The Spiders And The Flies
Reminder: You can enlarge any of the photos in this blog by clicking on it. Click again for a full-screen image.
“Will you step into my parlor?” said the spider to the fly;
’Tis the prettiest little parlor that ever you did spy. The way into my parlor is up a winding stair, And I have many pretty things to show when you are there.”
These are the opening lines to the poem “A Fable” by Mary Howett Williams. I thought of this poem when I made the photographs in tonight’s blog.
Autumn is the season of orb weaver spiders in southern Arizona. The little spiders are everywhere. They string their webs on bushes, on tree branches, on just about anything that they can use for anchors. They capture prodigious quantities of insects and flies have to rank among their primary prey. That’s good for us. Flies are prolific breeders and we’d drown in them if it weren’t for predators like spiders. We all owe spiders, including orb weavers, a great debt of gratitude for keeping the fly population under control
I photographed this orb weaver the other day, dining on a fly that she’d captured.
But, sometimes, the tables get turned. One day last week, Claude Wegscheider pointed out to me a remarkable drama in our backyard. A tiny fly, an insect so small as to be almost invisible to the naked eye, was repeatedly harassing an orb weaver. It kept attempting to land on the spider’s abdomen, much to the spider’s annoyance. The spider kicked at the fly with its hind legs as the fly made multiple forays. Finally, the fly settled down on the opposite side of a bee that the spider had captured and entombed in silk, and appeared to wait, patiently.
What was the fly attempting? I raised this question with one of the entomologists at the Arizona-Sonora Desert Museum. He told me that there are several species of parasitic files that specializing in laying their eggs on the abdomens of spiders. The eggs hatch and the larvae devour the spider, eventually killing it.
Which goes to show that no niche in nature goes unexploited. Spiders have evolved to prey on flies. Flies, in turn, have evolved to prey on spiders. And, I’m willing to bet that there’s something out there that preys on those parasitic flies.
Photos taken with a Canon 5Diii, 180 f3.5L Macro Lens, ISO 125, assisted by Canon 600EX-RT Speedlite. The first photo was taken at f14 @ 1/160. The second, at f13 @ 1/160.