Essays & Rants:
Bipolar disorder and the syphrid fly
by Bud Polk
I took a walk in Howes Prairie -- within the Indiana
Dunes National Lakeshore.
The Dunes do not yield up there beauty easily. It was
very warm and the mosquitos were voracious and out in
large numbers. Walking through wild grasses and brush
where there are no trails was difficult. And Depakote was
still raging within me and I was feeling the first
effects of Neurontin.
Yet the flowers the grasses, the trees, the
butterflies, the humming of cicadas, the migrating birds
were all there as I had imagined them. Find a butterfly
book in the library and look at spicebush and tiger
swallowtail butterflies. I would not attempt to paint
their beauty with words. Among the grasses was a glory of
wildflowers -- yellow, gold, purple, white.
I was tired, hot, itchy and winded after walking for
45 minutes. I came to a dune that borders Howes Prairie
and climbed part way up to escape the mosquitos, drink
some water and rest a bit.
Then I saw the syprhid fly just down the slope
drinking nectar from the tiny flowers of the twelve-inch
purple flower-spike of a dense blazing star. To the
casual eye, the fly would have appeared to be a
bumblebee. It was fat-bodied and black, and it had a wide
yellow wooly-band across its back. But the fly had two
wings instead of four and lacked a stinger.
That this species of syphrid fly resembles a bumblebee
is a form of adaptation biologists call
"mimicry." Biologists identify two types of
mimicry -- Batesian and Muellerian -- after the
scientists who first described them.
Batesian mimicry is when a creature resembles another
which is noxious or dangerous but is itself harmless.
Muellerian mimicry is when a creature is noxious or
dangerous and resembles other similar creatures.
There are several species of small spiders which
closely resemble ants. Some birds and other animals will
not eat ants because the formic acid in thier bodies
makes them distasteful. Although the ant-like spiders are
edible, they are left alone. This is Batesian mimicry.
Monarch butterflies are very unpalatable to birds and
other animals because of the glyscosides in their bodies
that come from milkweed plants -- their principal food.
The monarch butterfly is bright orange and has black
borders and veins and white spots. The viceroy butterfly
is similarly patterned and equally distasteful. Birds
learn by trial and error that any winged thing that is
bright orange, black and white is likely to be yucky. The
mimicry of the two butterflies reinforces each other.
This is Muellerian mimicry.
I observed the syphrid fly for twenty minutes.
Biologists have not determined which type of mimicry this
bumblebee-like fly manifests. And then I thought about
Bipolar Disorder and evolution.
Do our moodswings, thought patterns and behaviors
resemble something dangerous and noxious, but are we
really harmless? Is this Batesian mimicry that protects
us when we are vulnerable?
Or, are we noxious and dangerous and resemble others
with the same qualities? Do we broadcast a warning when
we are vulnerable: "Stay back, real danger
here?" Is our adaptation Muellerian?
So I communed with a syphrid fly and wondered about
you and I. Batesian or Muellerian? What hath evolution
Copyright, 1996 by Bud Polk
Modified December 11, 2002