A Little Bit More
The Friendly Fly is much more common across North America than you might imagine. We tend to view flies as being all alike and often don’t notice their differences. This particular species is a bit larger than the common House Fly, slower, and more hairy. When these flies land on your arm or leg, it’s not very wary and often needs to be brushed aside rather than simply shoo’ed away, as you might expect.
Populations of Friendly Flies go up or down in relation to Forest Tent Caterpillar (FTC) populations but when these flies are especially abundant, their presence can be a bit of a nuisance for livestock and people due to their habit of landing on their bodies. In years when the FTC population is low, the Friendly Fly is uncommon and relies on carrion or dung as a “home” for its young.
FTC Moths are found all across the continent where there are hardwood trees, preferring Quaking Aspen but feeding on all other hardwoods except Red Maple. This is our most common leaf-eating caterpillar of hardwoods in North America. In northern areas, their population cycles go from 6-16 years with highs that may last 3-4 years, although in southern areas there are infestations that may last 9 years or longer. In high population years, this insect can do a great deal of damage to forests, especially to diseased or stressed trees. Although you may not have a special liking for flies, this one can be an important force to limit the depredations of FTC.
Activities
Science – Can You Feel This?
Objectives: Illustrate the importance of body hair as it applies to insects
Materials: Tissue and willing subject
We’ve all had insects land on our body and most/all of us find it irritating, to say the least. But unless you actually see an insect land, how does one know that a mosquito, for example, has landed on your arm? In most cases, the tiny hairs on our body “tell” us it’s there!
This is an easy way to demonstrate just how valuable our sparse hair covering is.
1. Take a tissue and roll it to about the size of a pencil (you can use a small artist’s paintbrush to do this if you have one)
2. Ask for a subject to demonstrate on
3. Tell your subject that they are to tell you when/if they feel something touching their body (assure them this is totally painless!)
4. Ask the subject to close their eyes while you demonstrate and hold out one bare arm (only the forearm needs to be bared). Have them hold their arm outstretched so their thumb is uppermost
5. Ask the student to tell you when they “feel anything on their arm”
6. Using the end of your tissue, GENTLY wipe the tip across the underside of their forearm (this area has few, if any, hairs) – you may want to do this more than one time
7. Now do the same but this time wipe the tip across the upper side of their forearm (the hairy part) – again you may want to do this more than one time
In most cases, your subject will NOT feel anything when the tissue is wiped across the underside of their forearm but WILL feel a sensation when the tissue is wiped across the upper side of their forearm. The upper forearm has a fair amount of hair (this varies from person to person but all have at least some) and the disturbance of these hairs by the tissue allows us to feel a sensation. Without many/any hairs on the underside of the arm, a person is much less able to feel anything.
An interesting bit of information you may want to share with the girls (this will depend a bit on their ages too) is that if they shave their legs, they will be much less likely to notice an insect that lands on their legs. And now they know why!
Key Concepts
Populations and Ecosystems, Life Cycles, Identification, Growth and Development, Food Webs /Food Pyramids, Behavior and Regulation
Questions
Do you have a question for a naturalist? Go ahead and ask!
It's easy -- just fill out this form, submit your question and you'll receive an answer shortly.