156 The Naturalist in La Plata. 



made ; later in the season the old cocoons are 

 utilized for storing honey. The wax is chocolate- 

 coloured, and almost the only difference I can find 

 in the economy of the two species is that the black 

 bee uses a large quantity of wax in plastering the 

 interior of its nest. The egg-cell of the yellow bee 

 always contains from twelve to sixteen eggs ; that 

 of the black bee from ten to fourteen ; and the eggs 

 of this species are the largest though the bee is 

 smallest. At the entrance on the edge of the 

 mound one bee is usually stationed, and, when 

 approached, it hums a shrill challenge, and throws 

 itself into a menacing attitude. The sting is ex- 

 ceedingly painful. 



One summer I was so fortunate as to discover 

 two nests of the two kinds within twelve yards of 

 each other, and I resolved to watch them very 

 carefully, in order to see whether the two species 

 ever came into collision, as sometimes happens with 

 ants of different species living close together. 

 Several times I saw a yellow bee leave its own nest 

 and hover round or settle on the neighbouring one, 

 upon which the sentinel black bee would attack and 

 drive it off. One day, while watching, I was de- 

 lighted to see a yellow bee actually enter its neigh- 

 bour's nest, the sentinel being off duty. In about 

 five minutes' time it came out again and flew away 

 unmolested. I concluded from this that humble- 

 bees, like their relations of the hive, occasionally 

 plunder each other's sweets. On another occasion 

 I found a black bee dead at the entrance of the 

 yellow bees' nest ; doubtless this individual had 

 been caught in the act of stealing honey, and, after 



