Diptera are usually winged, but have only one pair of wings with few veins. Hind wings are represented by a pair of slender, knobbed structures called halteres. A few forms are wingless as adults, primarily parasites. Mouthparts are formed for sucking or piercing and sucking.
Fly larvae are entirely different from the adults and are usually found in different habitats. Immatures usually are known as maggots. Immature Diptera have mouthparts, modified for sucking or for piercing and sucking. Primitive flies including midges and mosquitoes which have head capsules but most immature flies have poorly formed heads. Many fly larvae are associated with aquatic habitats or very moist areas with organic matter. Some are internal parasites of mammals. Larvae may be thin and elongate or thin and wide. Some are elaborately ornamented.
True flies or Diptera occur in many shapes and sizes and are a very important group. The order includes forms that are parasitic, predaceous and others that live on either living or dead plant or animal material. Some members of the order cause a great amount of damage to crops. Many harmful flies spread diseases, such as mosquitoes that carry yellow fever and malaria, and are responsible for millions of human deaths. This is one of the most important orders from the standpoint of human health because of the species that carry diseases.
Flies have complete metamorphosis. Flies can be very small to over 1 inch in length.
See Diptera for individual listings.