62 THE AEGENTINE ANT. 



An account of the methods used by the Argentme ants in over- 

 conimg other species of ants was published by the senior author ^ 

 in the Journal of Economic Entomology. 



Prof. W. M. Wheeler, in Entomological News for January, 1906, 

 gives an interesting account of the way in which this species obtained 

 a foothold in Madeira and supplanted another introduced species, 

 Pheidole megacephala Fabr. 



COCCID^ AND APHIDIDiE. 



The liquid excretions of the various species of scale insects and 

 aphides form one of the chief sources of food for the Argentine ant. 

 The large variety of trees and plants in the South gives support to a 

 great number of coccids and plant lice, and these insects in turn 

 yield sustenance to myriads of ants. In return for this food sui)ply 

 the ants shelter and protect these insects, with the result that the 

 latter increase beyond all customary i)rop()rtions. As the result of 

 this symbiotic manner of living we find that a comparatively small 

 area of land frequently supports enormous numbers of ants, scale 

 insects, and aphides, while the plants themselves become so severely 

 infested that some of them are killed and many more seriously 

 injured. 



All through the summer months, and also during warm days in 

 winter, heavy streams of ants can be seen ascending and descending 

 the trees and plants; the ascending ants empty, the descending ones 

 heavily laden with the liquid excretion which they have obtained 

 from the various scale insects and plant lice. Durmg the summer 

 this activity is well-nigh endless, and the ant trails can be observed 

 at all hours of the day and night. All scales and aphides are closely 

 attended, but some species a]ipear to attract more of the ants than 

 do others. The large unannored scales and the plant lice api)ear to 

 be the chief favorites, the mealy-bugs, however, following them very 

 closely in this regard. 



Aside from protecting the aphides and scale insects from ladybird 

 beetles and constructing earthen shelters over them, the ants only 

 rarely foster them directly. In one case only have insects of this 

 character been actually found in the ants' nests. In January, 1909, 

 Mr. G. D. Smith, in excavating an underground colony at Baton 

 Rouge, found a luimber of liarnacle scales, droplastes cirTi-pedlformis 

 Comst., on tree roots which passed through the formicary. These 

 scale insects were full grown and vigorous. At this season of the 

 year no live scales of this species could be found above ground. It 

 may be remarked in ])assing that this is one of the species to which 

 the ants are very attentive during the summer and autumn months. 



1 Notes on the Habits of the Argentine or "New Orleans" Ant, Iridomyrmex humilis Mayr. Wilmon 

 Newell, Journ. Kcon. Ent., vol. 1, no. 1, pp. 21-34, 1908. 



