We have something similiar to that also, and they do work great!
I bought some potting soil to repot my house plants. I guess it had gnats in the soil because all of a sudden gnats appeared right after I repotted my plants. They were bugging the crap out of us! They seemed to be attracted to our computers and kindles because they were constantly on the screens. So we read up on it and it seems those plug in traps have a blue light that flying insects are attracted too. We trapped them all on the sticky!