[DR.AR (OP)]

When I was a young child at school, I was taught that earthworms cannot survive for long in water and that is why they come to the surface when it rains.  They also allegedly come to the surface when it rains because they are escaping predators such as moles. The sound of raindrops falling onto the ground may be similar to the sound of a mole burrowing. It is also said that birds patter around on a lawn, trying to entice earthworms to the surface by mimicking the sound of heavy rain falling on grass.

However, having started gardening recently, I now regularly see several earthworms at the bottom of the water butts and other water containers in my garden. They appear to survive the underwater existence for days and perhaps even a few weeks, but having got into the containers, they are apparently unable to get out ie the behaviour appears to be self-destructive........but there must be a better reason.

Any explanations?

[lidadaidaihua]

When I was a young child at school, I was taught that earthworms cannot survive for long in water and that is why they come to the surface when it rains.  They also allegedly come to the surface when it rains because they are escaping predators such as moles. The sound of raindrops falling onto the ground may be similar to the sound of a mole burrowing. It is also said that birds patter around on a lawn, trying to entice earthworms to the surface by mimicking the sound of heavy rain falling on grass.

However, having started gardening recently, I now regularly see several earthworms at the bottom of the water butts and other water containers in my garden. They appear to survive the underwater existence for days and perhaps even a few weeks, but having got into the containers, they are apparently unable to get out ie the behaviour appears to be self-destructive........but there must be a better reason.

Any explanations?

[Airthumbs]

I used the search term "Aquatic worms" and ended up with this;

Limnodrilus hoffmeisteri; grows up to five centimeters long, and its body is about one millimeter wide. They have reddish bodies, which are split into segments. Just like earthworms, the ends of their bodies are pointed.

I suggest that you don't have Earth worms but Aquatic ones instead.

As to how they get in there..... well I imagine your water butt is collecting rain from guttering.  Maybe after heavy rainfall the odd Earth worm gets washed away into the butt.  This could also be a similar process for the Aquatic worms....

You could always try and identify the type of worms your butt has collected and that may give you more clues.

[CliffordK]

I don't think I've seen worms in the bottom of buckets and etc. 

Is it possible that you have birds that are kind enough to leave deposits in your buckets?

[DR.AR (OP)]

I will look further into the "aquatic worm" idea. Thanks.

[Schotten]

I noticed that a huge number of thin earthworms appeared in two of my waterbutts in September, some dead, some possibly alive.   A huge number of same seemed to have disappeared from my nearby rich and active compost heap.
We did have a severe heatwave in August, and worms hate hot/dry conditions, so it could be a weird and miraculous (and rather worrying) migration.
My waterbutts are wrapped with a bamboo screen, so it’s not too much of a leap, or climb, for them to get up and in, I guess.
My fault perhaps for not covering the heap, although I couldn't've kept it below 30°C in the August heat… which I think might be the critical temperature for those essential little wrigglers.
It's possibly the same sort of story with sudden shoal deaths, or beached whales/dolphins in the oceans… a huge patch of too-warm, or oxygen-depleted, or chemical-rich water.