Flies, the good and the bad

Spring is here and the insects are back. I bet when you hear the word “flies” it triggers negative feelings. Today, I’m going to explain the difference between two types of flies that look very similar to each other but are actually very different: midges (Chironomidae) and mosquitoes (Culicidae).

midge_drawingMidges and mosquitoes are closely related, but there is one major difference – midges don’t bite and  mosquitoes do. In fact, the best way to tell these two insects apart is by looking at their mouthparts. Adult mosquitoes have a proboscis, or extended straw-like tube extending from their face for sucking up fluids. Midges don’t eat as adults, so they don’t have a proboscis. Midge adults only live for a day or so, so all they need to do is mate and then they die.

Let’s start with the good flies, the midges. Midges are the most abundant aquatic insect in freshwater. I bet you encounter midges every day without realizing it. These are the tiny flies that form those massive swarms near the lake and near porch lights at dusk. Swarming is how they find their mates. Midges can vary in size from a few millimeters to a half-inch, and the males have fuzzy-looking antennae. These are also the flies that we tend to eat by accident when running around the lake! Don’t worry, they’re harmless and a good source of protein.

Their larval stage, commonly referred to as “bloodworms”, lives in the sediment in lakes and streams. Midges are extremely important in recycling nutrients and consuming organic matter on the lake floor. Since they are so numerous, they also play a major role in the food chain. When there is a large midge hatch the fish have a feeding frenzy, and this can often be a good time for fishing.

When there is midge hatch they leave their pupal skin, which can be thought of as the equivalent of a butterfly cocoon, floating on the top of the water. I bet you see this without realizing it as well. When the waves are crashing into shore and carrying a bunch of brown material, it is probably midge pupal skins. We actually use these pupal skins to identify the different types of midges.

Now onto mosquitoes, which are not all bad. Most mosquitoes actually just eat nectar. In fact, it is only the female mosquito that requires a blood meal. The females require protein for egg development, and there is no protein in nectar but there is in blood. Females locate their blood meal primarily through scent. They are attracted to the carbon dioxide that we breathe out and substances found in our sweat. That is why you may feel like you are getting attacked more while hiking on a hot day. Studies have shown that mosquitoes are more attracted to some people than others. Some factors for determining the risk of being bitten are your weight and blood-type. What makes mosquitoes bad is their ability to carry diseases such as West Nile Virus, which can develop into meningitis.

Mosquito larvae live in standing water, so they are usually not found in large lakes and streams. The best way to prevent them in your yard is to eliminate standing water. You can put screens over rain barrels to prevent mosquitoes from laying eggs there, replace the water in bird baths and outdoor pet dishes twice a week, make sure your eaves troughs are clean and not holding water, dump out any other containers in your yard that can hold water such as wheelbarrows and tires. The only thing really proven to work in preventing mosquito bites is using repellant containing DEET. Wearing light colors helps somewhat because mosquitoes are more attracted to dark colors.

In summary, when you see little flies outside this summer take a closer look. If they’re swarming in a sunbeam or by your porch light and they have fuzzy-looking antennae, they’re probably midges. If they have a long proboscis and land on your skin, they’re probably mosquitoes. While you’re out and about this summer, remember – not all flies are bad!