Hello, young scientists. Take a look at the photos with this blog. They are kind of scary, aren't they? These were taken today at my house, and one of these very large, scary insects was inside my screened-in porch!
Which one would you pick up in your bare hand? Neither one, you say? Most people would agree.
Sometimes animals can fool you. One would be dangerous to pick up, while the other only LOOKS dangerous.
Photos 1 and 2 are one of the largest of the hover flies. They are completely harmless to us, feeding on nectar from flowers. They couldn't sting you if they wanted to. However, they are a very successful look-alike mimic of a wasp.
It looks so much like a wasp that it is called the Yellow Jacket Hover Fly. A predator, or a person, who sees one immediately wants to get away from it, and leave it alone. This is exactly what this harmless fly wants you to do.
Photo 3 was the one on my porch, and it was so big that it scared me. As it turned out, I was wise to avoid this large wasp. It was a queen Southern Yellow Jacket, which is orange instead of yellow and about three times as big as a regular worker yellow jacket.
I've been on the stinging end of angry yellow jackets enough times to have a lot of respect for them, and I have learned to stay away from their nests. They live in holes in the ground. Usually it is an old chipmunk burrow or maybe a hole left when a root rots away. If you are unlucky enough to step on or get to close to a yellow jacket nest hole, lots of angry wasps swarm out of the hole to protect their nest. They will chase you with stinging on their mind, so you better run! Unless you see yellow jackets flying in and out of their nest hole, it is easy to stumble across one and pay the price with several painful stings.
The fly with almost the same colors and patterns as the wasp is a great example of Batesian mimicry (pronounced BATES-E-AN MIM-ICK-REE). When a harmless animal has the coloration of an animal that could hurt you, it gives that animal a lot of protection from predators.
How do you tell the difference? Remember insects have three major body segments, the head, the thorax (where the wings and legs are attached), and the back part called the abdomen.
So how do you tell the difference between a fly and a wasp? Notice that the wasp has a very thin "waist" where the thorax meets the abdomen. On the harmless fly, there is a thick waist. The fly has a blunt abdomen, and the wasp has a pointy abdomen because that is where its stinger is.
Now look at the head. Flies have very short antennae, while wasps have longer antennae. Flies also tend to have larger eyes, sometimes meeting at the top of the head. Wasp eyes are on the side of their head.
Flies have one pair of wings and a pair of tiny stunted wings called haltares, which help them keep balanced when they are flying. Wasps have two fully developed pairs of wings.
Good luck telling a fly from a wasp. You now know some things to look for. Of course, if you are not sure, play it safe, and leave it alone.
Look around your house for more Batesian mimics. Lots of flies are tricksters who pretend to be wasps or bees.