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On the Trails: Beauty from filth and squalor

Posted: November 15, 2013 - 1:03am
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A tiny fungus gnat visits a flower of northern ground cone.  Photo by Bob Armstrong
Photo by Bob Armstrong
A tiny fungus gnat visits a flower of northern ground cone.

On a cool, sunny day in early November, I found several lovely but conventional things to admire: sunlight on snowy peaks, hoarfrost patterns on fallen leaves, graceful golden-russet fronds of last summer’s lady ferns, a lichen-and-moss garden on an old stump.

However, it occurred to me that sometimes a beautiful or at least very useful thing can emerge from the ugly, filthy, and squalid. Here are some examples:

Moth flies are also known as drain flies and sewage flies. The larvae of some species live in stinky drains and sewage lagoons or on floating, oozy mats of algae; those that live in drains are very tough—able to survive soap, chemical cleaners, and hot water. The undistinguished-looking larvae give rise to pretty but tiny night-active adults with furry, moth-like wings. These adults feed on polluted water and flower nectar; maybe they even pollinate some flowers.

Some species of hover flies, a.k.a. flower flies, begin their lives as larvae that often live in shallow, polluted water and sewage lagoons, where they burrow into organic sediments. That habitat is notoriously low in oxygen, and the larvae breathe air from above the water surface through very long tubes on their rear ends. That long breathing tube has earned them the name of rat-tailed maggots. The adults are small, with black and yellow bands around the body. They mimic bees, in which the black and yellow coloration is a warning to would-be predators that the bee can be dangerous; in this way the hover flies are thought to gain some protection from predators. Adult hover flies feed on nectar and pollen and are important pollinators of many small, open-faced flowers. They can often be found on the broad, white multi-flowered inflorescence of cow parsnip, for example.

Blowflies produce undistinguished, white maggots on carrion; we often see them writhing in heaps on salmon carcasses, where bears, mallards, and songbirds feast upon them. They are very important agents of decomposition. Blowfly adults come in iridescent hues of green and blue and purple, earning them the name Calliphoridae — bearers of beauty! Recent studies by agriculturalists have shown that blowfly adults can be very effective pollinators of certain crops, such as leeks. We sometimes see them on local flowers also, particularly those with inflorescences (flower clusters) like those of cow parsnip.

Fungus gnat is a general terms for a diversity of small insect species. Some of them are tiny indeed, less than a millimeter in body length. Fungus gnats spend their larval life in decaying vegetation and fungi; some of them eat plant roots. The adults are short-lived, but research has shown that at least certain species are very effective pollinators of twayblade orchids (one of our local species). These orchids have ridiculously small flowers with minute amounts of nectar, but they are said to have a putrid smell that fungus gnats love. It turns out that fungus gnats also pollinate several other kinds of tiny-flowered plants, including alumroot, which also grows around here.

Dryomyza flies (no known common name) lay their eggs in carrion, including dead salmon. The males of one intensively studied species defend carcasses from each other and also defend egg-laying females. Their courtship is quite elaborate, and post-coital behavior of the male is important in ensuring his reproductive success. When they are not fighting and courting and egg-laying, the adults are known to visit certain flowers, including those of northern ground cone, but it is not known if they are effective pollinators. Their role should probably not be dismissed out of hand, however, given that other flies that are reared on substrates that are icky to humans have a truly important ecological role in the maintenance of flower populations. If not beautiful in and of themselves, they help create beauty!

 

Mary F. Willson is a retired professor of ecology.

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