HYMENOPTERA 



377 



species of the genus Andrena; some of these nearly or quite equal in size 

 the workers of the honey-bee. They build their nests in road sides and in 

 fields that support a scanty vegetation. They sink a vertical shaft with 

 broad cells branching from it. These bees, though strictly solitary, each 

 female building her own nest, frequently build their nests near together 

 forming large villages. We once received from a correspondent a descrip- 

 tion of a collection of nests of this kind which was fifteen feet in diameter, 

 and in the destruction of which about two thousand bees were killed; 

 what a terrible slaughter of innocent creatures! 



The small carpenter-bee, Ceratina dupla. — The nests of this bee are 

 built in dead twigs or sumac 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 \ of 

 an inch in length, 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 nectar and puts it in 

 the bottom of the nest, lays an egg on it, and then makes a partition 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 young 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 in the sunshine. 

 After the last of the brood has emerged from its cell, the sub- 

 stance 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 (Fig. 628) is used again by one of the bees. 



The large carpenter-bee, Xylocopa mrgmica. — This is a 

 large insect, measuring from about an inch in length and re- 

 sembling a bumblebee in size, and somewhat in appearance. 

 But it can be easily distinguished from a bumblebee, as the 

 female has a dense brush of hairs on the hind leg, instead of 

 a basket for carrying pollen. This bee builds its nest in 

 solid wood, and sometimes excavates a tunnel a foot in 

 length, which it divides into several cells. The partitions 

 between the cells are made of chips of wood, securely ce- 

 mented together, and arranged in a closely wound spiral. This 

 arrangement of chips is easily seen when the lower side of 

 a partition is examined ; but the upper side of a partition which 

 forms the floor of the cell above it is made concave and very smooth, so 

 that the arrangement of the chips is not visible. 



Family Megachilid^; 



The Leaf-cidter Bees and their Allies 



To this family belong those bees in which the pollen brush of the 

 female is borne on the ventral side of the abdomen and the parasitic 



