Marty, most likely they are polliating. Last year we had lots of bees (mostly bumble bees) in our peas (some purple hulls) and you could pull a pea off that they were on and they would just fly to the next. Only person that got stung was my bro-in-law's girlfriend and that was because she accidently grabbed one.
We need the bees.

Shot

Yellow jackets are very territorial compared to a lot of other "stingy things."

1- make sure they're not hoverflies (they look live very tiny waspy things) because they're good at pest control of the baddies.

2- if they are yellow jackets and visiting they're usually (mostly) harmless unless you're near the nest or scare the crap out of them.

Here is a link that might be useful: hoverfly pictures

Agree with nc-crn; Yellow Jackets are harmless to your plants, but they do love sweets and protein rich foods. That is why they do a number on fruits. Watch for a severe aphid infestation on your peas. Peas are very attractive to aphids, and Yellow Jackets love Honeydew which the aphids secrete.

Yeah, in general "stingy things" visiting plants are way more concerned with the food over what's around them.

I freak friends out by poking bees on their back while feeding. The bees couldn't really care less. That said, I wouldn't recommend poking any yellow jackets or wasps, though.

I've noticed a lot of wasps on my yardlongs too... not surprising, given that they are just a subspecies of cowpeas. They show up as soon as flowering begins. The odd thing is, while they land on the flower stalks, it doesn't seem to be the flowers themselves that attract them.

There are knobs/pads located just below the flowers, and they appear to give off a substance that is very attractive to some insects (ants & ladybugs too). The wasps & yellowjackets feeding there are uncharacteristically passive, almost as if they were intoxicated. They don't react aggressively to my presence, and I have never been stung while picking.

For the most part, the wasps are beneficial, as are the ladybugs... so growing yardlongs to attract them is part of my pest control program.

They have always been wasp magnets here. Not sure what attracts them to these but it must make them happy because the wasps could care less about you being in there with them.
Takes a bit of getting used to though ;)

One morning while camping I was reading the paper, sipping coffee and absentmindedly eating a donut. I bit into the donut and was stung on the tongue by a yellow jacket who had been attracted by the donut. It was a shock, but not so painful as it might sound.

Jim

Jim just reading that was painful! ouch! I stepped on a hornet once, it bit me on the sole of my foot, that hurt!

You all have flowers on your yard longs and purple hulls already? it is in the 60s here, warm weather stuff is not happy but everything else is doing so well. My yard longs have not even decided how they want to climb the pole. It has been raining too, what a treat!

Last year, I was out watering my garden, and a yellow jacket landed on the hose nozzle, about 2 inches from my hand. He/she sat there, drinking drops of water from the nozzle, and enjoyed the ride on the hose for about 10 minutes or so :D

My sister-in-law, who hates all things with stingers, was out in the garden with me while i was doing this. She could not believe my calm, or the fact that the insect did not sting me. I told her the YJs and I had a good working relationship--I don't swat at them, they don't sting me. I provide plants attractive to them, and they deal with pests. Win-win for all of us (except the pests) lol.

I think the lesson of these stories is "don't bite them and they won't bite you".

Jim

Wasps are also attracted to cleome flowers, which I grow throughout my garden. The benefit of this is that there is hardly a caterpillar to be found, and not many large spiders either. When I had a severe aphid infestation in one of my pepper cages, all I had to do was open it up, and the wasps were soon swarming on the aphids. I like having wasps in the garden... I just won't let them nest there.