270 A BOOK OF INSECTS 



more advanced species are accomplished architects. The 

 large and powerful carpenter bees burrow into timber, 

 and partition off their cells with wood chips mixed with 

 their glue-like saliva. Mason bees employ the same kind 

 of adhesive when preparing their concrete. But the most 

 interesting of all the solitary bees are the leaf-cutters. 

 There are several British species, the best-known being 

 Megachile willughbiella. The female first drives a burrow 

 in a rotten beam, post, or tree trunk, and then proceeds 

 to fill it with cells formed from pieces of rose leaf. She 

 alights upon a leaf, grasping with her legs the portion she 

 is about to remove. Then with her mandibles she makes 

 a rapid, curving cut ; and just as she severs the last shred 

 of her support, her wings begin to vibrate, and she soars 

 away with her spoil held firmly beneath her body. First 

 lozenge-shaped pieces of leaf are cut and rammed into 

 place to form a thimble-shaped cell, which is provisioned 

 with honey and pollen. Thereafter the egg is laid, and 

 the cell is closed with a wad of leaf fragments more or 

 less circular in outline. At least seven lozenge-shaped 

 and four circular pieces are cut and carried by this indus- 

 trious insect to form a single cell. 



A whole host of bees make no direct provision for 

 their young. They are not actually parasites, but — like 

 the cuckoo among birds — lay their eggs in the nests of 

 other species. One example will suffice to make clear the 

 nature of the relationship. The leaf-cutting bee forms 

 her cell, provisions it, and lays her egg. When she is 

 absent cutting the leaf fragments to cap the cell, a cuckoo 

 bee (CoeUoccys conoidea) steals into the tunnel and lays her 

 own egg side by side with that of the owner. The usual 

 result is that the cuckoo's grub (whose egg is the first to 

 hatch) devours most of the food, while the leaf-cutter's 

 grub is starved. Some of these cuckoo grubs so far forget 



