June, igoi.] SmITH : On SoME DiGGER BeES. 57 



Then the bee pushes forward, turns a complete suniersault at the 

 extreme end of the burrow and with its head forces the sand to the 

 surface. 



The front leg of Aui^ochlora huineralis is shown at Plate III, Fig. 

 I, and, as compared with the middle and hind legs (Figs. 3 and 5), 

 differs by the lack of hair or other apparent vestiture. There is no 

 distinctive digging structure ; but the sand in which they work is 

 generally soft and when obstacles are encountered the mandibles (Fig. 

 10) are brought in to assist. Femur and tibia are of almost equal size 

 and very powerful. Before the end of the tibia is an articulated spur 

 or process, toothed and forming a cover to a notch in the first tarsal 

 joint. This is, of course, the antenna cleaner, and it is shown, more 

 enlarged, at Fig. 2. The claws at the end of the fore tarsus are 

 different from those on the other feet in that they are longer, more 

 flattened, and inclosed for more than half their length in a membrane- 

 ous sheath, leaving only the teeth projecting. Whether the claws can 

 be completely withdrawn within this sheath, I do not know. 



May 15th was an unpleasant, rainy day on which no bees were fly- 

 ing ; but the i6th was again pleasant and on this day the first cast was 

 made by Mr. Brakeley of one of the new burrows on a field where the 

 bees were seen earliest. It was observed, first of all, before the casts 

 were made, that the mounds were never open on the surface as in 

 CoUetes. That active work was going on could be seen by the 

 increase in the size of the mound and the difference in the color of 

 the sand and clay brought up ; but all the work seemed to be done at 

 night. During the day everything remained undisturbed ; but next 

 morning every mound showed fresh, moist, colored sand or clay, 

 showing just where the insect had reached in its digging. As a matter 

 of fact the mounds never increased very much in size. The hot sun 

 of midday day dried them to a powder and any little breeze over the 

 surface carried off a portion to be spread evenly over the surrounding 

 surface ; a rain levelled the whole to the surface. 



The first cast was only 1 2 inches deep, but developed a new 

 feature : the insects do not start at the top and go straight down ! 

 To make the cast the sand was cleared out of the center of the mound 

 until a clean opening was obtained. The resulting cast was like Fig. 

 18 above the first cell cluster. It proved from this and other casts 

 and diggings, that at first the bee digs diagonally a distance of three 

 or four inches, to get about an inch and a half below the surface ; then 



