The True Bees 



are found in all parts of the world and look much like bumble- 

 bees. The pieces of leaf which they cut out very neatly are 

 either oblong or circular, the former being used for the sides and 

 the latter to cover the end of the cell. The burrows which they 

 use vary greatly in situation. Some burrow into the ground, 

 others into soft wood, while others make use of chance tunnels. 

 I have seen them in accidental auger holes, and in lead pipe, and 

 once knew the nozzle of an old pump to be packed full of cells. 

 According to Professor Putnam, a single female observed by him 

 took twenty days to complete and provision a series of cells un- 

 der a board. He found there were thirty cells in nine rows of 

 varying numbers. An estimate of the number of bits of leaf used 

 in the construction of these thirty cells amounted to more than a 

 thousand. 



The potter bees of this same family construct small globular 

 cells of earth and attach them to the stem of a plant. 



The parasitic bees of the family Stelidse live, like the No- 

 madidae, in the nests of other bees, choosing indifferently the 

 cell of almost any kind of bee, no matter what its situation. No 

 observations on any of the American species have been recorded, 

 and here is an interesting field of study. 



The habits of the European species Stelis minuta have been 

 observed with some care. It was found to be parasitic in the 

 nest of one of the mason bees, a female having laid her egg in 

 the cell after it was partly filled by the mason bee. Unaware of 

 the presence of the parasitic egg, the mason bee continued her 

 work, and after nearly filling the cell deposited her own egg on the 

 top of the food mass, closing the cell with a partition, and begin- 

 ning another one above. The Stelis larva hatched a little earlier 

 than that of the mason bee, and both began to feed, the parasite 

 larva from below and the mason bee larva from above. Unfor- 

 tunately for those who are interested in the triumph of right and 

 justice, the latter grows very slowly while the parasite larva 

 grows more rapidly, and gradually worked its way upward 

 through the food mass, thus approaching the mason bee larva. 

 In the words of Riley's summary of this tragic performance "the 

 crisis finally comes — the Stelis larva encounters the Osmia larva ; 

 a short but deadly combat ensues ; the Osmia larva is easily 

 overpowered and killed by the much larger and stronger parasite, 

 and its body is devoured by the latter within one or two days." 



