Zombie Dung Flies
While working in my front yard, I noticed insects flying around at ankle height. Soon enough one landed. I identified it as the familiar 'golden dung fly' (Scathophaga stercoraria). As its name implies, its life revolves around animal droppings, especially those of large herbivores. They spend their larval stage feeding on it, and as adults hang around preying on other insects attracted to it, finally laying the eggs of the next generation in it. They are agile aerial hunters. I have seen them taking insects as large as themselves on the wing. While they are not aggressive toward humans (we're a tad large for them to carry off), I can attest they bite if mishandled.
So, what's with the "zombie" thing? I went hunting with my macro lens and took pictures of everything including some of this species posing, some with prey and, finally, some perched atop some of the tallest sprigs of grass in my recently mowed lawn, dead. Many of the deceased ones were covered with a clumpy white growth, especially where the plates of their exoskeletons joined. A bit of online research indicated it was most likely Entomophthora muscae. This fungus infiltrates the bodies, feeds on the tissues, enters the central nervous system and causes the insect to land, climb to the top of a tall sprig, lock up and finally die. The fungus then erupts through the soft parts of the body and disperses its spores to attack another generation of flies.
Last night I mercilessly killed a couple hundred of the deadliest animals on the planet, maybe averted a plague and fed the hungry. I hardly worked up a sweat.
Statistically, more human deaths (not to mention misery) are caused annually by mosquito borne diseases than those carried by any other critter. At last count they average 725,000 human deaths per year. I netted a couple hundred wrigglers (a common name for mosquito larvae) from a tray under some plants where rainwater had accumulated. Looking at the stinking, tea brown water full of rotting leaves, you'd think it was too nasty for anything above algae on the evolutionary chart live in. That's just how they like it. Their mothers seek out such water in which to lay eggs. A few days later they hatch into tiny little wrigglers. After five moults, they change to the pupal form (tumblers), finally emerging into the adult form we all know and loathe. That bad brew is their big trick. Suspended head-down at the top of the water, they poke a snorkel through the surface film and breathe air. This allows them to inhabit places too oxygen deficient and polluted for fish and other aquatic insects to survive. There they are free of competitors and predators.
Our native North Coast mosquitoes don't carry many of the really nasty tropical diseases associated with them. They can, however, carry things like canine heartworm, bird malaria, and western equine encephalitis. We really don't know what other potential pathogens they might transmit, some of which might be yet undiscovered. So, 'tis the season to tip over those old tires, flower pots, unused kiddie pools and untended bird baths, and fill in puddles and wallows. While we can't eradicate them, we can reduce the numbers near our homes, since adults seldom fly far from spawning waters. This is no small thing. You, too, can kill thousands of the most vile and vicious parasites in the world. I fed mine to my goldfish humming the theme from Jaws.
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