Bug Muldoon and the Garden of Fear by Paul Shipton
This is the original 'Bug Muldoon' book, about a beetle detective told in a Raymond Chandler-type narrative. There's weird stuff going on in the garden and Bug has to get to the bottom of it. It started off as a run-of-the-mill missing insect case, but now the ants are acting strange and the Wasp Queen is threatening to kill him. Just what is going on?