There is a tree outside my window that is frequented by bees. Any time I look outside there are at least a few bees flying from leaf to leaf, and stopping to walk around the leaves that they land on (see Photo). I've seen individual bees continue this behaviour for a while. Why are they doing this?Charlie F, Berkeley, California, US
I have yellow jackets that hang around my roses and crawl around the leaves. I used to put traps up because you couldn't even eat a sandwich outside without them bothering you. They are meat eaters and seem to be especially attracted to mandarin chicken. One day I got up close to see what they were so interested in on the roses and I noticed that every once in a while they would find a small green worm and fly away with it. This explained why my roses were decimated when I put the hornet traps up. Now I leave them alone and my roses are fine.
The insect pictured is actually a wasp and there could be a good reason that they're there.''Seems like you have an infestation of a wooley bug. They secrete a very sweet substance that attracts wasps and butterflies. You will be able to tell because you will see what appears to be sooty streaks where they are, and they huddle together.'' - a quote from Tucksie on Yahoo answers about a similar question.
I'm no entomologist but that's a wasp or a hornet (too low res) not a bee. As it's a wasp and not a bee I'd suspect that they're eating some other bug on the leaves.
As the others have stated the "bee" in question seems to be a Yellow Jacket.Yellow Jackets feed primarily on insects in spring and early summer, then switch to a more omnivorous diet in late summer and fall, being especially attracted to fruits and anything containing sugar.So depending on the time of year they may be finding small insects on the leaves as someone has already stated or eating sugary tree sap from the leaf surface.They also chew up bark and wood to make their "paper" nests.
The Tree is a Liriodendron tulipefera, or tuliptree. They are a favorite host for many types of aphid( a sure sign is a sooty wet deposit all over the leaves...aphid poop!). Aphids are in turn an easy snack for any carnivorous bug passing by. Check closer you will likely find ants tending them as well as lacewings and other creatures feeding on them.P.S. dont park your car under this tree, it or anything else will get all gooey!