SOLITARY BEES THEIR HABITS AND WORK. 195 



the excavated material to a distance, so as not to betray 

 the burrow, the Xylocopa reserves a considerable portion 

 of the woody fragments for the purpose of separating her 

 burrow into a series of cells. Having placed a sufficient 

 quantity of food at the bottom of the burrow, and an egg 

 upon the food heap, she takes a number of wood chips, 

 moistening them with saliva, and places them in a ring- 

 like shape just above the food. When the first ring is 

 dry, she makes a second ring within it, and so proceeds 

 until she has made a nearly flat floor of concentric rings. 

 When finished, the floor is about as thick as a penny, and 

 it becomes exceedingly hard as it dries. 



Naturally we might think that the eggs which were 

 laid first would hatch first, and that therefore the 

 insect must injure its companions by breaking through 

 their cells in its way to the entrance of the burrow, even 

 if it had sufficient strength for the task. The solution 

 of the problem is beautifully simple, and is thus described 

 by the late Mr. F. Smith, whose knowledge of the 

 Hymenoptera was unrivalled : " The bees which first 

 arrive at their perfect condition, or rather those which 

 are first anxious to escape into day, are two or three in 

 the upper cells. These are males ; the females are 

 usually ten or twelve days later. This is the history of 

 every wood-boring bee which I have bred, and I have 

 reared broods of nearly every species indigenous to this 

 country." 



There is another burrowing bee (ChaUcodoma) which 

 makes partitions in a similar manner. But, as it is an 



