Some additional information to clear things up:
During evolution in aculeate Hymenoptera the ovipositor was turned into a sting. Thus all females (workers and reproductive females, but not the males!) primarily do have a sting in aculeate Hymenoptera.
But in a lot of aculeate taxa the sting has secondarily been reduced (in the females).
Hence today there are several ant taxa without a sting. (And bee taxa as well).
As Gordon already mentioned this is the case in the whole subfamily Formicinae.
In addition the Formicinae developed the ability to produce formic acid in their poison gland and developed an acidopore at the tip of their gaster through which they can spray the formic acid as a defense. This can easily be observed in wood ants (the genus
Formica) and which Doug most probably refers to.
But there are a lot of ant taxa that retained a functional sting that is sometimes able to penetrate the human skin which is the case in several myrmicine taxa, e. g.
Myrmica or the
Pogonomyrmex that is shown on Mike´s photo or the fire ants (
Solenopsis invicta). In this case it is not formic acid that causes skin irritation but the components (proteins and peptides etc.) of the poison from the poison gland which is attached to the sting.
Additionally a lot of ants will bite in defense.
So yes Ken, you can find the sting under the microscope if you have chosen the right genus of ant for your examination. Interestingly, it can be observed that during mating the young queen protrudes it´s sting and flaps it aside to enable copulation. (Here you can see the little sting that the queen has protruded and flapped aside:
http://www.ameisenschutzwarte.de/forum/ ... .php?id=91).
Hope this helps for clarification. Nature is tricky sometimes due to it´s enormous diversity.
Cheers.
Betty
but other harvester ants in the genus Messor 
).
