Today we have a photo-and-text story by Athayde Tonhasca Júnior. His topic: plants and gnats. His text is indented, and you can enlarge the photos by clicking on them.
Pesky little helpers
“He could put up with his meaningless office-life, because he never for an instant thought of it as permanent. God knew how or when, he was going to break free of it (…) The types he saw all around him, especially the older men, made him squirm. That is what it meant to worship the money-god! To settle down, to Make Good, to sell your soul for a villa and an aspidistra!” (Keep the Aspidistra Flying, 1936).
In George Orwell’s (1903-1950) novel, Gordon Comstock leaves a successful career in advertising (‘the rattling of a stick inside a swill bucket’) to become a poet. But Comstock’s literary shortcomings push him slowly and inexorably into poverty, so the idealist and bitter writer pontificates about the materialism, dryness and mediocrity of the English middle class. And nothing could better symbolise society’s predictability and pedestrianism than the common aspidistra, aka bar room plant, iron plant or cast-iron plant (Aspidistra elatior). A native of Japan, the common aspidistra is widely cultivated as a houseplant around the world. Because of its sturdiness and tolerance to neglect, it became a favourite in English homes in Victorian times, although its popularity has since waned a bit.
The once ubiquitous common aspidistra © Nino Barbieri, Wikimedia Commons:
W. F. Harvey (1885-1937), the Quaker author of macabre and horror stories, told the tale of Ferdinand Wilton, who tried unsuccessfully to destroy aspidistras, only to get some creepy just deserts… Image from Tatler magazine, 1930, British Library:
Orwell would be pleased to know that other characters could have embodied dullness and obscurity in Comstock’s social narrative: gnats.
‘Gnat’ is a loose term to refer to small (usually less than 1 cm), unremarkable and poorly known flies in the suborder Nematocera, which include crane flies, mosquitoes, black flies, and midges. Gardeners will be familiar with one particular group: the dark-winged fungus gnats (family Sciaridae). These tiny black flies make a nuisance of themselves by flying erratically and in great numbers around potted plants, often finding their way to rubbish bins, kitchen drains, window panes, and fruit bowls. The adults feed on nectar or on nothing at all (they have very short lives), and the larvae eat mostly fungi or organic matter in damp soil – that’s why potted plants are ideal for them. Fungus gnats are largely harmless, but if their larvae became too abundant, they may start to feed on plants’ tender roots, damaging them or transmitting pathogens. Seedling ‘damping off’ is a sign of possible fungus gnat infestation. Predictably, if you search for ‘gnats’ in the internet, most pages will be focused on ‘how to get rid of’.
Sciara hemerobioides fungus gnats © gailhampshire, Wikimedia Commons:
Fungus gnats may be an occasional headache in households, but these uninvited guests represent a minute portion of their fauna. Besides the 2,500 or so species of Sciaridae, there are more than 4,500 species in the family Mycetophilidae and numerous species from related groups. Most of these fungus gnats live in shady, damp spots under forest canopies, along water courses or wetlands – places offering ideal conditions for their larvae. These permanently moist environments may be great for gnats, but are not so good for most pollinating insects, who require warmer, drier habitats and open spaces. So plants in fungus gnat territory. such as Aspidistra spp., have to find alternatives.
Flowers of the common aspidistra are nothing to look at. Oddly shaped, fleshy and coloured with a purple-reddish hue, they emerge directly from the rhizome at ground level or are sometimes hidden underneath the litter. People may not even notice their potted aspidistra has bloomed. And no aroma wafts from this plant: only a faint musty odour that some people can’t even detect. Everything from this flower gives it a mushroom appearance, so it’s far from ideal to bees and butterflies. And there’s more to put off run-of-the-mill pollinators: to access the pollen, they have to squeeze by a large stigma (the female part of the flower) to reach the pollen-producing stamens tucked underneath; only the smallest insects can do it. You probably can see where this is going.
Flowers from a ca. 50 years-old potted aspidistra © Boervos, Wikimedia Commons:
The common aspidistra and related species cannot self-fertilise, but their pollination mechanism remained a mystery for years. Slugs, snails, springtails and other ground-dwelling invertebrates have been suggested as potential pollen vectors, but none of these candidates were backed up by data. Enter Suetsugu & Sueyoshi (2018), who spent two years investigating the common aspidistra in Kuroshima Island, Japan, where this plant grows wild. Their efforts paid off: they recorded two species of fungus gnats covered in pollen leaving and landing on flowers, and observed the successful development of fruits in gnat-visited flowers. These observations suggest the puzzle has been resolved. The researchers proposed, reasonably, that Aspidistra have evolved flowers that look and smell like fungi, thus becoming irresistible to fungus-eating gnats.
A male dark-winged fungus gnat, a Sciaridae species © John Tann, Wikimedia Commons:
Flies are considered the second most important group of insect pollinators after bees; house flies (Muscidae), blow flies (Calliphoridae), flesh flies (Sarcophagidae) and especially hover flies (Syrphidae) pollinate a range of crop and wild plants. Some flies are essential pollinators in high altitudes, where bees are scarce or absent. Fungus gnats are hardly thought as members of the pollinators club because they don’t seem to have what it takes: they are too small to carry a decent pollen load, their ‘hair’ (bristles) – an important pollen-carrying apparatus – are puny, and they are weak fliers. Yet, pollination by fungus gnats occurs in 20 genera of eight plant families over the world.
Fungus gnats and other small dipteran insects such as midges and drosophilid flies are diverse and abundant, but we know very little about most of them because they are difficult to identify and study in the field. Worse yet, many species are nocturnal, and the flowers they visit are inconspicuous. So just like the midge-pollinated cacao, the gnat-pollinated aspidistra suggests there are many discoveries to be made about these pesky little flies.