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Figure 3. Nest tumulus. Nests in which bees were actively digging were readily 
discerned by the presence of a dirt mound around the nest entrance. 
the tunnel changed directions again at at a depth of 24 cm, con- 
tinued downward at a 75° angle another 8 cm, and diverged into 
two tunnels. One of these angled toward the embankment at an 
angle of 50° from vertical for another 12 cm, then at a depth of 
41 cm continued slightly below horizontal for another 18 cm. A 
single, terminal cell was found at the end of that tunnel. The other 
tunnel continued downward another 16 cm from the branching 
point before becoming nearly horizontal at a depth of 47 cm. This 
tunnel could not be followed because the soil was too soft. 
Two additional nests were excavated on the nearly vertical 
embankment at aggregation No. 1. These nests differed from those 
in level ground in having very short (3-5 cm) vertical portions of the 
tunnel before becoming nearly horizontal. Nest B (Fig. 5) had a 
single horizontal tunnel that extended 22 cm into the embankment. 
Along the slight downward slope of this main tunnel were 6 nearly 
horizontal lateral tunnels 4-8 cm long. The two closest to the exte- 
rior contained pupae and the tunnels had been filled with soil. The 
next three contained larvae, and the distal cell was empty. Nest C 
