Aaron, everyone seems to agree that there are a lot less now than there used to be. But the evidence is anecdotal; real proof is hard to come by, as nobody has actual data, over a period of decades, that would stand up to statistical scrutiny. Having said that, I personally don't doubt that their numbers are down in Canberra, having in the 1960s observed hundreds of beetles on Eucalyptus blakelyi street trees, leaving them with very ragged crowns by the end of January.