True flies are members of the insect family Diptera. This family includes gnats, botflies, horse flies, deer flies and blow flies. The most common of these is the housefly, or Musca domestica. Flies have many specialized body parts that help them see, fly and climb on vertical surfaces.
All species of flies have a segmented body with three main parts: the head, abdomen and thorax. The thorax is the middle portion of the body and the abdomen is the end. A fly's entire body has a hard outer surface called an exoskeleton which serves to protect the internal organs. Fully grown, most flies are about 1/4 to 1/2 of an inch in length and their wingspans measure approximately 13 to 15 mm.
Flies have three pairs of jointed legs that are attached to the thorax. Each leg has five segments: the coxa, femur, tibia, trochanter and tarsus. The bottom segment of the leg, the tarsus, has two small claws and a pad with small glandular hairs. The claws and hairs allow the fly to stick to surfaces even sideways or upside down.
The fly has two large compound eyes, one on each side of its head. They are brownish purple in color. The surface of each eye is divided into 400 different facets, allowing the fly to see 360 degrees. The fly sees a mosaic of a scene rather than one solid scene when it looks at something.
Flies' wings are transparent and have a system of veins and ridges that provide support. These veins provide blood and oxygen to the developing wings during the fly's larval stage. The housefly can fly up to 30 miles per hour and beat its wings over 200 times a minute. There are tiny hairs on the surface of each wing which are used to detect changes in air pressure during flight.