The spectacular fall weather this week has made it hard to work indoors. As Midwesterners, we know to appreciate the current warm spell as winter is just around the corner. If you’re like me, you’ve probably made it outside to take care of yard work, hike, grill out, or simply enjoy the fall colors. Speaking of colors, you’ve probably notices flashes of orange on the side of your home—multicolored Asian lady beetles (Harmonia axyridis). This fall, we’re seeing surprisingly high numbers of these lady beetles across Wisconsin.
An adult multicolored Asian lady beetle (Harmonia axyridis). Note the black “W” pattern just behind the head which helps identify this species. Photo credit: PJ Liesch, UW Insect Diagnostic Lab.
Just like us, the final warm days of autumn have worked these lady beetles into a frenzy of outdoor activity and our recent weather patterns are the key to this phenomenon. While not native to North America, the Asian lady beetle is an adaptable species and has a good feel for the seasons—it also knows that winter is coming. An important cue for lady beetle activity is the first frost or period of near-freezing temperatures in fall. This sets the stage and when the temperatures creep back up into the mid-60’s or 70’s, it initiates a massive game of hide-and-seek-shelter for these insects.
A group of overwintering Asian lady beetles beneath the loose bark of a dead tree. Photo credit: PJ Liesch, UW Insect Diagnostic Lab
But why our homes? It turns out that Asian lady beetles don’t necessarily want to invade our homes—they simply look for sheltered spots to spend the winter. In more natural settings, I’ve found dozens of these beetles beneath the loose bark of dead trees or in firewood piles during the winter months.
In their native range of eastern Asia, multicolored Asian lady beetles are cliff dwellers. These beetles use visual cues to actively seek out conspicuous, exposed rock faces with cracks to squeeze into. They’re particularly fond of south or west facing cliffs, which get warmed by the sun in the afternoon when they’re most active. The lady beetles fly to these rock outcrops and examine the cracks and crevices to see if a suitable overwintering site has been found. To us, our homes don’t necessarily resemble cliffs, but to the Asian lady beetles, the basic formula is there: large contrasting objects that stand out in the landscape with an abundance of vertical and horizontal lines resulting from modern design and construction methods. To the beetles, this looks close enough that they’ll fly to structures and wander around seeking out nooks and crannies to slip into as shown in the video clip below from the UW-Madison campus.
From the lady beetle’s point of view, these insects would really prefer to slip into a sheltered crack or crevice, hunker down for the winter, and leave again in the spring. However, when these insects get beneath siding or into a soffit area of our homes, they can accidentally pop out in the living quarters of the home—much to the dismay of the human inhabitants. This isn’t ideal for the insects either, which can face death by desiccation in the dry winter air indoors.
Enjoy these final warm days of autumn, because we’ll all be bundled up inside soon enough—with or without a bunch of lady beetles.
My final two cents: One of the best, long-term approaches to prevent nuisance issues with multicolored Asian lady beetles and other insects (like boxelder bugs and brown marmorated stink bugs) is to have good physical exclusion. This refers to making sure that potential entrance points on structures are sealed up due to good construction methods, caulk, expanding insulation foam, weatherstripping, or similar means.
Given their small general size, multicolored Asian lady beetles can squeeze through cracks or gaps as small as ⅛ inch in size. For perspective, this is about the same height as two pennies stacked atop one another. With that said, if you can easily slide two stacked pennies into a crack or crevice on the side of your house—it’s a big enough opening for multicolored Asian lady beetles to potentially get in!
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.
An adult polyphemus moth (Antheraea polyphemus) resting on a tree trunk in northern Wisconsin. Photo credit: PJ Liesch, UW Insect Diagnostic Lab.
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.
An impressive cecropia moth caterpillar (Hyalophora cecropia). Photo Credit: Judy Gallagher via Wikipedia.
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.
An adult female black witch (Ascalapha odorata) moth, which was spotted in a warehouse in Door County, Wisconsin in September of 2020. The moth is in surprisingly good condition for having been transported several thousand miles in a short period of time. Credit: photo submitted to the UW Insect Diagnostic Lab.
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.
Asian giant hornets have hit the news recently, sometimes going by the name of “murder hornets”. Below are six key things to know about these insects and the situation in North America:
1) What is the Asian Giant Hornet?
The Asian giant hornet (Vespa mandarinia), which is also known as the “great sparrow bee” in its native range (or recently sensationalized as the “murder hornet”) is a wasp species native to parts of southern and eastern Asia. The Asian giant hornet is amongst the world’s largest wasps, with queens approaching a length of 2 inches (typically ~1.5 inches). Workers and males are smaller, but still measure over an inch long. Asian giant hornets have a distinctive appearance with a bright yellowish-orange head, a dark body, and alternating dark and yellowish stripes on the gaster (“abdomen”). This species creates subterranean nests, which commonly have a peak workforce of around 100 workers.
A distinctive Asian giant hornet adult. Photo Credit: Washington State Dept. Agriculture, Bugwood.org
Asian giant hornets pose threats as an invasive species in North America. These insects are efficient predators with complex hunting behaviors. While Asian giant hornets prey upon a wide range of insects, they are capable of attacking honey bees. Under the right conditions, Asian giant hornets can decimate hives of European honey bees (Apis mellifera) within a few hours. Their potent stings can also pose medical concerns for humans.
2) What’s the risk in the Midwest?
Based on the current situation, the risk from Asian giant hornets in Wisconsin and the Midwestern US is extremely low. To date, Asian giant hornets have never been found in Wisconsin or surrounding states. A very small number of Asian giant hornets were spotted in southwestern British Columbia and northwestern Washington state in the second half of 2019. For Wisconsin, these sightings have been roughly 1,500 miles from us. At the time this article was written (early May 2020), Asian giant hornets had not been spotted in North America in 2020. Update 5/27: we recently learned that AGHs have made it through the winter in North America. This species recently resurfaced, as reported in the New York Times. Despite this recent finding, all confirmed sightings of the AGH are from the Pacific Northwest and these insects pose little risk for the Midwest at this time.
3) What’s the timeline of the Asian giant hornet story?
Asian giant hornets have gotten a lot of attention in the news recently, but these stories really missed the main “action”, which occurred roughly half a year ago. (Imagine if Sport Illustrated took half a year to write about the Super Bowl’s winning team!). The story of the Asian giant hornet in North America began in August of 2019 when a beekeeper in Nanaimo, British Columbia (SE Vancouver Island) spotted these wasps. Three specimens were collected at the time and their identity was confirmed.
Also in August of 2019, a beekeeper in Northern Bellingham, Washington (US) observed Asian giant hornets, but no specimens were collected. Back in Nanaimo, British Columbia, an Asian giant hornet nest was located and eradicated in an urban park (Robin’s Park) in September. A month later (late October, 2019) a specimen was photographed in nearby mainland British Columbia (White Rock, BC). Around that time, the same beekeeper in Northern Bellingham, Washington observed Asian giant hornets attacking a hive. The last sighting of the Asian giant hornet occurred near Blaine, Washington in December of 2019, when a dead specimen was collected and a live specimen was spotted at a hummingbird feeder.
Update June, 2020: Small numbers of AGHs have been reported in North America—but only in the pacific Northwest.
4) Have Asian giant hornets become established in North America?
The ability of the Asian giant hornet to survive and spread in North America is not understood at this time. In its native range, the Asian giant hornet is associated with forested and low mountainous areas with temperate or subtropical climates. A key unanswered question at the moment is: have the Asian giant hornets successfully overwintered in North America? Update 5/27: we recently learned that AGHs have made it through the winter. This species recently resurfaced, as reported in the New York Times.
Asian giant hornets overwinter as queens. If previously fertilized, queens attempt to establish nests during the spring months. Established nests won’t produce the next batch of queens to carry on their “blood lines” until mid-fall, meaning that responders monitoring the situation in the Pacific northwest will have roughly half a year to hunt down any nests. For this reason, 2020 will be a critical “make or break” year in the story of the Asian giant hornet in North America.
Responders in the Pacific Northwest have plans to monitor for Asian giant hornets with traps and visual methods. If spotted, individual hornets can potentially be tracked back to their nest to allow responders to eradicate the colonies. Full details of the USDA response plan can be viewed here.
5) Health risks to humans are low
By referring to the Asian giant hornet as “murder hornets”, recent news stories have given the false impression that these insects pose a regular threat to humans. Many stories have repeated the claim that Asian giant hornets kill around 50 people a year in Japan, where these hornets naturally occur. In reality, the actual numbers are much lower. Based on publicly available data from the Japanese e-Stat statistics portal, from 2009-2018 an average of 18 deaths were reported annually in Japan from hornets, wasps, and bees combined. For comparative purposes, roughly twice as many annual deaths (average of 35) were reported as the result of slipping and drowning in bathtubs over that same period of time.
Annual Deaths in Japan due to hornets, wasps and bees. Data source: Japan e-State website (https://www.e-stat.go.jp/en)
Nonetheless, Asian giant hornets do have potent venom and 1/4 inch-long stingers, which pack a punch. Due to their large physical size, a relatively large volume of venom can be injected leading to painful stings. If many stings occur (such as if one were to disrupt a nest), medical attention is advised.
6) Are there any look-alikes?
While we don’t have Asian giant hornets in Wisconsin or the Midwest, we have plenty of other insects that are currently being mistaken for the Asian giant hornet or could be mistaken for these hornets later this year. Panicked individuals thinking they’ve found an Asian giant hornet might end up killing native, beneficial insects which pose little risk to humans—such as bumble bee queens, which are currently trying to establish their nests for the year.
Historically, the UW Insect Diagnostic Lab receives many suspected reports of Asian giant hornets every year—all of these have been misidentifications by the submitters.To date, no confirmed sightings of the Asian giant hornet have occurred in Wisconsin or the Midwestern US. However, with the media spotlight on the Asian giant hornet, an increase in false reports is expected at the UW Insect Diagnostic Lab this year. Click the diagram below to view a
Asian giant hornets and common look-alikes of the Midwest. Diagram organized by PJ Liesch, UW Insect Diagnostic Lab. Click for larger version.
full-size version.
Some of the commonest look-alikes include:
Cicada Killer Wasps (Sphecius speciosus) These are the closest match in terms of size. However, these solitary ground-nesting wasps are really quite harmless, unless you happen to be a cicada... Because these insects don’t have a colony to defend, they are very unlikely to sting. This is the top look-alike reported to the UW Insect Diagnostic Lab every year. For additional details see this post: Asian Giant Hornets—Nope!
Great Golden Digger Wasps (Sphex ichneumoneus) These solitary ground nesting wasps capture and feed katydids and related insects to their young. Because these insects don’t have a colony to defend, they tend to be docile.
Pigeon Horntails (Tremex columba) These primitive wasp-like insects develop inside of decaying trees as larvae and can be common. They are not capable of stinging, but females do possess a prominent egg-laying structure (ovipositor).
Elm Sawflies (Cimbex americana) These plump, wasp-like insects cannot sting. The caterpillar-like larvae can feed on elms, willows, birches, and other hardwood trees.
Bumble Bees (Bombus spp.) The Midwest is home to over 20 species of bumble bees. These beneficial pollinators play important roles in the ecosystem. Bumble bees do live together as colonies and can act defensively if the nest is directly disturbed, but these important pollinators are generally docile. Annual colonies reach maximum size in late summer and naturally die out in the fall.
Yellowjackets (Vespula spp. & Dolichovespula spp.) The Midwest is home to more than 10 species of yellowjackets. Common species, such as the German yellowjacket (Vespula germanica) are typically around ½ inch in length. Yellowjackets are social insects and depending on the species, nests can occur in the ground, in hollow voids (such as soffit overhangs or wall voids), or as exposed as papier-mâché type aerial nests. Annual colonies reach maximum size in late summer and die out naturally in the fall.
Bald-Faced Hornets (Dolichovespula maculata) Our largest social wasp in the Midwestern US, reaching lengths of approximately ¾ inch. Bald-faced hornets are technically a type of “yellowjacket” but have a distinctive black and white appearance. These insects create large papier-mâché type nests, which can approach the size of a basketball. Annual colonies reach maximum size in late summer and die out in the fall.
In the last month, COVID-19 has changed the ways that Americans go about their everyday lives. Here in Madison, WI, the University of Wisconsin-Madison has taken a number of steps in response to the COVID-19 situation such as switching to online classes for the remainder of the semester and having most employees work remotely. The full details of UW-Madison’s response can be found here: covid19.wisc.edu.
Despite the disruptions, part of the Wisconsin Idea is that the activities of institutions like UW-Madison should provide benefits to residents in all reaches of the state. To that end, the UW Insect Diagnostic Lab remains open to provide insect/arthropod identification and outreach services to residents of Wisconsin, with some notable changes. Bookmark this page for updates which will be posted as they arise.
General Diagnostics & Questions:
Many of the services of the IDL, such as email photo submissions, remain unchanged. Important points are noted below:
Arthropod ID requests (insects, spiders, etc.) can still be submitted to the UW Insect Diagnostic Lab
Digital photographs are the best way to submit an ID request in the time of COVID-19. See this webpage for required information and tips on submitting insect images.
Physical samples can also still be submitted to the diagnostic lab by mail. Per UW-CALS policy, the IDL’s building on campus is locked until further notice and samples cannot be dropped off in-person at this time. Please be aware that processing times will be slightly longer than usual for mailed-in samples, but I will be able to check for mail submissions on a regular basis. Please see this webpage for instructions on how to submit physical samples by mail.
General insect questions can still be submitted by email to pliesch@wisc.edu (best option) or by phone. I will continue to have regular email access while working remotely, but phone responses will likely be delayed. Email will be the best way to reach me for the time being.
Outreach:
The UW Insect Diagnostic Lab regularly provides outreach around Wisconsin via public radio, workshops, public seminars, and other venues. Unfortunately, the COVID-19 situation is impacting in-person delivery of this outreach. See below for additional details:
In-person presentations provided by the UW Insect Diagnostic Lab have been cancelled until further notice.
If interested in distance education (via Zoom, Skype, Google Hangouts, etc.), feel free to reach out to me by email (pliesch@wisc.edu) to coordinate.
In the meantime, stay safe and feel free to check out the many insect-related blog posts over the last few years to take your mind off of COVID-19: https://insectlab.russell.wisc.edu/blog/
Current auxiliary location of the UW-Insect Diagnostic Lab.
Every year is different when it comes to mosquito-borne diseases.During the summer and fall of 2019, the eastern US has seen a bump in cases of a potentially lethal disease—Eastern Equine Encephalitis (EEE)—which has led to health concerns. Here are five key things to know about Eastern Equine Encephalitis:
1. Eastern Equine Encephalitis is a mosquito-borne disease. But one species in particular,Culiseta melanura, plays a critical role.Culiseta melanura is widely distributed across the eastern US, but is specifically associated with freshwater swamps with standing trees.The larvae of this mosquito tend to develop in small, protected, naturally occurring cavities (“crypts”) amongst the roots of trees such as maple, hemlock, and cedar. Interestingly, Culiseta melanura, does not like to bite humans and almost exclusively takes blood meals from birds.However, as EEE builds up in local bird populations, other mosquito species with more flexible feeding habits can act as a “bridge” and allow the disease to move from birds to mammals with subsequent blood meals.A dozen or more mosquito species from the genera Aedes, Coquillettidia, Culex, and Ochlerotatus have been implicated in vectoring the disease from birds to humans.
Culiseta melanura—a key player in the Eastern Equine Encephalitis story. Photo Credit: CDC Public Health Image Library.
2. Eastern Equine Encephalitis can pose significant risks to human health, but most human infections result in minor or no symptoms.Eastern Equine Encephalitis is a disease caused by a virus (the Eastern Equine Encephalitis Virus).According to the CDC, only a small percentage (4-5%) of human infections with this virus actually lead to Eastern Equine Encephalitis.Thus, the vast majority of human infections lead to minor or no symptoms.
However, in severe cases of EEE, inflammation of the brain can lead to symptoms including fever, headache, vomiting, confusion, convulsions, and coma.Roughly a third of such human cases are fatal and survivors often suffer from permanent neurological complications.Individuals younger than 15 or older than 50 are at greatest risk, as well as individuals that live, work, or recreate near swampy areas. In the US, cases of EEE tend to occur in states along the Atlantic coast and the Gulf coast.The New England states of Connecticut, Massachusetts, and Rhode Island have seen nearly 20 human EEE cases this year.Cases can also occur in the Midwest, with a cluster of nearly a dozen reports in southwestern Michigan and northern Indiana in 2019.
3. Humans aren’t the only species impacted by Eastern Equine Encephalitis.In fact, EEE is primarily a bird disease.For example, many passerine birds (a group that includes our common songbirds such as robins and starlings) can readily become infected with the EEE virus. Some states even use “sentinel” birds to monitor EEE activity.If the conditions are right in a given year, populations of the ornithophilic mosquito Culiseta melanura can cause EEE to build up in a local bird population.Eventually, other mosquito species allow the disease to jump from birds to humans.Horses can also become infected with the EEE virus and because equine infections typically precede human cases by a few weeks, an uptick in horse cases can serve as a general indicator of potential risk to humans in an area.There is a vaccine available for horses to help protect them from EEE.
Cedar swamp in New Jersey. Photo Credit: Famartin, via Wikipedia. CC 3.0.
4. Eastern Equine Encephalitis is very rare in humans.Case numbers vary around the eastern US every year, but over the last decade the country has averaged only seven human EEE cases per year.In Wisconsin, there have only been three documented human cases of EEE between 1964 and 2018.The limited habitat of the key mosquito species and its restricted feeding behaviours help explain the rarity of human cases.Despite news reports within the last month, the EEE threat should nearly be done for the year in the Upper Midwest.Eastern Equine Encephalitis cases typically peak in late summer or early autumn, and with temperatures dipping in the region (and snow in the forecast), mosquito activity is on the decline in our area.
5. General mosquito precautions are one of the simplest ways to protect against Eastern Equine Encephalitis.Because the key mosquito species involved with EEE (Culiseta melanura) is associated with freshwater swamps, chemical insecticide treatments to such areas are often not an option for individual land owners and can pose environmental concerns.Instead, practices such as wearing long-sleeved clothing, using EPA-registered repellents (such as DEET and picaridin), avoiding areas and periods of high mosquito activity, and removing standing water on a property are some of the best precautions to take.
Update September 2020: Wisconsin has recently had two confirmed human cases this year.
Without looking at a calendar, certain things tell you autumn is approaching—pumpkin spice encroaches upon your food and beverage options, weekends are filled with football, the leaves are turning various hues, and brightly-colored orbweaver spiders adorn the landscape.
A beautifully patterned shamrock orbweaver (Araneus trifolium) on the side of a Northwoods cabin. Photo Credit: PJ Liesch, UW Entomology.
Like the overwhelming majority of spiders, the orbweavers (Family Araneidae) of autumn are harmless to humans. There are a dozen or more common species in the Great Lakes Region and these can be good sized as far as spiders are concerned—easily over 1” long when you include their legs. Our commonest species are from the genus Araneus and include the cross orbweaver, shamrock orbweaver, and the marbled orbweaver. They can be quite common in yards, gardens, on plants, and on your back patio. Other common species in the genus Argiope (the “garden” spiders) are even larger, spanning over 2” with outstretched legs. In addition to their large size, flashy “fall” colors and patterns conspicuously adorn these spiders—yellows, oranges, reds, stripes, polka-dots, and more.
Despite the large size, orbweaver spiders are harmless. Photo credit: PJ Liesch, UW Entomology.
Their life cycle is another reason why many orbweavers can be so noticeable in autumn. Our common species overwinter in the egg sac and the young spiderlings usually go unnoticed as they grow and develop the following spring and summer. By the time they’ve reached maturity in late summer, it’s mating season and the adults have a month or two to go about their business. During that time, they’re easiest to spot sitting in their large circular webs, which were an inspiration for the children’s classic Charlotte’s Web.
Further Reading:
Unfortunately, most folks never take the time to learn about these beautiful and fascinating creatures. If you ask someone their thoughts of spiders, feelings of fear, disgust, repulsion, and anxiety might come to mind. In society as a whole, there seems to be a feeling that spiders are something to be loathed or feared, which really shouldn’t be the case. It doesn’t help when the internet has an abundance of myths and preposterous stories about spiders [here’s a good source to debunk some of those myths]. In the grand scheme of things, you’re more likely to be injured by a pet dog than you are to be harmed by a spider. If anything, spiders should be considered beneficial as they eat an astonishing mass of insects every year.
If you’d like to learn more about spiders, one of my favorite books for the Midwest is Spiders of the Northwoods by Larry Weber. There are also some great spider blogs out there; my favorites include: SpiderBytes by Catherine Scott and Arthropod Ecology by Chris Buddle. To this day, two of my all-time favorite spider posts are from Chris Buddle’s blog and have the self-explanatory titles of “Spiders do not bite” and “Update: spiders STILL don’t bite”.
