THE ARGENTINE ANT IN RELATION TO CITRUS GROVES. 35 



very scatteringly and, as a rule, was parasitized or had been de- 

 stroyed by its natural enemies. This was true in orchards overrun 

 by ants and in orchards free from ants, indicating, at least, that 

 so far in southern California the helpful influence of the ant, if any, 

 in relation to this scale insect has not overcome the effective control 

 of the scale by its natural enemies. 



Aside from the well-known effectiveness of the Australian lady- 

 beetle (Novius cardinalis Muls.), this control seems to be due, in 

 Los Angeles County, chiefly to the parasitic fly Cryptochaetum mono- 

 fhlebi Skuse, aided, however, by hymenopterous parasites and the 

 larva? of lacewing flies. 



INFLUENCE OF THE ANT ON ABUNDANCE OF THE BLACK SCALE IN LOUISIANA. 



As already stated, the black scale {Saissetia oleae Bern.) does not 

 yet occur in the orange groves proper of Louisiana, and, Mierefore, 

 as with the fluted scale, no extensive tree-banding experiments could 

 be conducted in this State during the seasons 1913 to 1915 to deter- 

 mine the effect of ant attendance on its abundance. 



The black scale occurred in moderate numbers on oleander in 

 New Orleans, and from these trees was transferred and colonized 

 on young orange trees and an experiment of this nature attempted. 

 The progeny of the colonized scales made an equally good start on 

 both ant-free and ant-invaded orange trees. Nevertheless, the scales 

 failed to reach maturity in a single instance, even where constantly 

 attended by ants, and although they decreased a trifle more slowly 

 where attended than where not attended by ants, all scales had dis- 

 appeared from both banded and nonbanded trees within six weeks 

 from the starting of the experiment. 



INFLUENCE OF THE ANT ON ABUNDANCE OF THE BLACK SCALE IN CALIFOKNIA. 



The black scale has been rated as the most economically important 

 of the citrus scales in California, 1 where it is generally controlled by 

 fumigation. The observations on the relation of the ant to this scale 

 were made in orchards in which fumigation had been temporarily 

 neglected. In an experiment in which five scale-infested orange trees 

 were banded to exclude ants in April, and a similar five left accessible 

 to them, the amount of scale infestation remained practically equal 

 on both sets of trees throughout the summer, from April to 

 September. 



In other words, after excluding the ants from five of these trees 

 for a period of nearly five months but little difference in the amount 

 of black-scale infestation or in quantity of sooty mold could be de- 

 tected between them and five similar trees very heavily invaded by 



1 Quayle, H. J., op. cit., p. 445. 



