268 CLARENCE P. CUSTER AND CHARLES H. HICKS. 



Dianthidium sayi Cockerell syn. interruptum Say. (nom. preocc.). 

 The bees of the genus Dianthidium have been known to construct 

 nests of resin on rocks, in stems of plants, in deserted snail shells 

 and other places, but, so far as we know, seldom in the ground 

 as does Dianthidium sayi. We have found no reference to the 

 nesting habits of this species except that in 1926 by Hicks (5). 

 This latter information was derived from a number of cells dug 

 up from a small area at White Rocks, during fall of 1925 near 

 Boulder, Colorado. We have obtained our field notes during 

 the summer of 1926 mainly at this locality where two colonies, 

 one hundred yards apart, were found and studied. 



The six colonies of D. sayi, observed during the latter part 

 of the summers of 1925 and 1926, were all located on hillsides 

 that face south and slightly east. Scattered over these hillsides 

 were tufts of Bromus brizxformis Fisch. and Mey., 1 to the roots 

 of which some of the resin cells were attached. We find that 

 the species may nest as a colony of from eight to fifty or more 

 females, although one apparently solitary female was found 

 nesting in a vertical clay bank. The colony is at its maximum 

 activity during the month of September. 



The picture shows a small colony of D. sayi on a grass-covered 

 mound of sandy soil one yard in diameter. Base rock surrounds 

 this on all sides, the nearest soil being five feet away. Tall 



1 Kindly determined by Dr. Francis Ramaley. 



