An issue I can see is that in other countries where these hornets are established, most of their nests are in trees, and often way high in very tall trees. Which might be why the assumed one last year was never spotted. But the nests discovered so far this year are all in buildings. IE places where they will readily be seen. But for every one in a building, if behaviour here is the same as overseas, there will probably be several high up in trees. Of course at this stage with only one queen per nest or perhaps a few workers, there will be little activity to attract attention, and the nests themselves will be almost invisible. MPI simply does not have the resources or the money to thoroughly check all available habitats. In my view the public should be more educated so if large numbers of people are carefully inspecting trees in their areas, there will be a better chance to find and eradicate these things.