Review on Riddex Plus Insect Repellent Deterrent by Miguel Saiz

I've been using this product for about 3 months and I have to admit that I'm not sure if it works. It plugs into an outlet in the "habitable" part of a small (30ft) caravan. I've noticed that the red light sometimes flashes, indicating it's "working". I live in a rural RV park with no bushes or bushes. In the last 45 days I've only seen 2 "big" cockroaches. But I keep seeing these tiny ants. Sometimes I find them on the kitchen counter and on my bed mattress. In this case, I supplement the electronic device with a spray. Is it possible that the product only works on "selected" insects and rodents?