UNITED STATES DEPARTMENT OF AGRICULTURE 
BULLETIN No. 965 
Contribution from the Bureau of Entomology 
L. O. HOWARD, Chief 
Washington, D. C. 
October 18, 1921 
CONTROL OF THE ARGENTINE ANT IN CALIFORNIA CITRUS 
ORCHARDS. 
By R. S. Woglum, Entomologist, and A. D. Borden, Scientific Assistant, Fruit 
Insect Investigations. 1 
CONTENTS. 
Introduction 1 
Relation of the ant to the citrus industry 2 
Other relations 4 
Distribution 4 
Characteristics and habits 6 
Control 9 
3anding 9 
Trap nesting 18 
Poisoned sirups 20 
Page. 
Control — Continued . 
Factors influencing control 34 
Control on marginal trees 37 
Clean culture 38 
Control on house lots or about build- 
ings 40 
Comprehensive demonstration of con- 
trol 41 
Summary 41 
INTRODUCTION. 
Supposedly introduced into the United States at the close of the 
nineteenth century the Argentine ant (Iridomyrmex humilis Mayr) 
has since become widely distributed through the more temperate 
regions, where its complete occupancy, in long-infested localities, 
and its omnivorous habit bear an important relation to crop pro- 
duction and food storage and rank it as one of the most annoying of 
household pests. Its discovery in 1908 in cities bordering San Fran- 
cisco Bay resulted in the initiation of a control campaign under the 
direction of Prof. C. W. Woodworth, of the University of California, 
and subsequently led to the development of an arsenical poisoned 
sirup of considerable merit. 
The Argentine ant was recorded in citrus orchards in California 
almost from the date of its reported presence in the State. It 
appeared to cause no alarm to orchardists, however, usually remained 
unnoticed except about the buildings, and where observed was classed 
1 Photographs by senior writer; figure 3 drawn by Miss A. Hotter. Mr. "VVoglum resigned from the 
Bureau of Entomology September 11, 1920. 
48155°— 21— Bull. 905 1 
