As with everything in beekeeping, it’s best to try to understand things from the bees’ perspective. So, allow me to go into some detail about what is actually happening when bees decide they want to swarm and how they go about choosing their nesting site before I get into details about the best ways to attract them.
Timing is Everything
Depending on your location, swarming can happen spring through fall. However, bees don’t consult a calendar when they are deciding whether or not to swarm, they judge the proper timing by certain conditions that are traditionally found in the spring and summer. They tend to swarm when particularly fine weather coincides with a nectar flow happening. We are in perfect summer-like weather and are simultaneously experiencing a significant nectar flow from the recent rains we received. This combination is creating a strong swarming urge in almost all of my colonies. When you start to see swarm cups in your hives, you know it’s time to put your bait hives and swarm traps out!
Before a swarm actually departs, it will put a lot of energy into finding the perfect new home. Cue the scout bees! These foragers turned house hunters will seek out ideal nesting locations often spending 30 minutes or more thoroughly evaluating the site. This process can take days and the more attractive a site is to the swarm, the more scouts will appear. Having witnessed this behavior many times in my own front yard, it often starts with one to two bees hovering around their potential home. I can always tell when this is happening because the bees seem to be scanning the surface and entrances very carefully. On one occasion, I even witnessed several scout bees who stayed overnight! If the scouts approve of the site, they will shortly be joined by many more scouts who will all perform the same thorough examination. As the swarm gets closer to “moving day” the number of scouts will surge. I often see as many as a hundred scouts investigating a nesting site the day before the swarm arrives! During this site evaluation period, it is important not to disturb anything or you might dissuade the bees from settling there. Scouts from a single swarm will scout as many as 10 different nesting sites, often narrowing the choices down to two or three by the end.
Much ado has been made about what kind of cavity a beekeeper hoping to lure a swarm should construct. In my experience doing live bee removals, I see swarms move into all kinds of cavities, but they do seem to have favorites. I often joke that swarm catching hopefuls should simply start composting or set up an owl box! There is some research to suggest that bees prefer cavities of a certain volume and lean towards homes with small entrances. Thomas Seely in his must-read book, Honeybee Democracy went to great lengths to test and study swarm behavior and came up with some figures on a swarm’s preferred dimensions. He found that swarms like nesting cavities of that are approximately 40 liters with entrances that are approximately 2 inches. Seely also found that height plays a role in the attractiveness of a nesting site (bees like to nest an average of 21 feet from the ground), but I have caught and lured most of my swarms close to the ground and height makes things more complicated for the beekeeper. So, I am going to advise that you save yourself the extra trouble and set your traps within 10ft of the ground. This brings us to what one should use as their cavity. You can buy light weight swarm traps and mount them high in the trees or even on the side of your house if you want to forgo my advice about height. The light weight quality of these traps is probably their one real advantage. I used one last year and caught two swarms in it. One mounted 20 ft high in a tree, the other mounted to the front of a client’s house, about 15ft up. Some people prefer to build their own traps to precise dimensions, but I have never understood this. The simplest swarm trap is whatever hive you intend to keep your bees in. If you are using a Langstroth hive, a single deep is conveniently close to 40 liters. If you are using a Top Bar Hive, it might be advisable to create a smaller cavity within it using your follower boards. Luring a swarm to their permanent home will save you the trouble of having to transfer them and the bees are less likely to abscond in this scenario since they get to stay in their chosen home.
Baiting your hives is critical for luring a swarm and I have heard of everything from lemon scented Pine Sol to melted slum-gum. I say, go ahead and try them all! Just don’t overdo it. I once had a student who coated the entire inside of her hive box with lemon grass mixed with beeswax. It was a goopy mess with a scent so strong, it overwhelmed my nose! You only need a small amount of bait to attract your bees. If you use too much, it can have the opposite effect. When using the trap I mentioned before we utilized a pheromone lure in a small vial, but I catch most swarms just by leaving out empty equipment with old brood comb in it. Bees love living in locations where other bees have lived before and if theres already comb inside, it’s like finding a furnished apartment! Don’t worry about how perfect the combs are. I’ve even witnessed swarms who bring in a clean up crew before they move in. Scouts drag out debris and I’ve even seen them chewing away at moldy combs in the days prior to moving day. Keep in mind scout bees must find your trap before they can decide to move in. Bait helps this along, but if you aren’t seeing any bee activity, you might want to consider putting a sugar water feeding station nearby. Seely discovered in his research that most scout bees start out as foragers so, if you can attract foragers to your location, there is a chance some of them may scout your swarm trap!
If you successfully lure a swarm, be careful not to disturb them for the first week. When the bees arrive they will immediately start building comb and the queen will start to lay eggs, but new comb and eggs aren’t a big enough investment to hold the bees to their location. A disturbance could cause them to abandon the nesting site in favor of another. If you wait a week, the eggs will have hatched into larvae by then and this will compel the bees to stay even in the face of a hive inspection. After a week I do recommend you look in on your new bees. Not all swarms are created equal. Some are queenless or come with a virgin queen. Therefore, it’s important that you inspect them and search for eggs to verify that your colony is queenright and the queen is laying! Please remember also that bee swarms are always docile at first, but once they get established their temperament can change dramatically (be especially aware of this if you live in an Africanized zone).