Certified GKH Gardening Expert
Chiggers are a type of immature mite, whereas no see ums or biting midges are minute flies that look like tiny mosquitoes.
Midges belong to the Ceratopogonidae family and chiggers belong to the arthropod family known as Trombiculidae.
So they are not related but they both bite!
Incidentally, while researching this, I read that chiggers do not suck blood, a common belief, but eat skin cells.