Backyard Birder: Oh dear, it’s deer fly season

  • With deer flies out in full force, take extra precautions this summer to protect from those painful bites. Courtesy photo

Backyard Birder
Published: 8/12/2019 8:37:09 AM

Have you noticed this summer that the deer flies are insane? But then again, I’m pretty sure I think this every year. It always happens like this. I feel triumphant for having survived the furious onslaught of blackflies and mosquitoes of early summer and I’m just noticing that the tick population seems to have taken a vacation. I head out to soak in all the joys of summer from hiking and biking to running and gardening when I am sadly reminded that July and August should be renamed Deer flies and More Deer flies.

Deer flies are members of the horse fly family, Tabanidae. This family also includes the notorious greenhead flies that have sent families running for home during seaside holidays and the mammoth horse flies that are Willard Pond’s best weapon for keeping number of daily visitors down.

Similar to mosquitoes and blackflies, it is the female deer fly that bites you. A meal of protein-rich blood from a vertebrate, most often a mammal, is required for deer fly eggs to become viable. Humans are not the only source of this blood meal. If you own a dog, especially a dark colored one, you will notice that deer flies are especially drawn to them and some studies on cattle have shown that the impact of deer flies on dairy cows is a 20 to 30% decrease in milk production.

When a female bites it’s actually cutting your skin open in search of a blood vessel, unlike a mosquito that gives you a sort-of-reversed injection. The mouth of a female deer fly is equipped with a pair of scissor like blades that makes the initial bite. An anti-coagulant in the saliva keeps the blood from clotting, so it can lap up the blood with a sponge-like mouth. Since the bite of this fly is painful, most mammals will swipe it away, forcing the deer fly to leave its meal. Therefore, most have to make multiple bites before gathering enough blood to lay their eggs.

During daylight hours on warm sunny summer days the female deer fly is ruthless. She has many tools to find her prey. While the male feeds on nectar and pollen, the female waits for an unsuspecting hiker to bumble by and then her assault begins. Her huge compound eyes track movement and with their large size and upright position on her head, she has an almost 360 degree view of her surroundings. Keyed into movement and drawn to dark colors, she along with all the other deerflies in the area will attempt to feed on the highest point of their prey, which for humans is our heads. She also uses her antennae to pick-up on chemical cues of her prey including carbon dioxide.

Basically you can’t move or even breath if you want to get outside in NH in the summer and avoid the deer flies. So what’s a person to do?

Here are a few tips on how to beat the flies:

Leave your Bug Spray at Home: Yep, it doesn’t work against deer flies!

Instead try these solutions:

Dress in Light Colors: Deer flies are drawn to dark colors, especially dark blue. Think of another summer tradition, Wimbledon, and dress in whites. If you are feeling like playing tennis, take one of those electric bug racquets with you on your walk. Dressed in whites and with your racquet, you’ll at least be in ready position!

Go Nocturnal: Since deer flies are active during the day, try your outside adventures at dawn, dusk and night.

Avoid Them: Look for new routes that don’t take you along forest edges especially near wetlands like streams and rivers. Instead explore our lovely Monadnock Region downtowns.

Put on a Strip: Russ Cobb, an avid bicycler, uses “deer fly strips” which is basically a rectangle of sticky tape. Put the strip on a baseball hat and when the deer fly try to land on your head, they get stuck on the tape. His only additional recommendation is to use a hat you don’t care too much about since the tape leaves a sticky residue.

Wear a Net: Eric Aldrich, former columnist of the Monadnock Ledger-Transcript’s “The Bobcat’s Tail” and manager of the Hancock’s Wildlife Cam project, spends a lot of time outside. His go-to solution is old school – a baseball hat topped by a bug net. Basically he puts this outfit on in May and doesn’t take it off until the first real frost.

Train a Dragon(Fly): This would be my favorite solution if only you could train a dragonfly. Dragonflies, especially the large darner dragonflies, eat deer flies like candy. Next time you are out walking and the deer flies are getting you, hope a dragonfly is somewhere in the neighborhood. Perhaps, this might also help you see that deer flies are good for something – feeding dragonflies.

Don’t Let a Fly Get the Better of You: UNH ‘s Cooperative Extension Forester for Cheshire County and Peterborough resident, Steve Roberge gives good basic advice for deer flies and life in general when he says, “Like all the flies I work with, you learn to live with them. If you don’t, then they win.”


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