It’s a spider. It will not hurt the plant. It’ll eat pests. It actually looks like a garden spider rather than a house spider so just chuck it out of the window.

That little spider is a beneficial;). I use to HATE spiders, but they do a really good job at eating the insects that eat your plants. My Dorstenia had a little bit of mealybug. This spring I noticed these tiny webs. At first I thought “great my nightmare has finally arrived, red spider mites”. Then one day while watering a little tiny spider came down. That little spider has kept my Dorstenia mealy free for months.

There are other beneficial insects like ladybugs, green lacewings, and my personal fav praying mantis;).

Being a garden spider it is not going to survive long indoors. In fact the way its legs are scrunched up it could already be on its way out. You see them around a lot this time of year and their lovely webs are everywhere in autumn.

p.s. no mantises in London.

Kara, I consider mantids to be the enemy, eaters of butterflies, honeybees, and other beneficial insects. They go after anything that moves.

Do you know a good way to kill caterpillar ?

Do you have caterpillars? The creature in your photo is a spider and is totally beneficial. The US posters are discussing caterpillars in relation to mantises. We don’t have mantises in the British Isles.

eta if you do have caterpillars pick them off and squash them.

I pick them off & squish them, too, but check out this post https://www.gardenweb.com/discussions/5508359/worm-and-caterpillar-control#n=1

Is this or a similar Bt product available in the UK?

I am not sure but I will check

You haven't shown us any pictures of caterpillars in any of your posts, so far. Nor have you shown any damage which might be caused by them. Is there something which makes you think you might have them?

Just happened to see this today. As it turns out, its not only Praying mantis that feed on butterflies. Who knew...

I thought spiders gave out get out of “jail free” cards to all the butterflies;).

HA! Apparently not! Not this spider. Not this time.

I had cut off the dragon fruit stem that has bite. But the following pictures are my poor epiphyllum stems that have bites on. And the last photo is the worm I form on the soil. But I just found one though. I think my plants don’t have any new bites after I run grow light on them during the whole evening.

Ms....the insect pictured looks like the larvae of some sort of beetle.