February, '14] XEWELL: ENEMY OF ARGENTINE ANT 147 



doubtful as at present there are a goodly number of people who are 

 opposed to spraying in any form. 



A NATURAL ENEMY OF THE ARGENTINE ANT 

 By WiLMON Newell, College Station, Texas 



The phenomenal abundance of Iridomyrmex humilis in the southern 

 parts of Louisiana and iVIississippi is doubtless explained by the absence 

 of both parasites and predaceous enemies. During the ten 3'ears in 

 which this ant has been under alm.ost constant observation no enemies 

 of importance have been observed until recently. 



During September last Mr. R. S. Moore, an extensive orange 

 grower in the Louisiana citrus-growing section, sent to the writer 

 specim.ens of an ant which he had found very active in raiding the 

 colonies of Iridomyrmex humilis, destroying adults and carrying off 

 the larvae and pupae of the latter. The specimens were thought to be 

 one of the legionary ants, Eciton (Acamatus) schmiiti Emmery, and this 

 was subsequently confirmed by Dr. W. M. Wheeler upon examination 

 of specimens. 



Mr. Moore is, fortunately, a very close observer and is not without 

 considerable reputation locally on account of his intim.ate knowledge 

 of all the common injurious insects of the orange groves. During 

 the past year Mr. Moore has frequently observed the Ecitons in their 

 foraging expeditions and gives a graphic account of the thorough man- 

 ner in which their pillaging colonies destroy practically all the individ- 

 uals of I. humilis in the territory which they raid. In fact, in some 

 of the orange groves which were formerly threatened with complete' 

 destruction on account of the great abundance and activities of humilis, 

 and which have been favored with several \dsits of the Ecitons, hardly 

 a specimen of the former species can now be found. 



The territoryin which the Ecitons have thus been active is upon the 

 west bank of the Mississippi River below New Orleans, where the only 

 arable land is a narrow strip just within the levee. The entire territory 

 is practically surrounded by water, the river being on the east side and 

 a constant succession of swamps and bayous occurring on the west 

 from opposite New Orleans to Barataria Bay on the Gulf of ^Mexico. 

 It seems hardly probable that the migratory Ecitons will be able to 

 leave this area on account of the water barriers. One is, at the same 

 time, forced to the conclusion that the species has been established 

 there for many years past and that it is increasing in numbers on 

 account of the gTeat abundance of the Argentine ant. It is also in- 

 teresting to note that this, the first important enemy of the Argentine 

 ant to be discovered, is a native form operating against an introduced 

 species belonging to the same family as itself. 



