Around the Island

Mashomack Musings: Deer flies

As the warm weather begins in earnest, we all love to get outside. Birds are nesting, plants are flowering — but unfortunately the annoying insect season is gearing up as well.

Most people are well aware of ticks and mosquitoes, but biting flies also make their appearance at this time of year. While it’s nice to know that the emergence of these pesky critters is helping to feed many young birds, frogs and dragonflies, it’s still rather bothersome to be mobbed by them while out for a walk.

Deer flies tend to make an appearance in mid-June and persist for about a month. These yellow and black flies are a bit bigger than a house fly, but smaller than the related horsefly. They are slower than many other species, so you can occasionally land a satisfying slap.

Found in areas of moist woods and wetlands, the flies use their sharp mouth parts to slice the skin and quickly lap up blood, like mosquitoes, only the females bite because they need the nutrients to lay fertile eggs.

The flies will take a blood meal from humans, deer, horses or cows. Livestock have tails to help whisk the biting annoyances away; humans rely on the less efficient windmilling of arms.

Deer flies seem to key in on movement and carbon dioxide output to find their hosts. They are resistant to most repellents so wearing a hat or covering up with layers helps, but avoid dark colors, especially blue, which seem to attract them.

Luckily, flies are often concentrated in small areas, so if you persevere through a tough stretch you should be able to emerge into a pest-free area and enjoy the rest of your stroll.