6 



BULLETIN 1218, U. S. DEPARTMENT OF AGRICULTURE. 



and pasturage. This flooding, together with the wastage from 

 higher areas, makes the floor of the valley a succession of swamps. 

 In certain parts these swamps and sluggish channels are grown to 

 tules. Areas slightly more elevated are grown to water grass and 

 moss. In the fall of the year, when irrigation is discontinued, much 

 of this semiswampy area affords wonderful pasturage; during the 

 wet season it affords breeding places for an abundance of tabanids. 

 At the northwest corner of the valley proper, nature, fortunately 

 in some respects and unfortunately in others, left a reservoir. In 

 this low spot, from the irrigation of the northwestern part of the 

 valley, has accumulated a body of water known as Alkali Lake, about 

 a mile long and one-half mile wide (fig 4). The shores of this 

 lake and the swampy area adjacent are choice breeding places of 

 Tabanus punctifer and T. phaenops, the former being found abun- 

 dant in moist humus near the edge of the water. The lake has no 

 outlet. 



Fig. 4. — Alkali Lake, Antelope Valley, looking south towards Topaz, Calif. 



The intervals between irrigations of the more sandy land of the 

 higher slopes of the valley average about two weeks. The flooding 

 of the floor of the valley has no cessation until about the middle of 

 the summer, when the water becomes more scarce. Then it is 

 diverted into the higher ditches for the irrigation of the more im- 

 portant crops. 



The ultimate destination of the overflowing wastage is the West 

 Walker Eiver, which runs through the valley. Provision of ade- 

 quate drainage channels for this wastage is, as will be discussed later 

 in this paper, one of the solutions of the tabanid problem. 



BREEDING METHODS AND EQUIPMENT. 



On account of the cannibalistic habit of tabanid larvse, it was 

 found necessary in rearing to isolate each larva. Glass fruit jars of 

 1 pint capacity were used for this. The disk of the cover was dis- 

 carded and in its place a circle of galvanized wire gauze or screen 

 was soldered into the ring (fig. 5). This arrangement admitted 

 plenty of air and completed the isolation. In each jar was placed 

 mud or debris similar to -that from which the larva was taken in 



