Apart from Adders why does the U.K. not have any deadly venomous snakes or spiders?

Answer 1

My guess is that the climate is too harsh and cold for these species. Even the Adder of the U.K. has a very dark color variation that seems to be perpetuated by it's superior ability to heat up faster in direct sun exposure.

Answer 2

I wonder if the venomous snakes were eliminated by humans. UK has had human population for very long. I don't really buy the cold climate theory. In North America there are rattlesnakes and venomous spiders and insects in areas that have much colder winters than the UK.

Answer 3

Our climate is not the kind of place where there is a high number of species that have a tendency to be poisonous e.g they have loads more species of spiders and snakes in tropical countries, so there is a greater probability that there will be higher number of poisonous ones. As for the proportion of poisonous to non poisonous species - that would be an obscure but interesting answer.

Answer 4

Two reasons...

1) Climate

But more importantly...

2) How would they get there, spiders and snakes, for the most part don't swim or fly.