sharp prick of the bite bei.ng often the- first intimation of the 

 presence of the fly. The larger species of Tabanm betray their ap- 

 proach by their deep hum. When one operation of sucking blood has 

 commenced, horse-flies, like other blood-sucking Diptera, especially 

 Culiddae, may easily be captured or killed. Owing to the size of the 

 Tabanidae, the wound inflicted by the mouth-parts of many of the 

 species is especially severe. Anyone who has seen T. trigonus attack- 

 ing horse, or TV exolicus attacking cattle, 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 only victims, for in Formosa mules and buffaloes suffer severely, while 

 in other countries, camels and elephants are known as the usual victims. 

 Wild animals are similarly tormented, as the late Sir Sameul Baker 

 states that herds of game were retreated from the South before the 

 attacks of the several species of Tadanus and Pangonia ; among the 

 savages of Formosa it is well known that certain species of deer some- 

 times suffer from the biting of certain species of Tabanidae. In regard 

 to the attacks of horse-flies upon human beings, abundant though 

 certain species such as those of Haematopota occasionally are in the 

 Japanese Islands, we have to turn to European records in order to 

 understand how serious a pest these flies may become owing to their 

 extraordinary blood-thirstiness. Thus, according to Portschinsky, in the 

 Gdov district of the Petrograd Government, in Russia, horse-flies in 

 summer are so excessively numerous and blood-thirsty, that agricultural 

 operations have to be cairied 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. 



The horse flies are known as a suspected vector of certain 

 diseases of both human beings and animals, and at the present time 

 we are well acquainted with many insect vectors of diseases, among 

 which is well known that of Trypanosoma evani, which causes Surra of 

 horses, mules and camels, and transmits from one to another by Tabanns 



