63 



Family Simuliidae — The Black Flies 



Larva of Simulium venustum showing- the mouth fans 

 (left) used for securing food. (After Metcalf and Sander- 

 son). 



Small, usually dark colored flies, rarely over 5 mm. in length, wiili 

 short, thick legs. 



Head rather hemispherical; face short, eyes round or reniform, 

 holoptic in the males; ocelli absent. Proboscis rather short, with small, 

 horny labella?, palpi incurved, four segmented, the basal segment short, 

 tlie two following of etiual length, the fourth longer and more slender 

 than the preceding. Thorax arched, without transverse suture; scutel- 

 lum small. Abdomen rather cylindrical, tapering in the males, composed 

 of seven or eight segments; genitalia concealed. Legs short and strong, 

 the femora broad and flat; tibia? usually with terminal spurs; basal 

 segment of the tarsi elongate, the apical segment small. Wings large 

 and broad, Avith distinct allula", the anterior veins thickened, the others 

 weak. Auxiliary vein ending in the costa near the middle of the wung, 

 the second vein absent, the first and third approximate; anterior cross- 

 vein very short; fourth vein curved, forked nearly opposite the anterior 

 cross-vein, the branches terminating near the apex of the wnng. 



The Black-Flies, Buffalo Gnats, Turkey (Inats, to use some of the 

 common names for these pests, need no introduction to the hunter or 

 fisherman. To most people they are extremely annoying and as they 

 frequently occur in enormous numbers in the neighborhood of streams 

 fishermen are only too well acquainted with them. As a rule their bites 

 do not attract immediate attention but after a short time they cause 

 painful swellings and, if in sufficient numbers, may result in the serious 

 illness of the sufferer and even death. The adults attack all warm 

 blooded animals and are known from all parts of the world, being par- 

 ticularly abundant in the north temperate and subarctic zones. 



