CHELOSTOMA. 287 



do nothing further to it but collect a sufficient store of 

 provender for the nutriment of the young one, upon 

 which they deposit the egg which is to produce it. The 

 insect then flies away to collect a small quantity of clay 

 intermingled with sand, and this they knead together 

 by means of a viscous secretion which they disgorge, 

 and this forms a concrete that hardens firmly and 

 rapidly ; to anticipate its rapid drying they speedily fly 

 back, carrying this small ball within their mandibles, 

 and with it they cover over the provision they have col- 

 lected, and which, adhering to the sides of the cavity, 

 forms a firm and hard division, effectually separating it 

 from the next store of provision that is to be accumulated 

 for the supply of the larva that will be hatched from the 

 egg that is to be deposited, and the same process is 

 repeated again and again until all the eggs are laid. In 

 their development, which takes place near midsummer, 

 the males precede the females by about ten days. They 

 associate sometimes in colonies, often using the tubes of 

 the straw thatch which covers cottages for their nidus. 



These bees are subject to the parasitical intrusion of 

 Fcenus jaculator and assectator, which I have repeatedly 

 caught at Battersea, hovering opposite the cells of these 

 insects bored in the shingles forming the enclosure of 

 an old garden outhouse. These parasites are themselves 

 peculiar creatures, forming a type distinct from the 

 Ichneumons, and belonging to the group Aulacus, upon 

 which see my paper in the ' Entomologist/ June, 1841. 

 In these insects, the abdomen springs from immediately 

 beneath the scutellum. Chrysis cyanea and ignita are also 

 bred at the expense of these bees, neither of the species of 

 which are uncommon ; the smaller one, the C. campanu- 

 larum, which is the smallest of our true bees, excepting 



