226 TABANID^ [CH. 



(iv) Wing with three or four posterior cells, anal cell often small ; 

 femora and tibiae often with combs of spinules ; small dull-coloured pre- 

 daceous flies usually with a stiff proboscis for impaling prey . . Empidides. 



(v) Wings with three posterior cells ; proboscis not projecting ; 

 small flies often found on windows . . . . . . . . ScenopinidcB. 



IV. Third antennal segment simple, with or without an 

 arista ; the empodia, when present, are bristle-hke ; third 

 longitudinal vein not forked. 



(a) Wings shaped like a lance-head, the venation somewhat as in the 

 Psychodidae . . . . . . . . . . . . . . Lonchopterida. 



(ft) Second basal cell confluent with discal cell ; anal cell, if present, 

 small ; usually brilliantly coloured flies with metallic sheen . . Dolichopodidce . 



(c) Second basal and discal cells either confluent or distinct ; anal cell, 

 if present, small ; not brilliantly coloured flies . . . . . . Empidida . 



{d) Antennae apparently two-jointed, with a three-jointed arista ; wings 

 (rarely wanting) with several stout veins anteriorly and other, weaker ones 

 apparently connected with them and running obliquely across the wing ; 

 small hunchbacked, quick running, bristly flies.. .. .. Phoridee. 



CHAPTER XIV 



FAMILY TABANIDiE (BREEZE-FLIES, CLEGGS, HORSE- 

 FLIES, GAD-FLIES, SERUT-FLIES) 



Description. The members of this extensive and important 

 family are usually large and strongly built flies, the females 

 of which feed on blood. The head is large ; the antennae are 

 projecting, and the third joint is composed of four to eight 

 indistinct segments, or annuli. The eyes are very large and 

 laterally extended ; in the male they meet along the middle line 

 (holoptic), but in the female the eyes are smaller and a narrow 

 streak is left between them (dichoptic). In the living insect 

 the eyes are often iridescent and usually marked with green, 

 purple, or brown bands, or spots. 



The proboscis is projecting, sometimes as long as, or longer 

 than, the body, and the mouth parts are adapted for piercing 

 and cutting. Generally the labium is coarse and fleshy 

 and the labella are large; the epipharynx and hypopharynx 

 are strong dagger-shaped structures ; the mandibles are 



