I’ve seen on certain channels like Discovery, entomologists using some gas to knock out spiders (which I know spiders aren’t really insects). I think it was simply Carbon Dioxide, but I can’t be sure, anyway, is there something that will knock out most insects for a while? Specifically crickets, if it matters?
sing them a lullaby, ‘itsy bitsy spider’ might work for them but scare prey species.
carbon dioxide to used to kill or smaller doses to put to sleep.
We always used ether to knock out the fruit flies.
Ahh, okay, thanks!
We use carbon dioxide in the lab to knock out fruit flies. It doesn’t put them to sleep, but it does temporarily and reversibly paralyze their muscles. It’s easier than ether, with which you need to be careful about the dose.
How do you get the cloth over their mouth and nose? 
If the insects are already in a container of some sort, putting them in the fridge for a few minutes often shuts them down for a bit.
In an AP Bio lab in high school, we had to knock our fruit flies out. We’d dip a bristle in something, tap the flies down to the bottom of their tube, then open the lid/stick the bristle in/replace the lid before they could fly/crawl back up. Not 100% sure what the substance was, but I think it may have been ether.