All About Solitary Bees
Most of the smaller furry bees we see flying from flower to flower are solitary bees that do not produce honey or wax. As their name suggests, they live alone, unlike their well known social cousins, (honey bees, bumble bees and some stingless bees) which live in colonies.
They have no queen, are not territorial or aggressive, and they do not swarm. They rarely sting, mainly because of their size (ca 5 – 24 mm max.). People often mistake them thinking they are wasps, honey bees, or hover flies.
The vast majority of the 20,000 bee species worldwide are solitary bees. Only around 9 species of honey bees, 250 species of bumblebees, and around 11 species of stingless bees are social bees that live in colonies.
How do I know what is a solitary bee?
There are a few distinguishable difference:
- Wings – Bees have four and flies only have two wings and are usually hairier than wasps.
- Timing – Not all species appear at the same time. For example, the first bees to emerge are red mason bees which pollinate fruit trees. The leaf cutter bees can be seen until September.
- Nesting – Although there are huge difference among solitary bees, check what material they use to close the tubes with near the entrance. They can only be seen for a few weeks from spring to summer, although their life cycle is ab
Collecting Pollen
Solitary bees, just as their social cousins play a crucial part in pollinating plants. In fact, they easily surpass them! One single red mason bee pollinates about the same amount of flowers than 120 more honey bee workers combined!
Their techniques vary due do differences in their anatomy. While honey bees collect pollen in baskets (corbiculae) made of tightly-woven leg hairs on their hind legs, most solitary bees have special hairs (scopa) on their legs to which the pollen sticks. Because they lose a lot of pollen when they fly, they are often called ´star pollinators´.
Bees that actively collect pollen sometimes moisten it with nectar to make sure the pollen sticks more readily. Leaf cutter- and mason-bees collect pollen on similar hairs underneath their abdomen, while some yellow faced bees swallow the pollen and regurgitate it when they return to their nest.
Nesting
About 70% of solitary bees build their nests in underground burrows (mining bees), while the remaining 30% nest in tubes or holes houses (cavity nesting bees). In addition to the nectar and pollen wild flowers provide for these busy bees, they also offer ample nesting opportunities in their dry, hollow stems.
Some live in bee hotels in close proximity to each other, others are very particular. The harebell carpenter bee for example is so dependent on bell flowers that it cannot survive without it.
Solitary females bees typically build their own nests and prepare it for their offspring. Although their mating process is the same as honey bees, they never meet their offspring. After they lay their eggs, they die.
Life Cycle
Although solitary bees have the same life cycle as social bees, there are some differences:
The female gathers building materials for the nests and food for the larvae. She lays around 20 to 30 eggs in her life, and each egg is laid into an individual cell. She places a ball of pollen that is stuck together with nectar in each cell for the larvae to feed on. The eggs are separated and sealed by a partition and the process repeated. When the hole or tube is full, the female closes it with mud, leaves, or fine hairs before she moves on to the next tube or hole. Unlike most bumblebees and honeybees, the offspring is left to their own devices until they hatch.
When the eggs hatch into larvae, they eat the pollen and enter hibernation. They stay in their cocoon for about 11 months, – all summer and winter. Hatching time is in the following spring, when the pupae turn into adult bees. Once they emerge from their nest, they live for an average of 4-6 weeks. Male solitary bees share the same purpose and fate as honey bees; mate and die.
Predators
Solitary bees are anything but safe when it comes to being attacked, even though the larvae is sealed within individual cells in the nest. Parasites and other insects are only too eager to raid and attack their nests when the females are away from their nest.
The predators of solitary bees fall into three main categories, although some parasites like certain species of bees, wasps, flies and beetles can belong to all three. The attacks vary,
- Kleptoparasites, steal food from other creatures
- Brood Parasites lay their eggs in other insects´ nests, similar to a cuckoo, and
- Parasites that feed on the host.