138 INTERNAL ANATOMY OF INSECTS. 
firmed this discovery *; and concluding that this acid WAS 
of a peculiar kind, they gave it the name of the Formic 
acid. This name, however, is now exploded ; the subse- 
quent experiments of Deyeux, Fourcroy and Vauquelin 
having ascertained that the acid of ants is not of a di- 
stinct kind, but a mixture of the Acetic and Malic®. 
These acids are in such considerable quantities, and so. 
concentrated in these animals, that, when a number of 
Formica rufa ave bruised in a mortar, the vapour is so 
sharp that it is scarcely possible to endure it at a short di- 
stance. It also transpires from them, for they leave traces 
of it on the bodies which they traverse: and hence, ac- 
- cording to the experiments of Mr. Coleridge, the vulgar 
notion that ants cannot pass over a line of chalk is cor- 
rect; the effervescence produced by the contact of the 
acid and alkaline being so considerable, as in some de- 
gree to burn their legs®. The circumstance of much of 
the food of ants being of a saccharine nature may ac- 
count for this copious secretion of acid, the use of which 
is probably to defend themselves and their habitations 
from the attack and intrusion of their enemies: if a frog 
be put into a nest of Formica rufathat has been deranged, 
it will be suffocated in five minutes¢. That which they 
gaculate from their anus when attacked, as formerly 
stated °, must be secreted in an zoterium; but their very 
blood seems of an acid nature. It is very probable, as 
Dr. Thomson has observed‘, that acids may be ob- 
tained from many other insects, and that they are various 
modifications of the acetic. 
« Amoreux Ins, Venim.236—.  » N. Dict. d’ Hist. Nat. xii. 94. 
° Southey’s Brazil, i. 645. “ N. Dict. d Hist. Nat. wbi supr. 
© Vou. IL, p. 69. f Syst. of Chemist. 533. 
