Nov 18, 2009

Fall pollinator

November seems late for flowers and bees, but a few hardy specimens stay active throughout fall. New England aster produces flowers even after most plants have shed leaves and withdrawn their life force underground.

Underground is where halictid bees nest. An underground burrow offers protection from cold, especially as falling leaves blanket the ground. 56 species in eight genera are known in Great Smoky Mountains National Park, and I'm not sure which species this is. You need to examine wing veins and subtle features of the head and legs to tell them apart, though occurrence in mid November could be diagnostic.

These bees, important pollinators of many native plants, come in greens, oranges, blues and blacks. Often their color varies with the angle of light, and this one shimmered with both green and orange. Most halictids are solitary, but others are social, cooperatively building and provisioning nests. They are a favorite object of study among biologists hoping to understand the evolution of sociality in insects. Whether working alone or together, these bees gather pollen and store it underground. They lay one or more eggs in a burrow, seal it for protection and when the egg hatches, the larva consumes the pollen to fuel its growth to adult form.

Asters are usually white, but fall blossoms often carry a hint of purple. With so few plants flowering in November, asters are often busy with insect activity. Green and black bees were visiting this plant, and a couple types of nectar-sipping flies also made appearances. Flowering witch hazels were also abuzz with visitors. As diverse as Southern Appalachian forests are, some living thing is taking advantage of any niche and any opportunity, including the sunny weeks between when leafy shade fades and winter takes it grip.

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