This lump was known as a warble, and, because of its habit of forming such lumps on various kinds of mammals, including cattle and sheep, farmers commonly called her species a warble fly, and they hated her with a passion. A single adult bot fly buzzing over a herd of cattle or horses could cause them to stampede in panic. According to some sources they may attain speeds of up to 90 mph.
Instinctively knowing that the time was drawing close for her final metamorphosis, the larva had at last turned her attention away from the muscle fiber of the woodchuck and set about gnawing a hole about the diameter of a pencil through the animal’s outer skin.
February became March and then March began to wane before the larva finally thrust her way out of the opening she had made in the skin and fell to the ground while the woodchuck was dining on some freshly sprouted clover near the mouth of its burrow. Immediately upon hitting the ground, the larva dug a hole just large enough for her body and buried herself to a depth of six inches.
And here, underground, the ugly gray skin of the maggot split and fell away, revealing a dark purplish-brown pupa, upon the tough shell of which could be seen only vaguely the outlines of the adult bot fly. For three weeks the pupa had remained underground here in a dormant state and then, as the late April sun warmed the earth, the final transition had taken place. The pulpal case split and from within emerged the adult female bot fly. She had to force her way to the surface and sat there quietly for many long minutes, allowing her damp, furled wings to open and dry into the stiff strong membranes they were now.
Within days of her emergence she had met and mated with a newly emerged male bot fly, and within her body now were over six hundred fertile eggs waiting to be deposited. Since then she had been very busy. Last evening’s deer was the seventh mammal upon which her eggs had been laid, sometimes only one egg, but occasionally as many as four or five when her aim had been a little off and there was a chance the eggs would not reach the moisture of the mouth.
As soon as daylight came again, she would leave this fence-post burrow and search for other mammals upon which to lay still more eggs. The deep booming sound of thunder had begun several hours before dawn, causing the fence post to vibrate, and she stirred uneasily.
At one point the rumbling and vibration bothered her so that she backed out of the hole, holding tightly so the strong wind would not rip her away. She hesitated at the mouth of the hole, her front feet still inside the cavity. Abruptly a huge drop of rain smacked into her body, nearly loosing her grip, and in a moment more drops were hitting the post with audible splats. With a fury the clouds broke and a deluge of rain lashed down. The hissing drops beat her unmercifully and she was left with no alternative. It was with the greatest of difficulty that she was able to drag herself back into the hole and crawl inward until her body was just below the level of the top of the post.
Had the storm been no more than a brief thundershower the hole would have protected her, but throughout the rest of the night the heavy rain fell steadily while forks of lightning ripped jagged streaks across the sky and sharp cracks of thunder vibrated the earth.
The storm ended with the dawn, and by the time the sun arose the sky was clear and the air sweet and fresh from the drenching it had undergone. The trees and fields were alive with birds rejoicing in the new day. From out in the marsh the red-winged blackbirds warbled incessantly, and robins, bluebirds and, song sparrows sang from trees and fields, swallows swooped and dived in the sky.
The female bot fly was still alive, but just barely. The hole into which she had crept had become a trap rather than a haven. It had filled to the brim with water and she had almost drowned. Slowly, dazedly, she backed out of the hole and weakly positioned herself in the bright sunlight. Until her wings dried and she warmed thoroughly she would be unable to fly, and so she was very vulnerable. Too vulnerable.
An Eastern Wood Pewee, a flycatcher, perched on a dead snag some forty yards away saw the slight movement she made backing out of the hole and immediately swooped down to the post. Almost before its feet had found a purchase, the bird snapped up the insect, crushed her in its sharp bill, and swallowed her.
And so the career of this bot fly ended as it had begun-in the stomach of another creature.
Peter Dring is a retired nature biologist and phenologist who lives in the Land ‘O Lakes area. To comment on this story, visit the “Outdoors” section of StarJournalNOW.com.