One hypothesis for this behavior is that the bees that are sitting on the
Larkspur are initially attracted by fragrance from the leaves.  Larkspur has
a pleasant, attractive aroma to it's leaves.  The floweres that come out
later have a slightly different fragrance. As the leaf parts and seeds of the
Larkspur are considered to be "poisonous", it has been suggested that the
bees become "doped" temporarily when they land on the leaves and absorb a
small amount through their "feet".  They remain on the leaf for the time that
it takes the initial effects of the toxin to wear off, then fly away.  Some
seem to sit longer than others.  If they don't move around much on the leaf,
they would not rupture or disturb the leaf tissue to get any more of the
poison, and can fly off when they recover.  Other bees that  see them sitting
there and come to investigate, suffer the same "doping".  Hence, the little
crowd on the leaf.  An interesting explanation, but we shall probably never
truly know.           Emily Johnson, IN