Are You a Bee or Are You a Fly?

Spend a little time watching native plants in bloom and you are likely to witness a diverse array of colorful flying insects of all sizes, shapes, and colors.  Most  are seeking nectar, pollen, or both. Some will inadvertently transport pollen from one blossom to another.   Exactly what the native plant had in mind!

Some of these insects are likely to belong to our 4,000 species of native bees.   Others may be wasps.   A third and generally less well-known group are colorfully marked flies visiting flowers in search of nectar and pollen.    All three groups are important pollinators of native plants. A first step in identifying any one pollinator is deciding whether it is a bee, a wasp, or a fly.  And that is not always easy!

All 3 groups have bodies divided into a head, a thorax, and an abdomen.  All 3 groups have 6 legs and pairs of wings attached to the thorax.   Members of all 3 groups can be very colorful with intricate markings.  Bees tend to be hairy/fuzzy and wasps less so.

A carpenter bee and a Vespid wasp visit Titi blossoms.  Both have 2 pairs of wings.

Check the Wings and Wing Position

A fundamental difference between bees and flies is their number of wings.  Flies belong to the order Diptera and have a single pair of wings.   Bees and wasps have 2 pairs of wings, but the wings on either side of the body are linked.  In many cases, bees will rest with wings aligned on top of their abdomens while flies usually land with wings angled away from their bodies.

A flower fly, Helophilus, visits a fall aster.

Check the Antennae

A second and very useful clue is the size and shape of antennae.  Bees have long, slender antennae while flies have short, stubby antennae.  Compare the very short antennae on the above flower fly to the long, slender antennae of the below “polyester bee”.   Also take a moment to compare the “resting” wing position on the flower fly and the bee.

Colletes species emerge in early spring.  They line underground nests with a waterproof cellophane-like secretion and are often called “plasterer” bees.

Check the Size and Position of the Eyes

A third clue is the size and position of the eyes.  Bees have eyes on the sides of their heads. Flies have larger, forward-facing eyes.   Eristalis tenax, below, has large, forward facing eyes, stubby antennae, and a single pair of outward angled wings.

Eristalis is a commonly seen genus of flower fly.

Check for Pollen Sacs

Fourth, bees have specially adapted hairs on their legs or abdomens used to transport pollen to their nests.  If you see bulging pollen sacs, you are looking at a bee.  Both our native Mellisodes dentiventris (left) and the European honey bee (right) have specially adapted hairs on their legs to transport pollen.

Flies are considered second only to bees in their importance in pollinating our native plants.  With a little practice, these 4 tips may help you to decide, bee or fly?