Home: Writings: Essays & Rants: Syphrid fly

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 wrought?

Copyright, 1996 by Bud Polk