BURROWING AND CARPENTER BEES 



empty cells, as though to insure greater safety to the 

 young. The nurseries are barrel-shaped, about three- 

 fourths of an inch long, clay-lined, and smooth inside; 

 the larval food is a roimd pollen loaf, dry and compact, 

 and the bottom cells are not covered with dumpings 

 from the upper laterals. There are marked differences 

 from the single brood-cells of Colletes, with their mem- 

 branous linings and pasty larval store, although in 

 general structure they agree. 



There is another point of difference. The blue dig- 

 ger bee has the odd habit — as it seems to us — of closing 

 up its door while at home and leaving it open when 

 afield. One would think the reverse conduct would be 

 better, since the contents of the cell would appear to 

 be safer from all sorts of depredators when the mother 

 is at home, and therefore she would have less need to 

 put up the portcullis. It looks as if the danger she 

 guards against is rather to her person than to her 

 progeny. 



The mature Augochloras commence to break from 

 their native burrows and at once begin to dig their 

 hibernating burrows. Only a week or ten days of its 

 career is given to sunlight and flowers, a revolutionary 

 fact in one's idea of bee life. 



The author knows by many fruitless and some suc- 

 cessful experiments the patience, time, and immense 

 labor required to study accurately the burrowing habits 

 of insects and spiders. The chief difficulty lies in the 

 constant crumbling of the soil and breaking-down of the 

 structure. Mr. Brakeley overcame much of the diffi- 

 culty and assured a larger success by the ingenious 

 method of pouring liquid plaster into the holes. He 

 used fine dental plaster, well mixed, ounce for fluid 



169 



