CHAPTER XXXII 



THE DIPTERA 

 CULICIDiE AND THEIR ALLIED FAMILIES 



Diptera : Morphology — Classification- — Culicidae — Corethridae — Chironomidae 

 — Psychodidae — Simuli dae— References . 



DIPTERA. 



Definition. — Hexapoda with two well-developed transparent wings 

 and two rudimentary wings in the form of halteres. Mouth parts 

 well developed, adapted for piercing and sucking or for suction. 

 Mesonotum forms by far the larger portion of the thorax. Meta- 

 morphosis is complete. 



Remarks. — The Diptera are by far the most important order of 

 the Hexapoda as regards tropical medicine, for they include the 

 blood-sucking flies, which are capa.ble of carrying disease; also 

 certain flies which cause disease by depositing their eggs in cavities 

 or on the surface of the body, with the result that the larvae enter the 

 nose, and cause disease by gnav/ing away mucous membrane, 

 cartilage, and even bone, or the alimentary canal, in which they may 

 cause serious symptoms. Apart from these, it must be remembered 

 that flies, particularly the common house-fly, may mechanically, 

 either externally or by its alimentary canal, carry and deposit germs 

 on food, by which means human beings become infected with disease. 



Morphology. — ^The most important points in the morphology of the Diptera 

 in general may be briefly mentioned. 



Head. — The head in certain families shovv-s an anterior depressed area, 

 the lunula, bounded by an arched suture, which passes over the base of the 

 antennae. This is the invaginated ' ptilinum,' or vesicle, by which the imago 

 breaks its way out of the pupa. With regard to the antenna, it is of great 

 importance whether it is many- or few- jointed. In the latter case it often 

 carries an arista on the third joint, which may be looked upon as represent- 

 ing the remainder of the larger antennae of other species. 



The mouth parts, though composed of the typical labrum, epipharynx, 

 maxillae, mandibles, hypopharynx, and labium, will be found to be very 

 different in the various species of biting flies. More especially are the labial 

 palps altered in Glossina and Stomoxvs, becoming armed with teeth and 

 capable of making the hole in the skin which is necessary for the sucking of 

 the blood. 



Thorax— In m^any cases the thorax is largely composed of mesothorax, 

 the pro- and meta-thoraces being much reduced. The wings are of impor- 

 tance. Some genera possess a prolongation backwards, called the squama, 

 which conceals the halter. The venation of the wing has a peculiar nomen- 



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