UNITED STATES DEPARTMENT OF AGRICULTURE 



Washington, D. C. 



BULLETIN No. 647 



Contribution front the Bureau of Entomology 

 L. O. HOWARD, Chief 



May 3, 1918 



THE ARGENTINE ANT 1 IN RELATION TO CITRUS 



GROVES. 



By J. R. Horton, Scientific Assistant, Tropical and Subtropical Fruit Insect 



Investigations' 



CONTENTS. 



Introduction 1 



General belief as to damage to orange trees... 2 

 General account of orange culture in 



Louisiana 4 



Distribution of the ant in the orange groves 



of the United States 7 



Feeding habits of the ant 8 



Relations with insects injurious to citrus trees 15 

 Relations with insect enemies of scales and 



aphids 48 



Nests and protective structures of the Argen- 

 tine ant 52 



Cultural conditions in ant-invaded vs. ant- 

 free orange groves in Louisiana 56 



Demonstration in improvement of ant- 

 invaded groves in Louisiana 57 



Experiments in controlling the Argentine ant 60 



Summary and conclusions 71 



INTRODUCTION. 



The Argentine ant {Iridomyrmex humilis Mayr) is a native of 

 tropical America, occurring in Argentina, Brazil, Chile, and Uru- 

 guay. It was first introduced into the United States at New Orleans 

 about 30 years ago and was fairly numerous in parts of that city as 

 early as 1891. 3 A few years later it had become established thor- 

 oughly in and around New Orleans and was causing great annoyance 

 as a household, garden, and field pest. Early it was carried to Cali- 

 fornia, where it has become established widely. It is especially 

 numerous in parts of the citrus districts of Los Angeles and River- 

 side Counties and in the city of Los Angeles and occurs as far north 

 as San Francisco and as far south as San Diego. 



1 For a discussion of other phases of the Argentine ant problem see Department of 

 Agriculture Bulletin No. 377, by E. R. Barber, entitled " The Argentine Ant : Distribution 

 and Control in the United States." 



2 Transferred to Cereal and Forage Insect Investigations, Oct. 1, 1917. 



•Foster, Ed. The introduction of Iridomyrmex humilis into New Orleans. In Jour. 

 Econ. Ent., v. 1, p. 289-293. 1908. 



Note. — This bulletin Is of especial Interest to citrus growers in the southeastern States 

 id generally to the public in that section. 

 27139°— 18— Bull. 647 1 



