266 CLARENCE P. CUSTER AND CHARLES H. HICKS. 



of excrement mixed with down were all about the down and 

 between the cocoon and the outside (h). 



The outer surface of the cocoon has a thin layer of rather light, 

 loosely woven silk. Removing this the denser, darker cocoon is 

 found. An average cocoon measured 10 mm. in length and 5 

 mm. wide, being oval in shape with the ends somewhat flattened. 

 The anterior end bears a mammillary point which externally 

 contains an opening. This point is not so long nor so conspicuous 

 as the one on the cocoon of Dianthidium sayi. One large cocoon 

 measured 12 mm. in length and 7 mm. in width. The cocoons 

 found have been reddish brown. One of the cocoons described, 

 held to a bright light showed the outline of the larva within (h). 



We made certain investigations in which we attempted to find 

 if A. portera? would carry pebbles indefinitely to the nest. While 

 the bee was away for a few seconds to obtain another pebble we 

 removed the one, with a pair of forceps, she had last dropped in. 

 Thus the nest was kept continuously empty or partially so. 



On July 27, 1926, at Point East at 3:15 P.M. we found a bee 

 carrying large pebbles from the nest of the red ant (Pogonomyrmex 

 occidentalis Cress.) 9 yards away. The nest at that time was 

 about half full. We removed 175 pebbles by 5:20 P.M. when 

 the bee quit working for the day. The nest was watched until 

 7:00 P.M. and from 7:15 A.M. the following morning but the 

 bee was not there at either time and no pebbles had been carried 

 in the interval. She started again to carry pebbles at 7:55 

 (July 28). From 7:55 to 8:20 she carried 100 stones, which is 

 an average of 4 stones a minute. Later in the day (10:00 A.M.) 

 she was found to be averaging 8 a minute, probably due to the 

 increased intensity and heat of the sunlight. She carried 311 

 pebbles before noon, having fed early in the morning, suddenly 

 stopped and was seen no more. Although the nest was watched 

 for days, no more pebbles were carried. The total number 

 carried was 741. The bee was not frightened away and ap- 

 parently quit voluntarily, leaving a number of pebbles in the 

 nest. 



To another nest a bee carried at least 400 pebbles and suddenly 

 left, although the hole was kept partly empty as in the other case. 

 Before stopping, in each instance, there was no apparent slowing 



