Nothing has stirred up taxonomic relationships faster than genetic analysis. Relationships between species—both plant and animal—have been turned upside down. Some relationships that were “set in stone” are now known to be non-existent, and living things thought to have no relationship whatsoever are now considered “kissing cousins.” New family trees are being drawn, names are changing, and no one, it seems, agrees with anyone else. In this post I’m going to describe a little about the families of bees, but remember: these may change tomorrow.
The broad categories we call ants, bees, and wasps all belong to the order Hymenoptera. The order comprises roughly 150,000 species, of which about 20,000 are bees. However all 20,000 bee species are divided into just seven families. Six of these are widespread; the seventh is found only in Australia.
In the past, taxonomists believed that wasps and bees were descended from a common ancestor. They believed that the descendants of the common ancestor evolved different methods of feeding their larvae which ultimately gave rise to the modern differences between wasps and bees.
However, new evidence shows that bees probably evolved directly from wasps with no common ancestor. You can think of bees as the “vegetarian” branch of the family tree. While the rest of the crew was still eating meat, a few read “The Ethics of Eating Animals” and broke with tradition. The wasp hierarchy considered these fools to be low class (grade B) citizens and they’ve been known as “Bs” ever since . . . or something like that.
Anyway, here’s a quick rundown of the seven families of bees:
Andrenidae: This family comprises the mining bees, all of which live underground. The bees carry pollen on their hind legs and many species are incapable of stinging.
Apidae: This family includes, honey bees, bumble bees, digger bees, squash bees, and carpenter bees. Many of the bees in this family carry pollen on their hind legs, although some species are cleptoparasitic (meaning they steal the nest provisions of other bees) and don’t carry pollen at all. There is a huge range of nesting habits, behavior, and life cycles in this large group of bees.
Colletidae: This family includes the yellow-faces bees, polyester bees, cellophane bees, and the plasterer bees. Depending on the species, these bees live in the ground or in hollow stems. All of the Colletidae species line their nests with a plastic-like substance that is secreted from their abdomens. The female carries pollen back to the nest inside her body rather than outside.
Halictidae: These are the sweat bees. This is a large and varied family that includes bees that are attracted to human perspiration and some that aren’t. Some nest in the soil, some in wood. Some are solitary, some live in groups. Some are cleptoparasitic and some are not.
Megachilidae: This family includes carder bees, mason bees, leafcutters, and resin bees. The bees in this family carry pollen on their abdomens instead of in pollen baskets. Also, they build homes by carrying construction materials to the job site. Depending on the species, they use mud, leaves, plant fibers, resins, or other materials to build their nests in pre-existing holes or cavities.
Melittidae: This small family includes the oil-collecting bees. These bees nest in the soil in dry regions and collect oils from specific species of plants. The bees mix pollen with the plant oils (instead of nectar) to form larval food stores.
Stenotritidae: This is the small family found only in Australia. The bees are large, fast, and solitary. They nest in borrows and build cells lined with a plastic-like secretion. The larvae are fed provisions of pollen and nectar. Oddly, the larvae of this family do not spin cocoons.
Rusty
I’ve never understood why bees–a highly coherent group morphologically and behaviorally–had to be split into multiple families that are each rather more difficult to circumscribe. The present scheme needlessly complicates the teaching of insect taxonomy, and it isn’t like large families are unheard of. Ground Beetles are twice the age and several times the diversity of bees, for example, but no one has any trouble with keeping Carabidae as a single family.
Taxonomists have always known that bees were descended from wasps. What changed wasn’t the knowledge of relationships (although those have been refined), but the philosophy of taxonomy. Most taxonomists now classify based on evolutionary relationships, and before they used various measures of gross morphology.
Thanks, Alex. In his book Bees, Wasps, and Ants (2010), Eric Grissell says, “The bees and these wasps [predatory Sphecidae] have always been treated as lineages distinct from one another, and each was even included in its own superfamily group. That is, both groups were thought to be distantly related, but perhaps with a common ancestor. . . . It is now evident, however, that bees are, to put it simply, specialized wasps. They arose from within the wasp lineage, not from an ancestor common to both groups.” I see now that he meant the Sphecidae family only and the seven families of bees were once thought to have a common ancestor.
Grissell goes on to mention that many researches believe all bees should be recognized as a single family. Perhaps the move toward classification based on evolutionary relationships will some day do away with the awkward seven-family structure that now exists.
This is a very good site.