OK, I'm not an expert but do have a son with Aspergers who suffered horribly from OCD and pretty-much-anything phobia (chemicals, insects, birds, yew trees, berries, furry animals, lead poisoning...) for two years when he was your boy's age. In the end he had two courses of cognitive behavioral therapy with a trained therapist, but it was a long, long wait to get the appointments. With big reservations, then, here's what we learnt.
Basically, their approach to each phobia was 'exposure; response prevention; distraction', but starting very, very low key. From the sound of it, his (logical) initial fear has spread to all insects, not just bees and wasps, so it really is a phobia. Right, that gives you something to work with. You start by finding the point at which he is NOT badly frightened, and work up very gently.
The whole aim is to build up tolerance slowly, not to protect and reassure him too much. (We tried for ages to tell DS that he was safe -- cleaned surfaces, shooed away insects, explained, reassured... It didn't work. It just escalated the fear and 'justified' the obsession.)
Is he OK with pictures of insects, or mentioning their names? If he's even worried by these, you could start inside, with a cuddly ladybird or a picture of a grasshopper something safe. See if he can cope with having it in the same room ('exposure'). If he can even briefly he gets a reward for staying ('response prevention') and you quickly start doing something else that he likes (distraction play trains, watch a video, eat chocolate, whatever!).
Once he can play happily with the safe toy/model nearby, the next stage would probably be to get some unfortunate ladybird, woodlouse or spider (nothing too flappy) in a jar and have it around while you play, distract and reward. It might take one session, or it might take lots. Then maybe see if he can manage to play inside with the door open; or have a (safe) bug in an open jar. Keep on with the treats for successfully coping. Sod his teeth for the moment -- a few chocolate buttons may need to be sacrificed in a good cause.
He may need expert help -- as I said, I'm only an expert on my own child. But this softly softly approach has now seen off DS's fear of metals, birds, trees, strange cars and buses, and (mostly) chemicals.
God, I seem to have written you an essay. You've probably bought him a beekeeping hat and gone for a picnic by now!
All the best, anyhow.