2/6 CLARENCE P. CUSTER AND CHARLES H. HICKS. 



D. sayi has been observed to feed on the flowers of the following 



plants: 



(1) Grindelia sgiiarrosa. 



(2) Helianthus petiolaris. 1 



(3) Sideranthus spinulosus. 1 



(4) Lygodesmia juncea. 1 



After a rain, which partially filled the entrances of some holes, 

 we completed the closing of these with wet sand to observe the 

 later action of the owners. One, entrapped within the nest, 

 used the mandibles to remove the plug; another, returning from 

 the fields, also used her mandibles to gain entrance. The latter 

 was observed to place head and mandibles into a small excavation, 

 which she had formed, and to walk in a clockwise direction around 

 the hole with the tip of the abdomen describing a circle. The 

 forelegs were practically useless in this process. The abdomen 

 was not used in this case to pack the soil in repairing the walls, 

 as has been observed in a bee of the genus Augochlora under 

 similar circumstances. 



D. sayi has not been found feeding beyond a radius of one 

 hundred yards from the nest. However, of six marked females 

 released four hundred and fifty-five yards from the colony, four 

 returned within five hours. The shortest time required to return 

 this distance was twenty-one minutes. Two specimens released 

 one hundred yards from the nest returned shortly, the first 

 within fifteen minutes, after feeding along the way (c). 



The only parasite of D. sayi which has been bred is a fly of the 

 genus Villa (Anthrax), 1 Hicks (5). Some mutillids and chrysids 

 may be parasitic since they have been frequently observed to 

 enter the open or partially plugged-up nests. 



SUMMARY. 



i. Several instances of a female bee, Dianthidium sayi, working 

 alternately on two nests in the process of construction, have 

 been found. This has also been observed in a species of wasp, 

 Sphex varipes. Apparently these are the first records of this 

 habit. 



1 Determined by Professor T. D. A. Cockerell. 



