A typical life cycle of a solitary bee

Did you know there are approximately 230 species of solitary bees in the UK?

There are approximately 230 species of solitary bees in the UK. The number is gradually increasing. Unfortunately, many are now becoming rarer due to chemical use and loss of habitat so it is possible that some species may disappear without ever having been discovered and described. There are six families, Colletidae, Andrenidae, Halictidae, Melittidae, Megachilidae and Apidae. Solitary bees along with bumblebees, butterflies, moths, and flies make up about 45% of the pollinating force so are therefore very important for producing our food.

They are called solitary bees collectively because they have a simple life cycle compared to social honeybees. Some, however, live together in aggregations but don’t assist each other. Others act as cuckoo bees effectively parasitising on other bees’ work.

Hylaeus pectoralis from the Colletidae family has a typical life cycle. This is a small primitive bee, approx. 6-7 mms long and found in marshy areas. In early summer the males and female’s mate. The female then seeks to nest in the disused gall of the reed gall fly made from dead leaves on the flowering stem of the common reed. She builds one cell at a time and lines it with a mucous membrane (weatherproofing). The cell is generously provisioned with a paste of nectar and pollen. An egg is laid, and the cell is sealed up. Further cells are built, between 5-8 on the same gall. Once completed the female bee dies. The eggs hatch in a few weeks and the larvae feed on the provided larder.

By the autumn they are fully grown and remain dormant until next Spring. The larvae pupate in their cells and emerge as fully adult insects in about May or June when they leave the nest. Mating then occurs and the process repeats itself. The males die after mating and the females start another nest in a disused gall.

Many solitary bees have a similar life cycle not only in the UK but across the world. You will note that the female has no contact with her offspring, and they complete the lifecycle entirely on their own. The pollen provision means that they are contributing to pollination in their own way.  Solitary bees vary in size and many of them are very small that we would not notice them or mistake them for flies. First appeared on earth approximately 120 million years ago.