2 BULLETIX 965, U. S. DEPARTMENT OF AGKICr/LTTJBE. 
merely as "•an ant" whose presence was believed in no way detri- 
mental to the trees. The role of the Argentine ant as an orchard 
pest in California was discovered by Mr. J. D. Xeuls and the senior 
writer in 1915 while conducting an investigation of the common 
mealybug, and its very direct bearing on the control of the mealybug 
was conclusively proved by an extended series of experiments. This 
immediately led to an investigation into methods of ant control with 
which the junior writer became associated in 1917. The great success 
which attended these experimental efforts led to control demonstra- 
tions of considerable proportions in severely ant-infested communi- 
ties and proved a stimulus to widespread interest in the pest. The 
demand for relief which followed this awakened interest has already 
resulted in the treatment of several thousand acres, from a very large 
part of which the ants have been totally eradicated. This bulletin 
presents the results of the various remedial methods pursued during 
the period 1915-1920 and gives full instructions for the control and 
eradication of ants in the citrus orchards of California. 
RELATION OF THE ANT TO THE CITRUS INDUSTRY. 
The spread of the Argentine ant in California bears an important 
relation to citrus growing, a relation certain to become more promi- 
nent with wider distribution and lonsf-established infestations. The 
very severe damage which this pest can sometimes do in citrus 
orchards has been impressively stated by Xeweil and Barber 2 as 
follows: The bearing qualities of an orchard are severely impaired 
by the second season of infestation, the crop is almost entirely lost 
by the third season, and the trees are dying by the fourth year of 
infestation. This conclusion is based on conditions in Louisiana, 
and in this respect it should be noted that no systematic effort is 
made in that State to control citrus scale pests. Such extreme 
damage has never been observed under California orchard conditions 
where fumigation and other insecticidal control measures are prac- 
ticed constantly. 
The damage to trees in ant-infested orchards in California does not 
arise from direct attacks on the blossoms, fruits, and roots, as has 
been reported from some regions, but is attributable very largely 
to its so-called symbiotic manner of living with mealybugs, aphids, 
and various scales, which results in their increase beyond all custom- 
ary proportions. The constant attendance of the ant protects the 
mealybugs or scales from then natural enemies and results in their 
abnormal increase. (.See fig. 1.) The degree of infestation is 
further stimulated and extended through the fact that the ant 
distributes these injurious insects to other parts of the tree or even 
3 Newell, Wilmon, and Baebee, T. C. the abgexten'e axt. U. S. Dept. Agr., Bur. Ent. Bui. 
122, p. 192. 1913. 
