THEME: Road to Lajamanu
SUBJECT: Science
TOPIC: flies
The branch whacked me across the back of the head and shoulders, sending a multitude of flies into the air! When we’d left camp this morning, I was literally covered from my cap to my waist, including my arms, with millions of the pesky beasts. I looked like a scene from a Hitchcock film, flies crawling up my nose, in my eyes, out of my ears as I rode along, swatting furiously while trying not to fall off my bike on the sandy track. It was actually a relief to have Jason swat at them with the tree branch, even though most of them came back at me with a vengeance! They’d been an extreme nuisance to us all in camp the past couple of days and moving air, either from a breeze or from the back of a bike seemed the only relief.
So what is this phenomenon here in the Bush? The common fly occurs everywhere on the continent, but seems to prefer the wide open spaces. It roosts at night, but returns with first light of day. It begins its life in a dung heap, where creamy white eggs are deposited. The larvae hatch and, after eating its way through the dung, leave to pupate in the soil. The longer the larvae have to feed, the bigger the fly.
The adult fly needs a diet of protein; blood, pus, milk, tears, and saliva. That’s why their voracious appetites lead them to wherever we’ve scratched ourselves, sweated heavily, or near our dinner table at tea! And, the smaller the fly, the more starved it is for protein. Females in search of protein for their developing eggs seem to be the most tenacious of all, outnumbering their brothers three to one in search of essential juices.
The nuisance value of these flies has been measured. If we put our hand into a cage filled with them, ten blood-fed flies will be attracted to your hand per minute. However, if they are protein starved, the figure increases to 48 per minute. Flies with an underprivileged upbringing in a low protein dung heap, once adult and continuing to be undernourished, are up to 70 times a nuisance factor. These must have been the ones we’ve lived with the past couple of days!
Suggested activities: Investigate what attracts flies in your area. Compare the attraction value of table scraps, animal dung, sweat, to name a few, creating a graph of fly attractors. Which seems the most palatable to flies? Why do you think that is? What time of day are they the most annoying? Are there certain weather patterns that make them more of a nuisance? What is the role of the common fly in our ecosystem? Why is it important for them to be a part of the food chain?
April