264 CLARENCE P. CUSTER AND CHARLES H. HICKS. 



distance above the cell varies. From 135 to 300 pebbles are 

 used, 250 being about the average. 



Sometimes a bee loses its hold or attempts to carry a pebble 

 too heavy and is forced to drop it. She then goes at once to the 

 place, from which she secured the one dropped, for another. 

 However in one instance, upon dropping the pebble midway to 

 the nest, the bee alighted at the spot, seized another, and con- 

 tinued on her way. The bee usually drops the pebble from above 

 the hole into the tunnel but on a few occasions she was observed 

 to alight on the edge before dropping it in. Sometimes the 

 pebble fails to hit the hole and remains close to the edge. While 

 filling the hole the bee frequently enters to arrange the pebbles. 

 In doing this she turns them with her mandibles and fits them 

 into position snugly. In only one instance, after the bee had 

 gone inside to arrange the pebbles, have we observed her on 

 leaving to rake in some pebbles and soil from near the edge with 

 her mandibles and foie legs. 



On July 24, 1926, found bee filling tunnel. She was watched 

 until the end of this period. The following is an extract from 

 more detailed notes taken in the field (h) . 



At 8:50 A.M. found A. porterae entering hole in ground with 

 piece of dry dirt. The hole was large enough to see inside and 

 it was noted that only a few pieces had been deposited for the 

 down was not covered. When first observed the bee was carrying 

 material from a place 12 feet east of nest. She carried 10 loads 

 in an average time of 12 seconds. Each time the bee alighted 

 on the ground and selected the piece of dirt. These chunks 

 varied somewhat although the average was quite uniform. 



After she carried a few more, a circle of stones was placed about 

 the nest while she was after a load. The stones were about the 

 size of a hen's egg and were 3 inches from hole. On returning 

 she circled 3 times about the hole, then flew 10 feet away, returned, 

 alighted on ground, returned and entered hole. She then went 

 to collect again and continued, returning direct and without 

 further hesitation, paying no more attention to the change. 

 After 15 more loads she changed her place of selecting materials 

 to 1 8 feet south of nest. The bee, after every few loads, went 

 and arranged them. After 56th trip changed back to position 



