Long-Horned Bees – Melissodes
Long horned bees are named for the extra long antennae found on the males; females have short antennae in comparison. These bees are represented in North America by 120 species.
Males like these two Melissodes agilis can be found feeding and sleeping along the ege of flowers like this false sunflower.
The female carries pollen on the long hairs of her hind legs called scopa. She will carry this pollen back to her underground nest to make into “bee bread” that is used to provision growing larvae.
This Melissodes trinodis are specialists of sunflowers. Look for them in late July and August.
Long horn bees are often specialists of their preferred flowers. The males can often be seen in the day looking for females, and at night cluster together to sleep.
Melissodes bimaculatus unlike other long horn bee species are generalist that visit a variety of flowers like this monarda.
Thistle long horn bee (Melissodes Subillata) as its common name implies is a specialist of thistle.
Melissodes Denticulatus is a specialist of ironweed, seen here on a knapweed.
Native Beeology 
I would love to know more of these bees. We have them on our sunflowers. They are one the few bees that could careless if we are around. They fly into everything, they run into us and we have never been stung. I would like to know more about how they nest.
I found them in my pool this year. I always rescue the honey bees that fall in, but this year I have seen almost no honey bees and now these black bees are here. I have never seen this bee. From what I have gleaned from the net the nest in the ground and are not aggressive. I really hope my wild bees come back
I think these might be what I have been noticing on the flower stems of some of my tall grasses in the rain garden! They line up together & I have never seen this before! Is this line of bees what these longhorned bees do?
Evidently! I had a bunch that would sleep on my blue grama grass.