What is this insect?

I found these insect clustered om top of a basil plant! Anyone can id it? is it good or bad?
Thanks

 

They look like some sort of fly. One I've never seen tho. Are your plants excreting something?

 

No. But the Basil top leaves are curled probably because of some kind of disease. However, this curling had been for a long time now, but the insect just appeared today.

 

Been out where you are, I would not know other than a fly, which is no help I.m sure.

 

The leaf curling may be due to some kind of little insect like aphids or a fungus. The flies may be eating them.