No see ums?
All summer we have been bitten by something on our screened porch and in our yard. They usually go for the ankles and leave an itchy welt, but not like a flea bite. This has never happened before in the last 31 years! We sprayed a repellent around the porch to no avail. Suggestions?
Howard County Maryland
This sounds like mosquitoes, most likely the Asian tiger mosquito.
They are small, and can get through cracks around screens, and even come inside with you when you enter your home.
Females are silent and stealthy (only males buzz but don't bite so they're not coming to you). They bite low whereas other mosquitoes bite higher on the body.
Here is a page with a photo of them and how to protect yourself if you can't tighten up the porch, which is difficult.