"Death-Waters" by Frank Belknap Long

Published in Weird Tales in December 1924.

culebra de sangre: a.k.a. blood snake. There is shockingly little information available about this critter, at least in English language websites. It's Latin name is Stenorrhina freminvillei, but that doesn't net me much info either. About all I can find is that it appears to be non-venomous, and eats scorpions and spiders and insects. There is a 1890 text I found which talks about a vibora de sangre, the bite of which causes a person's blood to sweat through their pores, but I have no idea if that is what Long actually had in mind.

taboboa: a type of venomous snake, information about which is even more obscure than the culebra de sangre. I found an 1857 book that documents the taboba as being even more deadly than a coral snake, with its bites being instantly fatal. An 1890 book says much the same, noting there is no antidote for this snake's bite. Sounds quite nasty!

That said, it sometimes happens during this time period that locals who don't like the white man coming into their countries tell them exaggerated tales of extreme peril hoping it will frighten them off. Alternately, they sometimes tell exaggerated tales in the other direction if they believe bringing in more of the white man will be a large boost to the local economy. So you have to be very careful in interpreting these kinds of historical tales related by locals to visiting white men in remote areas like this.

The picture used is the cover art from the 1924 Weird Tales volume in which the story was published, by Andrew Brosnatch.