I'm starting work on a short series set in a standard fantasy sky world: floating islands and so forth - with the added element of insects and bugs large enough to move humans around. Bees the size of horses, beetles as big as an elephant, etc. Now I'm fairly attached to the premise, so I'm more than willing to have magic fill in the gaps where real biology can't, but I'm curious: How possible is this? There are also a couple of environmental factors that might affect things. Outside of specially protected human settlements, the concentration of oxygen in the atmosphere is much higher, around %80 as a starting "not sure how this affects things yet" number. (Suffice it to say that it is too high a concentration for humans to survive without breathing equipment.) The gravity outside of human settlements is also much lighter, about 1/5 what it is here in reality. So, with these factors in mind, how well would these massive bugs do?