Feb. '08] JOURNAL OF ECONOMIC ENTOMOLOGY 33 



species obtained a foothold in Madeira and supplanted another intro- 

 duced species, Pheidole megacephala Fabr. 



In New Orleans where /. humilis is thoroughly established every- 

 where, it is rare indeed to find any other species. Titus in recount- 

 ing his observations in 1904 said, "they have driven or kiUed out all 

 other ants in the regions infested by them." The extermination of 

 other species in the city of New Orleans has not been complete, but 

 very nearly so. At Baton Rouge and other points which are now 

 becoming quite heavily infested, the displacement of the native ants 

 is easily observed. As examples I may cite two or three cases which 

 have come under my observation. One day in August I noticed a 

 small colony of I. humilis constructing a nest but a few inches dis- 

 tant from a colony of their near relatives, Iridomyrmex analis.^ It 

 was not long until the foraging workers from the humilis colony dis- 

 covered their neighbors and whenever workers from the two colonies 

 met a fierce battle ensued, usually ending in the analis worker being 

 severely bitten and left to die. Five hours after these preliminary 

 * * skirmishes ' ' were noticed I returned to the nest, to find humilis fully 

 in possession and none of the former occupants of the nest anywhere 

 in sight. The nest was dug up, but no trace of analis was found in it. 



In September I witnessed an interesting attack by the humilis 

 workers upon a fairly strong colony of Solenopsis geminata. The 

 latter species is famed for its vindictiveness and for the effectiveness 

 with which it uses its sting. In this case the victory was by no means 

 an easy one for the Argentine ants, for the small (minor) workers of 

 geminata were, one with another, as good fighters as the former. 

 Both species made the petiole of the abdomen the objective point of 

 attack, gripping it firmly between the jaws. About as many of the 

 humilis workers were killed in these encounters as of the other species. 



In attacking the larger (major) workers of geminata the humilis 

 workers adopted somewhat different tactics. The geminata majors 

 were several times larger than their antagonists and while far less 

 active, quickly destroyed any humilis so unfortunate as to get between 

 their mandibles. The Argentine ants therefore attacked them by 

 rushing up and biting a leg or antenna and immediately retreating, 

 sometimes as many as ten of the Argentines being thus engaged in 

 the attack upon one of these major workers. Eventually the battle 

 was won by I. humilis, purely by having innumerable reinforcements, 

 and in about twenty hours had possession of the fortress they had 

 stormed so long and faithfully. 



The next morning in looking over the battleground I found many 

 of the geminata major workers still alive but divested of all their legs. 



^Determined by Dr. W. E. Hinds. 



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