Solitary bees, unlike honeybees, do not live in hives. True to their name, they instead live alone, each building individual nests for their eggs, and collecting nectar and pollen to feed them, without the help of a colony. This also makes them very nonaggressive; without a colony to protect, they are much less likely to sting, only resorting to it when crushed or otherwise trapped. Solitary bees come in a large variety of colors, shapes, sizes, and textures, with many different cool behaviors as well. Click here to learn about some of the common types of solitary bees you might encounter in California!

While honeybees are active year round, solitary bees only live for a year, and are generally active as adults for only 3-6 weeks. In the spring, solitary bees will emerge from their nests, after which they will mate. Males will die shortly after this, while females will begin building their nests, which can take the form of anything from burrows to deep cavities to even things like snail shells. At this time, they will also be collecting pollen and nectar for their young, which is when you will most likely see them. The female will lay each of her eggs in a separate cell, or room, in her nest, generally providing each with a pollen loaf - a ball of pollen and nectar that will feed the young until they can find food on their own. After this, the female will die as well, leaving the eggs to hatch, pupate, and develop into adults inside. The adults will then sleep through the winter, emerging as the new generation in the next spring.

Solitary bees, by being native, also hold another advantage over honeybees. Since they evolved locally, they are much better at reaching flowers that honeybees can't, since the European Honeybees evolved with European and African plants - for example, the California Buckeye is a favorite among solitary bees, but is toxic to honeybees. This means that many of our native plants rely on solitary bees for their pollination. In addition, many solitary bees species are specialists, only collecting food from a very small collection of flower species, or even just one of them, making them even more important in pollinating those plant species, as they come to rely on the bees in turn for their pollination. If solitary bees were to disappear, many of our native plant species would decline or even die out, greatly harming our ecosystem.

Unfortunately, solitary bees are experiencing decline due to many human activities.

1. Development, both urban and agricultural, destroys many of the habitat locations and food sources that solitary bees need: the ground is paved over, preventing burrowing, and foliage is cleared, removing potential cavity nesting sites along with many of the native plants that solitary bees rely on. This greatly reduces the range that they can exist in, especially due to the fact that solitary bees only fly a few hundred yards from their nests in search of food, as opposed to miles that honeybees can fly.

2. Pesticides are commonly used in agriculture to get rid of pests that might harm crops, but are also commonly used in cities to remove harmful pests like mosquitos. However, these pesticides contain Neonicotinoids, which kill many other important native insects that they don't target, including solitary bees. 

3. Human-caused climate change is also a major problem that solitary bees face. Increasing temperatures change the environment so that invasive plants and diseases can proliferate, which harms the bees. These changes in climate also generally stress the bees out, making them more vulnerable to many of the other threats they face. Increasing temperatures can also make flowers bloom earlier, which may result in solitary bees emerging too early and missing many food sources they rely on.

Given how important they are to our ecosystem, it is very important for us to help solitary bees thrive against the threats that they face. 

Here are a few things you can do to help save solitary bees, and help your yard and our ecosystem flourish! 

1. Spread Awareness! Few people know about the existence of solitary bees. it is much harder for us as a society to take action if no one knows about the problem, after all!

2. Plant native plants! This will provide food sources for many types of solitary bees in your area, as well as many other native pollinators. Here is a list of some good native plants that solitary bees are attracted to.

3. Avoid Pesticides and Chemicals! These really harm solitary bees and are a major cause of their decline. Don't use them in your garden, and advocate against pesticide use by your city - a lot of cities spray pesticides on hedges and other plants by the streets, maybe even right outside your house, in order to kill pests like mosquitos, but these of course harm many other insects as well.

4. Leave your garden a little messy! Leave some ground bare so that solitary bees can make their burrows there, and leave some foliage to provide habitats for cavity-nesting bees. This will open up many more potential habitat locations that solitary bees can use.

5. Build bee houses! These will provide more much-needed habitats for solitary bees. Here is a tutorial on how to build and take care of one. Note that this is not the only way to build a bee house, as there are many other good designs that work too.