Barry2 

The Perfect Storm.
With Corona going on, I did a buzz cut on my hair. I didn't leave much in the way of protection.
I've been doing a lot of riding on Canal Trails (beside water)... And, Bees like the water source.
Mix this with the Bug Magnet helmet I'm using and I keep having to stop and empty out the large insects that I'm scooping up on my travels.

Not my idea, but a hair net over the helmet works great. I was unsure which to buy (size & Construction) and could find no recommendation.

So here you go. Not saying this is the only choice, but these cover my Kask (Size Large, no jokes please) just fine.

Qiansou Disposable Hair Nets Durable Nylon Breathable Honeycomb Latex Free Pack of 100 Black
At $14 per 100 - If anyone laughs at you using a hairnet, you can afford to offer them one or two.
The Honeycomb construction does not obstruct airflow and the 1/8" holes stop the big stuff that bugs people in our area.

All the best

Barry

skidder

Are the holes in a hair net small enough to keep bees and wasps out? I have problems with both of those infrequently. Bigger problem is the mating swarms of small gnats that hang in the air in the early morning; you don't see them until you're right in the middle of them; inhale too many and you'll suddenly have a coughing fit trying to get them out of your throat!. I used to wear a neck-gaiter type of covering that I could pull up/pull down when approaching areas I knew would have them, but those gaiters are all sold out right now (coronavirus).

Barry2 

Yep - So far, So good!
Pic I added may help

Barry

coffeesnob

just spray your head down with some kind of safe repellent

Slightspeed

I've had trouble with bees inside the helmet too. Since having pre-cancerous spots removed from my bald old head, I usually wear a cycling cap under my helmet, but this Smith helmet has a honeycomp helmet liner/cushion that works very well at letting air in and keeping critters out. The holes are less than 1/8" diameter. The worse one was getting a bee in my helmet strap, and getting stung on the exposed area below the helmet. Got one on my inner knee too.

atwl77

Reminds me of that Bontrager WaveCel helmet thingy...

jpescatore

My bees in helmet count is pretty low, but I like that idea.

Doing the Seattle to Portland ride last year I had a bee go right into my mouth and sting my inner lip before I spit it out. It started to swell up. Years ago, riding a motorcycle, I something sting me on my neck and had an allergic reaction that required an emergency visit, so I stopped at the next rest stop with a medical tent and they said it didn't look too bad in there - kept going, felt fine.

Most times seems like bee hits me in the chest, occasionally goes down my shirt in summer. Stopping quickly to deal with that led to an embarrassing "Oops, forgot I was clipped in" incident many years ago which provided much amusement for my wife on that ride.

noimagination

Nice! Cheap, convenient, effective, unobtrusive. I like it.

Low bee density around here, so I've only been stung on the head once, when a bee got trapped between a helmet strap and my face just in front of my ear, which your solution would not prevent - nothing is perfect. I have had large-ish bugs (bees? dunno, can't always tell) fly into helmet vents and down my jersey - I suppose I provided some entertainment to passers-by as I sat up and whipped off glasses/helmet or unzipped jersey (as appropriate) while riding down the road.

I also left my helmet outside to dry overnight once, and did not realize that earwigs had decided my helmet made a nice spot to nap. That time I actually stopped to brush the earwigs off my head and shake them out of my helmet (5 - 6 or so of the little suckers). I had the willies for a while after that, and air moving over my head felt like bugs crawling for a time on that ride.