Tuesday, June 10, 2008

Yellow and Deer Flies

They're back!! "Why are those visitors waving at us? They haven't even met us yet. Maybe they're just extra friendly." Actually, they're swatting at the Yellow Flies (Diachlorus ferrugatus) that have appeared over the last few days making the trip from the parking area to the Francis Beidler Forest nature center an annoying insect adventure and a torturous gauntlet if both hands are full.

As previously reported: The flies (deer, horse, and yellow) are from the family Tabanidae. The males are easily identified because their eyes are connected while the eyes of the females are widely separated. However, after smashing the fly between the palm and scalp in response to a painful bite, it is difficult to ascertain if the eyes were originally connected. It will undoubtedly be a female, because as with mosiquotes, it is only the females that bite humans and other animals.

The flies are ambush predators. They lie in wait in shady area until they perceive a meal passing by. Darker clothing in motion appears to be the most attractive to the flies. Using their scissor-like mandibles, they can inflict a wound deep enough to cause bleeding. They also add an anti-coagulant to keep the blood flowing. A group of 20-30 flies feeding on a cow for six hours can remove 100 cc of blood! Beef cattle can lose substantial weight and dairy cattle milk production can be dimished.

The fly problem is mainly in the parking area and the dry forest, but with the low water (zero in many places) in the swamp, the flies have ventured into previously unexploited territory. The fawn in the image was bedded down near the snake sign at #8 along the boardwalk. Although, quite close to the boardwalk and disturbed by our proximity, the fawn's attention was mainly on the fly that was tormenting it. The fly can be seen between the fawn's left eye and left ear. Even though movement might disclose its location (it thought itself better hidden than it truly was), the fawn could not resist an occasional twitch to get the gnawing fly airborne.

Hopefully, the flies will stay only for their normal two weeks and not the 6+ weeks they spent gnawing on us last year!

Image by Mark Musselman

No comments: