a 
248 NORTH AMERICAN INSECTS. 
form an excellent food for all kinds of warblers, such as 
mocking-birds and nightingales. In the cities of Europe 
they are sold by the quart in the markets. These misealled 
ant-eggs, which are as large, and even larger than the ants 
themselves, can not be their eggs, but are the cocoons of 
the metamorphosed maggots, of which the workers take so 
much care. If they are taken out of the hill and scattered 
about over the ground, it is curious and astonishing to see 
with what anxious solicitude and indefatigable zeal the 
workers pick them up again with their jaws and carry them 
back into the hill, for greater safety transporting them deep- 
er than ever in the ground. In order to collect these pupx, 
or cocoons, as food for warblers kept in cages, it is only 
necessary to fix a dry and shady spot of ground near one of 
their ant-hills, then stir up the hill with a stick, or pour a 
considerable quantity of water in it, and after a few mo- 
ments the workers will convey the cocoons to the shady and 
dry spot, where they can be collected at pleasure. 
The real eggs of ants are as small as a grain of sand, and 
almost invisible, white and shining as if they had been var- 
nished. The maggot, issuing from each egg, has twelve 
ringlets, and in the pupa, which is semi-transparent, all the 
members of the perfect insect are visible. 
Most of the ants are provided with a small sting, which, 
when applied to human flesh, produces a little itching, some- 
times a slight swelling and inflammation, caused by the 
venom of the insect, which enters the wound with the sting. 
This venom is nothing else than the well-known formic acid, 
which produces the pleasant sour odor when the ant-hill is 
stirred up, and which is procured by druggists for medicinal 
purposes. ‘This acid substance may be obtained by putting 
a certain quantity of ants into a bag, placing the bag under 
a press, and then squeezing out their fluids, but it may also 
be obtained much easier by a chemical process. This for- 
mic acid changes vegetable blue to red; so that if ants pass 
