18 BRITISH FLIES 



on the middle pair, and sometimes on the hind pair. Thoracal 

 squamse large, but not enormous ; rather raised and not con- 

 cealino; the halteres. Perfect insects all blood-suckers and 

 never small. IV. Tabanid^. 



The 'rahanidct' are the well-known biting "Horse Flies,"* which 

 annoy mankind as well as horses and cattle. They are often very large 

 (but hardly gigantic)bulky flies, ranging down to moderate but never small 

 size, and they are square-built with the thorax and abdomen moderately 

 flattened. Their colours are, as a rule, mottled broAvn and grey, exce]it 

 in the brightly colored species of Chri/sojis, and in life the eyes exhil)it 

 most brilliant hues of green with usually i)urple si»ots or bands. _ The 

 proboscis is inconspicuous in all British species, but in many species of 

 Pan/jonia is remarkably long, thin, and porrect. The Tahaniche may 

 be easily known by their general appearance, peculiarly annulated third 

 antennal joint, and their large thoracal squamse, Avhile the wide open 

 triangular fork of the cubital vein never truly occurs in any others of 

 the Eeemoch.'ETA. 



The Pangonince may exlribit some little variation in venation, l)ut 

 only of an unimportant nature, such as the closing of the first and 

 fourth posterior cells near the wingmargin through the approximation 

 and fusion of the veins. 



10 (9) Head very small and inconspicuous, being almost globular and so 

 much depressed as to be overshadowed by the large gibbous 

 thorax, very holoptic in both sexes ; antennae with the third 

 joint never annulated, though sometimes elongate and strap- 

 shaped without any style or arista, but usually very short 

 and with a long apical arista. Thorax and abdomen very 



Fia. 40. — Acrocera ylobulvs $. x 7'. 



gibbous, the abdomen being rounded or even inflated like 

 a balloon; prothorax sometimes (Philopota) exceedingly de- 

 veloped, and forming a dorsal shield on the front part of the 

 thorax ; genitalia never prominent. Venation usually eccen- 

 tric; posterior cells varying from two to five (or apparently 

 six) ; small cross-vein usually absent, but sometimes indistinctly 

 present ; ambient vein absent ; discal cross-vein (when present) 

 close to the end of the prsefurca and close to the base of the 

 discal cell, and there is often a second cross-vein placed near 



* I use the terms Horse Fly for Tahanido;, and Gad Fly or Bot Fly for CEstridce. 



