CREATION BY EVOLUTION 



is formed from a slime that gradually hardens. In this 

 group, as in many others, the male is considerably smaller 

 than the female. 



Still higher up in the scale of progress we find a solitary 

 bee, which also burrows into the ground — in gravel paths or 

 among grass — and also stores its cells with honey and pollen. 

 Although these bees are in a sense solitary they live in col- 

 onies that consist of large numbers; a colony may comprise a 



thousand cells. The sexes differ very 

 much in appearance and are not 

 often found together. The bees of 

 this group are of economic value, for 

 they aid in the fertilization of fruit 

 trees. The bees of one particular 

 branch of this group construct for a 

 number of families a common gal- 

 lery, which ramifies about in the soil, 

 and these bees thus perform a certain 

 collective or social work (Fig. 12). 

 But the task of constructing each cell 

 and of providing food for the larvae 

 is the work of one family and not 

 the collective work of many bees. 

 . Another group of bees falls under the common name of 

 leaf-cutting bees (Fig. 13) . This bee is more robust than the 

 ordinary hive bee and has a broader head. It makes nests 

 in hollows in stems, in wood, or in the soil. The cell is made 

 of leaves or of parts of leaves or petals of roses and other 

 plants, which are moulded into a thimble-like form that has 

 a lid composed of a smaller round piece of leaf. The cells 

 are placed end to end and not side by side, and the pieces of 

 leaves are gummed together. The string of cells thus made 

 rarely exceeds seven. When completed each cell is half 



[196] 



Fig. 12. — A series of 

 end to end cells that 

 have a common open- 

 ing, indicated by the 

 arrow. After the eggs 

 are deposited the open- 

 ing of the tunnel is 

 closed. 



