Flies have bedeviled animalkind since they were created in 4004 (I think it was a Thursday). Exodus even shows them to be one of God’s special punishments. There are many ways of killing them quickly and cleanly, but most introduce toxic materials into the home and swatting them takes away valuable goofing off time.
Some years ago we were beset with a plague of flies in the yard. Swatting them was unsatisfying because there were always more, so I sought a more efficient method. I set up a yellow jacket trap (they were out of fly traps because everybody had flies that year), which was a hanging, plastic bag with a pagoda cap that bugs were supposed to be smart enough to climb in but not out. This was the last one on the shelf and lacked the bait capsule but I put in a cup of water, hung it up, and watched what happened.
At first a few flies flew around it but not into it, then a couple soulless demons from Hell got adventurous and climbed in. After a couple days they got tired, fell in the water, and began to rot. They made fly bait for me, and soon word of the trap got around as THE place to die. I continued checking on it after work and found that a subset of the population had been born, grown, and died in the trap, feeding on the corpses of their kin. There were hundreds, even thousands of mostly dead flies and the bag grew so heavy that it broke its hanger, ending the experiment around the same time the plague ended.
But that was Science and though I watched it with amazement and some pleasure and took no notes and collected no data useful for other researches other than “This is freakin’ awesome,” I try to not see myself as the flies’ Dr Mengele. I save that for flypaper.
Many people are surprised that flypaper still exists and don’t understand how useful it is in fighting Mankind’s Oldest Battle. For the uninitiated it is paper coated with something very sticky. Usually today it is only available in tightly-rolled strips that unfurl when you tack (thumbtack included) one end to someplace near where flies are found. The old sheets are hard to find because too many children re-enacted Three Stooges bits with them. A fly happens along, lands for a rest or a cleaning session, and is stuck. Others are caught by the wing when they fly too close. Then there was the one that thought a female fly was drunk and passed out, so he landed on her in order to couple. That date rape lasted into eternity, but she was already dead. Creepy necro fly. I laughed at him, which raises the “sadistic monster” part of my question, but one which I fear I have already answered.
As for the cruelty, flypaper kills through any combination of exhaustion, starvation, and dehydration. I may have a shred of a conscience somewhere because I see how that can be Not Very Nice, and I’m pretty sure that being nice is supposed to be a goal to which I should aspire. Should I find another, more humane way to rid my home of flies, like my spider friend and her nursery under the laundry sink, or can I continue to laugh at the foibles of our insect overlords?
Okay, one last anecdote. Stop me if I’ve told this one before. Glue mousetraps are actually fairly humane if you check them often and listen for the plaintive cries of the mice. You take the trap, mouse, and a bottle of vegetable oil to the yard of a neighbor you don’t like and pour oil on the mouse’s feet. Do NOT do this while you are still inside because the mouse will become free in seconds, no mater how glued down. He’ll stop and lick off the oil and move into your neighbor’s house. Anyway, I had a glue trap in an easily-monitored location. We had roaches because my children are idiots and Wife found the odd, sub-tropical roaches they brought back from Washington DC too interesting to kill. A big American cockroach tried sprinting across the trap and made it halfway. “Aha!” he thought, “I have wings and can fly away,” so he worked all but his back legs free, reared up and spread his wings to make his getaway. Only his rear feet were still stuck so he fell backwards, embedding his wingtips and anus in the glue like a two-inch tripod. I kept that one around for years as a reminder of the futility of being a roach that had ideas.
TL;DR!