My Year of Darwin (3/2/2014): Clash of Arthropod Titans!

"I was much interested one day by watching a deadly contest between a Pepsis and a large spider of the genus Lycosa. the wast made a sudden dash at its prey, and then flew away; the spider was evidently wounded, for, trying to escape, it rolled down a little slope, but had still strength sufficient to crawl into a thick tuft of grass. The wasp soon returned, and seemed surprised at not immediately finding its victim. It then commenced as regular a hunt as ever hound did after fox; making short semicircular casts, and all the time rapidly vibrating its wings and antennae. The spider, though well concealed, was soon discovered, and the wasp, evidently still afraid of its adversary's jaws, after much manoeuvering, inflicted two stings on the under side of its thorax. At last, carefully examining with its antennae the now motionless spider, it proceeded to drag away the body ." Charles Darwin, Voyage of the Beagle

This is the drama played out between a tarantula and a large wasp known as a tarantula hawk or tarantula hunter. Wasps hunt spiders throughout the world. Here in the northeast US, a group of wasps, called mud daubers, collect spiders and place them in their mud nests on the sides of houses, bridges, and barns. In the Neotropics, the wasps are big and the spiders are huge. I've seen these wasps once or twice patrolling the forest and once I was able to see one female dragging off a tarantula. She will drag him down to her burrow, lay an egg on the spider, and the young will eat the paralyzed spider. Mud daubers will put many more spiders in their cache.

Returning from camp one sweaty afternoon, one of these thumb-sized wasps flew in our jeep and we all set into a panic. Once of our crew was stung on his ring finger and he barely was able to remove his wedding ring before his finger swelled to twice its normal size. The species I came across in the tropics had a bright red abdomen - indicating you should leave them alone. I will. You should.