60 Journal New York Entomological Society. [Voi ix. 



heavy rain beat all the mounds over a noted area, perfectly flat. For 

 five days thereafter there was no external sign of work done, but after 

 that everything went on in the usual way. The ordinary rate of prog- 

 ress is about five inches each day. 



For several days after May i6th bees began digging in increasing 

 numbers, and May 24th, Mr. Brakeley wrote "As for old Cock-Robin 

 Park mine it is a sight — a horrible upheaving of the underneath — and 

 for 20 or 30 feet all around the hole the ground looks as if it had a 

 bad case of hives." 



When the perpendicular is from 20 to 24 inches down, laterals are 

 made and cell clusters are begun. May 2 2d, two casts were made. 

 No. I showed a depth of 21}^ inches and one cell cluster. The 

 second was down 24 inches and had two cell clusters. This cast is 

 fairly represented by Fig. 18 on Plate IV and it also illustrates the 

 average system of a breeding burrow. There are rarely more than 

 two cell clusters ; but the number of cells in the clusters varies. 



A section of a cell cluster containing only a single brood cell is 

 shown at Fig. 22 (Plate IV), and many of the earliest clustery 

 were of this type. After driving a round lateral back about an inch 

 and a half, the insect expands it into a circular chamber, varying in 

 diameter and in the center of this she digs a single cell somewhat 

 barrel shaped and about three-fourth inch in depth. This cell is clay- 

 lined on the inside and carefully smoothed down. Usually there is 

 clay in the tube which she is digging ; but if not, the bee digs out a 

 little pocket as shown near the bottom of Fig. 18 (Plate IV), and 

 thus obtains the material for finishing up her cradle. After this cen- 

 tral cell is completed she digs a series of four or five around it, and of 

 the same depth. These are not at first clay-lined but are left while 

 the insect secures pollen to store the central cell. The pollen is 

 formed into a round loaf, plano-convex in section, dry and firmly 

 compacted. Upon this an egg is laid as shown in the figure. The 

 cell is closed with a capping of clay, and the mother's work on this is 

 done. Now the insect may either make brood cells of two or of all 

 of the surrounding cavities or she may leave them open and unfilled. 

 If she does the latter she deepens and curves them under the central 

 cell until they nearly meet. In this way there is an almost continuous 

 space all around the brood cell, only enough material being left to 

 support the structure. If, on the other hand, she decides to turn 

 others of these into brood cells, she enlarges the chamber accordingly 



