HYMENOPTERA. 669 



to place their cells. We have found these cells in a crack- 

 between shingles on a roof, in the cavity of a large branch 

 of sumach, beneath stones lying on the ground, and in 

 Florida in the tubular leaves of a pitcher-plant. 



Some species of bees make nests similar to those of the 

 leaf-cutter bees, except that the cells are formed of pieces of 

 petals of flowers. The petals of Pelargonium are often used 

 for this purpose. 



The small Carpenter-bee, Ceratina dupla (Ce-rat'i-na 

 du'pla). The nests of this bee are built in dead twigs of 

 sumach and in the hollows of brambles and other plants. 

 They are more common than those of any other of our 

 solitary bees that build in these situations. This is a dainty 

 little bee, about a quarter of an inch long, and of a metallic 

 blue color. She always selects a twig with a soft pith 

 which she excavates with her mandibles, and so makes a 

 long tunnel. Then she gathers pollen and puts it in the 

 bottom of the nest, lays an egg on it, and then makes a par- 

 tition out of pith-chips, which serves as a roof to this cell 

 and a floor to the one above it. This process she repeats 

 until the tunnel is nearly full, then she rests in the space 

 above the last cell, and waits for her children to grow up. 

 The lower one hatches first; and, after it has attained its 

 growth, it tears down the partition above it, and then waits 

 patiently for the one above to do the same. Finally, after 

 the last one in the top cell has matured, the mother leads 

 forth her full-fledged family in a flight into the sunshine. 

 This is the only case known to the writer where a solitary 

 bee watches her nest till her young mature. After the last 

 of the brood has emerged from its cell, the substance of 

 which the partitions were made, and which has been forced 

 to the bottom of the nest by the young bees when making 

 their escape, is cleaned out by the family, the old bee and 

 the young ones all working together. Then the nest is used 

 again by one of the bees. We have collected hundreds of 

 these nests, and, by opening different nests at different sea- 



