52 THE ARGENTINE ANT. 



"When the temperatiiie falls as low as 60° F. tlie ants become 

 sluggish, and foraging is largely suspended. At from 50° to 55° F. 

 there is practically no foraging, and when this temperature is reached 

 within the nest all adult ants become inactive, moving only occasion- 

 ally, and even then with apparent difficulty. Activity is not strictly 

 limited by these temperatures, however. On one occasion we found 

 workers foraging in a building the ulterior of which was at 43° F., 

 but the colony itself was outside the building and at a higher tem- 

 perature. Very few refrigerators are cold enough to keep out these 

 invaders when the outside temperature is warm enough for them to 

 forage normally. On the very hottest days of siunmer they will 

 enter refrigerators and even crawl into the ice chamber itself in order 

 to reach some much-desired delicacy. 



The most ideal location for the large winter colonies is in piles of 

 decomposing vegetable matter. This material gives off a large quan- 

 tity of heat during the process of rotting and consequently furnishes 

 the ants with automatically heated apartments. In the same manner 

 in which the ants seek optimum humidity conditions during the 

 summer months, so they will regulate their location to preserve an 

 even temperature in their nests in the winter. In cold weather they 

 will carry the young stages toward the center of the piles, while in 

 warmer weather they will be found near the surface. 



Of course all the ants are not able to find ideal locations for the 

 winter months, and great numbers have to locate themselves as well 

 as they can. In open fields great numbers will be found under large 

 ridges, or along ditch banks, particularly those which have a southern 

 exposure. Many will burrow into the ground at the bases of large 

 trees, where their tunnels and galleries will sometimes attain a depth 

 of 12 to 14 inches. 



Under Louisiana conditions the winter colonies are in evidence 

 during the months of December, January, and February. The segre- 

 gating tendency becomes marked durmg November, and the "divis- 

 ional migration" normally occurs in February, but may not take 

 place until March if the spring is cold and wet. 



SUMMER COLONIES. 



As soon as the weather gets warmer in the spring and food becomes 

 abundant the large winter colonics break up into a great number of 

 smaller colonies. These usually consist of one or more queens and a 

 considerable number of workers, and they establish themselves in 

 any good location where a supply of food is available. In places 

 where food is exceptionally abundant these summer colonies will still 

 remain very strong in numbers. Under large magnolia or oak trees, 

 for example, colonies with 10 or 20 queens and many thousand 

 workers are nearly always present. 



