One of the first steps of identifying a bee in the field is making certain that the insect you are watching is, in fact, a bee! Many flower-visiting insects like flies and wasps closely resemble bees (and vice versa), which can cause headaches for first time bee watchers. This guide is meant to introduce you some of the common flies and wasps that we think are most often confused for bees.
As you learn more about flower-visiting flies and wasps you might also become interested in learning about how to identify these other pollinators too. Check out our resources page for guides that cover non-bees.
Flies vs. bees
Flies, members of the order Diptera, cannot sting but they often resemble insects that can. This kind of mimicry–when a harmless organism masquerades as a more dangerous one–is referred to as Batesian mimicry.
Many fly mimics can be seen on flowers alongside their bee and wasp models. Some fly mimics have even evolved to resemble their model so closely that it is possible to make an educated guess as to the particular species of bee or wasp that is being impersonated.
General characteristics of flies
Flies can be distinguished from bees and wasps by the following:
- Only one pair of developed wings. Flies’ second pair of wings have been reduced to stubby halteres – sensory organs that work like a gyroscope to allow flies hover in place.
- Stubby antennae. Flies have short club-like antennae whereas bees have longer antennae.
- Big eyes. Flies have large eyes that nearly meet at the top. In contrast, most bees have slender eyes on the sides of the head. (Note: some male bumble bees notably Bombus griseocollis and Bombus auricomus have large fly-like eyes but always have long antennae.)
Fly groups covered
We cover two main morpho-groups of flies: mimics of big fuzzy bees and mimics of striped wasps.
The most commonly encountered mimic flies belong to flower flies (Syrphidae), bee flies (Bombyliidae), and robber flies (Asilidae).
- Syrphids are common in a variety of habitats, including gardens, but are particularly diverse in wetter, forested areas. Adults consume nectar and pollen and most species either lay eggs on leaves or near decaying organic matter.
- Bombyliids are commonly nest parasites of bees, with adult flies flicking eggs into the open nests of ground-nesting bees. Other bombyliid species are thought to be parasitoids of various other insect groups, including Lepidoptera (butterflies and moths).
- Asilids are predators of adult bees, with one genus (Laphria) being highly effective mimics of bumble bees in order to hunt them without being detected.
Flies that mimic big fuzzy bees
This group contains flies that are stocky and fuzzy, just like bumble bees.
Flies that mimic striped wasps
This group also contains flies that are not very hairy and striped like their wasp models. This group is largely represented by the flower flies (Syrphidae).
Wasps vs. bees
Wasps, members of the order Hymenoptera, can sting and therefore engage in a different kind of mimicry with bees. Müllerian mimicry occurs when both the model and the mimic are dangerous. Then, one can ask, which came first, the model or the mimic? In a true Müllerian mimicry complex, the species evolve together, alongside one another, each changing in response to changes in the others–the model is the mimic and vice versa.
Unlike with flies, there is not a clean set of field marks that distinguishes all flower-visiting wasps from bees. This is because bees are wasps. The main difference between wasps and bees is that bees derive their protein from pollen whereas wasps derive their protein from other insects.
As such, bees have evolved features and body shapes that favor collecting pollen whereas wasps have evolved to hunt insects. In some cases it is straightforward, like distinguishing a hairy bumble bee from a hairless, skinny-waisted wasp. Other times, it is harder like distinguishing a slender, hairless cuckoo bee from a slender, hairless wasp. The best way to learn to distinguish bees and wasps in the field is to learn the different body shapes and structures of the species present in your area.
General characteristics of wasps
In general (keeping in mind that there are exceptions), wasps can be distinguished from bees by the following:
- Skinny, defined waist. Many hunting wasps have a skinny waist which helps them more precisely sting their captured prey. Bees do not have an obviously constricted waist.
- Not distinctly hairy. Generally wasps are not very hairy, unlike bees which are often covered in long hairs. Some bee groups like masked bees Hylaeus and cuckoo bees including Nomada, Epeolus, Triepeolus, Sphecodes do not have long hairs. Learning the shapes of these hairless bees vs. wasps will go a long way towards making a field identification.
- Folded wings. Wasps in the family Vespidae fold their wings while foraging and hold their wings out at a 45-degree angle. Bees do not fold their wings.
- Antennae low down on face. Jewel wasps in the family Chrysididae and some hunting wasps in the family Crabronidae have antennae that are very low down on the face. Bees typically have antennae that are more centrally located on the face.
- Distinct color patterns. In general there are very few truly black-and-yellow striped bees in the northeast (with the exception of some anthidiines like Anthidium oblongatum.)
Wasp groups covered
Wasps are an incredibly diverse group of insects, with only a small fraction of them regularly encountered on flowers seeking nectar or hunting prey. We cover these flower-visiting wasps, members of the families Vespidae, Crabronidae, Sphecidae, and Chrysididae.
- Vespids include both the much-maligned social wasps (the yellow-jackets, bald-faced hornets, and paper wasps) that are known to crash picnics as well as the solitary mason wasps (Eumenini) that build nests out of mud.
- Crabronids are hunting wasps and take a variety of prey items including biting flies (by Bembix), stink bugs (by Bicyrtes), grasshoppers (by Tachytes) and even bees (by Philanthus)!
- Sphecids are often large and flashy with very skinny waists and a bulbous abdomen; they take spiders (by Sceliphron caementarium), katydids (by Sphex), cicadas (by Sphecius speciosus), and crickets (by Isodontia).
- Chrysidids are a most exquisite group of wasps, known as jewel wasps because of their metallic emerald, sapphire, and ruby coloration. Chryidids are cuckoos, laying eggs in the nests of other insects including other wasps and bees. Adults nectar on flowers with short corollas, often Asteraceae like Erigeron.