out by many bees, flies and butterflies. Bumblebees especially delight in these blossoms, which they visit with astonishing rapidity—Bombus consimilis making about seventy visits per minute. On the middle lobe of the upper lip there are two bright yellow spots, which tell of the presence and guide to the exact location of the nectar concealed within the tube of the perianth. When the pickerel-weed bee makes its appearance about the middle of July, there is no other flower in southern Maine which can offer it so many inducements as the pickerel-weed. But let us look farther and see if there are any other bees, which behave in a similar manner.
In the quiet bays of the river, floating upon the surface of the water, bloom the yellow water lilies (Nymphæa advena).
Again the wild cow-lily floats
Her golden-freighted, tented boats,
O'ershadowed by the whispering reed,
And purple plumes of pickerel-weed.
The flower is securely anchored to the bottom of the stream by a long stem. At first the opening in the bud is no larger than a bee's body, and the chamber within offers a dry and snug shelter amid the waves. It may truly be called a haven of refuge. Directly below the entrance is a broad, many-rayed, crown-shaped stigma, as in the poppy. The petals are thick, wedge-shaped bodies which are orange-yellow on the outer side near the top, where they freely secrete nectar. Under a microscope both large and minute drops can readily be seen. The stamens are indefinite in number; and reveling in the pollen, their bodies completely covered, there is a large and lively company of small flies called Hilara atra. Less common are two beetles, Donacia piscatrix and Donacia rufa; but what chiefly interests us is a small bee, Halictus nelumbonis, or the water-lily bee. This bee in this locality is never found on any other flower, but elsewhere it is met with on other species of the water-lily family, or Nymphæaceæ. It is an oligotropic bee, and the only species of the great genus Halictus that is known to behave in this way.
But in Andrena this is a common phenomenon, for instance, in Washington County, Wisconsin, according to Dr. Graenicher, twenty-four of the forty-seven indigenous species of Andrena are oligotropic. This is the largest genus of North American bees. They are sometimes called ground-bees, since they build branched tunnels eight to ten inches deep in the soil of sandy pastures and hillsides. A part of the species are vernal or fly in springtime, while a part are autumnal and fly only in autumn. They provision their cells with balls of "bee-bread," about the size of a garden-pea, composed of pollen moistened with nectar. An egg is laid on the top of the mass of bee-bread, and the cell is then closed.
The bright yellow staminate aments of the pussy-willow (Salix