6 FARMERS” BULLETIN 740. 
INTRODUCED TROPICAL NEW-WORLD ANTS. 
Of the ants introduced into North America from the New-World 
Tropics the one of greatest economic importance is what has now 
come to be generally known as the Argentine ant (fig. 4)1 from its 
supposed Argentine origin. It is known, however, to be a serious 
pest in Brazil and Uruguay, as well as in Argentina. It is some- 
times also called the New Orleans ant, from the fact that it gained 
its first foothold from colonies brought in, presumably from Brazil, 
Fic. 4.—The Argentine ant (Jridomyrmer humilis). 1, Wingless female. 2, Worker. 
2 
3, Immature stages: a, Eggs; b, young larva; ¢, full-grown larva; d, pupa, side view; 
e, pupa, ventral view; f, pupa, dorsal view. 4, Male. .All enlarged to the same scale, 
(Original.) 
by some ships’ cargoes to the port of New Orleans. It is a much 
worse house pest than even the little red ant or any of the other 
house ants and is in addition a very serious enemy of field and 
garden crops and orchard trees. Ithasrapidly spread from the point 
of introduction throughout Louisiana and has been carried by traffic 
to California, where it has become a serious pest in citrus orchards 
in the southern part of the State, and in houses as far north as San 
Francisco. It is undoubtedly destined to extend its outdoor range 
1Jridomyrmer humilis Mayr. 
