Humane wasp trap Wasps are lured by the sweet smell of syrup placed in a cartridge, which hangs freely in the opening of the glass top part. By separating the liquid from the caught wasps they will not drown compared with the traps you find on the market today. Wasps will always try to find the highest point to fly away, so if you take out the cartridge there is a big chance all wasps are able to fly out again.