The Yuck Factor

Carpenter bee, I thought to myself, as a large black insect buzzed past me, zigzagging along the trail high above the sage-scrub hillside and sun-flecked sea stretching onward to the horizon. But there was something odd about its movement that pulled it back from being just another part of the landscape. It stopped on a low leaf, still buzzing. Odder still!

A closer look told me this was not bee. The eyes were all fly. Maybe a cactus fly with that fat, shiny abdomen? But no, even that was not right. Wrong shape. Nor would any self-respecting cactus fly settle itself on this flowerless junk vegetation; prickly oxtoungue. Ruderal stuff. Beat into the ground by passing foot traffic at that.

Furthermore, this fly showed white below. Then it struck me, I was looking at a bot fly, one of nature’s more bizarre – let’s face it, yucky – creations! A fly scarce and shy enough that I had only seen one before, and that a distance. That one had zoomed by me in an open field, stopped on a tall weed, and scrammed the moment I tried to get close enough to take its picture.

Now here was another right in front of me, posing for my camera. The fly clung to its leaf, then buzzed a bit further on, selecting another bit of stuff to sit on. Strange behavior, it seemed to me, but who was I to argue with this fabulous chance to take pictures of something so unusual. I got a dozen or more. Later, these explained to me what I had been seeing.

This is where the yuck factor kicks in.

Scarce as bot flies are, most seen are males. This was a female, truly rare, and out on this trail laying eggs, as the photos showed. Those eggs will soon hatch into grubs. Grubs that attach themselves to body hairs of a passing rabbit, who will now be its host.

The grubs enter the rabbit’s body, licked inwards during grooming, or crawling in through some other opening. Any will do. And then they burrow through the rabbit’s body, ending up just under the skin, the exact location depending on the fly’s species. There they cut a breathing hole through the hide, forming the warble in which they will mature. Oh, yuck!

And there the grub will grow fat and heavy over the next few weeks, feeding on the rabbit’s body fluids. When it is mature, the grub will squeeze through the breathing hole, fall to the ground and pupate under cover, emerging as an adult perhaps a year later to begin the cycle anew. What an idyllic life, I muse to myself. Of course, I could go into the even less toothsome aspects of a bot fly’s life should the grub end up in the wrong animal. But we’ve had enough of the yuck factor for one day. Ain’t life grand?