spider and fly

while showering a couple of nights ago, I was surprised to see a rather large fly flying about in the bathroom - it probably entered through the open window, attracted by the light - that usually attracts moths, but there's always a first, and this fly was it. while it was buzzing around one of the downlights, I noticed there was a single line of spider-web-silk that started somewhere else at the bathroom and ended at the light. nothing unusal about it, but the light made the web particularly obvious - so obvious, that I could spot the peturbation in the web, as the fly flew around it. it wasn't very clear if the fly flew into the thread or not, but it was clearly having many close passes at the very least, as it seemed to be flying around the light. there were a couple of rather big jerks to the web which were clearly the fly making contact.

shortly after that, the fly seemed to come to rest on the light. my first assumption was that it was basically as close to the light as it could get to and couldn't figure what else to do. I had also finished my shower, so I turned the light off while I dried myself off, so that the fly's movement from that spot might indicate if it was free to move about. I also noticed the the fly was not moving quite as a fly might be expected to - perhaps indicating that it was struggling with the web, although maybe it was also having some sort of seizure due to being so close to such a bright light.

dried off, I switched the light back on to observe the fly. it was still moving in that weird manner - it seemed like it couldn't move one wing in the same way as it could move the other, and same for one or two legs. I also looked around for any obvious spiders, especially around the web. there weren't any.

I switched off the light again and opened the window as wide as I could to air out the bathroom, and hopefully also give the fly as good a chance to fly out as it could have. I shut the door and went on with my evening, wondering what will happen next with the fly, and reminding myself to check on it when I bring the window to its normal ajar position.

about an hour later, I stopped back to check on the fly. to cause minimum disturbance to the fly, I switched off the lights outside the bathroom, opened the door as little as I could to get a look at the fly. I also didn't turn the room light on, but instead, I used my phone's torch. the fly was still there, and it didn't seem to be moving at all (unlike earlier when it was moving erratically). as my phone's light didn't seem to disturb the fly, I entered the bathroom and switched on the light. the fly was completely immobile and didn't respond to the light at all.

I was quite surprised. did a couple of encounters with the web (and not a big web, just one thread!) trap the fly to the point where it was unable to move at all, possibly dead?

how strong is a spider web, and is there something else to it like the stickiness, or the way it catches on the body of the fly, that causes even slight contact to get it into a more tangled position where it cannot move at all? or is there something on the web that paralyzes or otherwise affects the fly?

I spent a few moments observing the fly and thinking these thoughts, before I turned the light off, left the bathroom and shut the door. I considered taking a photo, as this blog post was definitely half-formed in my head (even the title, inspured by a memory of this animated series from my childhood!), but my phone was charging, and thought I could get a better photo the next morning.

next morning, I went to the bathroom, phone ready.

there was no trace of the fly. none whatsoever. not on the light, not on the ground. no trace of the web either.

since the window was left very slightly ajar (in fact it had shut enough overnight to not allow a fly to get through) it was impossible (or maybe very very unlikely) that the fly had revived and escaped.

the only other plausible explanation was that the fly had been completely consumed by the spider overnight.