John Vandenbrooks of Arizona U, you are the hyperoxygenated wind beneath my enormous wings.
As you all know, way back in the Carboniferous the dragonflies, and various other insects, were enormous, as the fossil record records. The assumption has been for a long time that the atmosphere back then was more highly oxygenated, and therefore that the chief limiter on size for insects is their respiratory system (1).
Vandenbrooks, however, seems to be the first person to actually try and test this by rearing insects in high oxygen conditions. This was actually a bit of a risk, I assume — just because conditions would allow a big bug doesn't mean that existing species would spontaneously grow to outlandish sizes. However, joyfully, it works (2).
Of course, if you're going to do it, you have to do it with dragonflies, because they're the giant Carboniferous insect poster child. However, dragonflies are very difficult to rear, and the adults need live prey, so Vandenbrooks had to hand feed them. The subtext is obvious: he has not only created a race of giant dragonflies, but a race of tame giant dragonflies that will obey his every whim! I am so happy with this news.
He has giant beetles too, apparently, but not giant cockroaches. The cockroach thing sounds like a disappointment, but in actual fact they still give less space over to their breathing apparatus: rather than using the extra O2 to get bigger, they've used it to become more efficient.
Annoyingly, I haven't yet found any pictures to show just how giant these insects have become, as this is presumably just a model. Or possibly fortunately. After all, they've almost certainly just become "a bit bigger" whilst if I haven't seen any pictures, I can imagine that they're big enough to give kiddies rides on.
(1) Insect respiration 101: most insects are kind of passive breathers. They have a series of holes down their sides that let the air into their innards through a series of tubes, so that oxygen exchange can occur. Larger insects need more tubes, and as an insect gets bigger the percentage of its volume taken up by this tube system increases disproportionately, meaning that eventually there'd be nothing but tube and no insect inside the carapace. A higher oxygen content to the air means that you need less air to get the same amount of oxygen, and therefore fewer tubes for the same volume of insect. Some insects, as an addendum, do sort of breath — Wasps (I think I have this right) flex their abdomens, changing the interior volume and therefore drawing air in actively for an extra boost.
(2) And surely this is exactly what Vandenbrooks cried out, witnessing his creations for the first time, possibly adding, "and they called me mad!".