LETTERS ON ENTOMOLOGY. 133 
walls built of flint and mortar. Although their ob- 
ject is to make a hole, it appears quite otherwise ; 
for they raise a kind of hollow tube of the earth 
they dig out, and which is sometimes two inches 
long ; it is not however made to last, being only 
a kind of scaffolding or bulwark till the work is 
done. You may perhaps wonder how this insect 
can penetrate so hard a substance as dried clay 
or mortar ; but she is provided with a liquor in 
her mouth to soften it, and this serves to make 
the particles of earth, of which the tube is made, 
stick together. When this liquor is exhausted 
she fetches water, or probably some juice of 
plants, and proceeds with her work. This is 
performed so rapidly that one has been observed 
to dig, in about an hour and a half, a hole equal 
to the length of her body, and to raise the tube 
in proportion. We need not ask why this hole 
is made, for we must conclude it is for the re- 
ception of her egg and the provision for the 
maggot ; but it does not appear at first why the 
tube has been made with so much care ; but the 
more we see, the more we shall be convinced 
that there is nothing useless in nature, and the 
less we shall be inclined to judge hastily. When 
the egg and its provision are lodged in the bottom, 
this tube is to her what a heap of bricks is to a 
