methanoic acid

It is an important intermediate in chemical synthesis and
occurs naturally,  most notably in  the venom of  bee and
ant stings.

ethanoic acid

Acetic acid, CH3COOH, also  known as ethanoic acid, is an
organic  acid  that  gives  vinegar its  sour  taste  and
pungent smell.  It is a weak  acid, in that it  is only a
partially dissociated acid in an aqueous solution.

http://en.wikipedia.org/wiki/Acetic_acid