BUREAU OF ENTOMOLOGY. 629 



WORK ON THE ABGENTINE ANT. 



The main line of work undertaken on the Argentine ant was a 

 large-scale test of a method of extermination which appears to have 

 been followed successfully in California. The method in brief is 

 to expose jars containing a very dilute mixture of sodium arsenite 

 with sugar so that the ants will visit them and be poisoned. In the 

 work in California the mere placing of receptacles containing this 

 preparation appears to have resulted in the extermination of the 

 ants. At Hattiesburg, Miss., this method was tested on a series of 

 colonies of the ant which infested about five city blocks. Several 

 hundred jars containing the poison mixture were exposed during the 

 fall of 1911, under a cooperative agreement with the city authorities. 

 This method shows its effects slowly and it will be necessary to prose- 

 cute the work through another season to determine whether it is an 

 effective method of combating the ants. Another line of work was 

 directed against the ants in orange groves, where they have been the 

 indirect cause of the loss of many trees. The system of traps described 

 in the preceding annual report was tested on a considerable scale and 

 its practicability within certain limits was demonstrated. Other 

 work relating to the Argentine ant consisted of the determination of 

 the spread, experiments with a large number of poisons that had not 

 hitherto been tried, and the relation between the ant and other insects. 

 In connection with the last study it was determined that the ant 

 protects the sugar-cane mealy bug and thereby becomes of im- 

 portance in connection with cane culture. In the orange groves it 

 Protects the plant lice feeding upon the trees and at the same time 

 rives away the enemies of the plant lice and of other insects destruc- 

 tive to the trees. In addition to the weakening and death of many of 

 the orange trees in the manner described it was found that the ant 

 indirectly causes the trees to be more susceptible to frost. In a num- 

 ber of cases where observations were made on trees to which the ants 

 had access and where, consequently, the enemies of the trees were 

 protected, considerable loss from freezing occurred during the winter, 

 while trees from which the ants had been excluded were not affected. 

 Substantial progress was made in the control of the ant in orange 

 groves by the use of special sticky mixtures applied with brushes to 

 the trunks of the trees. 



BED SPIDER ON COTTON. 



The work on the red spider on cotton was conducted at Batesburg, 

 S. C, although the agent engaged in this work made a surve^y at the 

 ond of the season to determine the extent of red-spider injury in other 

 States. At Batesburg the principal efforts were directed toward 

 practical demonstration of economical means of control. Success was 

 attained by several methods. Previous findings in regard to the im- 

 portance of cultivated violets in carrying the spiders through the 

 winter were verified. Where the pests were destroyed on the violets 

 in dooryards it was found that such infestations of adjoining cotton 

 fields as had been of regular annual occurrence were prevented. In 

 another experiment the wild plants which support the cotton red 



