1903.] NATURAL SCJEN'CES OF PHILADELPHIA. 617 



EXPEKIMENTS WITH ANTS INDUCED TO SWIM. 



BY ADELE M. FIELDE. 



The behavior of ants often appears to originate in mental processes/ 

 and the myrmecologist is ])erpetually lured to further experiment by 

 a tantalizing expectation of ascertaining whether the cause of their 

 action be psychic. 



One afternoon in the summer of 1901 I inadvertently left, upon 

 the base of a Lubbock nest in the laboratory, a score or two of ants, 

 Stenamma fulvum, with a few of their larvae and a little damp earth. 

 Before the next noonday they had built with particles of the earth 

 what looked like a roundish hut, not more than two centimeters long, 

 with a doorway and a smoke-hole. Its outside shape was like that 

 of the interior of one of their recesses in their wild nests. They had 

 carried their larvae into it, and had thereby screened them from light 

 and from the wind. The air of the room was dry, and after a few 

 hours the edifice disintegrated from the evaporation of its moisture. 



These ants live under loose stones and among the roots of grasses, 

 an(| do not build habitations on a surface. In opening scores of their 

 nests, I have never found any similar structure. The little hut seemed 

 to be evidence of a purposeful adjustment to new conditions. 



' In August, 1903, I left upon the bottom of a dish, surrounded b}^ water in 

 a larger dish, about seventy Lasius latipes workers, with fifty of their tiny co- 

 coons, in two centimeters of earth, covered by a pane of orange glass ten centi- 

 meters long and eight centimeters broad. Such glass excludes, partial!}^ but 

 not wholly, the ultra-violet light-rays always avoided by the ants. The earth 

 extended about four centimeters beyond the glass. There was a morsel of 

 food on the glass. 



The ants had been undisturbed and unobserved for ten days, when I saw that 

 they had nearly covered their roof-glass to the depth of about two millimeters 

 with particles of earth. ]\Iany of the particles were half as long as the longest 

 of the ants, and certainly heavier than any one of them, and could not have been 

 laid on the glass without considerable effort on the part of the ants. This over- 

 laying of the glass secured darkness for the workers and the young under the 

 glass; and numerous runs with exits outside the edge of the glass had been made 

 •in the earth below, as is done in their wild nests under stones. 



Thinking that the presence of the food on the glass might have influenced the 

 deposit of the particles of earth, I removed the food to the end of the dish, washed 

 the glass clean and replaced it. In a few days the ants had again covered the 

 glass with like particles of earth. The work was always carried on in the night, 

 and I did not witness its performance. 



I made a similar arrangement of dishes, earth and glass for Stenamma fulvum, 

 but these ants did not overlay their semi-transparent roof. 



