CAVE-DWELLING INSECTS. 



159 



FIG. 53. — CAVE AND CEI.L-NEST OF HUMBLE-BEES. 



by wax cement that they were separated with difficulty. 

 Sorae of the cells were open ; most of them were closed. 

 Of the latter some were filled with a number of small 

 yellowish-white grubs of various sizes ; others contained 

 but one grub each ; a large white one, which was 

 doubtless a young princess in training for futui'C queen- 

 ship. 



