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.
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 UW 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!
Does the COVID-19 situation have you cooped up at home? If so, you’re not alone during these unusual times. With the shift towards working from home, folks are spending more time in their own yards and gardens as well as nearby parks and nature trails. Spending time out in nature can have notable health benefits, but it also gives us a great opportunity to observe the creatures around us—including insects, such as butterflies.
In Wisconsin and the Upper Midwest, summer may be “peak” butterfly season, but a number of species can be active early in the year. These creatures might brighten your day during these tough times, and this guide will help you identify five of the commonest spring butterfly species in the Upper Midwest:
Mourning Cloak (Nymphalisantiopa):
This butterfly is often the first one seen in spring. It’s an easy species to identify given its large size (3-4 inch wingspan) and colors on the upper wing surface—dark wings bordered with a row of small blue spots and pale edges. Mourning cloaks overwinter as adult butterflies amongst leaf litter or in other sheltered spots, so as soon as it’s warm enough they can become active. This butterfly can catch people off guard if they fly while snow remains on the ground. In early spring when flowers haven’t bloomed yet, mourning cloak butterflies are fond of visiting the sap flows on trees caused by the activity of the yellow-bellied sapsucker.
Eastern Comma (Polygonia comma):
Like the mourning cloak, eastern commas overwinter as adult butterflies, so they’re ready to go as temperatures creep upwards. Eastern commas have a wingspan of approximately 2 inches. When spread, the wings are mostly orange with black spots and borders. The edges of the wings also have a “wavy” or “scalloped” appearance. The most distinguishing feature can be seen on the undersides of the wings when folded upwards: a small pale curved mark in the shape of a comma—hence the name. The closely-related question mark (Polygonia interrogationis) can also become active fairly early in the season and looks similar, but has a “?” shape on the underside of the hindwings.
Red Admiral (Vanessa atalanta):
The monarch butterfly (Danaus plexippus) is perhaps the best known migratory insect in our part of the world, but red admiral butterflies also migrate northwards in spring. The migratory behavior means that the arrival date and numbers can vary greatly from year to year, but red admirals can frequently be encountered in spring in the Upper Midwest. These butterflies have a wingspan of approximately 2 inches and have black wings with prominent white “!” marks near the tips of their forewings and a distinctive reddish-orange band cutting across the surface of their forewings.
Cabbage White (Pieris rapae):
Right around the start of the Civil War, the cabbage white made its first appearance in North America. Today, this European butterfly can be found widely distributed across much of the planet. Cabbage whites are indeed a whitish color with sooty black patches at the tips of their forewings. The forewings also possess black spots—1 spot for males, 2 for females. Their pale appearance and decent size (approximately 1 ¾ inch wingspan) make them easy to identify this time of the year.
Cabbage whites overwinter as chrysalises in the Upper Midwest, so they aren’t active quite as early as the mourning cloaks or eastern comma. However, the warmth of the sun can still lead to early spring sightings. Gardeners and vegetable farmers are well aware of this species since the caterpillars (“imported cabbageworms”) feed on plants from the mustard family—including broccoli, cabbage, and Brussels sprouts.
Spring Azure (Celastrina ladon ladon):
If you spot a cluster of small bluish butterflies around a puddle on a hiking trail in spring, there’s a good chance they’re spring azures. These butterflies are the smallest on this list, with a wingspan of only around 1 inch. The beautiful sky blue color of their wings can be seen in flight, but when they land, spring azures tend to keep their wings folded over their body, showing the grey undersides with an assortment of tiny black mark. There are many other species of small blue butterflies in our area throughout the year, but the spring azures are some of the earliest to fly and are wrapping things up for the year as June approaches.
The Upper Midwest is home to over 150 butterfly species—each unique in its appearance, biology, and distribution. If you’re looking for some additional resources to learn about our butterflies, some of my favorites include: Butterflies of the Northwoods by Larry Weber, A Swift Guide to Butterflies of North America by Jeffrey Glassberg, and the Wisconsin Butterflies website (wisconsinbutterflies.org) by photographer Mike Reese. The Wisconsin Butterflies website not only has wonderful photos and a wealth of information about each species, but users can view and submit butterfly sightings from around Wisconsin.
In this post, we’re continuing to count down the University of Wisconsin Insect Diagnostic Lab’s top arthropod trends of 2018. This is the second half of a two part series; the first half can be found here.
5) White-Lined and Other Sphinx Moths:
The white-lined sphinx moth (Hyleslineata) can be a common species, so encountering one of the 3 inch long hornworm caterpillars isn’t unusual. However, these caterpillars can also be encountered in massive road-traversing hordes if the conditions are just right. From midsummer onwards, large numbers of these caterpillars were observed around the state—in some cases by the tens of thousands. If you didn’t spot any of the caterpillars themselves, you might have encountered the large adult moths with their hummingbird-like behaviour in late summer. Several other sphinx moths species also had a strong presence in 2018, such as the clearwing hummingbird moths and the tobacco and tomato hornworm caterpillars which can regularly be encountered in gardens as they munch away on tomato and pepper plants.
Sawflies, the caterpillar copycats of the insect world, are a diverse group, so they’re always present to some extent. Last year saw an unexpected abundance of two particular types in Wisconsin—the dogwood sawfly and the non-native Monostegia abdominalis, which feeds on creeping Jenny and related plants from the loosestrife group (Lysimachia species). While sawflies are plant feeders, dogwood sawflies can also damage the soft wood of a home’s siding or trim when these insects excavate small chambers to pupate in. The UW Insect Diagnostic Lab saw a distinct bump in reports of wood damage from the dogwood sawfly last year.
True armyworms (Mythimna unipuncta) can be a dynamic and sporadic pest in the Midwest. This species doesn’t survive the cold winters of our area, so adult armyworm moths must invade from the south each spring. Depending on national weather patterns, the arrival of the adult moths can vary significantly from year to year. If an early mass arrival is followed by abundant food and ideal conditions for the ensuing caterpillars, large populations can result. Once they’ve arrived, true armyworms can go through 2-3 generations in the state and this second generation of caterpillars made an alarming appearance in mid-to-late July. Under the conditions last summer, massive hordes of these caterpillars decimated crop fields before marching across roads by the tens or hundreds of thousands to look for their next meal. In some cases, that next meal included turfgrass, meaning that some Wisconsinites came home from work to biblical hordes of caterpillars and half-eaten lawns in late July.
2) Monarch Butterflies:
Much to the delight of fans and conservationists, the iconic monarch butterfly (Danaus plexippus) appeared to have a banner year in the Midwest in 2018. Reports and observations of high numbers of monarchs poured into the Insect Diagnostic Lab during the summer months. As comforting as these reports were, the butterflies still faced a perilous 2,000 mile journey to reach their overwintering grounds in Mexico. The most consistent measurement of the eastern monarch population comes from estimating the area occupied by the densely-packed overwintering butterflies. In late January the latest count was released with encouraging news—the eastern monarch population is up 144% over last year and is estimated to be the largest in over a decade. In contrast, the western monarch population overwinters in southern California and has recently dipped to alarmingly low numbers. Regardless of the winter assessments, monarchs face tough challenges and Wisconsinites are encouraged to help conserve this iconic species. The Wisconsin Monarch Collaborative recently launched a website with resources for those wishing to join the effort.
1) Floodwater Mosquitoes:
Mosquitoes snagged the top spot on 2018’s list for good reason. The upper Great Lakes region is home to over 60 different mosquito species, but one subset—the “floodwater” mosquitoes—drove the storyline last year and impacted outdoor activities through much of the spring and summer months. Mosquitoes in this group, such as the inland floodwater mosquito (Aedes vexans), flourish when heavy rains come. Last year’s mosquito season kicked off in force with a batch of pesky and persistent floodwater mosquitoes just before Memorial Day weekend. Mosquito monitoring traps in southern Wisconsin captured record numbers of mosquitoes shortly thereafter. Later in the year, the Midwest experienced an unprecedented series of severe rainstorms, setting the stage for an encore performance of these mosquitoes. It was this second explosion of mosquitoes that caught the attention of anyone trying to enjoy the outdoors in late summer—a time of the year when mosquitoes are typically winding down in the state.
Over 2,500 cases flowed through the doors of the UW Insect Diagnostic Lab last year, ranging from the typical June beetles through bizarre creatures that most humans will never see in their entire lives (like the itch-inducing pyemotes grain mite). Perhaps Forrest Gump said it best when he quipped, “life was like a box of chocolates—you never know what you’re gonna get.” A distinction amongst insects, however, is that the “box” contains 20,000+ possibilities in Wisconsin alone and over well 1,000,000 globally. With that said, a year at the UW Insect Diagnostic Lab is like having one humongous, box of really awesome chocolates, without all the calories.
With insects and related creatures, the weather can of course have a big impact and there definitely were examples of this in 2017. The current cold winter aside, the last two winters had been otherwise mild, giving a few insects suited for warmer conditions a chance to inch their way northward. Last spring and summer, this meant a bunch of sightings of an otherwise uncommon bee for our area known as the carpenter bee due to its habit of tunneling into unpainted cedar trim and other wood. In a typical year, I might see a few cases out of the southeastern corner of Wisconsin, but 2017 had regular reports of these bumble bee look-alikes during the spring and summer months. Similarly, praying mantids often meet their maker at the hands of a cold winter, but were surprisingly abundant in late summer and fall of last year. Ticks were also extremely abundant last spring and with the rainy start to the summer, mosquito numbers were at an all-time high in some traps. Mosquitoes were also a big deal in the news, with Wisconsin’s first confirmed reports of the Asian Tiger Mosquito last July.
The creature that amassed the most phone calls and emails in 2017 was the notorious Japanese beetle, which likely also benefited from the warmer than average winters these past few years. For Wisconsin gardeners and farmers, the Japanese beetle is certainly a formidable foe, but at least there are ways to mitigate the damage. In contrast, there’s another destructive pest wiggling its way into the spotlight in the state, which is much more difficult to control—an invasive earthworm commonly known as the jumping worm. While they may not be insects, these earthworms are creepy-crawly and can wreak havoc in gardens and flower beds, so I received a fair number of reports and questions. What stood out to me in last year was the rapidity with which these destructive worms have been moved around the state (moved—as in humans have moved soil, plants, mulch, and similar materials). Jumping worms were first found in the state in 2013 (in Madison), but have now been spotted in roughly half of the counties in Wisconsin. To make matters worse, we don’t have any highly effective tactics to prevent these worms from turning rich garden soil into the consistency of dry, crusted coffee grounds—gardeners beware!
In other insect news, it seemed to be a good year for monarch butterflies in 2017, and the rusty-patched bumble bee finally made it onto the federal endangered species list. I was pleasantly surprised by a number of confirmed sightings of the rusty-patched bumble bee in the state as well. Perhaps my favorite “bug” story for the year involved black widow spiders. It’s not common knowledge, but we do technically have a native black widow species in the state (Northern Black Widow, Latrodectus variolus). It’s a reclusive species and is rarely encountered in Wisconsin, but reports trickled in once or twice a week at some points during the summer months (details to follow in a future blog post).
With so many cases last year, we’re really only touching the tips of the antennae. If you’re interested in hearing more of the unusual stories from the UW Insect Diagnostic Lab, I’ll be giving a “highlight” talk on May 4th on the UW campus.
Just like the bees, the beloved Monarch (Danaus plexippus), is facing declines in North America. Unlike the bee declines, which seem to be the result of a complex amalgam of factors, a major factor jumps out when it comes to monarch declines: habitat loss. Simply put, we’ve gotten rid of much of the formerly ubiquitous milkweed in the Midwest. There’s a number of reasons for this, ranging from continued land development, farm subsidies that have resulted in the cultivation of non-crop land, and heavy use of herbicide resistant crop varieties. One scientific report suggests that the Midwest has lost nearly 60% of its milkweed over the past fifteen years.
We all probably learned the general story of the monarch in elementary school: a spring northward migration, milkweed, eggs, more milkweed, striped caterpillars, even more milkweed, orange and black butterflies, and finally migration down to Mexico after a few generations (there’s a great migration video here). It’s bad enough that the sole summer food source of the monarchs (milkweed) has been disappearing, but monarchs are actually fighting a multi-front battle, as their overwintering habitat is disappearing as well. Over the past few decades, much of the overwintering territory in Mexico has been lost, degraded, and fragmented by logging (both large and small scale). What’s really concerning is that the overwintering territory isn’t all that big to begin with, making the insects vulnerable to extreme weather events. A brutal winter storm in January of 2002 killed roughly 75% of the monarchs at some overwintering sites. If monarchs keep getting squished into smaller and smaller areas, all it could take is a few bad winter storms to crash their numbers. Talk about putting all your eggs into one basket. . .
So why the fuss about monarchs now?
Over the past two years, the number of monarchs overwintering in Mexico has been the lowest in the history of the annual surveys.
With enough support, could we also pull the iconic monarch out of harms way? Having the assistance of the President of the United States certainly helps. Just yesterday, the white house announced that the Pollinator Task Force (created in 2014) has released its plan to help pollinators. The three main goals of the plan are: 1) reduce honey bee losses to sustainable levels, 2) preserve the monarch population in the US, and 3) increase and improve pollinator habitat (full details here).
This isn’t the first time we’ve recognized a species at risk and created a recovery plan. A classic success story: the iconic bald eagle. It’s estimated that in the mid 1900’s there were just over 400 pairs of bald eagles left in the contiguous US. These days, anyone passing through Sauk City, can tell you bald eagles have certainly rebounded.
While the Pollinator Task Force’s plan will take some time, there are things we can all do to immediately provide assistance for monarchs:
1) Plant milkweed to create a habitat for monarchs
2) Get involved with citizen science projects to educate ourselves and others
3) Use caution when using pesticides in the landscape to minimize impacts to monarchs, bees, and other beneficial species