Insects

Many different types of insects pollinate plants. Most are not as common or as efficient as bees. Nevertheless they are important to certain species. Below are some of the larger groups of insect pollinators.

Bee Flies

A lot of honey bees have been working the oregano in the last few weeks, but one day I noticed a bee that didn’t look quite right. It was slightly bigger than the rest and held its wings at a funny angle. Curious, I looked more carefully and realized it wasn’t a bee at all, but a fly.

In the past I would have assumed this was just a weird honey bee and not bothered to look further. But as I’ve studied pollinators more and more, I’ve come to realize the natural world is brimming with look-alikes—insects that mimic the appearance of other insects, especially bees.

Bee fly on oregano flower. Photos by R Burlew.

The insect I saw is known as a “bee fly.” It is in the very large Bombyliidae family in the order Diptera. The adults feed on nectar and pollen, which makes them pollinators. The female lays her eggs in the nests of other insects, such as beetles, wasps, and solitary bees. When the eggs hatch, the newborn larvae eat the developing pupae of the host insect, a practice that makes them predators as well as pollinators.

There are about 5,000 known species of bee flies, and scientists suspect there are many more that haven’t yet been described. For the most part, the species in this family are poorly understood—mostly because they live singly and never appear in large groups or clusters.

Two things to look at when trying to distinguish between a fly and a bee are the wings and the antennae.

Bee fly on the left, honey bee on the right.

  • Bees have two pairs of wings and flies have one pair. This can be tricky, however, because a bee’s wings hook together so they move as a unit. Often the two pairs look like one pair.
  • A bee antenna is elbowed or bent. Fly antennae are often short, stubby, or extremely thin and hair-like.

 

Hover Flies

Many of our native pollinating insects are not bees. Included in this group are the hover flies, also known as syrphid flies, flower flies, or drone flies. These are true flies—in the order Diptera—and they are easily recognized by their ability to hold a seemingly motionless position in the air.

Hover fly on herb-robert.

Some of the hover flies have distinctive stripes on their abdomens—black and yellow bars that mimic the markings of stinging bees. These markings are a biological adaptation that protects the flies from certain predators even though they are completely unable to sting. If you are unsure if you are looking at a bee or a fly, remember that a fly has one pair of wings while a bee has two pairs.

Many adult hover flies survive on nectar and pollen, but the larvae eat a much more varied diet that may include other insects or decaying plants and animals. It is hard to generalize, however, because the family Syrphidae consists of about 6000 species—all with slightly different habits. They are found on all continents except Antarctica and are harmless to humans.

Some species of hover fly are highly prized as biological control agents because the larval forms of those flies snack on aphids. Hedgerows and cover crops can be planted which attract hover flies to cropped areas. Flowers that produce pollen and nectar provide the energy the adult flies need to produce large numbers of eggs—all of which turn into aphid-munching larvae.

An excellent publication on hover flies as biological control agents can be downloaded at http://anrcatalog.ucdavis.edu/pdf/8285.

Moths

What looks like a combination of a bumble bee and a hummingbird and a skipper? I certainly didn’t know as I began taking photos of this creature in the ligustrum bush.

Hawk moth hovering while collecting nectar. Photo by R Burlew.

At first I thought it was an oversized bumble. But I soon realized that it never held still. Rather than folding its wings while nectaring, it hovered like a hummingbird. Then I saw its tongue, which unwrapped like a roll of toilet paper and reminded me of a skipper. Then I saw the antennae, which were straight and looked nothing like those on a bee.

A name came to me before I looked it up: hawk moth. I had seen pictures of these before, but never saw one in person. So I looked up hawk moth and there is was! And no wonder I was confused, these behemoths are often called “bumble bee moths” because they look like what?

Hawk moth unrolling its tongue. Photo by R Burlew.

The hawk moths are in the Sphingidae family and are listed as important pollinators. The one I photographed was probably Hemaris diffinis—common throughout our region according to Insects of the Pacific Northwest by Haggard and Haggard (2006).

The honey bees working the ligustrum had been chasing off other pollinators, but not this one. They give it first dibs on everything it touched. Sort of like a bank, this moth is just too big to fail.