Greenhouse beasties

Please, please help me to identify these flying "insects" that have suddenly appeared in my greenhouse! There is quite a lot of them and I have never had them before. They are roughly 14 - 17 mm long and black. Somehow they don't look good.....

 

I don't know metric sizes but it could be fungus gnats. They love wet soil and lay eggs and multiply in the pots. They destroy roots. I have found that drenching the soil with a mixture of weakened peroxide helps but must be repeated. Through a few cycles. I have had good success with putting a layer of sand on the surface of pots. They don't like it and can't lay more eggs when the sand stops them entering the soil.

Or I could be wrong!

 

Half to three quarters of an inch @CanadianLori

 

Yes, Pete beat me to it, they are not exactly small!

 

Oh dear. That is nasty. I do not know what they are. Sorry I can't help

 

Thanks anyway Lori. I hope somebody will be able to tell me what they are!

 

Was a simiar post the other day, though no answer.
Can anybody help ID these flies?

Wonder if yours are coming into the greenhouse or possibly coming out of some compost as seems to be the case in that thread.

Possibly some form of Soldier Fly or Flying Beetle ?? check your compost in the pots or even the bag for any signs of similarly sized grubs ?

 

That's interesting, I had a look at the other post and they look very much alike. I will have a closer look at compost etc, thanks!