Bees: How diverse can they be?
by Jaime Pawelek
When one thinks about bees, they typically think about the honey bee or bumble bee. These two bees actually represent only a very small fraction of the diversity of bees in the world. Locally, in California we have about 1,600 species of native bees, some social, but most are solitary. Their nest making strategies or behaviors usually partially describe each of the 1,600 bee species. In California we have many different types of bees including leafcutting bees, sweat bees, digger bees, mining bees, mason bees, carpenter bees, and cuckoo bees.
"Within these groups there is much variation in body size, coloring, and nest making strategies. One group, the leafcutting and mason bees (family Megachilidae) are fairly common in our Berkeley, CA garden, and they are represented by many species ranging in size from a few millimeters long to almost two centimeters long. Some of these bees are small, grey, and fuzzy, some are metallic blue and look like three BB’s stuck together, whereas others are much larger and have distinctly colored abdomens that almost look like they were painted on. Some of these bees collect leaves as nest materials, while others collect fine hairs from plant leaves like Lamb’s ears. Some nest in pre-made cavities like holes drilled in wood, however most dig nests in the ground. The differences are endless even with the simple ground nesting lifestyle.
Sizes of bees are variable and in our garden we have tiny bees that are only a few millimeters long as well as some larger bees that are on average two centimeters long and have a wingspan of three centimeters! The small bees are hard to identify and most people don’t even realize they’re bees. The larger carpenter bees are so big that when they visit flowers for nectar and pollen the whole branch will sometimes sag with their weight.
In addition to the different sizes of bees, there are also different shapes of bees. Some bees have very rounded abdomens, while others are very tapered and come to a point. Some bees have long slender bodies, whereas others can be quite robust. Some have relatively large heads, like leafcutters, which are filled with large muscles used for carefully cutting leaf discs for making nests. The difference in shapes may be due to how the bee forages on the flower or where it collects and stores pollen on its’ body.
Bees display a wide range of colors and it is not uncommon to see bright green bees, yellow and black striped bees, metallic blue bees, black bees with white polka dots, and white and black striped bees. It’s hard to say why these colors have evolved. One thought is that bright colors serve as warnings to predators. Another is that the colors help with mate recognition or recognition of the same species. There are also a lot of bee mimics among flies, moths, and beetles that display the color and behavior patterns of honey bees and bumble bees so they can avoid predation. All these bees can be easily seen even in your home garden, so go out and have a look!