While cutworms can be common during the summer months into the fall, we usually don’t expect to see them this time of the year. Surprisingly, there’s one cold-hardy species that has been common in Wisconsin recently—the “winter cutworm” (Noctua pronuba). This species gets its name due to the fact that the caterpillars are cold-tolerant and can be active when temperatures dip. While they won’t be out-and-about during a polar vortex, I’ve had many recent reports at the UW Insect Diagnostic Lab of winter cutworm caterpillars wandering on the snow when temperatures have been in the 20’s. Overall, there are very few caterpillars that venture onto the snow, period.
Similar to other cutworms, the winter cutworms are plump, earth-toned caterpillars—they are brownish with pairs of black dashes bordered by white running down the sides of their backside, which makes them easy to identify. (Technically, a greenish form of the caterpillars also occurs). In addition, if you see any caterpillar that even looks “cutworm-like” out on the snow, it’s almost certainly this species. They pass through the the winter as nearly-mature caterpillars before pupating in the spring. The adult moths are active during the warmer months and display an amazing array of different color forms—ranging from very light beige to grey or brownish—although the hindwings (typically tucked under the body at rest) are a diagnostic yellow color. Thus, adults are commonly known as “large yellow underwing” moths.
The winter cutwormcan be found from coast-to-coast in much of the US and Canada, although this wasn’t always the case. This species is common in Europe and wasn’t known from North America until 1979 when it was first spotted in Nova Scotia. While the caterpillars do feed on a wide range of plants, they’re rarely a notable pest. Outbreaks and reports of damage aren’t common, although there was a notable outbreak in Michigan around 2007-2008. In most cases, these caterpillars are simply a curiosity as they wander across the snow on mild winter days—sometimes by the thousands. In addition, winter cutworms can occasionally sneak into structures as well, which can be another surprise to see caterpillars actiely wandering in garages or barns when the temperature is in the 40’s.
With the arrival of fall, we’re starting to see pumpkins, spooky yard decorations, and pumpkin spiced everything (*shudder*). Not to be left out of the festivities, one insect can be quite noticeable this time of the year—the large milkweed bug (Oncopeltus fasciatus).
If you’re wondering, we do also have a small milkweed bugs (Lygaeus kalmii), although it’s not usually as common as the ubiquitous, larger cousin. Both juveniles (nymphs) and adults of the large milkweed bug are fittingly adorned for fall. Adults reach lengths of nearly 3/4 inch long and are mostly orange with black patches on the wings and body. Going through “simple metamorphosis” (technically, they’re paurometabolous), the juveniles or nymphs look similar in body shape to adults (although smaller) and are also orange with some black. In more mature nymphs, the developing blackish wing pads are quite noticeable. When you see a group of nymphs and adults hanging out on milkweed in the fall, it’s easy to recognize that they’re all the same species.
Large milkweed bugs specialize on milkweed plants and are one of the many creatures that can be found in and around milkweed patches. When they feed, large milkweed bugs use their sucking-type mouthparts to sip fluids from plants; they’re especially fond of the developing seed pods and are often spotted on pods. While home gardeners hoping to rear monarchs might be concerned about competition, these insects generally cause little harm to plants and are more of a curiosity than a pest.
Large milkweed bugs have a very seasonal pattern in the upper Midwest. They can’t survive the winter at more northern latitudes, so they must migrate northwards each year. Here in Wisconsin, you’d be hard pressed to find large milkweed bugs in spring, but by July they’ve often arrived in low numbers. Large milkweed bugs can become quite common by late summer and early fall as it typically takes 40+ days for a new generation of adults to appear from eggs laid in our area.
In much of Wisconsin, we’re just starting to see foliage change to reds, oranges, and yellows, but as you’re out enjoying the fall weather, keep an eye out for these festive-looking insects around milkweed patches.
Unbeknownst to most students, employees, and visitors at UW-Madison, there’s a room of flesh-eating beetles on campus.An unmarked door on Bascom Hill leads to the chamber more formerly known a the Dermestarium, which serves a rather peculiar yet specific purpose. No need to worry though—this isn’t 1999’s The Mummy. Rather, these insects are actually quite helpful in the way that they’re used.
Most insects are actually helpful in one way or another and provide ecosystem services as pollinators, predators, parasitoids, decomposers, or in other roles.Humans have also figured out some pretty unique ways in which insects can help us out.For example, mealworms can eat and break down certain types of plastics and are being looked at as a way to help reduce man-made waste materials.In the legal realm, knowledge about insects is used to help solve crimes—a field known as forensic entomology, which dates back nearly 1,000 years.In the case of UW-Madison and many other universities and museums, a specific type of beetle is used to help clean skeletal remains for research, teaching, and display in zoological museums.
The beetles in the UW Dermestarium are known as hide beetles (Dermestes maculatus) and they’re especially fond of dried-out, protein-rich materials such as remnants of muscles, sinew, fur, feathers, and similar materials.Out in nature, such insects do play a role in the natural break down of animals remains—but not right away.Rather, much of that initial work is left to the larvae (maggots) of blow flies (Family Calliphoridae) and flesh flies (Family Sarcophagidae).Hide beetles and close relatives from the “carpet beetle” group (Family Dermestidae) show up days, weeks, or even months later once the remains are drier.
In a museum setting, hide beetles can be helpful in the preparation of skeletal remains.With their small size (roughly 1/4-inch long) , these insects use their mandibles to efficiently remove leftover bits of tissue from tiny nooks and crannies.For a human trying to prepare remains, such a task would be tedious and may not be feasible for some structures (such as the inside of a skull).However, a tank of these beetles can easily clean skeletal remains in a matter of days with relatively little effort required, other than maintaining correct ambient conditions for them.
Interestingly, hide beetles and close relatives like the larder beetle (Dermestes lardarius) can be found in our own homes as well.Their presence poses little risk to humans, but could indicate the presence of a dead rodent or bird in a structure.Such insects can also develop on a range of protein-rich materials ranging from dead insects in a window sill to human and pet foods and they can occasionally be a pest in home pantries. Historically, such insects were notable pests of dried meats and cheeses in storage. If you’re curious to know more about these and other insects associated with our homes and everyday lives, Richard Jones has an excellent book on the topic: House Guests, House Pests: A Natural Hisotry of Animals of the Home.
A more detailed history of UW-Madison’s Dermestarium can be found here.
Despite the season, there’s a surprising number of insects and related arthropods that can be found on the snow during the winter months here in the Midwest.Such creatures have fascinating life histories and special adaptations (such as natural “antifreeze”or cryoprotectants) that allow them to not only survive, but remain active at low temperatures.Even these adaptations have limitations and winter insects generally aren’t active if temperatures are below ~20˚F (-7˚C).Most activity occurs on mild winter days when temps close to or just above freezing.
If you’re curious to learn more about the stories behind these winter creatures and others, I’d encourage you to check out Bernd Heinrich’s Winter World: The Ingenuity of Animal Survival. Read on to learn about some of our commonest “winter” insects in Wisconsin and nearby states:
Snow Fleas: If you follow this blog, you might recall the example of snow fleas from two winters ago.These dark-colored springtails (Collembola) can sometimes be abundant enough to give large swaths of snow a sooty appearance.Snow fleas can be common on mild winter days and if I’m out cross-country skiing in the Northwoods, I’m often more surprised if I don’t spot any.
Snow Flies: One of the weirdest examples of a “winter” insect would be “snow flies” from the genus Chionea. Despite their spider-like appearance, snow flies are actually a type of wingless Limoniidcrane fly.Being wingless and generally slow moving might sound like an easy target for predators, but by being active at cold temperatures these insects can actually avoid the many predators that feed upon related flies during the warmer months.Interestingly, their physiology is so specialized, that these unusual insects can be active between about 20˚F (-7˚C) and 32˚F (0˚C), but if it’s a warm winter day with melting snow it can actually be too hot for them!If you’d like a more detailed look at these insects, check out J.R. Schock’s article in The Kansas School Naturalist.
Winter Crane Flies: I occasionally get reports of “swarming mosquitoes” on winter days, and perhaps you’ve bumped into a cloud of tiny delicate flies out in the snowy woods or on a mild fall or spring day.What you’ve likely encountered are winter crane flies (Family Trichoceridae).These delicate flies are related to mosquitoes but have no interest in blood.The adults are simply trying to mate and the larvae are scavengers.
Snow Scorpionflies: In my mind, one of the more elusive winter insects is the snow scorpionfly.Despite having “scorpion” in the name, these aren’t scorpions (or true flies for that matter).Rather, they belong to a small order of insects (Mecoptera), which includes some bizarre examples, such as the common scorpionflies, hangingflies, and earwigflies.Like the snow flies, the snow scorpionflies are also flightless and simply wander about on the snow when conditions are right.In the Midwest, we only have two species from this group Boreus brumalis and Boreus nivoriundus, and both species are associated with mosses.
Aquatic insects: If you’re near open streams or rivers during the winter months, certain aquatic insects can sometimes emerge and be found on the snow. Caddisflies and stoneflies are two of the commonest examples. I recall ice climbing one winter’s night at Governor Dodge State Park west of Madison and reaching the top of a frozen waterfall only to spot dozens of adult “aquatic” insects active on the snow.The conditions must have been just right that evening, as I also saw hundreds of tiny Cynipid wasps (from oak galls) on the snow as I descended the access trail from the climb.
Spiders: Hexapods aren’t the only arthropods getting in on the winter fun.Species from at least a half-dozen families of spiders can occasionally be spotted on the snow on mild winter days.They might be pretty lethargic, but it’s still interesting to see creatures like that out-and-about on the snow. The video clip below shows a spider I spotted on the snow in Northern Wisconsin on New Year’s Eve a few years ago when the air temperature was right around 30˚F (-1˚C).
What a year it’s been. Things seemed like they were getting back to normal this past summer, only for the Omicron variant to pop up and say—not so fast. Despite all the ups-and-downs, services have carried on at the UW Insect Diagnostic Lab in one way or another through the second year of the COVID pandemic. Things have changed a bit and these days I’m on campus much more than a year ago. Throughout the pandemic, demand for services at the IDL has remained high with over 2,400 ID requests in 2021.
Since COVID first popped up, there have been some subtle shifts in lab statistics—an increase in the percentage of samples solely involving digital images (vs physical specimens) and an overall increase in the proportion of cases coming from the public. Considering the pandemic, this makes sense. Over the last two years, campus buildings and the IDL have been closed to visitors at various points, meaning that clients couldn’t drop off samples. In other cases, it might have been tough to make it to a post office or the UPS store to ship a sample in. Likewise, with many folks working from home, it likely led to more time out in yards and gardens, or visiting local parks or hiking trails—and more time to notice insects.
Looking back at the cases from this last year, 2021 was a unique year due to our unusually hot and dry weather conditions in Wisconsin. Based on data from the Wisconsin State Climatology Office, Madison was quite warm and saw an extra ~500 growing degree days in 2021, but was down about 15 inches of precipitation for the year. Some parts of the state were even hotter and/or drier than Madison and most of the state was categorized as either unusually dry or in some stage of drought during the year [US Drought Monitor].
The weather conditions this year led to some shifts in the insects and related arthropods seen at the UW Insect Diagnostic Lab. A pest that had been relatively quiet the last decade, Lymantria dispar (formerly known as the “gypsy moth”), thrived with the dry conditions this past spring. In “rainy” years, a beneficial fungus (Entomophaga maimaiga) can “kick in” to help keep their numbers in check. If 2022 is another dry year, we could be in store for even more problems from this invasive species. Certain mites also thrived this year and I saw a large number of cases of eriophyid mites causing damage to plants ranging from coneflowers to garlic. Springtails weren’t necessarily more abundant (they feed on decaying plant matter and thrive under damp conditions), but I suspect the hot & dry conditions sent them looking for any place darker, damper, and cooler. This led to lots of reports as they were trying to invade structures.
We’ll likely continue to see the impacts of the 2021 drought for some time. Plants, including established trees and shrubs, also suffered from the drought and this will likely lead to an increase in reports of “secondary” insect pests in the next few years. Certain insects can be generally “well behaved” and leave healthy plants alone, only to attack stressed and weakened plants. As an example, cases of the two-lined chestnut borer (a notable pest of oaks) often increase 1-3 years after a drought, and I’m expecting to see more cases in the coming years.
In the realm of medical entomology, it was a good year for ticks both in Wisconsin and other parts of the US. Black flies (Family Simuliidae) had another strong year in many parts of the state, although calls about these were shifted a bit earlier than in previous years (likely due to an “early” spring). If there’s a silver lining to the drought, it’s that mosquito pressure was down in Wisconsin for much of the summer. As we received a bit more rain in the latter half of summer we saw some late season activity, but disease pressure remained low (only three West Nile Virus cases in Wisconsin, compared to 50+ in a “bad” year). As recreational and work-related travel increased a bit more in 2021 compared to 2020, I did see an uptick in reports of bed bugs.
With the Asian giant hornet garnering attention in the news for the second year in a row, I continued to see lots of reports of cicada killer wasps, pigeon horntails, great golden digger wasps, and other large insects. Unfortunately, with the sensationalized hype about “murder hornets” (ahem—New York Times…) I had plenty of reports of other large harmless insects that were killed simply because they “looked big and scary” (one particular photo of a tomentose burying beetle comes to mind…). Overall, the Asian giant hornet story was really pretty quiet this year, with a limited amount of activity in a small part of the Pacific Northwest. As of December 2021, the Asian giant hornet has not been found in Wisconsin or anywhere close to us.
I had plenty of reports of social wasps (yellowjackets, bald-faced hornets, and paper wasps) as well as bumble bees this year—including three reports of the endangered rusty-patched bumble bee in the same week in early August! We missed the Brood X “cicada craze” here in Wisconsin, but I still had plenty of questions about them from reporters. We will, however, see some periodical cicadas (Brood XIII) in 2024 in southern Wisconsin.
Wisconsin is home to roughly 150 species of butterflies. Some of these, like monarchs (Danaus plexippus), are well-known and easily recognizable. Other species can be more subtle in appearance (such as the “skippers”) or may not be particularly abundant. Nonetheless, we occasionally see localized “booms” of certain butterfly species from time to time. This year, the hackberry emperor butterfly (Asterocampa celtis) has taken the stage in some parts of the state.
In the last month, I’ve had more reports of hackberry emperor butterflies at the UW Insect Diagnostic Lab than any other butterfly species. These reports have primarily come in from southcentral and southwestern Wisconsin. In some cases, hackberry emperors have been spotted by the thousands as they covered rural roads or transformed backyards into temporary live butterfly exhibits. Hackberry emperors primarily occur in southern parts of the state where the food plant of the caterpillars (hackberry trees) can be abundant; they’re also known from parts of central and west central Wisconsin.
Hackberry emperors are mid-to-large sized butterflies with a wingspan of approximately 2 inches. Their brownish-orange and black wings are somewhat similar to certain other butterflies (such as the “Satyrs”), which can make identifying them a bit more challenging to the uninitiated. Luckily, there’s a distinctive row of black spots on the wings—one distinctive spot on the topside of each forewing and seven slightly smaller spots on each hindwing. When the undersides of the wings are viewed (such as when the wings are folded upwards at rest), these black spots are bordered with a bit of yellow, giving them an “eyespot” appearance. A close relative and look-alike, the tawny emperor (Asterocampa clyton), lacks the large black spot on each forewing.
Adults butterflies often serve as pollinators when they visit flowers for nectar, but hackberry emperors have slightly different behaviors. They prefer to head to oozing tree wounds for sap or decaying plant materials in compost piles. They’re also fond of salts and can readily be spotted at puddles (a phenomenon simply known as “puddling”), at dung or carrion, lapping sweat from humans, or on roadways.
After overwintering as partially-grown caterpillars, hackberry emperors complete their development in late spring with two broods (batches of adults) in southern Wisconsin. We see the first batch of adults in June, with the other in August, so we may see more of this species later this summer. If you’re located in southern Wisconsin, keep an eye out for these abundant butterflies in 2021.
“Ground bee” season is officially here, but before we get any further, let’s clear up a few things about these insects.Ground-nesting bees get a lot of undeserved blame for stings that they simply aren’t responsible for.Despite their claims, many folks have probably never been stung by an actual “ground bee”.Every year I get plenty of calls about “angry stinging ground bees” in late summer, but these are almost always ground-nesting yellowjackets (Vespula spp.). Undoubtedly, if you stumble into an in-ground yellowjacket nest, you’ll be forced to make a hasty retreat from the area as the colony defends itself.But those aren’t bees…
While yellowjackets and bees are related (both belong to the insect order Hymenoptera along with the ants and sawflies), they belong to completely different families.From a standpoint of taxonomic classification,mixing up yellowjackets and bees would be like confusing dogs for cats, raccoons, or walruses (all belong to separate families within the mammalian order Carnivora).We do technically have social, ground-nesting bees that can be ornery if disturbed (i.e., bumble bees), but folks generally recognize bumble bees by their large size and robust appearance.
So what about these other “ground bees”? Most bees (about 2/3 of all bees) are actually ground-nesting species. In the Midwest, we’ve got around 500 different bee species, meaning there are hundreds of ground-nesting species around us.Our common ground-nesting bees include species of: cellophane bees, mining bees, squash bees, longhorned bees, sweat bees, and others. For the most part, these ground-nesting bees are solitary creatures that live alone, although many nests can occur in the same general area as shown in the video clip below. They often prefer sunny, open areas with thin ground cover or bare, sandy soil and can be common in parks and home lawns.
To a certain extent, solitary bees can be thought of as the insect equivalent of “preppers”. Each bee digs her own nest—a small, bunker-like tunnel in the ground, which looks like an ant hill.Not only do the females have to construct these shelters, but she has to gather all of the provisions needed for her young to survive inside—often in the matter of just a few weeks.The female bees collect pollen and nectar from flowers to create a nutritious substance called bee bread, which they place into small chambers (cells) and lay an egg. Once the eggs hatch, the young bees (larvae) have all the supplies they’ll need to grow and develop in their survival bunkers.
Most of these ground bees have a single generation per year.The adult bees are out and active for a short period of time (often a few weeks), before they’re done and gone for the year.When they are active, our solitary bees can be excellent pollinators and can be more efficient than honey bees in some regards.However, their pollination services often go unrecognized and unappreciated by the general public.While news articles regularly sound the alarm about honey bee declines, we should really be much more concerned about the potential loss of our solitary bee species, as they’re more sensitive to disturbances, pesticides, and other stressors.
If you spot ground bees this time of the year, is there any reason for concern? No. Solitary ground-nesting bees are great to have around. Being solitary nesters, these ground bees don’t have a large colony ofadult relatives to defend and they end up being surprisingly gentle and unlikely to sting.Overall, they pose little risk to people or pets.The best thing to do is to simply let them be and appreciate the pollination services they provide.
Will we see Brood X cicadas in Wisconsin or the upper Midwest this year? Read on to find out: Cicadas—they’re all over the news and soon to be out by the billions. All this buzz is about periodical cicadas, a group of species from the genus Magicicada which emerge once every 17 years (or every 13 years in some cases). Periodical cicadas are only found in the eastern United States and vary by location and the timing of their activity. To help categorize these insects, entomologists refer to each cohort of cicadas as a “brood” and have numbered them with Roman numerals. This year’s cicadas are referred to as Brood X (i.e., Brood ten) and last emerged in 2004.
Periodical cicadas are amongst the longest lived insects and their long life span and massive emergences are believed to be a survival strategy—by overwhelming predators with sheer numbers, they simply can’t all be eaten. But the wait for their appearance is a long one. Periodical cicadas spend 17 years below ground as juveniles (nymphs) feeding on the sap from tree roots, before making their way above ground. Their emergence is associated with soil temperatures, and when the soil has warmed to 64˚F, they emerge. This corresponds to parts of April, May, or June depending on the location on the map. Once they make their way above ground, the cicadas molt and transform into adults. Shortly thereafter, a raucous mating free-for-all commences. After mating, the females cut small slits into twigs of trees to deposit their eggs. The eggs hatch and the juveniles head to the soil for their lengthy development. Periodical cicadas don’t live long as adults (a matter of weeks), so it’s a long build up to a noisy grand finale.
With all the attention in the news, many Wisconsinites and other Midwesterners are wondering if they’ll be able to see or hear Brood X cicadas in their area this year. For Wisconsin, Minnesota, Iowa, and most of Michigan and Illinois the answer is no—although they aren’t terribly far away either. Brood X cicadas can be found in over a dozen eastern states, but primarily emerge in three main pockets:
Indiana, Ohio and nearby slivers of eastern Illinois and southern Michigan
Southern Pennsylvania and parts of nearby Delaware, Maryland, Virginia, New Jersey, and New York
Eastern Tennessee and nearby parts of North Carolina and Georgia
While we won’t see Brood X cicadas here in Wisconsin, we will see other periodical cicadas in the not so distant future. Wisconsin is home to Brood XIII cicadas, which last emerged in 2007, meaning that the next big emergence in the Badger State is only a few years off in 2024. In the meantime, we’ll still see and hear plenty of our typical “dog day” cicadas during the warm days of summer. To learn more about Brood XIII cicadas in Wisconsin, check out this post from last year.
The largest moths you’ll likely encounter in the northern United States are the giant silk moths (Family Saturniidae). We have a handful of species in the Upper Midwest which can be encountered with some regularity during the summer months: cecropia moths, polyphemus moths, luna moths, promethea moths, and imperial moths. True to their name, the giant silk moths don’t skimp on size—they generally have wingspans in the range of 3 – 6 inches, depending on the species. These moths are native to our area and the impressively large caterpillars feed on the leaves of various hardwood trees.
Finding an adult giant silk moth or one of the caterpillars is always a special occasion. However, there’s an even more impressive large moth, which occasionally pops up in our area—the Black Witch (Ascalapha odorata). The black witch has a wingspan of around 6 inches and can often be mistaken for a bat due to its dark colour. This tropical species doesn’t natively occur in our area and originates in parts of South America and Central America. However, the adult moths are somewhat regular “strays” and find their way as far north as parts of Canada. Still, black witches aren’t common in Wisconsin (or the US in general), and I typically only hear of a few reports in the state each year.
Wind plays an important role in the movement of black witches from their native habitat. One report even documented an adult black witch traveling with a strong westerly wind to an island in the south Atlantic—a distance of over 2,000 miles from South America. In the upper Midwest, dips in the jet stream and storm systems can play an important role. Since starting at the UW Insect Diagnostic Lab in 2014, I’ve seen several cases where black witches are spotted in late summer after hurricanes have hit the Gulf Coast states. Along these lines, hundreds of black witch moths arrived in Texas as Hurricane Claudette passed through in 2003. Following such an intense journey, the moths are often damaged, with tattered wings or other injuries. Surprisingly, some moths seem to arrive in nearly pristine condition, like this beautiful specimen spotted in Door County last month shortly after hurricane Sally made landfall.
If you do ever spot a black witch, consider yourself lucky. If you’re extremely lucky, you might even spot one of the rarest moths that strays to the Midwest—the “owl moth” (Thysania zenobia)—another large moth which has only ever been spotted in Wisconsin a few times and is much rarer than the elusive black witch.
With the media craze about “murder hornets” this past spring, I’ve seen a definite increase in reports of Asian giant hornet look-alikes at the UW Insect Diagnostic Lab this summer. Many folks recognize the commonest look-alike in the Midwest, the eastern cicada killer (Sphecius speciosus), which becomes active in July around the time that their prey (cicadas) start emerging. Another look-alike is one that you might not have bumped into before—the great golden digger wasp (Sphex ichneumoneus). Similar to Asian giant hornets, great golden digger wasps are large and nest in the ground, which are reasons why they may be mistaken for the former.
If you haven’t spotted one before, great golden digger wasps can be a bit intimidating in appearance as they can easily be over an inch long. However, their anatomy and appearance are quite different compared to Asian giant hornets. Great golden digger wasps are mostly black with a rusty-reddish color at the base of the gaster (“abdomen”). Their legs are the same reddish color and the black thorax and head possess fine golden setae or “hairs” (hence “golden” in their name). In contrast, Asian giant hornets have distinctive black and yellow stripes on their gaster and a vibrant yellowish-orange head. Great golden digger wasps belong to the “thread-waisted” wasp family (Family Sphecidae) and have a long, slender petiole (“waist”). This isn’t as thin and narrow as the “waist” of the related black and yellow mud dauber (Sceliphron caementarium), but still is quite noticeable when viewed from the side.
In terms of their biology, both Asian giant hornets and great golden digger wasps do nest in the ground, but the similarities end there. The Asian giant hornet is really quite similar to our ground-nesting yellowjackets in terms of their nesting behavior. These are social creatures which start nests from scratch in spring and build up in size over the course of the warmer months. Colonies ultimately die out in fall except for the “new” queens which overwinter. With a large colony of relatives to defend, social wasps can be defensive, especially when colonies are at peak size.
In contrast, great golden digger wasps are solitary ground nesters. Without a large colony of relatives to defend, they’re usually non-aggressive and very unlikely to sting. Stings are only likely if one were to pick one up bare-handed—in which case you might be asking for it! Similar to cicada killer wasps, each female great golden digger wasps excavates small tunnels in sandy soil and provisions them with prey for their young to feed on. In the case of the great golden digger wasp, prey consists of katydids, crickets, and relatives from the “grasshopper” group (Order Orthoptera). Rather than kill outright, the females inject their prey with a paralytic “cocktail” to keep them alive and fresh for their young to feed on—what a way to go! In addition to hunting katydids, adult great golden digger wasps visit flowers and can be beneficial pollinators.
Because they’re unlikely to sting humans, controlling great golden digger wasps is rarely justified and these magnificent creatures can simply be admired. Ultimately, these wasps are strongly associated with sandy soil, so if you see them in your yard every year and would prefer to not have them around, modifying the landscaping may be a long-term option to dissuade them from an area.
Author’s note: As of August 2020, Asian giant hornets have not been found in Wisconsin or anywhere in the Midwest. In North America, these insects are only known from far northwestern Washington state and nearby parts of British Columbia.
See this earlier post for additional details on the Asian giant hornet.