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Mining bees are important pollinators

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Little volcanoes of fine soil in your garden are caused by mining bees

Little volcanoes of fine soil in your garden are caused by mining bees

Little volcanoes of fine soil in your garden are caused by mining bees

Mining bees are active at present and their nests are very obvious. They nest in the ground and when they excavate their shafts, they are said to be mining hence the name mining bees.

A nest-building mining bee starts work by digging a hole in the ground. Soil characteristics have to be very precise: dry, fine soil with no humus or stones in a sheltered, sunny location. The nest site is very often in someone's garden, perhaps in a lawn or at the edge of a yard. Spoil from the hole is thrown up in a mound around the excavation site.

Good nest sites are scarce so a good spot may have several nests. Even though the bees are solitary, neighbours may nest close to each other at a good site giving the false impression that the insects are social and colonial nesters.

The hole that is dug is quite small. Rather than widening it, the bee mines vertically downwards digging a shaft that ends up many times the length of the owner's body.

Excavated soil is pushed up the shaft behind the digging bee and a little volcano begins to grow on the surface. Fussy gardeners may find these an untidy nuisance and be tempted to sweep them away. The temptation should be resisted. The volcanoes are only temporary structures, and mining bees are important plant pollinators.

As well as being important plant pollinators mining bees are also harmless; females can sting but they are not aggressive, so they seldom attack and even if they do so their venom is weak, so the impact of the sting is negligible.

It is the female bee that digs the vertical mine shaft. She does so to make a nest for her offspring. When the nesting tube is ready, she fills the bottom of it with a store of pollen and nectar, lays a single egg on top and departs to die shortly afterwards. A sudden summer shower may destroy the volcano on the surface and seal the top of the shaft.

The egg hatches and the emerging youngster feeds on the larder its mother provided for it. It is fully grown by autumn, but it stays in its burrow hibernating over the winter months. When spring arrives, it digs its way to the surface and flies off to feed thereby pollinating flowers, to find a mate and to start the cycle all over again.

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