64 THE ARGENTINE ANT. 



in great numbers on sugar cane, Johnson grass, willows, and oaks, 

 and, in fact, in all places where a number of coccids or plant lice are 

 exposed to the weather. 



The stimulation resultmg from the attentions of the ants while 

 collectmg the sweet liquids appears to have the effect of greatly 

 encouraging the numerical increase of the aphidids and coccids. 

 Durmg the summer of 1910 the junior author reared several genera- 

 tions of sugar-cane mealy-bugs on sugar cane planted m large pots. 

 One-half of these pots were isolated from the Argentine ants, whUe 

 to the others they were allowed free access. The mealy-bugs grew 

 and multiplied m both lots of cane, but there w^as great difference 

 between the thriftmess of the isolated and nonisolated msects. In the 

 pots to which the ants had access the mealy-bugs multiplied so freely 

 that finally they almost smothered out the sugar cane with their 

 cottony egg masses. In the isolated pots, w^hile the mealj-bugs 

 increased m numbers, they were not nearly so numerous or healthy 

 looldng as m the ant-infested pots. At the end of two months the 

 number of mealy-bugs m the ant-mfested pots probably exceeded 

 the luimber of mealy-bugs m the isolated pots to the extent of at 

 least five to one. 



That the same conditions exist in the cane fields is showai by the 

 number of mealy-bugs which can be found ui the fields infested by 

 the Argentine ant as compared to their scarcity m fields not infested 

 by the ant. Only one field under the latter conditions has been dis- 

 covered as yet, but it has been watched closely for two years. The 

 mealy-bugs have never become sufficiently numerous to attract the 

 attention of the workhig hands, and they can be found only with 

 considerable difficulty. On the other hand, m the fields where the 

 mealy-bugs and ants are associated the former have become so 

 numerous that the white cottony egg masses can be easUy observed 

 from the road w^hile drivhig through the fields. 



The same thing holds true with scale msects generally. In the 

 orange groves invasion by the ants is foUow^ed by a rapid increase of 

 scale insects, particularly the chafi' scale (Parlatoria pergandii Comst.) 

 and various species of Lecanium. So rapidly do these scales increase 

 that, unless promi)t measures arc taken against the ants, the second 

 year of infestation shows a severe curtailment of the crop, and the 

 fourth or fifth year witnesses the death of many of the trees. The 

 rapid dechne t)f orange trees under conditions of heavy ant mfestation 

 is w^'ll illustrated by Plate VI, which shows a tree after exposure to 

 attacks of the ants and chaff scales for three seasons. 



The ants constantly attend the citrus white fly (Aleyrodes citri 

 R. & II.), and a marked increase in this injurious pest always accom- 

 panies ant infestation. 



