June, 1901.] Smith : On Some Digger Bees. 63 



the danger should be much greater during the mother's absence than 

 when she is present. Practically there is nothing to prevent a para- 

 site or predaceous species from walking right into the burrow and 

 cleaning out the whole nest contents. No casts were made between 

 June 5th and nth, and there came thus an unfortunate blank. 



June I ith, cast i, poured into an open perpendicular ran down 27^ 

 inches and had 2 cell clusters, one of six and one of five brood cells. 

 In one of these was a pollen cake. Cast 2 had only one cell cluster. 

 In this was one empty, clay-lined cell, and one containing a pollen 

 cake with an egg on it. This was the first completed brood cell met 

 with. Cast 3 had a perpendicular running down 30 3^ inches. There 

 was one cluster of three brood cells : the first was clay-lined, empty ; 

 the second had a fully completed pollen cake ; the third had also an 

 egg and was capped. 



Cast 4 ran down 28 inches and had one claw cluster with three 

 brood cells. One of these was empty, the other two were completed 

 and with caps. 



Cast 5 had two cell clusters, upper with three, lower with two brood 

 cells and all completed with pollen, egg and cover. 



June 13th, cut back along the face of one of the walls of the bee 

 mine until a new burrow was reached and this was followed down care- 

 fully to observe the normal condition of affairs. There were two cell 

 clusters, one at 7^2? oi^e at 8J4 inches. The first contained one 

 completed cell with, pollen and egg. The second had three brood cells, 

 one empty, one fully loaded and sealed, the third with a recently 

 hatched larva. The empty cell had been recently clay-lined and in- 

 dicated that the bee moistened the material with saliva or some other 

 secretion. At all events the moisture penetrated to a little distance 

 into the sand and seemed to harden it. Probably, when working in 

 clay or a soil containing clay, this hardening mixture is all that is 

 needed. In fact in some cases observed I feel certain that just this 

 was done and no more. 



June 15th, a number of hatched larvte were found and then comes 

 a break, due to the death of Mr. Brakeley's father, until June 30th, 

 when I took up the observations myself. This makes a break during 

 the period of development of the larva and, as pupae were found on 

 the 30th, there is no certainty as to the shortest period between the 

 beginning of the larval and the pupal stage. It is certainly not over 

 15 days. 



