Counting plugged nest holes is a poor way to determine actual bee production. Plugged nests may contain few live larvae, may have diseased or parasitized cocoons, exhibit poor sex ratios, or even contain empty chambers.
To determine the health and size of a population, x-ray analysis (as described in Appendix B), or nest dissection is necessary. This is another reason why drilled blocks, without paper liners, make poor nests. Grooved boards are the most easily disassembled for inspection. Paper liners in cardboard tubes or solid blocks are easily disassembled, or can be inspected by viewing against a strong light. Reed or bamboo nest tubes can also be inspected by carefully splitting them apart with a sharp knife. To minimize damage, nest inspection should be performed after cocoon spinning in the fall.
With experience, cocoons are easy to sex based on position within the tube and size. Remember that female cells occupy the innermost section of the nest cavity and are larger than male cells. Diseased and parasitized cells are also often easy to identify and usually do not contain spun cocoons.
To determine overall health and sex ratios, collect a number of nests at random. The larger the sample size, the more accurate the sample will be. Record findings including the total number of cocoons, the number of male and female cocoons, the number of empty cells, parasitized and diseased cells, etc.
To calculate percentages of various categories for analysis, multiply the number of cocoons times 100, then divide by the total number of cocoons you found. Here is an example:
168 viable cocoons were counted among the nests that were opened. Of these there were 43 female cocoons. What is the percentage of female bees?
(43 female cocoons x 100) ÷ 168 total cocoons = 25.6% female bees
Despite the best efforts of a mason beekeeper, some nests fail to produce any emerging bees each season. These defective tubes should be carefully dissected at the end of the nesting season to determine the cause for failure. Previously unnoticed parasite or disease problems can often be identified in this way, as can other anomalies such as the presence of parsivoltine species. These defective nests should be opened away from stored bees and nesting sites to reduce the spread of pathogens and parasites.
Mason Beekeeping in Japan
In 1981 a rural inn in Fukushima Prefecture’s Minami Aizu district was declared a historic preservation site by the Japanese government. The house, which is several hundred years old, still retains the traditional thatch roof made of reed. Within these thick layers of reed matting, thousands of Osmia cornifrons can be observed nest ing each spring. This phenomenon provides a unique glimpse into Japan’s agricultural past, when man and mason bee occupied the same homes.
During that agrarian era, inquisitive farm kids quickly learned that the reeds could be split apart revealing the sweet tasting pollen-nectar provision within. This pollen-nectar mixture resembled kinako, a traditional food made of soybean flour and honey, leading to the moniker, “bean-powder bee,” or Mame-ko Bachi—a name which persists to this day. Active management of the mame-ko bachi (commonly called the Japanese hornfaced bee in the West) as a pollinator did not begin until the latter days of World War II.
Habitat loss and increasing pesticide use greatly reduced the number of wild pollinators in Japan’s northern apple growing regions by the early 1940s— leading to dramatic declines in yield. Matsuyama Eikyu, an apple grower in Aomori prefecture, had noticed the mame-ko bachi nesting in the cavities of utility poles and boards near his orchard and wondered if he could propagate the bee by providing additional nesting materials. His success was almost immediate, and following the war Matsuyama was awarded a government grant to further his research. Matsuyama went on to lecture about mason beekeeping at several universities. He was also among the first to recognize some of the fundamental principles of mason beekeeping, such as the importance of providing large visible orientation landmarks for bees—placing nest materials against the sides of buildings, rather than hanging them from trees.
Following on the heels of Matsuyama’s success, another apple grower, Takejima Gisuke, further refined nesting technology, making him a leading producer of mason bees. During a seven-year period in the 1950s Takejima produced 15,000 nest tubes, containing nearly 150,000 bees, most of which were distributed to other growers as well as University researchers across Japan. Takejima also founded the Mame-ko Bachi Preservation Group, a cooperative organization dedicated to shared research, nesting technology, and establishing distribution standards.
Active research into rearing practices and parasite control was performed throughout the 1960s and 70s at the Aomori Prefecture’s Apple Research Institute, primarily under the direction of Yamada Masashi. Today in Aomori’s Itayanagi village a monument stands to the mame-ko bachi, and apple growers gather every May 8th to celebrate “Mame-ko Bachi Appreciation Day,” complete with an outdoor festival.