THE ARGENTINE ANT IN RELATION TO CITRUS GROVES. 39 



was shared by the writer, was that the ants fostered the white fly 

 for its excretions, and when many ants were seen carrying adult 

 white flies down an orange tree it was taken as evidence that they 

 were transferring this pest to other trees and colonizing them thereon. 

 As a principal occupation of the ants on nearly every tree was carry- 

 ing white flies, however, and the reason for carrying only adults was 

 not clear, the opportunity was taken to observe this work more 

 closely. 



It was noticed that comparatively few ants were carrying white 

 flies up the trunk, but that a very large majority, certainly over 95 

 per cent, were carrying them clown only. If the ants were estab- 

 lishing the white flies on other trees, it seemed that at least there 

 should be somewhere near the same proportion carrying them up 

 as were carrying them down the trees. Many of the ants therefore 

 were traced as they carried the insects up and down the trees. In- 

 variably those going up trees were traced to some cranny, where 

 they poised in the dark for a rest or to avoid a breeze, or they would 

 go up a short distance and then turn and go down again. In- 

 variably those going down the tree were traced to the entrance to 

 an underground nest, where they disappeared from view. Some of 

 these entrances were directly at the base of the tree, but digging out 

 such tunnels proved that the ants were not nesting about the roots 

 of the trees or other plants on which the white fly might feed. It 

 also disclosed the complete absence of underground colonies of living 

 white flies and the presence of piles of dead remains of adults in the 

 ant tunnels. 



The next step was to examine white flies carried by the ants to de- 

 termine whether they were living or dead. Some of them were liv- 

 ing, and a good many more were dead, but the most important dis- 

 covery was that a very large majority still had their wings crumpled, 

 as they are immediately after emergence from the pupa case, show- 

 ing that they were captured just as they emerged. 



The percentage of white flies which the ants destroy must vary 

 widely in the various groves at different times, and is probably never 

 high enough to be of great economic importance. In a series of ten 

 examinations to determine what proportion of the ants descending 

 orange and privet trees with forage had captured white flies, the fol- 

 lowing data were gathered on the subject: 



All the ants passing a point on the trunk going down the tree in 

 a certain lengh of time, usually from 10 minutes to a half hour, 

 were counted and classified as to whether or not they carried forage. 

 Those carrying liquid forage could be distinguished by the distended 

 gaster. The kinds of insects carried were noted without disturb- 

 ing the ants where possible; otherwise the prey was collected. In 



