Now here’s a fun summer activity: fly-wrangling

Americans of today have greatly diminished opportunities for scientific experimentation. We have so successfully removed ourselves from the natural world that there are few opportunities to experiment on anything natural. We are left with only social experiments to perform.

Some of this is the result of culture, but some of it is the result of increasing technology, such a screens on our windows. We have fewer and fewer opportunities to observe nature because we don’t let it in the house anymore.

Here’s an experiment to turn summer’s insect pests, like flies, into a fun science experiment. Mix up some thin sugar water and add food coloring. Then paint the mixture on a sheet of paper and lay it out on the patio table. You can do this in the house if it’s hot out, but then you have to let the flies in. Anyway, the flies will land on this sheet of paper, walk around on it, flicking their little tongues in and out to eat the sugar.

When you retrieve the sheet of paper, you will see tiny, little lip-prints where the flies have licked the sugar. I have not investigated whether the dye stains the fly’s lips. I have heard of lipstick on pigs, pit bulls and soccer moms, but not flies.

How does the fly know there is sugar on the paper to eat? It turns out that flies, and many other insects such as bees, butterflies and even cockroaches, taste with their feet.

You can demonstrate this yourself by anesthetizing a convenient insect. Of course, first you have to catch an undamaged one. (There is a slick trick for doing that too, but I don’t have room to discuss it here today.) I’ll leave catching the insect up to you. Anesthetizing is easily accomplished by placing your insect in the freezer for a short period of time.

Then you must attach a handle to your insect because it does not come with one. Procure a stick the size of a lead pencil. An applicator stick or Q-tip would also do, depending on the size of you insect. Dip one end of your stick into melted beeswax, paraffin or glue. When a sufficient quantity has accumulated on the stick, touch it to the back of the insect. The experiment can now be performed untouched by human hands.

Once the insect has recovered from the anesthetic, gently use the handle to lower the insect over a bowl of water until its feet just touch the water. Because of their small size, insects lose water quickly and after this treatment they are usually thirsty. When your insect’s feet touches the water, it will stick out its tongue and drink.

When it’s no longer thirsty it will withdraw its tongue and cease drinking. This is good because otherwise it might trip on its tongue if it left it hanging out. Anyway, this demonstrates that they can taste with their feet, or maybe they just know when their feet get wet.

Next, gently lower the same insect over a bowl of sugar water and you will see that it reflexively sticks its tongue out to feed. Since you have already satisfied its thirst, you can be sure the insect is responding to the taste of sugar through its feet. Well, I guess it’s possible the insect can just tell when its feet are sticky.

However, if you were to line up a series of bowls with decreasing sugar content, you would be able to determine that at some point the insect could no longer sense the sugar on its feet. You could then try the test on yourself, although I would recommend making new solutions in clean bowls.

You would find that most insects have better taste than humans by 10 million times. But most people are not very interested in insects with good taste.

Personally, I would prefer an insect that tastes good. 

Gary McCallister, mccallis@ coloradomesa.edu, is a professor of biology at Colorado Mesa University.


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