94 THE ARGENTINE ANT. 



seems not to be lessened thereby. During flood time many of the ant 

 colonies migrate to the levee adjoining, while still others ascend the 

 trees out of the water's way. Curious nests or sheds, constructed 

 by the ants from particles of earth and trash, are of conamon occur- 

 rence in the tops of the willow trees. 



In some few places it is evident that the railroad has been the means 

 of introduction, the infestation having started at points on the railroad 

 where considerable merchandise from New Orleans was constantly 

 being unloaded. 



EXPERIMENTS IN THE ORANGE GROVES. 



The writers' first experiments with the pest in orange groves were 

 commenced in the spring of 1910. At that time only one grower in 

 the Louisiana orange section was attempting anythmg like a system- 

 atic campaign against the ants. This grower had adopted a novel 

 and rather effective method of destroying them. The infested por- 

 tion of his orchard immediately adjoined the levee and, as is usual 

 with land along the river, was lower by several feet than the water in 

 the river during flood stages. The water could therefore be siphoned 

 over the levee to the orchard as rapidly as needed. (See PL X.) To 

 prevent the spread of the ants to additional territory the infested 

 block had been surrounded by a ditch, a section of which may also be 

 seen m Plate X, in which water was kept at all times. Durmg flood 

 stages of the river the water was siphoned over for the ditches at small 

 expense and through the ditch system drained away to the swamp in 

 the rear of the plantation. At other times the water was kept in the 

 "ant ditches" by use of a gasoline engine and pump installed on the 

 levee, as shown in Plate X. It was, of course, necessary to take pre- 

 cautions that the ants should not find accidental and artificial means 

 of crossing the ditches. Permanent bridges for the passage of teams 

 could not be left, so a swinging bridge which could be lifted when not 

 in use was devised. The ditching system for preventing spread of the 

 ants was shortly adopted by many other growers, some of whom used 

 an ingenious divided bridge (PI. XI) w^hich could be crossed readUy 

 by teams, but which had a 2-inch crack through the middle that effec- 

 tuaUy prevented the passage of the ants. 



The grower referred to had put in practice tlie following method of 

 destroying the ants: A small levee or ridge was made around the 

 infested block of trees. Water was then admitted through the siphon 

 from the river untU the ground in the block was entirely covered. As 

 the water slowly rose the colonies of ants moved up into the orange 

 trees. Then the water was drawn off and the ants, descending, found 

 the ground still too wet to live in, whereupon they migrated en masse 

 to the surrounding smaU levee. The water was then turned on for 

 the second time to keep the ants on this ridge, and here they were 



