VIII, B, 3 Mitzmain: Biology of Tabanus striatus Fabricus 217 



to the host's skin. The palpi, the position of which may be seen 

 when the parts are withdrawn, are directed alongside the pro- 

 boscis bow-like on either side of the puncture. These parts bend 

 as the labium is thrust into the skin, and they probably aid by 

 their elasticity in the withdrawal of the proboscis. 



The head raises with a jerk in the withdrawal of the proboscis, 

 and the punctured site is marked by a distinct blooddrop. Only 

 a few seconds intervene prior to a repetition of the stab in an 

 adjoining spot, and as many as 7 punctures may be made in a 

 period of ten minutes. The biting m.ay continue for as long as 

 twenty-three minutes. The distention of the abdomen, only the 

 anterior part of which is affected, gives no indication of the 

 extent of satiation of the fly. They have been seen to feed with 

 the abdomens bulging laterally with food, which bulging some- 

 times persists for several days, after which time the fly may bite 

 once or even twice. The bites appear to be very painful to the 

 host. The insect is never satisfied with a single bite, but makes 

 several punctures before a complete meal is obtained. No doubt 

 this is due in part to the interruptions caused by the tormented 

 animal, and the fly may have acquired the habit of making short 

 swift stabs in order to facilitate its escape from the host. 



Tabanus striatus, although commonly termed a "horsefly," 

 is found biting cattle and carabaos as well as horses. During 

 over two years of personal observation, this fly has never been 

 known to annoy man in the Philippine Islands. Reports of at- 

 tacks from this fly can usually be attributed to the biting of 

 Stomoxys, which is frequently annoying to the native care- 

 takers of draft animals. Perhaps the carabao may be accepted 

 as the host of choice of the Philippine horsefly. This is at once 

 apparent when flies are very abundant. Many times I have seen 

 sparsely haired carabaos with their bodies actually covered with 

 droplets of dried blood resulting from the bites of tabanids. 

 I have collected from a single carabao 61 specimens of Tabanus 

 striatus in less than fifteen minutes. 



THE OCCXJRRENCE OF TABANUS STRIATUS 



The time of day when this species of fly is most active is 

 usually the same as that of other species of Tabanus. The fly 

 begins its activities usually between 7 and 8 o'clock in the morn- 

 ing, and during the greatest heat of the day is found on the shady 

 sides of houses and trees. Between the hours of 3.30 and 6 in 

 the afternoon it is again active, resting for the night on the con- 

 venient rain trees. These trees have been observed to harbor 



