My efforts for blowfly larvae control in nests have been successful, until quite recently. This set of larvae were so strong and in large numbers, the nestlings became too anemic and weak to survive the amount of feedings they were ingesting from Mom and Pop Blue. They were 9 days old when death came knocking at their nestbox door. The last time I lost a whole brood to blowflies was Spring 2008. Not all happenings on the bluebird trail are happy ones. I will continue my two methods of control: (1) hardware cloth bases below nesting material (helpful but not as effective as the only method of control) and (2) the use of puffing some organic food-grade Diatomaceous Earth inside the center of the nesting material and underneath the nest on the wood floor of the nestbox before bluebird eggs hatch. The key is to eradicate the larvae while very young, right after they hatch, which nature usually times around the same time the birds’ eggs hatch. I had treated this nestbox with the DE, like I have all others. This year and at this nestbox, I must not have applied the right amount of the DE to take care of the number of hatched larvae to cause the damage they did. Below are a set of photos of different methods I’ve used in past and presently (applying DE) and another method of using leftover hardware cloth from making the Noel Guards for my boxes for the bases to slide underneath completed nests. Captions will explain the pictures. Warning: The last photo in this series is not a pleasant one. I cropped out the dead bluebirds, but I wanted you to see the larvae that killed this brood. You will note how large the larvae got, some gorged with blood, and a dead bumblebee–which obviously was the last-ditch effort of feeding the parent birds attempted to make for their 8-day old kids, too weak to eat. This is a good representation photo of what the larvae looks like when healthy and successful feeding on the nestlings at night. I had to dissect the pine needle nest to find this big patch of them.