What specimen of caterpillar is this?
This appears to be a "Monkey slug" caterpillar (Phobetron spp) of the family Limacodidae (or slug moths).

According to these sites (here and here), caterpillars of this type are commonly referred to in Portuguese as "Lagarta-Aranha" (or "lesma-macaco") [literally, "spider caterpillar" and "monkey slug" in English]. 

The most common Phobetron species I can find in Brazil is Phobetron hipparchia.


The caterpillar of this species appears to be quite variable (ranging from browns to reds in color) as is made apparent by here, here, and here




 Phobetron hipparchia  (Source: http://caterpillars.unr.edu/)