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Family Dolichopidse — The Long-headed Flies 



Small flies rarely exceeding 10 mm. in length, usually metallic 

 green or blue, partly dusted with whitish, brownish or grayish, rarely 

 yellow or blackish. Discal cell united with the second basal cell. 



Head about as wide as the thorax, sometimes a little wider, usually 

 a little higher than wide; face variable in width, sometimes practically 

 eliminated by the approximation of the eyes, generally wider in the 

 females than in the males; front usually wide and widening above, 

 rarely obliterated by the approximation of the eyes in the males; with 

 bristles above. Posterior orbits usually with orbital cilia which may 

 be replaced below by fine hair. Proboscis fleshy, short, usually re- 

 tracted; palpi flat, usually reposing on the proboscis, sometimes modi- 

 fied and highly ornamental. Antennaj composed of three segments, 

 bearing a dorsal or apical arista; third segment usually more or less 

 oval, sometimes elongated, especially in the males. Thorax convex 

 above, sometimes with a conspicuous depression before the scutellum. 

 Abdomen with five or six segments, conical, cylindrical, flattened, 

 laterally compressed or more or less laterally compressed apically; 

 hypopygium large, or small and concealed. Coxge usually short, rarely 

 a little elongate, the legs of moderate length, the femora usually some- 

 what enlarged, the tarsi of the males frequently beautifully modified, 

 the tibias rarely so although sometimes brightly colored. Wings hyaline 

 or with dark markings, sometimes ornamented with black and white 

 or of peculiar shape. Second basal and discal cells united, the anal cell 

 short, the sixth vein short or absent, the fourth vein usually straight 

 or only gently curved forward, rarely forming a crossvein. 



The adults occur everywhere in the vicinity of water and are 

 particularly abundant in swamps and along lightly shaded streams 

 where they occur on mud or sand; on foliage, usually in the sun; on 

 stones in streams; on the trunks of trees and on fallen logs. Species of 

 Medeienis and Neurigona are normally found on tree trunks, especially 

 those having smooth bark; Hydrophorus and Campsicnonus occur on 

 the surface of small pools; most genera occur on mud along water, 

 some only on sand; DiapJwrus, Chnjsofus and Hercostomus occur 

 chiefly on foliage and the same is true of Condylostyhis, etc. ]Many 

 of the si)ecies are extremely local in habitat, occurring only where 

 conditions are perfectly suital)le. The adults are all predaceous, feeding 

 ui)on smaller insects and mites. I have frequently ol)served them 

 devouring midges and also small larva' occurring in the mud. 



