The Order Diptera: Two-Winged Flies

Diptera (flies) are a division of insect identification. The Phylum is Arthropoda and the Class is Insecta.

Diptera (flies) are a division of insect identification. The Phylum is Arthropoda and the Class is Insecta. Diptera Insects are the common arthropods on land. There are more than 120,000 species of flies. The body is divided into three regions. The head is one region that has a pair of antennae and the organs of sight. The chest (thorax) is one region and it contains three pair of legs. The final region is the abdomen that differs from species to species. The fly will differ and be in a well-differentiated group called the Diptera as one of its features is that it has only one pair of well developed wings in the front. There is a rear pair of wings that are used for balance. Diptera is the Greek name for 'two-winged' as these insects only have one pair of wings that are used for flying. The rear wings are called halteres as they are little club-shaped organs that oscillate rapidly when it flies as the real wings. These halteres as they are called are attached to the body with sturdy but thread-thin stalks. You might see them on very large flies but it is impossible to see them on smaller flies without magnification.

In the United States there are fifty families of flies and they vary in size from tiny to those that measure nearly 2 inches in length. The adult fly has a well-developed head that is joined to the thorax by a narrow stalk. The shape of the antennae will vary as to the age of the fly and the development. Eyes on a fly are compound and ocelli. According to the species the compound eyes will vary as to the development of the fly and may not even be available. The eyes appear large. The compound eyes differ from the simple ones by having a large number of corneal lenses, each conveying the light to a single road and cone. The theory is that each retinal cell perceives but a portion of the picture. The action of the brain causes the various parts to be together as a whole, as a veritable optical mosaic.

The mouth is on the lower anterior surface of the body, and is surrounded by the "mouth parts". These are the appendages of the adjacent segments, variously modified for eating. These are sometimes adapted for crushing and biting, at others for piercing and sucking. Usually these mouth parts are capable of motion, but they move in a horizontal plane, from side to side, and not vertically, as do the jaws of vertebrates. The mouth parts are designed for sucking, chewing, biting, lapping, and sponging. The mouth parts are able to pierce and then suck as most flies will feed on liquids. There is a food channel composed of separate structures that are brought together by a widening in the end portion of the labium or lower lip. The action of the pharynx is in sucking up the liquid. The pharynx is the front end of the alimentary canal, which dilates and contracts and literally pumps the liquid upward. Some of the liquids include animal secretions, nectar, liquid plant secretions that serve as food for the fly. These species will have sucking mouth parts. Other species have the mouth parts for piercing and sucking as they have a different kind of food, forms of blood or haemolymph that is known as insect blood. From the mouth the esophagus passes upward and backward through the nervous system and concludes in the Crustacea at the stomach, in the insects at the crop or ingluvies. In many forms the alimentary canal is a simple tube with no well-defined divisions.

In the fly the three segments of the thorax are often fused with the thorax also bearing the three pairs of legs. This shape will vary from species to species.

The Diptera are divided into ovoviviparous, oviparous and viviparous species. Ovoviviparous species lay eggs from which the larvae emerge right away or in a short time. Viviparous species have embryos that will completely develop in the mother's body and larvae are deposited straight from the covering of the egg. The Oviparous division lays eggs that do not have an embryo started and these eggs have to be incubated. These larvae are commonly called magnots. They will lack eyes and legs and sometimes have little protuberances on their bodies to help them move. They also have jaws to help them move. There are two hooks that are used to affix them in place.

There are three suborders of the Diptera, Nematocera, Brachycera and the Cyclorrhapha.

The Nematocera consists of a larve with a complete head and horizontal mandibles. There is also a pupa obtect, many segmented antennae and the pleural suture of the mesothorax. The Brachycera consists of a larve with an incomplete head and vertically biting mandibles, a pupa obtect, three segmented antennae and a twice bent pleural suture of the mesothorax. The Cyclorrhapha consists of a larva with a vestigial head, a pupa exarate in a puparium with three segmented antennae. The pleural suture is bent twice and the head has a frontal lunule and a ptilinum. The Nematocera consists of species with long, delicate antennae as the mosquito. Flies are of the suborder of Brachycera. There are four stages, first the egg, then the larva known as the maggot and the pupa and adult stages.

The life cycle of the fly is called holometabolous. The larvae emerge from eggs and are called maggots. These maggots lack legs and most of the time they will lack eyes. They are able to move through protuberances on their bodies and with their jaws. Three are two hooks that consist of the mouth parts. After these larvae or maggots grow it will need to advance to the last stage of development before becoming an adult fly. This development is called the pupa state. Some pupae of the Diptera are enclosed in cocoons while others are buried in soil, etc. Some have pupae that are in a cocoon of silk or remain in the larva's skin that has become hardened. It serves the same purpose as the cocoon and is called a puparium. When the pupa is ready to hatch it will burst out of the cocoon. Whe the pupa bursts outward it becomes a fly.

Flies are in all parts of the world no matter the climate. The Diptera are the most important of all insects. Flies include various species that have endangered the health of man and other animals by carrying disease germs in the digestive tract or on the hairy feet and legs. So many diseases have been caused by the fly carrying parasitic worms such as diarrhea, dysentery, typhoid, trachoma, yaws and cholera. There are many other diseases that the fly caused over the years. Some flies have larvae that will produce severe injuries in man and animals. These diseases are called myiasis. The name myiasis is applied to diseases caused by the larvae of Diptera that behave as parasites and develop in the skin or body orifices of their host. The family of flies known as Oestridae as adults will suck blood, especially the female.

There are some flies that have helped science and man such as the fruit fly. Geneticists have gained a greater knowledge of heredity due to this fly. The biologist is able to raise this fruit fly under controlled conditions and uses it as an aid to understanding the mechanism of heredity. The Syrphidae fly lives on aphids commonly called plant lice and keeps their population down. The carnivorous larvae of the Tachinidae will destroy many insects. The olive fruit fly will cause severe damage to fruit. Horseflies are a serious problem to domestic animals as they are blood suckers having a painful bite. When there are serious attacks on farm animals such as grazing stock the animals can be infested with various diseases.

There are many species of flies, too numerous to cover in this article. Man needs to protect himself and his home against most flies especially the common house fly. If food is not left open and is stored properly and cleanliness exists flies will move to another location.

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