As one of the coordinators of Wisconsin Insect Fest, I’m thrilled to announce that Insect Fest will be back this year and is coming to the Upham Woods Outdoor Learning Center (Wisconsin Dells) this August. The event will be held from 2–10 PM on Saturday, August 19th, 2023 and is free and open to the public. A family-style cookout will be provided to participants (please RSVP if interested). Insect enthusiasts of all ages are welcome to attend!
Wisconsin Insect Fest is a celebration of insects and attendees will have the opportunity to learn about the different types of insects found in Wisconsin and the many important roles they play in the environment. Insect Fest will feature a variety of indoor and outdoor activities suitable for insect enthusiasts of all ages, including educational presentations, hands-on activities, guided insect hikes, live insects, and an informal BioBlitz activity. This is also a great opportunity to meet entomologists and learn about what they do.
The Wisconsin Insect Fest is a family-friendly event, and we encourage everyone to attend and learn about the fascinating world of insects. We hope to see you there!
Spongy moth (Lymantriadispar) season has officially begun here in Wisconsin. Earlier this week (May 3rd), the Wisconsin Department of Agriculture, Trade and Consumer Protection (DATCP) Pest Survey Program reported caterpillars emerging from an egg mass in far southwestern Wisconsin. Based on forecasting models from the USA Plant Phenology Network, we should expect to see caterpillar emergence begin across much of southern Wisconsin over the next week. As things continue to warm up, the pattern will push further north in the state.
We may be facing a challenging year from this invasive insect. Dry conditions suppressed a beneficial fungal disease (Entomophagamaimaiga) the last two years and allowed spongy moth populations to build up. Along these lines, DATCP reported a 102% increase in male spongy moths caught in trapping surveys last year. Likewise, the Wisconsin Department of Natural Resources (DNR) Forest Health Team reported a significant uptick in defoliation last year—from 294 acres defoliated in 2021 to over 85,000 acres defoliated in 2022.
At this point in the season, it’s hard to know how much damage will ultimately occur on yard and forest trees in 2023. However, you can get an estimate of potential defoliation in your own yard by counting egg masses. Each overwintered spongy moth egg mass contains upwards of 1,000 eggs, so a yard with dozens of egg masses could soon face tens of thousands of hungry caterpillars in the near future.
Over the next few weeks, we can expect spongy moth caterpillar activity increase. These small caterpillars will cause a trivial amount of damage at first but will gradually become larger, hungrier, and more damaging over time. Keep an eye out for activity in your yard. If you are inundated with caterpillars, consider using sticky barrier bands and burlap barrier bands to trap them as described on the UW-Madison Extension Spongy Moth website.
Looking at the bigger picture, Mother Nature could hold a trump card for our spongy moth situation. If we end up having a rainy spring, damp conditions could encourage the fungal disease Entomophaga maimaiga to kick in and crash spongy moth populations (this halted outbreaks in SE Wisconsin in 2004 and 2010) . However, if we experience another dry season, it could allow spongy moth populations to build further—stay tuned and hope for rain!
The spongy moth, Lymantria dispar has recently been in the news because of its new name. If you haven’t heard of the “spongy moth” before, it’s probably because you learned of this insect as the “gypsy moth”. It’s the same exact creature, just with a new common name.
Why the change?The word “gypsy” in this insect’s name was originally a reference to persons of Romani descent—“the popular name of the gypsy was no doubt suggested by the brown, tanned kind of color of the male” [Forbush & Fernald, 1896]. In 2021, the Entomological Society of America’s Better Common Names Project started to review the common names used to communicate about insects. Common names that include derogatory or inappropriate terms are being assessed. After a lengthy review process, the term “spongy moth” was ultimately decided upon to describe Lymantria dispar—and fittingly so. The beige egg masses of this insect have a soft, spongy consistency. In French-speaking parts of its range, this species has long been known as La Spongieuse for this very reason. Thus, you’ll be hearing more about the “spongy moth” over time as the term “gypsy moth” is phased out from educational/government websites and other resources.
In addition to the name change, the spongy moth should be on our radar for other reasons. Despite being in Wisconsin for decades, this pest can still be a serious defoliator of hardwood trees, both in yards and forested areas. From the period of 2014 – 2020, spongy moths haven’t been much of an issue. An important reason for this is a beneficial fungus known as Entomophaga maimaiga. This fungus was introduced from Japan and it is strongly associated with the spongy moth. Although it took some time to make an impact in the US, this fungus is now viewed as an important “check” on spongy moth populations. Spring rains encourage this fungus, which can cause high mortality amongst spongy moth caterpillars. However, in many parts of Wisconsin we saw an unusually dry year in 2021 which likely curbed the impacts of this fungus. As a result, I saw an increase in cases and reports of spongy moth caterpillars and their damage, adults, and egg masses at the UW Insect Diagnostic Lab last year and Wisconsin also saw a subtle uptick in defoliation of forested areas.
As illustrated in the chart above, spongy moth populations can be very dynamic and can explode under the right conditions—leading to extensive defoliation. The egg-laying strategy of this species plays an important role in this dynamic. Adult female spongy moths deposit egg masses that can easily contain upwards of 1,000 eggs. In late summer and fall of 2021, I saw plenty of reports where trees contained dozens of egg masses, which could turn into tens of thousands of hungry caterpillars this spring.
Luckily, there’s still a bit of time to take advantage of this knowledge as the young caterpillars typically don’t become active until late April or early May. In the meantime, removal or destruction of the egg masses could help reduce local populations. While often found on trees, the egg masses can also be located on just about any surface in a yard—stacked boards, sides of structures, piles of firewood, and even on vehicles. Don’t delay if you noticed spongy moth activity in your area last year, since it won’t be long before the caterpillars are out and active this spring.
Reference: Forbush, E. H. and C.H. Fernald. 1896. The gypsy moth. Porthetria dispar A report of the work of destroying the insect in the commonwealth of Massachusetts, together with an account of its history and habits both in Massachusetts and Europe. Boston, Wright & Potter. 495pp.
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.
It’s been hard to miss the recent news headlines about fall armyworms “FAW” (Spodopterafrugiperda). States east of the Rockies have seen historical outbreaks of this insect in 2021, including a bit of fall armyworm activity here in Wisconsin. In some cases, the caterpillars have decimated entire crop fields or home lawns overnight before marching onwards in search of “greener pastures”.
We usually don’t see much of the fall armyworm in Wisconsin and it’s primarily a pest of warmer areas, such as the gulf coast states. The FAW is native to tropical and subtropical parts of the western hemisphere and the larvae (caterpillars) can feed on dozens of different types of plants—ranging from field crops to fruits and vegetables and even turfgrass. They can be particularly important pests to crops such as corn, grains, and alfalfa.
The fall armyworm can’t survive the winters in the US, other than the southernmost areas (e.g., southern Texas and Florida). However, in spring and summer the adult moths migrate northwards and lay eggs. Over the course of many generations and subsequent northward migration, fall armyworms can make it to the upper Midwest and even parts of southern Canada. Historically, fall armyworm has rarely been a notable pest in Wisconsin or the upper Midwest—it simply arrives too late or in too small of numbers to be a concern. To a certain extent, every year is a roll of the dice, but the odds are usually in our favor in Wisconsin and other northern states.
This year has been different though, with large numbers being spotted northwards and reports of significant damage coming in from nearby states such as Illinois, Indiana, Iowa, and Ohio. Many other states ranging from Kansas to the mid-Atlantic region have also been impacted in the later parts of summer. While there have been scattered reports of fall armyworm damage to field crops in southern parts of Wisconsin, the lateness of this pest’s arrival and our declining temperatures have likely spared us from the widespread damage seen in other states.
Under hot conditions (e.g. temps in the 90’s), the life cycle of the fall armyworm—from eggs to adult moths—can take only a few weeks. However, fall armyworms are “cold blooded” creatures and cooler temperatures slow down their growth and development. Depending on how chilly it is, their life cycle can be “stretched out” to take 60 days or longer—leaving them much more vulnerable to predation, parasitism, or exposure to frosts.
One study* found that fall armyworm eggs didn’t hatch at all if temperatures were cool enough (though not particularly chilly by Wisconsin standards). That particular study simulated daytime/nighttime temperatures of 21˚C (70˚F) and 8˚C (46˚F)—temperatures that are “in the ballpark” for many parts of Wisconsin by mid-September and are often considered downright “pleasant” by Wisconsinites. Eggs held at warmer temperatures in the experiment hatched just fine.
For eggs that did hatch this year in Wisconsin, cool temperatures also could have helped us out by slowing down their development. As they grow, fall armyworms pass through six sub-stages (instars). The early instar caterpillars are so small, they simply can’t eat much and cause little damage. It’s not until FAW caterpillars become more mature fifth and sixth instars that they really start to chow down and cause significant damage to plants. Thus, falling temps could help prevent the fall armyworm caterpillars from making it to the destructive late instar stages and could also leave them more exposed to a variety of threats.
The fall armyworm outbreak of 2021 could very well be a “once every few decades” type of event, and our northern location likely helped us avoid the significant problems seen in other states. However, if changing climate gives the fall armyworm a “head start” by overwintering farther north, it’s possible that we could see more of this pest in Wisconsin in the future.
*Barfield, Mitchell, and Poe. 1987. A Temperature-Dependent Model for Fall Armyworm Development. Annals of the Entomological Society of America. 71(1): 70-74.
Is the invasive spotted lanternfly (Lycormadelicatula) poised to be a problem in Wisconsin? Only time will tell, but the threat is definitely real.
What is the spotted lanternfly?
If you haven’t heard of the spotted lanternfly (SLF) before, it may be because this insect hasn’t been spotted in the upper Midwest yet. This invasive planthopper is native southeast Asia and was first spotted in the US (eastern Pennsylvania) in 2014. It has since spread to nearby states in the eastern part of the country. This plant-feeding pest poses significant concerns for both agricultural producers and the general public.
What do spotted lanternflies look like?
Spotted lanternfly adults and juveniles have a unique appearance and can easily be distinguished from our native insects. Adults are roughly 1 inch long with grey and black spotted forewings and bright pink patches on the hindwings; their abdomen is black and yellow. Although they have wings, adults are generally weak fliers and tend to walk or hop. The wingless juveniles (nymphs) are smaller than adults and are mostly black with white spots. When nearly mature, juveniles are red and black with white spots.
In contrast to the conspicuous adults and juveniles, the eggs have a subdued appearance. The small, brownish, seed-like eggs are laid in batches of 30-50 and are covered with a grayish putty-like material. These egg masses can resemble dried mud.
What is the life cycle of the spotted lanternfly?
The spotted lanternfly has one generation per year. In late summer, SLF females deposit egg masses containing 30-50 seed-like eggs on trees or other objects. After making it through the winter, the eggs hatch in late spring and juveniles emerge. Juveniles can’t fly, but can walk or hop on plants. The juveniles feed and grow over the course of two months before transforming to adults in mid-summer. Adults are present into the fall as they feed, mate, and lay eggs.
What do spotted lanternflies feed on?
Spotted lanternfies are plant feeders. Their preferred host plant is the invasive tree-of-heaven (Ailanthusaltissima), which occurs in its native range in China. However, this pest is known to feed on over 100 different plants. Certain agricultural crops can be attacked, including: hops, pome fruit (apples, pears, etc.), stone fruit (peaches, plums, cherries, etc.), nut trees, grapes, and others. The spotted lanternfly can also feed on a wide range of landscape and forest trees and shrubs which can pose concerns for plant nurseries, homeowners, landscapers, and tree care professionals. Tree and shrub species known to be attacked include: maples, oaks, hickories, walnuts, cherries, catalpa, willows, serviceberry, roses, lilacs, and many others. Spotted lanternflies can feed gregariously and hundreds or thousands of individuals are sometimes spotted on tree trunks or branches.
What type of damage to they cause?
When SLFs feed, they use needle-like mouthparts to pierce plant structures to drink sap. Not only does this wound plants and create potential entry points for disease pathogens, but wounds may continue to ooze for some time—creating an unsightly mess. Significant feeding could cause dieback of branches of trees or shrubs and reduce yields of agricultural crops. The presence of SLF adults at the time of harvest could also pose a potential contamination concern for certain crops. In addition, spotted lanternflies excrete honeydew (undigested sugars) in their waste, which can lead to the growth of black sooty mold on the trunk or base of trees.
What’s the invasion risk from spotted lanternfly?
There’s significant concern about the spread of the spotted lanternfly. Since the first detection in Pennsylvania in 2014, this insect has already spread to many other states in the eastern US. Overall, spotted lanternflies mostly walk or hop (adults are weak fliers), but they are good at “hitchhiking” which may contribute to their spread; eggs are of particular concern. Egg masses are often laid on plant materials (e.g. tree trunks), but they can also be laid on man-made objects such as pallets, crates, automobiles, trailers, and other items. With their subtle appearance, egg masses can easily be overlooked and could be transported long distances. The movement of eggs could end up playing an important role in the spread of this insect over time.
A 2019 study evaluated potential spotted lanternfly habitat in the United States. The Midwest (including parts of Wisconsin) is expected to be good habitat for this invasive insect, highlighting the importance of early detection of this pest. If you suspect you’ve found the spotted lanternfly in Wisconsin: please take pictures, save any specimens you find, and contact me at the UW Insect Diagnostic Lab.
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.
Endangered. It’s an imposing term and not one to be taken lightly. Monarchs have been in a perilous spot for years and there have been rumblings of potentially listing monarch butterflies (Danaus plexippus) as endangered by the US Fish & Wildlife Service. After delays, we finally received a decision in December of 2020—“warranted but precluded”.
In a technical sense, labeling a species as endangered isn’t as simple as merely placing it on a list. There’s a lengthy review process and potential species are evaluated in terms of how pressing their situation is. In the case of monarchs, the “warranted” part of the decision indicates that monarchs are indeed in need of protection. The alarming part is the “but precluded” statement—it essentially means that other species are facing even more pressing situations and are ahead in line. Some consider us to be in the midst of the “sixth” major extinction event on planet earth, although this one differs in that it’s caused by humans. In short, there are a lot of species that will be facing declines and extinction. At the time of the monarch’s decision from US FWS, there were currently 161 other species listed ahead of monarchs in the priority queue.
Unfortunately, since the US FWS decision last December, we’ve had some alarming news come out about monarch populations. First, it’s helpful to understand monarchs in the US as we actually have two main populations: a western population and an eastern population.
The western population can be found in states such as California, Oregon, Washington, Idaho, Nevada, and Utah west of the Rocky Mountains (a natural barrier to dispersal). While we may think of monarchs migrating to the area outside of Mexico City, this western population heads from their summer grounds to overwinter in parts of southern California. Unfortunately in January of 2021, the Xerces Society reported that only 1,914 total overwintering monarch butterflies were counted—a 99.9% decrease over the last 30 years. For comparison, a similar assessment conducted in 1997 estimated over 1.2 million overwintering monarchs. Experts have estimated a critical “extinction threshold” of 30,000 monarchs for this western population to hang on. With fewer than 2,000 monarchs spotted in late 2020, the western monarch’s situation can’t get any more urgent.
In the Midwest, we see the eastern monarch population which ranges over much of eastern North America east of the Rocky Mountains. These are the monarchs that make the long perilous flight to overwinter in the mountains outside of Mexico City. While the eastern monarch population’s situation isn’t necessarily as dire as out west, it’s still tenuous to say the least. An assessment of the eastern population is usually released in late winter and the most recent estimate found a 26% drop in overwintering monarch populations compared to last year. Over the last 20 years, the eastern monarch population has declined by approximately 90%. With larger numbers of butterflies in the eastern population, scientists don’t count individual butterflies to gauge their numbers. Instead they estimate the area occupied by densely-packed overwintering monarchs clustered together by the thousands on pine trees at their overwintering habitat in Mexico. The recent assessment found monarchs packed into an area of 2.1 hectares (5.2 acres). While this may sound like a big area packed to the gills with butterflies, it’s estimated that 6 hectares (14.8 acres) of overwintering monarchs is a “critical mass” needed to maintain the eastern population. Unfortunately, the news of both the eastern and western monarch populations comes as a punch to the gut since their numbers have been trending downwards over time.
While monarchs may be in a tight spot, they aren’t gone yet. With the “warranted but precluded” finding, the US Fish & Wildlife Service now considers monarchs a “candidate” species for listing and will continue to assess the situation as higher priority species are added to the endangered species list. In the meantime, if you’re looking for ways to help monarchs, the Wisconsin Monarch Collaborative was created in 2018 to coordinate conservation efforts of this species in our state—check out their website to see what you can do to help the monarchs: https://wiatri.net/Projects/Monarchs/.
When the COVID situation reared its head back in March of 2020, I wasn’t sure how it would impact activities at the UW Insect Diagnostic Lab.While there was a shift to handling diagnostics mostly remotely, in the end, 2020’s caseload of 2,533 ID requests was just shy of 2019’s all-time record of 2,542 cases.
With Governor Evers’ Stay-at-Home Order last spring, our attentions were occupied by the unraveling pandemic and caseload at the UW Insect Diagnostic Lab was lighter than usual around that time.However, as Wisconsinites shifted to working from home, it meant spending more time in yards and many Wisconsinites pulled out their green thumbs and established COVID “Victory Gardens”.As a result, the diagnostic lab saw a record number of cases in July of 2020, with close to 600 ID requests that month alone.
Outreach activities of the lab saw a dramatic shift as well.With in-person presentations and workshops off the table, virtual events afforded new opportunities—like a Japanese beetle seminar in July which drew nearly 900 participants. Regular events, like my appearances on WPR’s The Larry Meiller Show also continued through 2020, although I fielded calls from my home’s “reading nook” rather than the WPR studio.
Some invasive pests had big years as well. The viburnum leaf beetle, lily leaf beetle, purple carrot seed moth, and brown marmorated stink bug all increased their footholds in the state. Japanese beetle numbers varied a lot depending on where you were located in Wisconsin. Some areas saw little pressure during droughty periods, while other parts of Wisconsin saw high Japanese beetle activity. Gypsy moths had been quiet in Wisconsin for several years, but increased their numbers last year.I saw a distinct increase of gypsy moth cases in 2020, and I’ll be keeping a close eye on that species in 2021.
Come fall, we saw some stretches of unseasonably pleasant temperatures in October, November, and December.During those periods, multicolored Asian lady beetles—which had been lurking in the background for several years—returned to the spotlight. The multicolored Asian lady beetle activity around Wisconsin was some of the highest of the last decade.Not to be left out of the fun, minute pirate bugs were abundant in some parts of the state and made warm, sunny fall days a little less pleasant due to their biting habits. Speaking of biting insects, black flies were abundant in 2020 and made outdoor activities more challenging in June and July. Mosquito activity varied around the state, although we did see a few cases of the Eastern Equine Encephalitis in 2020.
No two years are the same at the UW Insect Diagnostic Lab and that includes some of the “X-Files” type cases as well.Some of my favorite cases from 2020 include identifying phorid flies from dead radioactive cats (it’s a long story…), a grim-reaper-esque dryinid wasp, several massive black-witch moths from Central America, and a case involving a black widow spider found in a head of broccoli from the grocery store.Never a dull moment at the UW Insect Diagnostic Lab!
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.