Bee, Wasp, or Yellow Jacket?
I have to confess, it's a huge pet peeve of mine when people call wasps and yellow jackets "bees." I'm not even a beekeeper, I guess it just upsets me because it gives bees a bad rap... and they're having enough trouble already without people thinking they're getting into their pop cans at picnics.
If you're allergic to bee stings, you have very good reason to be afraid of bees, but for the rest of us, the benefits far outweigh the risks of these generally gentle creatures. Bees are one of the most important pollinators in the world. In fact, it would be safe to say that the human race wouldn't exist if not for bees.
Bee identification is actually relatively easy. There are both visual and behavior clues that can help you decide exactly who is buzzing in your garden.
The common European Honeybee is not native to the Americas, but she was imported with European settlers and quickly made herself a vital assistant for American farmers and gardeners.
She is fuzzy and compact, and her black and yellow coloring is rather dull. Strictly vegetarian, she is not one to show interest in your picnic lunch, though she may occasionally come over to investigate a brightly colored shirt. Otherwise, she spends most of her time gathering pollen from flowers.
She has only a single sting and it kills her to use it, so she will generally choose flight rather than fight, unless she feels her hive is threatened. She might also sting if caught, sat on, slapped at, or otherwise cornered.
It should be noted that Africanized honeybees, which look very similar to the European variety, are more aggressive, particularly in defense of their nest. if you live in an area where Africanized honeybees are known to live, be wary of anything that looks like a honeybee and avoid swarms. (Africanized bees swarm more often than European bees.)
Bumble bees and Carpenter bees
I think bumble bees are cute. Much larger than honeybees, they are also even furrier, and their coloring is often brighter, though this varies from species to species.
Like honeybees, they are excellent pollinators who spend their lives visiting flowers and will not show interest in human foods.
Though bumble bees are capable of stinging multiple times, they are generally even less aggressive than honeybees. The exception is if their hive is threatened.
Bumble bees are commonly confused with carpenter bees, which are a similar size and form. However, carpenter bees have a shiny black butt instead of a furry striped (usually) one. Though considered a nuisance by some for their habit of nesting in deadwood, including sometimes the walls or windowframes of houses or barns, carpenter bees are good pollinators and it is worth attempting to move them to a more suitable location, rather than killing them outright. Drone carpenter bees might appear more aggressive than the gentle females, but they are generally just curious, and don't have a stinger even if they do intend harm. The sting of the females is fairly mild, and unlikely to occur unless handled.
You could almost say a yellow jacket looks more like a bee than a bee does. At any rate, they're smooth and shiny and their black and yellow stripes are bright flags yelling "bee! bee!" at people who don't know better.
Although yellow jackets, which are really a kind of wasp, occasionally visit flowers, they are extremely inefficient pollinators because of their smoothness, and their preferred food is actually other insects and fruit. They are considered semi-beneficial because they eat many caterpillars and other insect pests that damage crops and garden plants. However, when these natural food sources begin to decrease in late summer and fall, they become a nuisance species. They are attracted to odors that are meaty or sugary, which is why, if there's an annoying "bee" that persists in trying to steal your picnic, there's a very good chance it's actually a yellow jacket. Yellow jackets are also known to hang around bee hives attempting to steal honey.
Unlike bees, yellow jackets are aggressive and free to sting you as many times as they want without injury to themselves. Some people are allergic to yellow jacket stings, so they should be treated with considerably more caution than most honeybees.
Wasps and Hornets
There are many different varieties of wasp, with different appearances and habits. Many are carnivorous or omnivorous and are considered beneficial due to their taste for common garden pests such as caterpillars.
Wasps are generally smooth-bodied and shiny, with much less compact bodies than bees. For example, you might barely notice the legs of a bee when it is flying, but the legs of a wasp trail down behind it in flight very noticeably. Wasps also often have very narrow waists, and the term "wasp-waisted" was used in Victorian times for a certain type of silhouette that underwent several periods of popularity and resembled the segmented body of the wasp: with a tiny, heavily corseted waist accented by the broader bust and hips above and below.
Wasps look terrifying, with their long spidery legs and evil looking faces, but most are actually quite gentle. The primary exception, as with many bees, is the social wasps, if they feel their nest is threatened. If you have a caterpillar problem, a nest of hornets might be the best thing that ever happened to your garden, but whatever you do, DON'T try to move it! Those ladies are mean when angry and quite happy to sting you a hundred times each if they can.
North America has many native solitary bees. These bees are usually less aggressive than social bees, because they do not have a hive to defend. Most are also excellent pollinators and there is growing interest in their use as alternative pollinators due to Colony Collapse Disorder and other problems afflicting domesticated and feral honeybees.
Additionally, many species of fly mimic bees in appearance and/or behavior. Most are completely harmless to humans.