CLASSIFICATION AND DESCRIPTION OF COMMON INSECTS 357 



frequently the nests are close together. Some of the more common 

 genera are Andrena, Halictus and Prosopis. 



To the Apidce belong the Leaf-cutter bees (Megachile), Carpenter 

 bees {Ceratina and Xylocopa), Guest-bees {Psithyrus), Bumble Bees 

 (Bombus) and Honey Bees (Apis). The Leaf-cutter bees (Megachile) 

 make tubular cells out of nearly semi-circular pieces of leaves cut from 

 rose bushes and various plants. These cells are placed in burrows 

 made either in the ground or in soft wood. 



The Mason Bees (Osmia) construct nests of clay and sand in stone 

 walls, old fence posts and trunks of trees. The cells are composed of 

 sand, earth or clay mixed with pebbles or bits of wood, all glued firmly 

 together. (See Manuals of Comstock and Kellogg, and Sladen's 

 "Humble bee" for details regarding the habits of bees.) 



Social Habits of Bees. — Bees show a gradation from solitary 

 forms like Ceratina, Prosopis, Andrena and Halictus to colonial forms 

 like the bumble bee and honey bee. This gradation may be repre- 

 sented as follows: 



A. Solitary bees. 



B. Queen dies after egg-laying and providing food for larvae. 

 C. Nests quite apart. — Prosopis, Ceratina. 

 CC. Nests in colonies, but females work independently. — Andrena, 

 Anlhrophora, Osmia. 

 CCC. Females hibernate in companies. — Xylocopa. 

 CCCC. Two or more females use a common hole or refuge. — Halictus, 

 Panurgus. 

 BB. Queen survives to see the brood and watch over the nest. — Species 

 of Halictus. 

 AA. Social Bees. 



B. Fertilized female hibernates alone. — Bumble Bees. 

 BB. Permanent societies with perfect combs. — Honey Bees. 



Bumble Bees (Bombus spp.). — From an economic standpoint Bum- 

 ble Bees are of importance as agents in pollination of red and other 

 clovers. The over- wintering queen starts her nest in the spring usually 

 in a deserted mouse's nest. She places in it some pellets of pollen 

 and nectar and on them in a wax cell lays her first eggs. Next she 

 constructs a "honey-pot" for holding the honey collected at the 

 entrance to the nest. The larvae feed on the pollen, and when full 

 grown — about 11 days after the eggs are laid — form silken cocoons in 

 which they spend their pupal period of about 11 days. The first 



