36 BULLETIN 647, U. S. DEPARTMENT OF AGRICULTURE. 



ants during the entire period. What difference existed was unfavor- 

 able to the view that the ants cause greater increase of the black 

 scales. None of the trees had been fumigated since 1914. 



In another experiment two more black-scale infested trees were 

 banded against ants in June and two similar trees left accessible to 

 them. These trees had not been fumigated for three years. As in 

 the case of the first experiment, the amount of black-scale infestation 

 remained practically equal on both banded and nonbanded trees ' 

 throughout the remainder of the season. 



Sometimes there is a greater amount of black-scale infestation on 

 trees where there are no ants than on other trees of the same age and 

 condition overrun by ants. Thus, in a block of orange trees not fumi- 

 gated for two years more than half the fruit on a number of the 

 trees on which there were no ants was scaly, while on a number of 

 trees overrun by ants less than one-fourth of it was scaly. In this 

 case the greatest scale infestation occurred on trees located next to 

 older and heavily infested ones from which the scales had come by the 

 usual means of dissemination, but there was no indication that the 

 ants caused an increase of the scales on the trees on which they 

 occurred. 



In various orchards in Los Angeles and Ventura Counties, in which 

 there were no ants and in which fumigation had been neglected for 

 from two to four years, the black-scale infestation was quite as 

 severe as is ever seen where the ants are present. In fact, in order to 

 keep the black scale from reaching injurious numbers it has been found 

 necessary every year to fumigate some orchards in which there were no 

 Argentine ants and very few of other kinds. Sometimes a second 

 fumigation is needed in the same season because of rapid reinfesta- 

 tion bjr what is called an offhatch, or an extra generation of scales, 

 caused by their more rapid development on especially suitable trees. 



It is evident, therefore, that the black scale in southern California 

 is capable of reaching a very injurious degree of infestation in a; 

 single season, regardless of whether ants are present or not. Its 

 natural enemies are not sufficiently numerous to prevent severe in- i 

 festation, even though there is no interference from ants. The effect 

 of the ant in accelerating the increase of this scale is therefore of 

 little practical importance and does not compare with its importance 

 as affecting the mealybugs. 



INFLUENCE OF THE ANT ON ABUNDANCE OF THE SOFT BROWN SCALE IN LOUISIANA. 



As was the case with the black scale, it was impossible to find a 

 sufficient number of orange trees in Louisiana heavily infested with 

 the soft brown scale {Coccus hesperidum L.) to conduct extensive 



