2 BULLETIN 611, U. S. DEPARTMENT OF AGRICULTURE. 



The Argentine ant has been the subject of special study by this 

 bureau for several years, more particularly as to its activity as a 

 house pest, but also as to its general economy in relation to garden, 

 orchard, and field cultures. The facts secured in the investigations I 

 prior to 1913 indicated a very important injurious relationship of 

 this ant to citrus culture in Louisiana. As a result of this apparent 

 condition and in response to numerous complaints of injury to citrus 

 trees occasioned directly and indirectly by this ant, a special in- 

 vestigation was instituted in 1913 under the supervision of Mr. C. L. 

 Marlatt, Assistant Chief of the Bureau of Entomology, to deter- 

 mine the exact economic importance of the ant as a citrus pest and 

 to devise effective means of preventing damage in citrus orchards. 



GENERAL BELIEF AS TO DAMAGE TO ORANGE TREES. 



It has been recognized generally that a few species of ants may 

 injure orchard and other crops either directly, by feeding on plant 

 parts, or indirectly, through their symbiotic relations with scale 

 insects and aphids. 



The important features of the activities of ants toward certain 

 scales and aphids, viz., soliciting " honeydew " excretion from them, 

 carrying them about, constructing shelters over them, and combating 

 their enemies, were pointed out more than a century ago by Pierre 

 Huber, 2 some of whose observations were made upon orange-infesting 

 species. Huber, however, makes no mention of injury caused to 

 orange trees by these habits. 



Direct injury by ants, so severe as to cause the death of the trees 

 in orange, cacao, coffee, and cotton plantations in the West Indies, 

 is cited by the French historian Robin, 3 contemporaneous with 

 Huber. Robin probably referred to leaf-cutting ants, Atta spp., 

 several species of which destroy trees in tropical America by de- 

 foliation. 



Although the habits of ants in relation to plants and plant pests 

 have been studied by many observers since these early writers, ex-^ 

 treme views as to damage to orchard trees by ants, especially through 

 the fostering of insect pests, have developed only since the Argentine 

 ant became established thoroughly in southern Louisiana. This ant 

 made the greatest impression upon people by its unusual abundance 

 and aggressiveness, and became the subject of study by many laymen 

 as well as entomologists. Interest in ants, especially as orchard 



1 Titus, B. G. Report on the " New Orleans " Ant. U. S. Dept. Agr. Bur. Ent. Bui. 52. 

 1904. 



Newell, Wilmon, and Barber, T. C. The Argentine Ant. U. S. Dept. Agr. Bur. Ent. 

 Bui. 122, 1913. 



2 Huber, Jean Pierre. Recherches sur les Moeurs des Fourmis Indigenes. Paris, 1810. 



3 Robin, Cflaude] C. Voyages dans l'lnterieur de la Louisiane . . . 1802—1807, Tome I, 

 p. 215. Paris, 1807. 



