In the previous newsletter, I concentrated on my experience with honey bees and the dangers that the invasive Asian hornet presents to this species. However, honey bees are not the only pollinators that help ensure we enjoy a wide variety of crops. There are over 250 species of other pollinators in the UK, and they are very important in pollinating plants that are not frequented by honey bees. Beekeepers try their best to protect their honey bees from pests and predators to safeguard the honey crop, but there is little management for the solitary bees. So, what can be done? If left to nature, there is a real possibility that the Asian hornet may be the last straw for many of these species because they prey on all insects. This is an additional burden on top of existing diseases, loss of habitat, and pesticides. It is often said that in nature, there is safety in numbers, so if we can provide more habitat for these species, perhaps we can tip the balance back in their favour.
There are many bee and insect ‘houses’ on the market at various prices, but many of them are not really suitable to protect the larvae from rain. Also, some of these man-made nests are too shallow for many of the solitary bee species. For example, miner bees need nest cavities at least six inches deep because the female lays six eggs in each tube, three female eggs first and then three male eggs last. Each one is separated by a plug of mud, and the exit is also blocked. The eggs develop into larvae, then cocoons, and spend the winter hibernating in the nest until the weather warms sufficiently in spring, usually around May/June. The warm weather triggers the three outer cocoons to hatch first, and, all being male, they congregate around the nest exit. The other three cocoons then hatch soon afterwards and, all being female, are quickly pursued by the males on mating flights. The females then go and collect pollen and nectar from plants, which they put into each cell with an egg, hence the next generation is created.
I was first introduced to solitary bees by a regional bee inspector who was advocating using solitary bees in enclosed environments such as greenhouses and polytunnels because they were more efficient pollinators and, with safety in mind, they do not sting like honey bees, wasps, or hornets. This makes them an ideal choice to introduce bees to children who can safely watch them come and go from their nest without the fear of being stung. He gave me a nest box with larvae already in residence, and I took them down to our community farm where, several years later, they still thrive. I set about making some homemade nests and found that a length of circular drain pipe about 7 inches (17.78 cm) long could accommodate several off-cuts of bamboo cane about 6 inches (15.24 cm) long and between 1/4 to 5/16 inches (6 to 8 mm) in internal diameter. One end is blocked off with a lid from a 1 lb (454 g) jam jar, and the bamboo canes, cut through at a knuckle and 6 inches away in the hollow part, are introduced into the open end. Depending on how knobbly the canes are, it may be necessary to use a rasp to round off each cane to fit snugly into the drain pipe. Use a long (7 inch) drill to clean out the insides of the canes and then fit a pipe bracket. The nest is ready to be installed in a south-facing position (some websites say east, but that means they suffer cold east winds in the UK), well off the ground and under an overhang if possible, pointing slightly downwards to allow water runoff (under the gutter of a shed is ideal). If you are not DIY-minded, then 6-inch mason bee nesting tubes are available online in cardboard and bamboo at reasonable prices. There are websites that show how to ‘manage’ mason bees by removing the cocoons before the hibernation period, but this is beyond the scope of this newsletter.