Re: Which types of ants are edible to humans?

Actually Native Americans commonly ate the replete workers of the honeypot 
ants (Myrmecocystus spp.) David George Gordon has several recipes for ants 
and he generally recommends those of the subfamily Formicinae (the ant 
family is Formicidae), including Myrmecocystus, Formica and Camponotus- 
all of which lack a sting (but do have formic acid).   Except for the 
honeypot ants these are generally baked, which probably cuts the acid 
effect.  Many creatures eat ants, including some spiders, ant lions, worm 
lions (larvae of certain flies), other ants, and horned lizards.   They 
all have ways of dealing with the venom.

I am, however, not sure that the chimpanzees that you mentioned were 
catching ants.  They may have been collecting termites!  These do not 
sting or have a toxin and are quite edible, both to chimpanzees and humans.

References:

Gordon, D. G. 1998. The Eat-A-Bug Cookbook. Ten Speed Press, Berkeley, CA.

Hölldobler, B., and E. O. Wilson. 1990. The Ants. Harvard Univ. Press, 
Cambridge, Massachusetts.