200 to 330 times a second (research findings differ).

With an average speed of 4.5 miles an hour, he can, however, just keep
up with a walking horse. And because wing muscles account for 11
percent of his body weight, he can trail that horse for hours. Another example
of nature`s delicate balance.

The fly`s six feet make possible those seemingly effortless wall walks
and ceiling climbs. He either grabs rough surfaces with each foot`s
pair of curved claws or uses the continually wet and sticky tiny glandular
hairs at their tip.

For years researchers were divided over how flies managed to land on
ceilings. One camp claimed they performed an inside loop. Another said
they executed a half-roll as they neared the surface.

E.D. Eyles of Kodak Research Laboratories in England, cleared it all
up in 1945 after filming the feat in slow motion: half-roll it was.

An issue they`re still divided on, Greenberg says, is where in the
world they all come from each year. ``Most likely they`ve been here all
winter, surviving in animal houses, dairy barns`` and the like. ``They, like
cockroaches, can survive in the coldest part of the world as long as man`s
there to provide a home.``

But another theory says migration is the answer. Greenberg thinks
``both are probably true.``

``They`re not native Americans. When man came around, the fly hopped a
ride. They probably came over with Columbus, or before. Before the
1300-1400s, we may not have had any flies at all.``

But all flies, like man, he says, ``probably got their start in
Africa. You`ll find the greatest number of species and sub-species there.``

You`ll also find there the greatest danger of fly-borne disease. Those
horrid television images of Ethiopia`s starving, too weak to wave away
the dozens of flies feeding on their eyes` and lips` moisture, brought
that home. ``In our sanitized, plastic-wrapped society, fly-borne
disease is a relatively unimportant thing,`` says Greenberg, author of a two-volume
treatise on the subject. ``Especially since we stopped using the horse to get around.``

``But in Mexico, too--all of Latin America really--these countries are
loaded. They`re struggling at a very primitive level.``

Parts of the U.S. fair no better.

Some researchers say it`s possible for a single city slum fly to carry
as many as 33 million bacteria internally and have another half
billion swarming all over its body. Among the possible diseases
carried: typhoid, cholera, dysentery, salmonella, polio and several parasitic aliments like tapeworm.

But the danger, Greenberg points out, rests more with the community
than on the back of the fly: ``The cleaner the neighborhood, the relatively
cleaner flies you`ll have.

``But people in (rich neighborhoods) shouldn`t feel so smug--they do travel,``
up to 15 miles, ``passing up gorgeous, dirty stables and barns along the
way.`` The housefly`s typical flight range though, is under a 1/4-mile.

Fortunately, disease-causing bacteria are highly vulnerable to even
the slightest light and temperature change. So the trip to the table, no
matter how short, is a difficult one.

Even so, most researchers agree, this common pest does pose a
potential health problem, and not only because he`s likely to land on Dalmatian
dung one minute, then dance on your doughnut the next. While their
feet are filthy, their manner of dining is even more dangerously disgusting--a fact they almost seem conscious of. Why else then would they so thoroughly
wipe their hands and face after eating?

While exploring solid or semi-solid surfaces--like candy, corn flakes
or your mashed potatoes--the first thing they`ll do is cough up some of
their last meal. This mixes with and helps dissolve the new find, most of
which then gets sucked through the proboscis.

Most, though, is the best they can do. A fly always leaves a little
something wherever he`s been. Just another reason why ``Hey, waiter!``
jokes aren`t funny.

Despite our most determined efforts, houseflies continue to resist any
meaningful long-term control. We came close right after World War II
though, when DDT and other potent chlorinated hydrocarbons were used
extensively in homes, restaurants and dairy barns. Only later did we realize some flies developed immunity, passing the trick on to their kids, while we
poisoned ourselves in the process.

``No spray is absolutely safe,`` Greenberg says. ``If it can kill an
insect, it can damage us.``

By far, the safest and best approach to summer fly control is
preventative--cleaning up after the dog and keeping a tight lid on the
garbage --to at least cut down on the filth in which they feed and breed.

Some of us wouldn`t want the housefly wiped out anyway. There`s still
enough hunter lurking in our reptilian brains to appreciate an occasional kill. Especially midair on the very first swat.
 
 

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This article first appeared in the Chicago Tribune on June 5, 1986
   © 1986 Hyde Park Media