Buffalo gnats / Black flies in Indiana THEY WERE NOT HERE YEARS AGO, WHY?

I Live in Southwestern Indiana. I grew up in this state. I have been here 42 years. People keep asking "where did these buffalo gnats come from?" and the answer always seems to be "Because there is so much water this year." or "Mild Winter" Well, I am here to tell you, and so would a lot of people I know, they didn't used to be a problem ever. We always had a few gnats growing up, but never these Condor sized biters. We did not have these several years ago, and we had years that were mild and years with standing water. So my question is.....Where did they really come from? Was it an agricultural test like the "lady Bug" type beetles that went astray? Surely there is someone out there that knows the truth. If you are from around here, do you remember as a kid not being able to go outside because of gnats?