Common Green Darners Migrating
The Common Green Darner, Anax junius, is one of our largest dragonflies, measuring three inches long, with a four-inch wingspread. It is strikingly colored, with a green thorax and a bright blue (male) or reddish (female) abdomen. As if that weren’t enough to set this dragonfly apart, it is also migratory. Common Green Darners migrate south from August to November, stopping over (like migrating birds) occasionally along the way, resuming flight after resting and refueling. Thanks to radio telemetry, we now know that over a two-month migration, Common Green Darners, each weighing about one gram, can migrate over 400 miles. (Photograph is of a Common Green Darner perched on Bottle Gentian.)
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Bottle Gentian Flowering
Bottle Gentian, Gentiana andrewsii, is one of our latest blooming wildflowers, and one of our most beautiful. Because its petals are closed so tightly, only bumblebees (pictured) and a few other insects have the strength to push their way inside the flower to reach Bottle Gentian’s sugar-laden nectar.
Like many other flowers, Bottle Gentian times the maturation of its reproductive parts to discourage self-pollination. Male pollen-bearing stamens mature first, and by the time the female pistil is mature, the stamens have gone by so the flower’s pistil can’t receive its own pollen (see central pistil surrounded by withered stamens in insert).
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Bottle Gentian & Bumblebees
Bumblebees are nothing if not perseverant. Prying Bottle Gentian’s (Gentiana andrewsii) petals open is a monumental task, and one that few insects, other than large species of bumblebees, attempt — much less accomplish. The relationship of bumblebees and Bottle Gentian is an example of a mutualistic association — the bees benefit by having exclusive access to a bountiful and sugary nectar supply, and the plants benefit by attracting “loyal” pollinators that improve the chances for cross pollination.
Bottle Gentian
One of our latest flowering plants is the brilliant blue bottle, or closed, gentian (Gentiana andrewsii ). It is so-called because the tips of its petals come together like the neck of a bottle, protecting the nectar from rain. The lure of bottle gentian for insects is both the abundance of nectar, as well as its high (40%) sugar content . Only the strongest of insects, however, are able to struggle their way down into the flower in order to reach the nectaries. Because of their strength and perseverance, bumblebees are the primary pollinator of bottle gentian. Once a flower has been visited and its nectar collected, the tips of its petals turn white, signaling other bees that it would be a waste of time and energy to fight their way into the flower. (Yellow lumps are pollen in the bee’s pollen baskets, specialized hairs on the bee’s hind legs.)
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