254 



TIJK MONTHLY BUMxETIN. 



THE ARGENTINE ANT AS AN ORCHARD PEST. 



By Harry S. Smith. 



"The Argentine ant (Iridomyrmex humilis Mayr) * * * is the first 

 among the FormicicUe to attain the front rank among injurious insects of 

 the United States. In its field, the Argentine ant is not excelled in 

 destruetiveness by even the gipsy moth, the boll weevil or the San Jose 

 scale. Though this ant is limited as yet to comparatively small areas, 

 the observations and experiments of the authors fully convinced them 

 that future years will see this insect steadily invading new territory and 

 forcing its depredations upon the inhabitants of all southern California 

 and most of the Gulf states." 



At the time the above paragraph was written (1912) by Newel] and 

 Barber, of the United States Department of Agriculture, the Argentine 

 ant was considered primarily a municipal pest, although even at that 



Fig. 69. — Worker of the Argentine ant, Iridomyrmex humilis, and detail of a mandible, 

 showing the arrangement of the teeth. Greatly enlarged. (After Essig, Inj. and 

 Ben. Insects of Cal. ) 



time its potentiality as an indirect pest of orchards was realized by the 

 authors. It is only recently, however, that the "rowers themselves have 

 come to appreciate the possibilities of this insect for damage to the fruit 

 industry, mainly through its influence on infestations of mealybugs, 

 black and soft brown scales. 



The Argentine ant is, as its name indicates, a native of Argentina 

 and is also common in Brazil. It was supposedly introduced on coffee 

 ships into New Orleans, and was first noticed there in 1891. It also 

 occurs in South Africa and Chile. In the United States at the present 

 time it is found in a number of the Gulf states, as well as in California. 

 Professor Woodworth gives its occurrence in this state as follows: 

 Alameda, Azusa, Berkeley, Byron Hot Springs, Campbell, Claremont, 

 College Park, Corona. Cupertino, Emeryville, Fruitvale, Los Angeles, 

 Martinez, Melrose, Monrovia, Montecito, Oakland, Piedmont, Riverside, 

 San Francisco, San Jose, Santa Clara, San Mateo, Stege, Stockton and 

 Upland. During the past season we found it in several places in 

 Sacramento. 



