Backyard Biology

Nature stories from my backyard and beyond

Nature Stories

Deer Flies Revisited

Thursday, July 18, 2013

It is that time of year again when a walk outdoors is quickly turned into a torture trek by attacking deer flies. A Nature Story in September of 2009 discusses the deer fly and talks about a way to control them.
A recent ten minute walk around my house netted me 70 deer flies, so I thought it might be helpful to repost that nature story. If you are bothered by deer flies and what to know what to do about them, read on:

The Isles of Shoals in the springtime is a magical place. This group of nine islands six miles off the coast of Portsmouth, NH is a birders paradise, a stopping place for birds migrating across the open ocean. Appledore Island, the largest of the islands is also the site of a college campus. A visit to the campus in the spring presents one with a rather strange sight. Outside every door of every building is a pile of sticks.
Appledore Island is, before all else, a gull nesting island. Both black-back and herring gulls nest on this tiny island by the thousands. In fact, during the height of breeding season, one would be hard pressed to walk 20 feet without stepping on a gull egg or chick. Obviously the parent gulls are none too thrilled with this situation and they do what many other parent animals do - they attack. Dive bomb would be a more precise term. They aim at the highest point of the intruder, the head. A peck on the head from a sharp gull’s beak is sufficient to give one a nasty gash and draw blood.
To walk anywhere on Appledore Island is to be attacked by gulls. So whenever possible, it is wise to walk next to a much taller person. When this is not possible, a gull stick is the next best remedy. Since the gulls attack the highest object, a stick held above the head attracts the gull’s ire. And beak. Whenever leaving a building for a walk across the island, it is wise to grab a stick from the pile outside each door and give the gulls a target higher than your head.

My back yard in the summer is a magical place. This three acre plot of land in Pembroke is a naturalist’s delight, including a field, hemlock forest, swamp and river. And like Appledore Island, my back yard is also the home of a dive bomber. This dive bomber is much smaller than a gull, but just as likely to draw blood, and all for the benefit of its offspring.
Like the mosquito, the female deer fly needs a blood meal to help her eggs develop. And like the mosquito, it is only the females that bite. However, where the mosquito will insert a needlelike mouth and suck blood, the deer fly cuts open the skin and laps up the blood. This hurts!
Deer flies are ambush predators. They sit in the vegetation and wait til they see moving prey. Then, like the gulls, they will attack the highest point of their prey - the head. For some reason, they like to circle the head and buzz it for a while before landing for a meal. Sometimes, they will start their attack at the edge of the woods and continue their head buzzing as I cross the field until they find a suitable place to bite or until I reach the house and I escape unscathed. As can be imagined, a healthy crop of hungry, dive-bombing deer flies following you around the back yard can quickly turn paradise into purgatory, if not worse.

In the past, I have had two techniques for dealing with deer flies, neither one very satisfactory. The first is to swat at the flies and to slap at my head where I think they have landed. And since I am paranoid about getting bitten, I am always slapping my head. This technique is not very effective although very entertaining for my neighbors (watching from a screened porch).
The second is to wear a lot of clothes, including a hat. Offering as little naked skin as possible reduces the possible feeding surfaces for the fly, and the hat makes the head buzzing less annoying. This second technique is more effective than the first, but not very comfortable on a hot summer day.

A while ago, I learned a third technique for dealing with these pesky flies. In this technique, deer fly cupit is the dive-bombing habit of the deer fly that will be its undoing. And it employs a “deer fly” stick. To make the stick, a large plastic cup (research shows that blue is the optimal color) is placed upside-down on the stick. The cup is covered with Tanglefoot, a sticky material. Any deer fly buzzing the cup will stick - forever. (Editors note: I cover my cup with fluy paper. When the fly paper is completely covered with deer flies, it is easily removed from the cup and a fresh piece of fly paper added.)

A trip to my neighborhood this summer should present one with a rather strange sight. Outside every door of every building, expect to see a pile of sticks with blue cups attached. And many deer flies attached to the cup. And me once again able to enjoy the delights of my back yard.

for more information on the deer fly trap, check out the web site:
http://ufinsect.ifas.ufl.edu/deerfly_trap.htm