by James Morris
Illustrations by Talia Niederman
Every summer, my family and I spend time in the Adirondacks, where we rent a log cabin by a roaring brook. We open the cabin to many friends – children and adults – like one big family.
Last summer, one member of our extended family was Oliver, a tall 17-year-old boy with a mop of curly brown hair and wry sense of humor. He had spent the previous two weeks on a school trip to Belize, and was excited to be back in the Adirondacks, where he and my sons lead hiking, canoeing, and rock-climbing trips in the High Peaks region.
One day during his stay with us, Oliver showed me a lump on his arm. It looked like a typical bite, except that it was swollen and had a bit of dry blood at the top. The lump itself was red, but there were no other worrisome signs – no red streaking up his arm, fever, pain, or itchiness.
At first, we weren’t concerned, thinking it would go away on its own. But it didn’t. It didn’t get worse, but it didn’t get better.
Perhaps it was infected, so we kept it very clean. Every night, we washed it with water, hydrogen peroxide, or iodine, then put on some antibiotic ointment and covered it with a Band-Aid or gauze.
Still it persisted. There is a small emergency room not far from the cabin, so we thought about having it examined there. But each morning, we thought it was getting better, or at least not worse, so we waited.
Just about then, we heard from his mother, Emily. She told us that a counselor on the trip had a lump on her arm from a spider bite. That made a lot of sense. Of course, Oliver must have the same thing.
One night, Oliver was tired from a long day of hiking and getting a bit worried about the lump. He kept washing and looking at it, when he thought he saw something coming out of it where it was open at the top. We all looked, but couldn’t convince ourselves that we saw anything. Maybe a bit of motion? Something alive?
Because he was going home in a day or two, we decided not to go to the emergency room. When he got home, he went to the local doctor. At first, everyone was stumped too. It looked like an abscess (a walled-off collection of pus from an infection), so they lanced it. When no pus came out, they began to suspect that this was not an infection or even a spider bite. A little research uncovered what was actually going on.
It was a botfly. A botfly larva to be exact.
It turns out that botflies are not uncommon in Belize. The adult botfly lays eggs on a fly, mosquito, or tick, where they hatch into larvae and drop onto a human host. The larva burrows under the skin, where it grows. After several weeks, the larva emerges, drops to the ground, and pupates. Eventually, the adult emerges and goes on its way.
What Oliver saw moving that night were the mouth parts of the growing larva. When he washed it, the larva was deprived of oxygen, so it came out for some fresh air.
Here’s how Emily described what happened next in an email after the mystery was solved:
Hi guys! I thought I’d give the complete story…Oliver went to the doctor’s office on Monday. Of course no one there had ever seen a botfly, but they confirmed that it was in fact a botfly. All of the nurses gathered around to see this exotic bug in their office! They sent him home hoping that covering it with plastic would deprive it oxygen so that it would sneak out enough that Oliver would be able to get it out at home with tweezers. No such luck, so back he went to the doc on Tuesday. A new bevy of nurses hovers around in fascination. This time they put double amounts of plastic on it to make sure it is fully deprived of oxygen so that in 24 hours he can return and hopefully this time it will in fact have been so deprived of oxygen that it will move out towards the air when they remove the plastic. Day 3 at the docs, and that is exactly what happened. They tweezed out Angelica, who now resides in a specimen jar in Oliver’s room….
But is it? Or is it just disgusting from our point of view? The botfly is, after all, just trying to get by, like all of us.
Charles Darwin used these sorts of seemingly abhorrent animal behaviors to make an unexpected argument for evolution by natural selection. He described birds that eject eggs from other birds’ nests, killing them; ants that raid other ant colonies, enslaving the captives; and wasps that lay their eggs in caterpillars, where they hatch and eat the caterpillar alive. Then he asked – is it better to think of these behaviors as the result of a natural process or divinely created? Here is what he wrote in On the Origin of Species –
Finally, it may not be a logical deduction, but to my imagination it is far more satisfactory to look at such instincts as the young cuckoo ejecting its foster-brothers, ants making slaves, the larvae of ichneumonidae feeding within the live bodies of caterpillars, not as specially endowed or created instincts, but as small consequences of one general law.
It’s interesting that none of us thought to do some internet research while we were there. As Emily pointed out, a simple search turns up botfly right away:
Oliver googled something like “common insect bites in Belize” and immediately “botfly” came up. It made complete sense, from the look of the bite to the fact that monkeys often get them in the jungle, and Oliver had spent a hot night sleeping outside of his tent in the jungle.
Perhaps we didn’t look it up because we thought we knew what it was. Emily continues,
Occam’s razor suggests that the simplest explanation is usually the correct explanation. But in the case of Oliver and the botfly, that proved not to be the case: the simplest explanation was that he had a spider bite as did another member of the crew who went to Belize. Thus it would seem that Occam’s razor didn’t help because in fact it was not the simplest explanation. However, perhaps we need to add that simplest explanation is usually the correct explanation if you have all of the information.
Or perhaps it was because we were in a vacation mindset where we didn’t immediately turn to Google to answer all of our questions. In the Adirondacks, we don’t have easy access to the internet. We can go to a local library with Wi-Fi, but we didn’t even think to use it.
We were truly in a different world, which is what vacation is all about.
© James Morris and Science Whys, 2017