10 BULXETIN 377, U. S. DEPARTMENT OF AGRICULTURE. 



over practically the whole town, as well as near-by corn and cotton 

 iields. 



During the same winter (1911-12) similar conditions were expe- 

 rienced at New Orleans, the winter months being accompanied by a 

 rainfall of 41.56 inches, as compared to the 10-year average of but 

 26.1 inches. The numbers of ants were greatly reduced, the mortality 

 probably being at least 70 per cent. The ability of this species to 

 overcome such a catastrophe was well illustrated, for by September, 

 1912, the ants had apparently reached their maximum numbers. 



REPRESSION. 



OUTDOOR BARRIERS. 



A number of experiments have been conducted to discover, if 

 possible, an efficient outdoor barrier. 



The sticky substance which is used in coating flypaper and is also 

 sold in bulk for banding trees was effective for only a few days. The 

 ants would carry particles of dirt and build a bridge over it. This 

 substance, made much thinner than usual, as suggested by Mr. D. M. 

 Eogers for use in the gipsy-moth work, was tried and with more 

 successful results. Heavy bands 4 inches wide spread on two mag- 

 nolia trees were effective for two months in the summer without 

 having to be replenished or combed.^ 



In the cooler parts of the year these bands require frequent atten- 

 tion on account of the growth of mold on the surface. During wet 

 weather in the winter in Louisiana this mold will form in a very 

 few days, and the efficiency of the sticky band will be entirely 

 destroyed. 



It was found that 5 per cent of a carbolized oil added to the thinner 

 preparation increased the effectiveness of the bands considerably 

 and entirely prevented the growth of mold. The band^ were also 

 rendered more repellent and more resistant to winter conditions. A 

 thin crust forms over the surface of the bands in the winter, but this 

 is readily combed into the band in the spring and the band is as 

 effective as ever. The crust on bands of the thinner preparation 

 without the carbolized oil becomes too hard during the winter, and 

 it is necessary to use fresh material in the spring. These bands 

 were used on fig, magnolia, pecan, and orange trees and no injury to 

 the trees was apparent. There is a possibility that the substance 

 may be harmful to trees with a more tender bark, however. 



To the thinner preparation were added in different tests 1 per 

 cent of bichlorid of mercury, 2 per cent of nicotine sulphate, 10 per 



^ A wooden comb is supplied by the manufacturers for the purpose of combing the bands 

 when a coating of dirt, insects, or any other foreign matter collects on the band. This 

 foreign material is mixed in with a clean sticky substance, immediately under the surface 

 of the band, and the band is as efficient as ever. 



