Although this bumble-bee was caught in flight across my meadow, her photograph shows beyond the shadow of a doubt that she had been a recent visitor to the blossom of some milkweed, for, projecting from her right hind leg and plainly visible, are the pollen masses of the milkweed flower. They look like little paddles and hang in pairs, although this you cannot see in the picture.
We know that flowers depend upon the bees to fertilize them, but somehow I do not think we grasp the completeness of this dependence, nor realize how many flowers there are which, unless they have their own pet insect visitors, would soon become extinct.
The milkweed lures its visitor with little cups of nectar, and beside each cup it sets a trap which is as carefully worked out as the steel traps which the modern trappers use. Across the top of a little slit, wide below and narrow above, lie the small ends of the paddles or pollen masses, firmly joined together. As the bee alights to sup the nectar, her foot slips into this crack, and in trying to extricate it she pulls up the pair of paddles which fasten themselves onto a hair of her leg like a clothespin on a line. In drying, the paddles clap together in such a way that by the time another milkweed flower is visited they can slip with the leg right into the little slit and are broken off and left there as the bee again pulls out her leg. Once inside, these pollen grains throw out a score or more of tiny, rootlike tubes which grow into the lining of the slit and carry to the ovary below the fertilizing germ plasm which makes the seed develop.
The bumble-bee, of course, is strong enough to slip into these traps and pull her legs out as a routine thing, but many small moths and butterflies are not, and these get caught and die upon the blossoms.
THE POOR MALE BUMBLE-BEE
(Bombus americanorum, Fab.)
It was late in October before I noticed, flying low here and there across the clover tops, large bumble-bees, which seemed to be more covered with golden hairs than those which I had watched throughout the summer time. At first I thought them queens, but as their number multiplied I felt I must be mistaken, and one of my insect-knowing friends explained that they were only males, and that with the approaching days of winter they were all doomed to death. Already, he pointed out, their wings were battered and frayed from flying against the autumn winds.