Oh yeah. The Japanese ones definitely do eat the pests. I've read that they're at least as good at, or possibly better than, the native red ones. That's apparently why several attempts have been made to bring the little bastards into the US. But what drives me nuts is how every fall they start coming inside. IMO, they're just annoying pests (at least during fall and winter). They can get to be about as annoying as houseflies.