GUESTS AND PARASITES OF HALICTUS. 3 



sers and robbers, too, have ceased their work, and the colony 

 slumbers in peace. 



The structure of the nest was ascertained by the ingenious 

 plaster-cast method advocated by Prof. J. B. Smith. By this 

 means the galleries of Halictus are seen to depart but little from 

 those of the other burrowing bees. A passage-way for exit and 

 entrance in addition to the regular one opening on the dumping 

 ground, such as is constructed by Aiigochlora humeralis Patton,^ 

 was never noticed in the case of H. pruinosus, the vigilance re- 

 quired to guard two openings having probably prevented such an. 

 extravagance. All the burrows which we dug out, a dozen or so- 

 in number, extended in a nearly horizontal direction, and were 

 always built on the very steep slopes along the roadsides. By- 



Fig. I. Diagram of //rt//V/;« nest, a, plan; b, elevation. 



this means none of the excavated dirt accumulated about the 

 doorway, which was even cleared of all debris with but little effort 

 on the part of the bee. The relatives of pniinosus in Texas,, 

 morphologically of the same species, select a level spot for their 

 nesting-site, dig vertical burrows, and place the accumulated dirt 

 in an irregular cone about the openmg. A photograph of these 

 nests is given for comparison. 



During the latter part of nest-construction when the pollen has 

 been gathered and the eggs laid, their home is continually threat- 

 ened by thieves and kidnappers against whom a guarded watch- 

 fulness must be maintained. The sentinels are generally the 



ij. B. Smith, Proc. Am. Ass. Adv. Sci., 1898, p. 368. 



