Well it isn't an aphid. That's as far as I can help. Not many insects eat entire leaves and I can't think of any that turn leaves yellow. I really would suspect a watering issue given those symptoms. Any chance of a picture of the damage ? There is always a tendency for lower leaves to decline on mature plants.

Looks like fungus gnats, which are almost always a sign of excess moisture. Often, the potting medium itself can be the cause of a fungus gnat infestation.

The presence of these gnats plus the yellowing and dying leaves point to a moisture issue.

It would help to get some sense of scale. Is it the same size as an aphid?

I assumed that the description "which looks similar to [sic] a fruit fly" meant size, too.........maybe not. Many people find it difficult to tell a flying aphid, a fruit fly, and a fungus gnat apart.....with reason.

I do not think its a watering issue. It the size of an ant. It does not eat the leaves. But i think i suck the juices out of my plants. I do not know how to get rid of them...i will post a picture as soon as i get home. But as soon as i see one of the leaves drying and dying..i pluck them out for prevention.

Thanks for the comments. I think it might be a moisture issue. I will post a photo this afternoon

It does make sense? So how is that insect called? and how to get rid of it?
I use Osmocote Herb and Vegetable mix.

I had a feeling the larvae might be eating from the bottom of the plant. So what is my next step to prevent and reduce those insects? get rid of them?

Go with the fungus gnat diagnosis. I have had them in the house and tried the mosquito dunk remedy, but they stopped being a problem when I did essentially what rhizo said: thorough excessive saturation watering and then surface drying. I don't agree with peat being a problem, but we have very arid air here, inside and out, and surfaces can dry fast, which you need.

So prevent by controlling the watering. and isnt there any insect stuff i can spray to kill them or to get rid of them meanwhile?