They are just thunder bugs, I think. Not harming your plants. They come and go.
Pollen beetles, and they're pollinating your courgettes ... they are your friends.
I call those Pollen Beetles, otherwise agree with FireThink hard before 'dealing with' they're all part of the cycle of life and if you spray those the beneficial insects will die as well
It turns out there are lots of insects called thunder bugs and lots called pollen beetles.