At the April WVBA meeting Morris Ostrofsky gave lots of practical information, most from his own experience, on how to capture swarms via swarm traps. If you’re looking to increase your number of colonies, consider setting out one or more swarm/bait boxes, an inexpensive means of starting additional colonies. Swarm traps can bring the swarms to you, rather than your chasing the swarms into the trees.
Bees make extensive preparations in their hive before swarm emergence. Same is true for the swarm before it moves into a new home. When the swarm exits their parental colony, the bees fly in a circular pattern moving away in just a few minutes to form as a clustered swarm (the swarm bivouac). Movement may be only a matter of feet but can be 300 yards or more; the bivouac site is often within sight of the apiary they have exited and often is at the same exact site of settled swarms of previous seasons. Bees tend to leave the original hive (swarm) when nice weather follows less ideal forage conditions.
Clustered swarms may remain at the temporary bivouac site for a short time or remain overnight and even for more than a day. Scout bees leave the cluster to seek a new nesting site, starting their search even before a swarm has exited the parent hive. The scouts spend 30 minutes or more thoroughly evaluating potential cavities, walking and flying the interior of a potential cavity. The scouts return to their cluster and dance to inform sisters about their cavity find. They will even check out competing sites after following other dancers. When a site is “agreed upon,” the bees again become air bourn and as a group fly to a new cavity site. Such sites may be at some distance (> ½ mile) from the original site.
Beekeepers have intervened since forever to “capture” clustered swarms to start a new colony. Captured swarms can be readily transferred to an apiary location. Swarm captures usually expand rapidly when hived by the beekeeper; they are recognized as excellent wax producers, apparently a function of wax gland stimulation aided by their hanging as a cluster. Swarms are often “easy” to capture, depending upon the cluster location, but once inhabiting a new homesite, capture and transfer becomes a serious challenge. I usually suggest try doing a “cut-out” one time, then decide if you ever want to do a second.
Instead of trying to capture a swarm from their temporary bivouac site, beekeepers can attract home-seeking scout bees to a baited hive. Basically, a bait hive is nothing more than a cavity offered by the beekeepers that encourages scout bee discovery, investigation and then into which the swarm cluster moves, adopting the proffered cavity as their new home. Bees have definite preferences when selecting a new homesite, detailed by research conducted by Tom Seeley, among others (see Tom’s Honeybee Democracy for details of his investigations). Beekeeper bait hives optimize what bees seek in a potential homesite.
What is a bait hive?
Bees prefer, when searching for a home, a dry, unoccupied cavity of approximately 40 liters [2450 in3]. A 10-frame deep Langstroth box =2600 in3. The bees prefer a cavity opening that is small and low. A circular entrance hole of 1 ¾ inches is perfect; a standard hive bottom board entrance should be reduced to 3-5 inches. A 5-frame cardboard (or wooden) nuc box or 8 frame hive box can be substituted. Use of a standard bee box means not having to subsequently transfer the bees when captured.
Morris Ostrofsky recommends a cardboard container box, 20 inches X 16 inches X 10 inches deep. He cuts 1-2 inch pieces of wood which he stables on both16 inch sides of the cardboard box; the inner side board is positioned below the cover fold to provide a ledge to hang frames. The outer piece becomes a handy handhold. The folded top should be covered with a rain shield. The cardboard trap weighs and costs less than a bee box, while comb transfer of catches is as convenient as nuc frame transfer. See photo. 
Morris, nor I are in favor of non hive-size containers, such as cardboard planters or the Cornell bait box. Their major drawback is, because bees begin almost immediately to construct parallel comb, transfer to a hive involves cutting out comb and piecing it into frames. Transfer is messy, highly disruptive and sometimes results in loss or killing of bees and/or the queen. It is an extra unnecessary step. Using standard frames/standard boxes or cardboard boxes of hive dimensions with standard frames means simplified transfer of captures.
Attracting Bees
Bees searching for a home (or swarm cluster bivouac site) are attracted to the smell of bees. Previous bee use, even if weathered a year or more, remains attractive. Thus a used bee box, if available, will attract their attention. Adding a drawn comb frame used previously for brood, or a piece of darker comb, with its wax and propolis smells, works well. Likewise, hive entrances previous used by bees, are highly attractive. Bees are not looking for honey so frames should be empty. If wax moths/small hive beetles infest the comb it will be less attractive. You can use Xentari for moth control.
Morris’s recommends stocking his cardboard bait box (or a standard bee box/cardboard nuc box) with one drawn brood frame which he places at back side of the box and filling out box with empty horizontally-wired frames. He adds a starter strip to the empty frames (as shown in photo). In addition to a drawn comb, there are special swarm attractant chemicals that mimic the Nasanov (scent) gland pheromone, such as Swarm Commander, that help attract scout bees looking for a new home. Additionally, use of an essential oil, such as lemon grass, will help entice scout bees to check out a bait hive. Morris says you only need a little scent – more is not better – but suggests replenishing every 2 weeks.
Where to place bait hive?
You can put a bait box on a hive stand in your apiary. However “normal” scout bee searching activity is where “natural cavities” occur such as tree hollows or small openings into empty cavities of buildings. Therefore it is recommended to select a partially shaded spot, visible to foraging bees, 7 to 20 feet high. Orient bait box opening to the south or east. Place several bait boxes, even asking neighbors for sites. If permitted, bait boxes near natural sites, may be helpful. You need be very careful when placing, inspecting and/or retrieving bait hives, especially when elevated over your head. Consider using a temporary platform to hold the bait hive. It should be sturdy and not wobbly. Morris says he sometimes experiences vandalism of his boxes.
Success!
When you successfully lure a swarm, and bees adopt your baited hive, they should immediately start building comb and the queen start to lay eggs in a day or two. Be mindful not to disturb them for the first week. Beekeeper disturbance could cause them to abandon the nesting site in favor of another. IF a non-hive is used transfer frames to a standard bee box 3 weeks after capture. Consider treating your new livestock with oxalic acid dribble before there is capped brood. Continue to monitor hive development during the season. If they are too weak, use the swarm capture to augment another or add brood or a “resource” nuc to bolster them. You might consider replacement of the queen to help insure successful wintering and a strong spring start next year.