OUTLINES OF ENTOMOLOGY. 35 



pletion of the first and last cells, and whether the first laid eggs are 

 last to hatch, or whether, upon development, the young bees in the 

 more remote cells, remain quiet until those nearest the entrance open 

 open a passage-way, has not been ascertained ; but at all events, they 

 do not emerge until their younger brothers and sisters have passed out 

 before them. 



The Mason bees (genus OsmiaJ are a group of small, handsome 

 bees of a metallic bluish or green color. They derive their name from 

 their habit of using clay, or a peculiar mortar which they prepare from 

 fine gravel, in the construction of their variously shaped cells. These 

 may often be found plastered against the sides of buildings, upon the 

 branches of trees, and sometimes even upon leaves, or within oak-galls, 

 separately, or in small groups. They are rough on the outside but 

 smooth and polished within. A few species belonging to this genus 

 are said to excavate tunnels in soft or decayed wood in which to pro- 

 tect their cells. Dr. Riley says of Anthopora sponsa, an allied species, 

 that it u builds mostly in steeply inclined or perpendicular clay-banks, 

 and, in addition, extends a tube of clay from the entrance. The bur- 

 row has usually two branches, which decline about an inch from the 

 surface of the bank, and (in them) six or eight cells are arranged end to 

 end. By means of saliva the inside of the cell is rendered impervious 

 to the moisture of the honey and bee-bread stored in it for the young." 



The Upholsterer bees (genus Ceratina) resemble the Mason bees 

 in form and color. They build their nests on a plan very similar to that 

 of the Carpenter bees, but instead of boring into solid wood they se- 

 lect that which is soft from decay, or confine themselves to the pithy 

 stems of such shrubs as the elder or blackberry, or the stalks of the 

 more robust weeds. The walls of the cells are lined and the partitions 

 made of a delicate silken web the " upholstery " from which they 

 derive their popular name. 



The Leaf- cutter or Taylor bees (genus MegachileJ, also in most 

 instances excavate the pithy stems of shrubs in which to build their 

 nests. In other cases they select tough leaves, which they contrive to 

 roll into cylinders and fasten firmly for the protection of the cells. 

 Within these tunnels they prepare a number of cells, forming the 

 partitions and covering the walls with sections of delicate leaves or 

 of the petals of flowers. One species, N. centuncularis, is a serious 

 pest to the flower garden, always, with rare good taste, selecting the 

 most delicately colored of the roses, geraniums and other choice flow- 

 ers for her curtains and coverlets. This is a rather stout, short-bodied 

 bee of a dull black color, banded with yellowish gray. The head is 

 broad and the scissors-like jaws are very strong, and the swiftness 



