25 



cells were covered with a thin layer of ice, inclosing the ants and 

 their larva; in an icy cell. These ants on being thawed out became 

 active immediately. In two of these nests I found eggs of the corn- 

 root louse, Aphis maid irad ids Forbes. These were in little packets 

 in cells by themselves, not with, the larv?e. In the nest containing 

 the largest number of eggs, the cells containing the eggs of the plant- 

 louse were four and a half inches below the surface. By working 

 carefully with a trowel I was able to get the largest packet of eggs 

 out with very little dirt, and on taking them to the laboratory and 

 counting them I found that 1 had thus separated 894 eggs, and as 

 there were other smaller packets in the nest, there was probably 

 twice that number of aphid eggs in the nest altogether. These eggs 

 had probably been laid by oviparous females which had been carried 

 down into the galleries by the ants. November 10, I found one 

 oviparous female and some eggs in the galleries of a large colony 

 about 5 inches below the surface, although the main galleries of this 

 nest extended downward to a depth of from 12 to 18 inches. In 

 such nests the youngest larv?e were in the deepest portions of the 

 nest, while the larger ones were nearer the surface. 



The fact that larv?e are found in the nests during the winter 

 shows that the length of the larval period is variable, depending upon 

 temperature, and also probably upon other factors, as nourishment, 

 moisture, etc. If a colony containing a large number of larv?e all of 

 about the same size be fed heavily, the workers do not feed the larvae 

 uniformly, but separate a relatively small number from the rest and 

 give them much more nourishment, which causes them to pupate 

 much sooner. Then they separate a few more and feed them in the 

 same wav. The latter may have hatched as early as the former, but 

 their larval period is much longer. 



In one of my colonies some of the larvae remained as such for 

 more than a year. This colony was collected November 6, and con- 

 tained about 300 workers and a large number of larvrc but no queen. 

 I kept them for a while in the greenhouse mentioned above, but 

 about the middle of the winter transferred them to a warm room 

 and fed them heavily. The larvcT began to grow rapidly and on 

 March 2, 25 of them spun cocoons. The next day there were be- 

 tween /^ and 100 cocoons in the nest, and new cocoons were formed 

 every day from that time. It was interesting to see how busy the 

 ants were when so many larvae were spinning cocoons at once. Every 

 larva, when it was ready to spin a cocoon, was covered with fine 

 pieces torn from the sponge, or other debris, in order to give it 

 something to which to attach its first silken threads. As though to 



