As makers of the Sundance pollen traps, we know something about the subject. Peter Chaing Mai said "I have been measuring the holes on a pollen trap. The bees pass through the holes to remove the pollen. They are drilled through plastic and are 3/16" (4.76mm). I am proposing to use a metal mesh and that is available only in metric measure so the closest diameter holes will be 5mm. Does anyone see any problem with the increased diameter, it is small (5%) but are bees going to retain materially more pollen?" For some reason, the manufacturers of wire screening use English (or, Imperial) measures rather than metric. The mesh counts refer to how many openings are in an inch of fabric (screen). Well-designed pollen traps use five, seven and eight mesh for the trap itself and 16-24 mesh for the screen in the bottom of the pollen trap. HOWEVER, the number of openings to the inch is not the only important factor and the wire diameter needs to also be taken into account. Wire diameters are also expressed in English measurements. Combined, they produce the amount of open area in the mesh which is very important when considering damage to bees, amount of pollen retained for brood, and trap ventilation to retard mold damage to the pollen. The OAG trap is the ancestor of all modern pollen traps, but has major design deficiencies. Most modern pollen traps are constructed with screen. Some use perforated metal, but these have a nasty habit of removing bee wings until the burrs are removed by several days or weeks of wear. I have never seen a plastic performation that was not junk. (Sorry.) Perhaps such a trap exists and I have not seen it. Those who want to make an improved trap need to make a list of important attributes, such as: 1. Collection of 50%-60% of pollen, with the remaining amount going to the brood nest. 2. Bee escapes that do not slow outgoing traffic from the hives. 3. Drone escapes that will largely not be used by incoming bees to avoid the trap. 4. Means of reducing mold by distributing pollen more or less evenly into a collection drawer. 5. Means of preventing rainwater from entering the pollen collection area. Etc. Hope this is helpful. *********************************************** The BEE-L mailing list is powered by L-Soft's renowned LISTSERV(R) list management software. For more information, go to: http://www.lsoft.com/LISTSERV-powered.html Guidelines for posting to BEE-L can be found at: http://honeybeeworld.com/bee-l/guidelines.htm