Urgent!!!

yesterday while weeding the veg patch i noticed a fly on my carrot seedlings, its abdomen was shiny bottle green (it was definately not a green housefly type) it was veryn slender and small. I immediately killed it in case it was carrot root fly! Is it by my description?? If so any solutions to stop fiurther damage?

thank you.

 

or this?

this is a potato capsid which I read is quite fond of carrots and chrysanthemums too.