March, igoi.] SmITH : On SoMF. DiGGER BeES. 35 



be found. In one case a lot of red ants were found robbing the store 

 and where ants are as plentiful as they are at Lahaway, no doubt they 

 are responsible for the disappearance of many bee cells. 



It seems certain that Colletes compacta digs down from the first to 

 the extreme depth of the burrow ; it runs off then, to one side, from 

 two to four or rarely six inches, makes and fills a cell and lays an egg 

 in it. Two or three inches higher another lateral is started, running 

 in a different direction, and the sand taken from this lateral is dropped 

 into the main tube whence it washes into the first lateral so that when 

 the second is completed, the first is pretty well filled up. The second 

 lateral is filled with material from the third if a third is run and, finally, 

 the entire tube is filled ; whether gradually by a sifting in of sand 

 from the top, or intentionally by the insect, I cannot say. It is cer- 

 tain, at all events, that the burrows do not remain open and that the 

 young bees that hatch two feet more or less below the surface, must 

 dig up through the soil to that point. Whether they follow the line 

 of the parent burrow in doing this, or whether they work out on lines 

 of their own, is not yet known. One finds in digging about after the 

 new cartridges, old ones that are filled with sand and black with decay. 

 Evidently its old larval home serves the new bee by providing a first 

 space to store the sand removed in getting out. Unless the mother 

 bee lays not over three eggs, she must make two or more diggings. 



July ist, spent part of the morning in digging for more cartridges 

 and as the net result found four in which were larvae so far developed 

 that they came near to filling the entire cell. Nearly all the food 

 store had been devoured and growth must have been nearly completed. 

 Expecting to secure other examples these larvae were put into alcohol, 

 but no other specimens were found in spite of all digging. Nor could 

 I secure any others later in the season. The date of pupation is thus 

 left undetermined, and it is also uncertain whether or not the insects 

 reach the adult stage in the fall and winter in the ground, or whether 

 they winter as pupae and change to adults very early in spring. I 

 would be inclined to believe that the change takes place in fall, be- 

 cause so early as these insects appear, the soil does not feel spring 

 warmth sufficient to induce much active cell development, while it is 

 probably enough to induce an already mature individual to start for 

 the surface. 



To recapitulate : Colletes compacta makes its appearance — both 

 sexes — prior to March 12th and the females begin at once to dig bur- 



