33 



blood-sucking Diptera, ma}- easil)- be captured or killed. Owing to 

 the size of the Tabanida;, the wound inflicted by the mouth-parts of 

 many of the species is especially severe. Anyone who has seen 

 Tabanus boviniis (Plate 19) attacking horses must have noticed the 

 large drops of blood that exude and trickle from the spots bitten by 

 the flies. Among domestic animals, however, horses and cattle are 

 not the onl}- victims, for in other countries mules, camels, and 

 elephants sufier severely. Wild animals are similarly tormented ; 

 thus in 'The Nile Tributaries of Ab_\-ssinia ' (London: Macmillan 

 & Co., 1867), p. 210, the late Sir Samuel Baker, writing of the country 

 between the Settite and the Atbara Rivers, mentions herds of game as 

 retreating from the south before the attacks of the " Seroot," under 

 which name several species of Tabanus and Pangonia are known to 

 Europeans on the Blue and White Xiles. As regards the attacks of 

 horse-flies upon human beings, abundant though certain species such 

 as those of HcBtnatopota occasionally are in the British Islands, we 

 have to turn to continental records in order to understand how seriiius 

 a pest these flies ma}- become owing to their extraordinar}- blood- 

 thirstiness. Thus, according to Portschinsky (' Die Bremsen (Tabanidx) 

 und die einfachste Methode dieselben auszurotten.' [In Russian.] Pub- 

 lished by the Ministry of Agriculture and State Domains : St. Peters- 

 burg, 1899, pp. 19. — Summary in German b}' N. Von Adelung, 'Zoolo- 

 gisches Centralblatt,' VII. Jahrg. (1900), pp. 807-808), in the Gdov 

 District of the St. Petersburg Government, in Russia, horse-flies in 

 summer are so excessively numerous and bloodthirsty that agricultural 

 operations have to be carried out by night ; while in parts of Siberia, such 

 as the shores of the River Om, settlers have been compelled entirely to 

 abandon the zone infested by these flies. Noticing that horse-flies 

 frequent!}- seek pools in order to drink, Portschinsky hit upon the expe- 

 dient of covering with a thin layer of petroleum the surface of the water 

 in certain lakes and pools in districts infested b}' the flies. The result 

 was a brilliant success, and the insects were destro}-ed in enormous 

 numbers, the majority on attempting to drink adhering to the la}'er 

 of oil, while others although they managed to fly away, w'ere 

 subsequently choked or poisoned b}- the petroleum. In this way 

 certain localities, such as the Park of Pawlowsk near St. Petersburg, 

 were complete!}- cleared of these troublesome Diptera. It is interesting 



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