Text by Becky Hamm; images by Kent Anderson (aka “surfman”) in his iNaturalist entries, except as noted.
Ah, summer: Warm breezes, colorful flowers, and lots of pollinating butterflies, bees, and … beetles? Oh yes, and flies and wasps too.
While they might be overshadowed by pollinating insects that are cuter and more colorful, these less popular insects are also crucially important to the success of our food web.
These three types of winged insects are not what most people—including me!—think of when they consider “important” insects, but I was surprised to learn of their pollination, predation, and decomposition functions that enable us to have a balanced ecological system.
Non-bee pollinators are critical for pollinating much of the world’s agricultural crops. In fact, certain flies are starting to be bred specifically for the task since they are easier to raise than bees. Wasps are excellent predators of pest species, and beetles aid in decomposition of dead animals and plants. It is tempting to silo these insects into a single function, but many perform multiple tasks well, making them workhorses of the insect world. With the planet’s insect population in decline, we need to raise awareness of their importance.
So formidable, there’s an NBA basketball team named after them (Charlotte Hornets), wasps are much feared in our culture. However, understanding their behavior may help you better understand their place in your yard.
Wasps are in the family Hymenoptera—cousins to bees and ants. Some wasps are eusocial, meaning they live together in a nest, typically with a queen. This includes species common in Virginia like the yellow jacket (Vespula spp.) and the paper wasp (Polistes spp.). These types of wasps are known to be aggressive but will leave you alone if unprovoked, so don’t swat at them! To discourage yellow jackets, make sure all trash is sealed off, especially fruit, sodas, and other sweets, as they are attracted to those food sources. (Yellow jackets are sometimes confused with honeybees. Here’s a guide to learn the difference.)
Wasps play an important role in our food web. And despite their bad rap, only 1.5% of wasp species are likely to sting people if provoked.
Most wasp species are solitary. Common solitary wasps in Virginia, like the scary-looking Ichneumonid (parasitic) wasp, pose no actual threat to humans or pets because they do not sting. Others, like the yellow-legged mud-dauber (Sceliphron caementarium) wasp that built a nest near my back door this summer, only sting if provoked.
Many people also assume that wasps are carnivores. However, it is more accurate to say that wasp larvae are carnivorous while adult wasps are herbivores, feeding primarily on nectar.
Wasps are known to visit between 20% and 25% of the world’s crops, making them important pollinators in agriculture. Some of their favorite native plants locally are goldenrod, mountain mint, and buttonbush.
However, wasps really shine when viewed as natural pest control, via predation and parasitism. Commonly seen in Virginia, the parasitoid braconid wasp, Cotesia congregates will lay eggs in the skin of the tomato hornworm. The hornworm is then rather gruesomely eaten from the inside out. The diminutive Aphidiinae are a subfamily of parasitic wasps that lays eggs on or near aphids, so their larvae have a ready-made meal next to them when they hatch.
As predators, wasps help to control aphids, grasshoppers, beetles, caterpillars, and flies. For example, the Hidalgo Mason Wasp (Euodynerus hidalgo), Blue-winged Scoliid Wasp (Scolia dubia), and yellow jacket will paralyze their prey and bring them back to their nest for their larvae to eat.
Beetles are the most diverse group of any living animal; there are nearly 30,000 species in North America alone. Beetles are distinguishable from other insects due to their hard outer forewings that protect a set of inner wings that are used in flight. While some beetles, especially those that are from other countries, are seen as pests both in the garden and agriculturally, many beetles serve ecological functions such as pollination, predation, and decomposition.
If you have a compost pile, there is a good chance a species of beetle may be helping your table scraps decompose. Beetles such as the American Carrion Beetle (Necrophila americana) eat decaying plants and deceased animals, providing a miniature “trash removal” service for us.
Beetles were the first ever pollinators, starting to visit flowers in the Jurassic period. “Beetles are still the primary movers of pollen for numerous plant families, especially primitive ones like magnolias”, said Alonso Abugattas on his Capital Naturalist blog. In our area, they will feed on pollen and nectar from plants such as spicebush (Lindera spp.), yarrow (Achillea spp.), and sunflower (Helianthus spp.).
One beetle everyone likes is the firefly (Photuris spp.). Widely miscategorized as flies, fireflies are in the Lampyridae family of beetles. They are best known for their bioluminescence, though not all adults can produce light. They are also predators of snails, slugs, worms, or other insect larvae, and some adults eat pollen and nectar.
There’s a world of flies beyond the common and annoying house fly or fruit fly. In fact, there are over 85,000 species in the order Diptera, including some remarkable beauties. Take a look at the Golden-backed Snipe Fly (Chrysopilus thoracicus), a stand-out that can be spotted on understory leaves locally in spring.
Believe it or not, we would be in trouble without flies: they are the second most common pollinator behind bees, even more helpful in crop pollination than butterflies!
Hoverflies (in the family Syrphidae, also known as Syrphid flies or flower flies) and metallic-colored blow flies (Calliphoridae family) are the “powerhouse” pollinators. Hoverflies are best known as bee mimics, usually sporting stripes that belie their inability to sting. Hoverflies are also capable of flying huge distances and some species are migratory, giving them the ability to spread pollen much further than most bees. They are known to lay their eggs near aphid infestations; they are tasty morsels for the larvae, which can eat up to 400 aphids before pupating.
Key players in a balanced ecosystem
To keep them around, try planting natives and avoid using pesticide sprays that will kill wasps, beetles, and flies along with mosquitoes. While you may also be trying to target aphids or pesky slugs, other beneficial insects are greatly affected by these chemicals. Also, consider letting leaves decompose naturally in beds and create a brush or dead wood pile, since many beetles, including fireflies, pupate in leaf litter while wasps use stems and wood to make their nests.
While they may never be cherished like butterflies or revered like bees, wasps, beetles, and flies play a key role in the ecosystem. Accepting and even celebrating their role in nature can help lead to a healthier world for all of us.