How We Can Stop Hating Wasps

Recent studies have shown that wasps are among the most loathed of all insects. Consequently, much time and money is wasted on trying to eradicate them, especially by homeowners. Let’s consider why we have the attitudes we do, and how we can achieve coexistence with wasps.

A trio of Western Yellowjakcet workers dispatches a pest caterpillar.

Why do we hate wasps?

There are three main reasons wasps evoke fear and loathing.

• The sting. Females of some species can inflict painful stings on us tender humans. This is occasionally for self-defense, but mostly in defense of a nest full of immobile and otherwise vulnerable eggs, larvae, and pupae inside a nest. Only social wasps will bother us this way.
• Narrow definition of “wasp.” Most people equate the word “wasp” with “hornet,” “yellowjacket,” or “paper wasp.” All of these are social wasps, the ones most abundant in urban and suburban settings, and by far the ones we have the most negative encounters with. Some people recognize other kinds of wasps, particularly mud daubers, but consider their nests unsightly, a nuisance, or a potential threat. In reality, the overwhelming majority of wasps are solitary, like mud daubers, each female making her own nest, or using a host animal or plant in situ. Most wasps cannot sting people. Many cannot sting at all. Most are tiny, only ten millimeters or less in length.
• Social wasps exploit our habits and weaknesses. Yellowjackets (including the Bald-faced “Hornet,” and paper wasps make their nests in and around our homes and buildings. This is because our architecture mimics the cliff faces, rock overhangs, and natural hollows where they nest “in the wild.” A few yellowjacket species are scavengers, and your barbecue or picnic resembles an abandoned animal carcass that can be exploited. The wasps take protein matter back to the nest to feed their growing larval siblings. Meanwhile, your open soda or beer container offers sugary carbohydrates the adult wasps need to fuel their flight muscles. We like to think we are masters of our domain, or at least our private property, and wasps defy that desire with maddening efficiency.

Most wasps, like this "fairyfly," are tiny, solitary, and don't sting people.

Benefits of Tolerating Wasps

Positive outcomes from tolerating wasps, or even accommodating them, far outweigh any perceived benefits of eradication or control, excepting rare cases where you or another family member has hypersensitivity to insect venom, and there is demonstrable risk of a life-threatening incident.

• Saving money on products or services. This point is seldom made when arguing against the use of DIY pest control products, or the employment of professional pest control services, but it can be of profound financial consideration. Prevention is easier and more effective. More on that in a moment.
• Wasps are a pest control service. Most social wasps, even those that scavenge occasionally, are predatory on insects that are problematic in our yards, gardens, barns, and sheds. Solitary wasps are parasitoids of even more species that can be truly pestiferous. Among the hosts for wasps are caterpillars that eat garden plants, aphids that suck plant sap, flies that can potentially spread bacteria, cockroaches both outdoors and indoors, and spiders. There is scarcely any terrestrial arthropod that is not host to at least one wasp species.
• Wasps are pollinators. Technically, most wasps are “flower visitors,” coming to blossoms for nectar to fuel their flight muscles. They still effect pollination services, and there are some species in western North America that are obligate pollinators of certain wildflowers.
• Wasps dispose of animal carcasses. Those scavenging yellowjackets make quick work of the remains of small animal carcasses that vultures and other vertebrate scavengers ignore or cannot find. This prevents the accumulation of decaying animal matter, lessens risks to human health from problematic bacteria, and prevents explosions of filth flies that would otherwise use those dead animal resources.
• Wasps are a source of fascination and intrigue. Wasps can be easily and safely observed as they go about their activities of host-seeking, flower-visiting, and nest-making. You will be surprised by how many wasp species are living in obscurity in your yard and garden. Watching them will reveal amazing relationships with many other organisms.

Paper wasp nests can be safely observed and offer hours of fascination.

How do we get along?

We can prevent most negative encounters with wasps by taking a few precautions. It will literally save you physical pain and financial discomfort.

• Learn wasp body language. Paper wasps, the ones that make uncovered paper combs under eaves, in door and window frames, and elsewhere, are usually amicable neighbors. If you do approach a nest too closely, one or more wasps will stand on tiptoe and flare their wings. This means “back off.” You risk being stung if you ignore that warning.
• Inspect your yard regularly. Too often, underground yellowjacket nests, or those above ground, hidden in shrubs or rock walls, are not discovered until the lawnmower runs over one, or the hedge trimmer triggers an attack. Inspect your property thoroughly, including playground equipment, before using tools, or otherwise causing any strong vibration in the vicinity of a social wasp nest. It may take a little patience and keen observation to note the streams of wasps coming and going regularly from a specific location. Your kids may see them before you do.
• Serve beverages outdoors in clear glass or plastic.
Unattended beverages that are sweet or fermented will attract yellowjackets and other wasps that may crawl inside the container. Cans and opaque bottles mean that you will not notice a wasp inside. A sting to the tongue or throat can be a life-threatening experience regardless of whether you are allergic to stings.
• Cover food served outdoors. When not serving yourself or others, cover meats and sweets at the outdoor gathering. You can also set out a small, exposed plate of meat a good distance away from the serving table, to draw yellowjackets away.
• Seal cracks and crevices. To prevent wasps from nesting indoors, or seeking shelter in the winter, seal cracks and crevices. Mend holes in, or replace, window screens. Screen the attic vent with fine mesh. Replace worn weatherstripping around doors. This will help save on heating and cooling costs, too.
• Learn to recognize solitary wasps. Many wasps that are solitary may behave as if they are social. A large number of wasps flying low over your lawn are likely male wasps looking for females that have yet to emerge from the ground. An ominous gathering of iridescent blue mud daubers in a door frame at dusk means that males are bedding down for the night in a large group. Male wasps do not sting. Cicada killers are huge wasps, but solitary. Females may nest close together, making them appear social. Males keep watch over them and may fly “aggressively” to chase away any and all intruders. It is all bluff.

More information about wasps can be found in this blog, in my book Wasps: The Astonishing Diversity of a Misunderstood Insect, and elsewhere. Online, the most reliable sources remain college, university, and museum websites with a “.edu” or “.org” suffix in the URL. Thank you in advance for sharing a link to this post in social media, neighborhood groups, and other outlets.

A solitary thread-waisted wasp with a caterpillar she stung into paralysis. It will be food for her single larval offspring at the bottom of an underground burrow.

Sources: Schmack, Juila M., Monika Egerer, Susan Karlebowski, Astrid E. Neumann, and Ulrike Sturm. 2024. “Overlooked and misunderstood: how urban community gardeners perceive social wasps and their ecosystem functions,” Journal of Insect Conservation.

Book Review: The Social Wasps of North America

Chris Alice Kratzer’s new guide to The Social Wasps of North America stands to revolutionize the future of field guides. It certainly sets a new standard in many ways, through methodology, organization, and sheer honesty. It is my pleasure to recommend this wonderful reference without reservation.

This is a self-published book from Owlfly Publishing, one arm of Kratzer’s company, Owlfly, LLC. The other branch is an engineering firm. Kratzer has not only avoided all the usual pitfalls of self-publishing, she has taken great pains to make every aspect of that enterprise respectful and sustainable, right down to her choice in the packaging vendor she uses.

Why is this book so unique and important? Perhaps the most obvious feature is the geographic coverage. Kratzer rightly defines North America as everything north of South America. Most natural history publishers, and authors, would consider that to be overly ambitious, confusing, and impossible to execute given the increased biodiversity south of the Mexican border. It helps to choose a taxon that has relatively limited diversity, and social wasps in the family Vespidae do fit the bill nicely. However, one should not overlook the statement this book makes about inclusiveness. This book is useful to indigenous peoples in those other nations, as well as people traveling from other places. A Spanish translation, in digital format, will be available by the end of 2021, but if a publishing house is interested in producing a hard copy, please contact Kratzer at Owlfly Publishing.

This book also marks a return to illustrations, rather than photographs, as the best means to visually communicate each species. Kratzer is a master of digital renderings. Social wasps are maddeningly variable in color pattern, so she ingeniously fused the most common xanthic (mostly yellow) and melanic (mostly black/dark) forms of each species into a single drawing, capitalizing on the bilateral symmetry of her subjects to do so. Brilliant. Kratzer essentially crowdsourced her references by utilizing pinned specimens from many curated collections, and images of living specimens from the iNaturalist web portal. She gives credit to every single individual who furnished the material. Unheard of. Each species account includes female and male examples, plus queens, where relevant. Range maps are included. Photos of living specimens, and their nests, are featured under descriptions of the genera.

© Owlfly LLC

The first seventy or so pages of the book serve as an introduction and overview of social wasps, their biology, role within ecosystems, and how they impact humanity. This alone is worth the price of the book. The writing is outstanding in accuracy and honesty:

“All of the information in this book is wrong. All of it. Wasps are an appallingly understudied group of organisms, to the point that even this book – the most complete visual guide of social wasp to date – is built precariously upon the edge of a vast, unsolved jigsaw puzzle.”

The grammar is impeccable, and the tone is exceptionally friendly and empathetic, even to those readers who want nothing to do with wasps. It is easy for someone with an affinity for maligned animals to be unintentionally hostile towards those who do not share the same perspective and opinions. Kratzer is going to make many more “friends of wasps” with this book. Did I mention that there is also a glossary and extensive bibliography with links to online versions of actual scientific papers?

Overall, Kratzer’s embrace and navigation of the scientific ecosystem, inclusive of both academic professionals and well-informed non-professionals, is admirable and even ground-breaking. Rarely does one find a reference or author/illustrator so worthy of emulating. Maybe David Sibley and Kenn Kaufman, but add Chris Alice Kratzer to the list.

Are wasps not your thing at all? Stay tuned for Kratzer’s next effort, a guide to North American cicadas, in the works as I write this. Meanwhile, order The Social Wasps of North America for a friend, directly from Owlfly Publishing.

Makin' Paper

This has been an exceptional year for paper-making social wasps in the family Vespidae here along the Colorado Front Range. Most species of paper wasps and yellowjackets have been unusually abundant, much to the consternation of the average person who despises any stinging insect. However, there is much to admire about these industrious organisms, not the least of which is the amazing architecture of their nests.

Western Paper Wasp nest (Mischocyttarus flavitarsis)

Nests of most social vespids are made of repurposed or recycled cellulose from dead, woody plants and trees. The wasps manufacture the paper by scraping fibers and chewing them into a ball of pulp that is taken back to the nest and applied as a thin strip that soon dries into a surprisingly durable, stiff material.

Bald-faced Hornet worker scraping wood fibers

Paper wasps in the genera Polistes and Mischocyttarus here in Colorado make exposed paper combs that are frequently suspended under the eaves of buildings. Yellowjackets, including the Bald-faced "Hornet," Dolichovespula maculata, house their combs within a layered paper envelope. Species in the genus Dolichovespula build their nests above ground, usually in a tree, shrub, or among berry canes. Species in the genus Vespula normally build their nests underground in abandoned rodent burrows and other pre-existing cavities that they can expand by excavating around the nest.

Huge European Paper Wasp nest

I was surprised to find out that paper wasps will re-use old nests! One particularly impressive nest of European Paper Wasps (Polistes dominula) is situated under an overhang at my workplace in Colorado Springs. It appeared abandoned when I first started work there, but was quickly occupied and even expanded later in the season. This is an impressively large nest that would probably not fit on a dinner plate, very unusual for any species of Polistes.

Active nest of Bald-faced Hornets

I also discovered an active nest of the Bald-faced Hornet in North Cheyenne Cañon on August 21. Fortunately, it was far enough off the trail to not be a potential hazard to the many people that use the park; and far enough off the trail to make it difficult for anyone to destroy the nest. I went back a month later (September 18) and found the wasps had expanded the nest and changed its shape from oval to a roughly football shape. There was no evidence of activity, and indeed the colony cycle for this species is shorter than that of other social wasps.

Bald-faced Hornet nest on August 21

The same nest on September 18

Underground nests like that of the Western Yellowjacket (Vespula pensylvanica) and Prairie Yellowjacket (V. atropilosa) are more problematic because one can easily disturb an unseen nest with painful results. I only notice nests when my eye catches a steady stream of yellowjackets coming and going from a common point.

Western Yellowjacket nest entrance. Note exiting workers carrying soil pellets

Paper wasps are generally welcome predators of caterpillars and other soft-bodied insect pests. The Bald-faced Hornet is a predator of flies that is never a pest at picnics and barbecues. The same is true of the Prairie Yellowjacket. Meanwhile, the Western Yellowjacket is a scavenger that will take your lunch away from you given the opportunity. Gently waving your hand can eventually discourage the wasp's efforts.

Prairie Yellowjacket worker eating insect

We may have these wasps to thank for inspiring the invention of the paper that we use today. At least some accounts trace observations of wasps in ancient China to the origins of human papermaking.

Polistes metricus

Paper wasps tend to be quite variable in color and pattern, even within one species, so identifying them is not easy, even for experts. Case in point is differentiating the common Northern Paper Wasp, Polistes fuscatus, from the very similar Polistes metricus.

Dark specimens of the Northern Paper Wasp are nearly identical to Polistes metricus, a consistently dark species that I have found to be less abundant than P. fuscatus in areas where their geographic ranges overlap. One fairly reliable, if subtle, clue is the shape of the abdomen. Note that the abdomen of P. metricus is highly convex on the underside, creating a nearly acute angle with the underside of the petiole (stalk-like segment connecting abdomen with thorax). This is usually much less pronounced in P. fuscatus.

Another difference is in the face of the female wasps. Females of P. metricus have an almost completely red face, the black markings confined to the ocellar triangle. Ok, so what is an “ocellar triangle?” Most wasps have a trio of tiny, “simple” eyes at the top of the head, between the large compound eyes. These simple eyes are usually arranged in a triangular pattern. Females of the Northern Paper Wasp have the black marking extended from the ocelli to the base of the antennae. Males of both species have square, yellow faces.

Female P. fuscatus. Note black face; gently curved venter of abdomen
Female P. metricus. Note convex venter of abdomen.
Female P. metricus. Note all-red face.

Polistes metricus ranges from extreme southwestern Ontario and Maine south to Florida, and west to southern Ohio, Nebraska, Kansas, Oklahoma, and eastern Texas. The Northern Paper Wasp has a much larger geographic distribution.

I was fortunate enough to find three embryonic nests of P. metricus on a recent trip to Missouri. Two nests were under the exterior of a recessed door frame in Excelsior Springs. The other was under the roof of a sign and kiosk at Little Dixie Lake Conservation Area west of Kingdom City. These are typical nesting sites, though they can also be built among shrubbery and other more exposed locations.

Both the Northern Paper Wasp and P. metricus prey mostly on caterpillars, chewing up the larvae and feeding them to their own grubs back at the nest. Look for the adult wasps on flowers as they fuel themselves on nectar. They can also be seen around aphid colonies, lapping up the “honeydew” secreted by the aphids as a waste product.

Source: Buck, M., Marshall, S.A. and Cheung D.K.B. 2008. Identification Atlas of the Vespidae (Hymenoptera, Aculeata) of the northeastern Nearctic region. Canadian Journal of Arthropod Identification No. 5: 492 pp. (PDF version).

Wasp Wednesday: Polistes exclamans

Paper wasps in the genus Polistes are more diverse the farther south you go, reaching their zenith in tropical and subtropical climates. Global climate change may be nudging some species farther north, though, so it pays to keep your eyes open. One species that naturally ranges beyond the subtropics is the Common Paper Wasp, or “Guinea Wasp,” Polistes exclamans.

I recommend using the scientific name, as there is no official common English name. This is a widespread insect found from New Jersey south and west to Florida, Indiana, Illinois, Nebraska, Colorado, Arizona, and southern California. It also ranges into Mexico, and has been introduced to Hawaii; and there is one record for Ontario, Canada.

Look for their nests in sheltered places, such as beneath the eaves of homes. They will also nest in trees, but most of the time that I have found nests, they have been attached to some man-made structure. Here is one from beneath an interpretive sign on the hawk watch platform at Cape May Point State Park in New Jersey (October 17, 2010).

Here is another nest on the ceiling of a picnic shelter in the same park (October 3, 2012).

This is a fairly easy species to identify:

• Evenly patterned in red and yellow, usually with black coloration reduced to thin bands on abdomen (occasionally more extensive black markings, especially on top of thorax).
• Antennae banded with red, black, and yellow (most paper wasp species have antennae of one color).
• Size relatively small (forewing length 12-16.5 millimeters).

Like most paper wasps, this species preys on caterpillars that the worker wasps chew up and feed to the larvae in the nest. They feed on a wide variety of moth and butterfly caterpillars, including members of these families: Pieridae (white and sulphur butterflies), Hesperiidae (skippers), Noctuidae (owlet and tiger moths), Notodontidae (prominent moths), Sphingidae (sphinx moths or hawk moths), and Saturniidae (giant silkmoths).

You would think that social wasps in general would not be bothered by predators and parasites given the presence of many stinging adult wasps ready to defend the brood (eggs, larvae, and pupae), but such is not the case. Polistes exclamans can occasionally lose its entire brood to bird predation. The acrobat ant, Crematogaster laeviuscula can also destroy a nest. Partial losses can come from Elasmus polistis, a tiny wasp in the family Eulophidae that infests young paper wasp nests that are defenseless while the foundress is away foraging.

Note males on right have black on thorax and head

Irony of ironies, caterpillars of the pyralid moth Chalcoela iphitalis can take a toll due to their parasitic activities on the wasp larvae. The moths themselves are quite attractive:

This is one of the most studied of social wasps, and the literature cited below is only a fraction of the scholarly works devoted to P. exclamans. Despite this, the known distribution of the species has been clarified mostly through documentation by citizen scientists contributing their specimens and images to universities, museums, and websites like Bugguide.net that are monitored by professional entomologists. Keep up the good work, folks.

Sources: Buck, Matthias, Stephen A. Marshall, and D.K.B. Cheung. 2008. “Identification Atlas of the Vespidae (Hymenoptera, Aculeata) of the northeastern Nearctic region,” Canadian Journal of Arthropod Identification No. 5, 492 pp. (PDF version)
Starr, C.K. 1976. “Nest reutilization by Polistes metricus (Hymenoptera: Vespidae) and possible limitation of multiple foundress associations by parasitoids,” J. Kans. Entomol. Soc. 49(1): 142-144.
Strassmann, Joan E. 1981. “Parasitoids, Predators, and Group Size in the Paper Wasp Polistes Exclamans,” Ecology 62(5): 1225-1233.

Wasp Wednesday: A Real Surprise

I am certainly finding the Front Range region to be exceptionally diverse when it comes to wasps, but nothing could have prepared me for what I found in the field yesterday, August 7. I was looking over a White Sweet Clover (isn’t there a song about that?), when a very large wasp commanded my attention. I immediately recognized it as a paper wasp, but not a species I would have expected in Colorado Springs.

This is a male specimen of Polistes carolina or Polistes perplexus. Either way, it is most likely going to turn out to be a county record, potentially a state record, and perhaps even a range extension. Both species are recorded for Kansas, so what is a couple hundred more miles or so?

I also managed to collect the specimen, so I’ll be able to eventually examine it under a microscope for the details necessary to separate the two species. Until very recently, it was thought that the males could not be distinguished at all, but apparently there are transverse (horizontal) ridges on the propodeum (hindmost segment of the thorax) that are weak in P. carolina and much more evident in P. perplexus. Watch this space for the final determination of the species.

For now, I’m ecstatic over this discovery. I’d sure like to find the nest this fellow came from. Females are a little easier to identify, and finding the nest would verify that this is a species breeding here. Even so, this male is in immaculate condition, suggesting it did not travel a long distance.

Because these two species were once thought to be a single species (P. carolina), most documentation of their biology is somewhat suspect. Polistes carolina apparently nests in exposed situations, such as under the eaves of buildings, for example; and reports of that species nesting in hollow trees and other protected locations actually apply to Polistes perplexus. Prey is probably similar in both species, consisting mostly of caterpillars chewed up by the adult wasps and fed to the larvae in the nest. Still, wasps this large can probably tackle much larger prey, and a single record of an attack on a cicada (Tibicen auletes) could be for either species of wasp.

I find that in current literature the size of these wasps is measured by the length of the forewing, which is 15-20.5 millimeters in P. carolina, and 17-21.5 millimeters in P. perplexus. Contrast this with the measurements of the abundant and widespread Northern Paper Wasp, Polistes fuscatus. Forewing length for that species averages between about 13 and 17 millimeters.

Polistes carolina is most common in the southern U.S., but ranges from New York, Pennsylvania, and Ohio south to Florida and west to Illinois, Kansas, Arkansas, and eastern Texas. There is one record for Ontario, Canada, but the species is not established there. That could be the case here in Colorado, too: a fluke. P. perplexus ranges from Maryland to Georgia, and west to southern Illinois, Kansas, Oklahoma, and Texas. One recent record has come from Pennsylvania.

Keep your own eyes open for species that seem “misplaced.” Interstate (and international) commerce, climate change, and other factors are changing the distribution patterns and abundance of many species. We also haven’t looked that closely at insect species with little or no economic impact. You stand a good chance of adding to our collective knowledge with relatively minimal effort.

Source: Buck, Matthias, Stephen A. Marshall, and David K.B. Cheung. 2008. “Identification Atlas of the Vespidae (Hymenoptera, Aculeata) of the northeastern Nearctic region,” Canadian Journal of Arthropod Identification No. 5: 492 pp (PDF version).