0SM1A. 
297 
sand or earth mixed with minute pebbles, scarcely lar¬ 
ger than grains of sand, or raspings of wood combined 
in the same manner, with a secretion which they emit, 
and of which they form their cells. The instinct of the 
creature prompts it to be speedy in the operation, as the 
material, like plaster of Paris, dries very rapidly to a 
hard substance. Whether they have the power of 
softening the edges as the manufacture of the cell pro¬ 
ceeds is not known, nor whether, as they add the 
material, it instantaneously consolidates itself, but the 
colour of the structures themselves would indicate a 
simultaneous mixture. This could not be the case, if 
the mortar or mixture were formed away from the domicile 
and brought home in little pellets, each being added 
upon the insects* arrival, although they obtain it all from 
the same spot, whence arises its uniformity in colour, 
and they are speedy in the formation of their nests. 
These cells are rather rough externally, according to the 
nature of the material of which they are composed, but 
they are very smooth within. The nature of the cells 
varies with the places of their deposit, which is dependent 
upon the idiosyncrasy of the species. Thus, those which 
construct their cells in wood, form them of moistened 
particles of wood, and those which make them in cavi¬ 
ties of any kind, in the earth, beneath stones, or within 
empty snail-shells, make a mortar of earth and sand 
and small pebbles. Some are strictly uniform in the 
selection of the material wherein they build, but others 
are perfectly indifferent to its locality, and adopt either 
earth or wood, and sometimes the mortar of walls, sand¬ 
banks or chalk cliffs. According to the nature or the 
size of the receptacle which they select, is the adjust¬ 
ment of these cells. Where the cavity is restricted they 
