Carpenter- Wasps. 63 



the carpenter-bees, while the division of the chambers is 

 nothing more than the rubbish produced during the excava- 

 tion. 



The provision which is made for the grub consists of flies 

 or gnats piled into the chamber, but without the nice order 

 remarkable in the spiral columns of green caterpillars 

 provided by the mason- wasp (Odynerus murarius). The most 

 remarkable circumstance is, that in some of the species, when 

 the grub is about to go into the pupa state, it spins a case (a 

 cocoon), into which it interweaves the wings of the flies 

 whose bodies it has previously devoured. In other species, 

 the gnawings of the wood are employed in a similar manner. 



[Some of the solitary wasps are also carpenters, and the 

 genus Crabro has several species which are classed under 

 this head. There is, for example, Crabro clavipes, a little 

 black insect with red and black abdomen, that burrows into 

 dead bramble sticks, boring out the pith, and forming a 

 series of cells in the narrow tube thus made. Sometimes 

 this insect bores into decaying wood, but its general home 

 is the bramble-stick. The same habits are common to several 

 other British species of this genus, and the reader will find 

 that old, decaying willow trees are chiefly visited by these 

 pretty little insects. Their store of food, which they lay up 

 for their young, mostly consists of dipterous insects, and 

 various species of gnats are used for this purpose. 



Another of the carpenter-wasps (Pemphredon lugubris) is 

 really a useful insect. It makes its burrows in posts, 

 rails, and similar localities, and provides its future young 

 with a large stock of aphides. It has been seen to settle on 

 a rose-bush, scrape off the branches a number of aphides, 

 form them into a ball, and carry them off between its head 

 and front legs. 



The colour of this insect is dull black, from which cir- 

 cumstance it derives its name of lugubris. The head is large, 

 and squared, and the abdomen is attached to the thorax by 

 a large footstalk. Its length is about half an inch. It is a 

 very common insect, and is believed to be the only British 

 representation of its genus. 



