HORSE-FLIES AND WESTERN AGRICULTURE. 35 



of other species were seen. Two tabanids which ate some of the so- 

 lution in the laboratory died immediately. 



Poisoning tabanids by this method would be expensive and of 

 little value. 



A trap baited with bananas and set for several days caught only 

 two females of T. phaenoj)S. 



No bait was found which would attract any great number of these 

 flies into a trap. Xone of the species of tabanids in this region ap- 

 pear to congregate on buildings, as has been observed in the case 

 of certain other species, notably in southern Florida and Louisiana. 

 The chances of successfully trapping the species under discussion 

 therefore seem to be very remote. 



DRAINAGE. 



It was ascertained that a large majority of Tdbanus phaenops 

 breed in areas which by drainage, not inconsistent with good agri- 

 culture, could be rendered unfit for tabanid development. Much 

 time was spent in 1919 in determining whether tabanid larvae were 

 breeding in irrigated fields which drain readily or in irrigation 

 ditches supplying them with water. Xo tabanid larvae were found 

 in well-drained fields, although earthworms were quite abundant. 

 A few larvae of T. punctifer were found in a gravel bank of a main 

 irrigation ditch through which water flows nearly all the year. The 

 principal land and cattle company in Antelope Vally was making 

 plans and estimates for an extensive ditch drainage system which 

 would drain many of the swampy areas of the valley. Such a system 

 when completed and put into operation will render thousands of 

 acres more productive as well as greatly relieve the tabanid situa- 

 tion. It can not be hoped that the drainage of the floor of the valley 

 will eradicate tabanids. because there are springs and small streams 

 in the foothills and higher up in the mountains which will provide 

 limited breeding places. Of course Alkali Lake in the north end of 

 the valley will also provide breeding places for T. pwnctifer in some 

 numbers. It is firmly believed, however, that drainage will accom- 

 plish the ultimate control of the tabanid pest. 



