I found these creatures stuck to a leaf on my tomato plant in the greenhouse/glasshouse, in early June, in south Oxfordshire in the United Kingdom.
They are each about 1-2mm in size. They didn't move much, even when gently nudged, although some did crawl tentatively.
I would be very interested to know what these are, especially if they are a beneficial species or a pest!
These little creatures look a lot like White-margined Burrowing Bug or Sehirus cinctus nymphs.
Very interesting thing about the Sehirus cinctus is their brooding behavior. The female watches the eggs and even feeds the young for a few days. Have a look around. You might see it.
AFAIK they don't harm your plants.
More info:
http://polyploid.net/bugs/bugs.html
https://en.wikipedia.org/wiki/Sehirus_cinctus
