OMFG yes cazadors, they are just too powerful and fast for what they are. you shouldnt get killed by a butterfly in 5 secs flat!
Wasps, actually. Mutated http://en.wikipedia.org/wiki/Tarantula_hawk.
...the sting, particularly of Pepsis formosa, is among the most painful of any insect, but the intense pain only lasts for about 3 minutes. Commenting on his own experience, one researcher described the pain as "…immediate, excruciating pain that simply shuts down one's ability to do anything, except, perhaps, scream. Mental discipline simply does not work in these situations." In terms of scale, the wasp's sting is rated near the top of the Schmidt Sting Pain Index, second only to that of the bullet ant and is described by Schmidt as "blinding, fierce [and] shockingly electric". Because of their extremely large stingers, very few animals are able to eat them; one of the few animals that can is the roadrunner.
That's for normal ones. Imagine an eight inch barbed stinger pumping a pint of that kind of venom into you.
On the other hand, the Riot shotgun just annihilates them. Also if you cripple their wings, they aren't nearly as fast.