Subject: Are these venomous?
Geographic location of the bug: Sao Paulo, Brazil
Time: 10:09 PM EDT
Your letter to the bugman : Are these stinging caterpillars or slugs?
How you want your letter signed: Danirl
These caterpillars are not venomous and they do not sting. They are some species of Owl Butterfly Caterpillars from the genus Caligo based on this CanStock Photo image and this Alamy image. You can find some good information on Insetologia.