458 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



only 5 reacted more than half the time. On the whole, this resembles 

 the results obtained in regard to foraging. 



Figure 13 (p. 454), constructed as described on pages 455 and 456, 

 seems to show that there is a somewhat greater activity on the part of 

 the smaller individuals. So far as these observations go, this might 

 be considered, as in certain aspects of foraging (pp. 453-455), to be 

 due to a great alertness of some individuals in more than one activity, 

 which certainly exists, and will be discussed later (pp. 462-463) ; but in 

 corroboration of field experiments on C. pictus (pp. 468-469), it also 

 seems to me to point clearly to a greater activity on the part of the 

 smallest ants of C. americanus in tending the young. 



Figure 15. 



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Figure 16. 



It is somewhat peculiar that both deJilated and even winged queens, 

 as well as workers, took part in this activity. 



3. Building. 



1. Methods. — (a) Horizontal nest. Two kinds of nest were used in 

 investigating this part of the problem. The first was a Fielde nest, 

 such as was used in previously described experiments. In one cham- 

 ber, kept dark except during observations, was placed damp earth, 

 collected with the ants, so as to be of an appropriate sort. The nest 

 was nearly filled with the earth, only enough room being left to enable 

 the ants to walk comfortably between the earth and the roof. The 

 other chamber was exposed to daylight and contained the food. I call 

 this the horizontal nest. 



