Via Homely Scientist, I’m introduced to the shockingly large Vespa mandarinia (a.k.a. the Asian Giant Hornet, a.k.a. Japanese Hornet).
He quotes the wikipedia article on the species:
The venom contains 5% acetylcholine, a greater concentration than is present in bee or other wasp venoms. Acetylcholine stimulates the pain nerve fibres, intensifying the pain of the sting.
I haven’t seen anything anywhere that would corroborate that Acetylcholine stimulates pain receptors. Acetylcholine, like all the neurotransmitters, is used in a lot of different contexts, sometimes to contradictory effect (it’s not the transmitter; it’s the system), so it’s hard to pin down what it does. The only studies I’ve found suggest it actually increases pain thresholds, but that’s in a specific context. Interesting thing to me, though, is the further example of neurotransmitters appearing in venom.
