Greg Vincent's Hiking Site
Greg Vincent's Trail Tresaures - Spring Wild Flowers


This article is available as a print friendly PDF file. Click here.

Mosquitoes and Black Flies

Black fly


Black Fly

If we've been hiking long enough, there will be times when we have unwanted hiking partners, not the two legged variety but the biting insect kind. The basic biting insects that we have to contend with in Ontario are mosquitoes and black flies. Both are active by May and gradually become less of a problem as the summer goes on.

Mosquitoes breed in stagnate water and are the most active at dawn and dusk. Black flies breed in clear running water (as we have cleaned up our streams one result is an improved habitat for black fly breeding - they, like us, dislike dirty streams). Black flies remain active all day.

Mosquitoes and black flies are attracted to our body warmth and release of carbon dioxide, both pretty hard to turn off while we are hiking. There are a few strategies we can try such as wearing protective, lighter coloured clothing, and avoiding perfumed soaps and shampoos. Unfortunately, these have only limited success, so we should look at insect repellents.


The most effective repellent is Deet. It comes in various strengths and the good news is that it works. It is a powerful chemical compound and should be treated with caution. Check the percentage and use a low strength, and apply it more often. Apply it to your clothing first and if that does not work apply it to your skin - sparingly.

When applying it to your face, put a little on your hand and then your face. As soon as it is no longer required wash it off with soap and water. A special caution with children. Their livers are not fully developed and therefore not as able to deal with toxins. Use a lower percentage of Deet and apply it to their protective clothing only. Keep it away from their hands, which could lead to their mouths. Another drawback of using Deet is that it is a solvent and can damage some fabrics, plastics and paint.

Citronella is an oily substance derived from Asian grasses and has few of the problems that Deet has however it is not as effective. It is worth a try though, so look for a formula with a fairly high percentage of citronella. A Canadian made product, which I have only been able to purchase in the U.S., "Bite Blocker", is worth a try. It's active ingredient is soybean oil and again does not have the problems of Deet.


TickTicks are potentially a problem in the southern part of Ontario as they may carry Lyme disease. The deer tick that is the potential carrier is very small, no larger than the head of a pin. It can not fly and must wait on a plant for you to brush by. Protective clothing such as long pants tucked in to your socks and long sleeved shirts offer protection, Deet may also help. A close examination of yourself at the end of the day is a good practice and have a friend check your back and the back of your legs. There is lots written about tick removal however if your Swiss Army knife has a small pair of tweezers they will work just fine, just remove it as soon as you can.

Deer Flies

Deer flies, those triangular shaped jobs, are very persistent and I do not know of a repellent that works. My Woods "Don't Bug Me Shirt" with its hood and fine mesh face covering is effective and is also good for black flies and mosquitoes.

If you are prepared for these unwanted hiking companions they need not spoil your outing. It is unfortunate that they usually become active as the Spring flowers arrive, but I will be out enjoying them --- the flowers that is.

For more information about some of these "bugs" check the following websites.

Happy hiking,

Index to The Right Stuff articles
Trail Safety | Boots and Socks | Bugs | Clothing & Keeping Dry | Day Packs and What to Put in Them | GPS
Icy Walking or "On the Up and Up" | Medical Emergencies | Trekking Poles | Warm Weather Walking
Winter Walking | Snowshoeing | The Green Hiker

Go to Top of PageBack to Previous Page

Last updated 2007MAR03