A gentleman messaged me last week about the dimensions of my swarm traps and whether they've worked for me. The model below shows how I make my swarm traps out of a single 1" x 12" board. As for their effectiveness, I've had good luck with them. I find a tree along the forest edge, preferably with sunlight, and hang the trap 7 or 8 feet off the ground. I typically put a cotton ball with a few drops of Swarm Commander in the box, along with a couple frames of old comb. I'm never 100% sure if I'm catching a feral swarm or if I'm just re-capturing a swarm from one of my hives. Either way, these traps are an easy insurance policy, and worth the small cost of construction.
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