Sunday, December 7, 2014

Leaf-cutter bees

Leaf-cutter bees are solitary bees. They do not form colonies and do not produce honey. They are a large cosmopolitan group of insects which consists of about 1,500 species. in In Maltese the common leaf-cutting bee is known as mqass tal-weraq.

Leaf-cutter bees are important pollinators of both wild and cultivated plants. A leaf-cutting bee is a much better pollinator than a honey bee.

They build their nest in sheltered places usually in natural cavities in the ground, on rock faces or in hollow twigs. The nests are lined with disk-shaped pieces of leaf or petals which the female cuts using her large mandibles. It is thought that the leaves and petals maintain a higher humidity inside the nest. This prevents the stored food from drying up.

A typical nests consists of a tunnel with columns of cells along it. The female lays an egg in each cell, supplies it with food which usually consists of pollen which is sometimes mixed with nectar and then seals the egg and food inside.

The male larvae hatch before the female do but they die shortly after mating while the females live several weeks more during which time they build a new nest and lay eggs in each one of them.

Leaf-cutter bees can sting and will do so to defend themselves but their sting is much less painful than that of the honey bee. A tell-tale sign that gives away the presence of leaf-cutter bees are circular patterns cut in leaves. These can be found in a variety of plants but are not of concern even when the leaves belong to cultivated garden plants.

All bees and wasps are highly beneficial insects and should never be considered as pests. The presence of these and other bees and wasps is an indication of a rich biodiversity. They should be encouraged to build their nests in your garden by providing them with suitable nesting cavities. These can be made of short lengths of reed or cane tied together in bunches and placed in sheltered parts of the garden. Canes of different diameter are likely to attract different species of bees and wasps.

This article was published in The Times of Malta on 28 August 2014. 

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