Spider bites

[The Snark]

but the fact that they have them and don't use them on prey means there is a difference between offence and defense.

Or the difference in physiology, the immediate -awakeness- sensory awareness, the neurological stimulation, the muscular contractions from the stimulations, the muscular and neurological development, the environmental circumstances, the time of day/night, the temperature and probably several other factors.
As one example, Bungarus Fasciatus. Traits completely alter depending upon the time of day. Placid and laconic, disinclined to bite and often gives a dry bite in the early morning, fast, hyperactive and capable of delivering several bites in close succession in the early evening.

Heard a saying in Laos. Hannahs eat Kraits in the morning. Kraits eat Hannahs in the evening.

 

[SonsofArachne]

Or the difference in physiology, the immediate -awakeness- sensory awareness, the neurological stimulation, the muscular contractions from the stimulations, the muscular and neurological development, the environmental circumstances, the time of day/night, the temperature and probably several other factors.
As one example, Bungarus Fasciatus. Traits completely alter depending upon the time of day. Placid and laconic, disinclined to bite and often gives a dry bite in the early morning, fast, hyperactive and capable of delivering several bites in close succession in the early evening.

None of the things you mentioned would account for the evolution of a defensive threat display. I'm not sure why you're so resistant of the idea defense in in snakes, maybe because you were bit, but your getting too close to a rattlesnake triggered a defensive response rather than a feeding response. I've kept snakes for many years and went herping many times - I've been bit a number of times (non venomous). Most were defensive, some were feeding response (captive snakes who struck at rats, missed, got my hand instead), so I know from experience that there is definitely a difference.

 

[The Snark]

I'm not sure why you're so resistant of the idea defense in in snakes, maybe because you were bit, but your getting too close to a rattlesnake triggered a defensive response rather than a feeding response.

Or I spent several summers running pack trains in a rattler infested area. Probably encountered 200-300. Absolutely no difference between defense and offense. Always loaded guns ready to go off. Never predictable. Same when I worked at a nature center. Placid one week, ready to climb the walls and fire at anything that moves the next.

 

[SonsofArachne]

I can see this is pointless and we've completely derailed this thread, so I agree to disagree.