Update (5/10/21): Visitors are once again welcome to drop off samples at the diagnostic lab. Please follow all posted signs in Russell Labs regarding campus mask policies.
Some work of the IDL continues to be done remotely. A sample drop-box has been installed on the IDL lab door, if the lab happens to be closed when you stop by.
Original Post Date: 3/20/2020
Since early 2020, 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 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.
Visitors are still not allowed in the diagnostic lab at this time, but can drop off samples in the drop box on the lab door. Samples are picked up multiple times per week.
Physical samples are still accepted by mail, UPS, FedEx or other couriers. Please see this webpage for instructions on how to submit physical samples by mail.
General insect questions can still be submitted by email to firstname.lastname@example.org (best option) or by phone. I will continue to have regular email access while working remotely, but phone responses will likely be delayed. Email is the best way to reach me.
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 (email@example.com).
Despite being winter, Wisconsin has recently been in the news because of insects—blister beetles—and their potentially deadly impacts on horses. In addition to their medical significance, these insects have a long and interesting story with some surprising twists.
Blister beetles comprise a diverse family of insects (Family Meloidae), with over 3,000 species known from around the globe. In the Unites States, we’ve got approximately 400 species, with the bulk of the diversity centered in the dry southwestern part of the country. However, this group is widely distributed across the lower 48 states, with nearly 30 species known from Wisconsin alone.
The common blister beetles species of the Upper Midwest are oblong and typically range from ½-inch to ¾-inch long, although other species can vary in size. Unlike the stereotypical “crunch” of most other beetles—think of accidentally stepping on a May/June beetle—blister beetles have softer bodies and are similar to fireflies in this regard. A few of our Midwestern species are striped or brightly colored, but many common species are dark-colored, being mostly black, grey, or a dark metallic green.
But don’t let their drab appearance fool you. Blister beetles wield a potent defensive toxin—cantharidin. In adult blister beetles, this compound is produced by males, which provide it to females during courtship. Females then use it to chemically protect their eggs.
The properties of cantharidin are well-known, and this chemical irritant and its coleopteran source have a surprising history dating back thousands of years. For example, Pliny the Elder knew of the toxic effects and mentioned blister beetles in his writings. Old medical reference books list a number of potential uses for cantharidin, ranging from the treatment of skin conditions to a supposed remedy for baldness. However, cantharidin might have harmed more than it helped. Dermal exposure has long been known to cause irritation and blistering—hence the common name of “blister beetles”. If ingested, symptoms can be much more serious: severe irritation of the gastrointestinal and urinary tracts, kidney and heart damage, and a cascade of other undesirable effects. Human deaths have been recorded in the medical literature and in a recent report, a soldier consumed a single blister beetle on a dare and ended up hospitalized with acute kidney injury.
Surprisingly, cantharidin was also historically deployed as an aphrodisiac—Spanish fly. In the days before the little blue pill, Spanish fly was known for its ability to irritate the urethral lining to produce a “stimulating” effect. In one historical report, French Legionnaires in North Africa complained of priapism after feasting upon frogs that had happened to eat blister beetles (frogs seem to be unaffected by cantharidin).
Humans aren’t the only creatures affected by blister beetles and horses are especially sensitive. Ingestion of only a few grams of cantharidin can potentially be lethal to an adult horse. Blister beetle poisoning is rare in equines, but can occur if the adult beetles happen to be in an alfalfa field feeding on blossoms at the time of harvest and are crushed by farm equipment. In an unfortunate situation, blister beetles have recently been reported in connection with the deaths of over a dozen horses in Mauston, Wisconsin.
Blister beetles have another noteworthy Wisconsin connection from the history books. The former governor of Wisconsin, Robert “Fighting Bob” La Follette, was well-known for his progressive politics as well as an impressive head of hair. His secret?—a hair tonic containing cologne, oils of English lavender and rosemary, and a cantharidin-containing tincture made from blister beetles.
Elongate hemlock scale attacks over 40 species of conifers—especially hemlocks which can be common throughout the Appalachian Mountains, and Fraser firs and balsam firs, which are commonly grown as Christmas trees. Certain types of spruces and pines can also be attacked. Established populations of elongate hemlock scale are not known from Wisconsin, but a recent detection of this pest in the state raises concerns for Christmas tree growers, the plant nursery industry, tree care professionals, and homeowners with conifer trees in their yards. Forested areas are also at risk, meaning the stakes are potentially high with this insect.
While insect activity is quiet in the Midwest this time of the year, we’re hearing about the elongate hemlock scale now due to its Christmas connection. Similar to 2018, the Wisconsin Department of Agriculture, Trade and Consumer Protection recently found that fir Christmas trees, wreaths, and other holiday decorations infested with EHS had been shipped to Wisconsin from North Carolina. The picturesque Blue Ridge Mountains of western North Carolina provide ideal habitat for Fraser firs—one of the most popular species of Christmas trees. North Carolina grows approximately a quarter of all the Christmas trees sold in the US each year and with elongate hemlock scale established in that state, it increases the risk of movement of this invasive insect around the country.
Elongate hemlock scales look unusual as far as insects go. These insects have traded mobility for defense—they hunker down on plants and produce a waxy coating which helps protect them from predators and parasites. As a result, elongate hemlock scales aren’t easily recognizable as insects since the usual signs of segmentation—body regions, legs, antennae—are not readily visible. Instead, these insects have a vague, oblong appearance. Adult females are small (just under 1/10th of an inch long) and are covered with a waxy brownish coating. They are typically found on the undersides of needles. Males are slightly smaller and develop beneath pale whitish coverings. Mature males do emerge with wings but are weak fliers and travel short distances to mate with the wingless, immobile females.
Under their protective coatings, these insects use needle-like mouthparts to suck fluids from plants. With their small size, damage occurs when large numbers of individuals infest plants. Their waxy coverings also limit the effectiveness of insecticides, making EHS a challenging pest to control if they become established.
Because elongate hemlock scale has been detected in Wisconsin this year in Christmas trees and other holiday decorations, a key objective at this point is to prevent this insect from getting a foothold in the state. By all means, continue to enjoy your holiday decorations, but when you’re ready to remove these materials, take the following steps to help prevent this insect from becoming established in Wisconsin:
1) If your Christmas tree or natural wreaths, garlands, or other decorations are from a local Christmas tree farm or elsewhere in Wisconsin, no special precautions are needed for elongate hemlock scale. Because EHS is not established in the state, these materials can be removed as usual at the end of the holiday season.
2) If your Christmas tree or natural wreaths, garlands, or other decorations are from a big box store, grocery store, or similar vendor, or if you are not sure of the origins of these materials, it is advised to check these materials for signs of elongate hemlock scale (i.e., brown spots on the undersides of needles). The Wisconsin Department of Agriculture, Trade, and Consumer Protection is advising that infested or suspect materials preferably be burned (check with the DNR for any burning restrictions in your area). Alternatively, such materials could be bagged and discarded as waste. Infested or suspect materials should not be composted or used for wildlife habitat in your yard.
For additional information on elongate hemlock scale, visit the WI-DATCP EHS page and the recent press release about the 2019 EHS detection.
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.
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.
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.
“I think I’ve found a kissing bug and wanted to report it” is a surprisingly common line I get at the UW Insect Diagnostic Lab.
I’ve previously written about kissing bugs, but to quickly recap: these are blood-feeding assassin bugs found primarily in South and Central America. Kissing bugs tend to be associated with vertebrate nests outdoors but can bite humans and can also carry Trypanosoma cruzi—a parasite that causes Chagas disease. Due to this concern, I see a spike in website traffic and “reports” of suspected kissing bugs just about any time there’s national news coverage of these insects. While many kissing bug species exist, the vast majority are restricted to tropical and subtropical areas. The northernmost species—the eastern conenose kissing bug (Triatomasanguisuga)—ranges from Latin America as far north as southern Illinois.
Insects don’t care for geopolitical boundaries, but when humans shade in the entire state of Illinois on a distribution map of kissing bugs, it gives the false impression that these insects are on the tollway marching towards Wisconsin’s southern border. However, the eastern conenose kissing bug is rarely spotted in the northern parts of its range and there has never been a verified case of kissing bugs from within Wisconsin.
The regular occurrence of false reports can likely be attributed to hype in the news combined with a good ol’ case of mistaken identity. It turns out that there are a number of common insects that can resemble kissing bugs. One of these, the western conifer seed bug (Leptoglossus occidentalis), is regularly encountered in the upper Midwest because these insects sneak indoors in the fall just like boxelder bugs. Recently, the commonest look-alike I’ve been getting reports of is the masked hunter bug (Reduvius personatus), which can also be encountered indoors.
If you aren’t familiar with masked hunter bugs, there’s a good reason why these insects can sometimes mistaken for kissing bugs—they’re technically kissing cousins. Both kissing bugs and masked hunter bugs belong to the assassin bug family (Family Reduviidae). This is a diverse family of approximately 7,000 species worldwide and we have dozens of common species in the Midwest. The vast majority of these species (including masked hunter bugs) are really beneficial predators of other arthropods and are of little medical importance. In theory, if you picked up and mishandled one of our Midwestern assassin bugs species, it could bite—likely feeling similar to a wasp sting—although that’s about the worst it could do.
Masked hunter bugs are readily identifiable, although the nymphs (juveniles) can have you scratching your head if you haven’t encountered them before. The nymphs are often ¼” – ½” long and camouflage themselves with bits of lint and other debris—as a result, they can resemble miniature walking dust bunnies. Once you recognize this disguise, they’re easy to identify.
Adult masked hunter bugs are slender, roughly ¾” long, and entirely dark coloured. They have long, thin legs & antennae and stout beak-like mouthparts which they use to feed on insects and other arthropod prey. Several key features help distinguish masked hunter bugs from eastern conenose kissing bugs:
Masked hunter bugs are entirely dark while eastern conenose kissing bugs have red on their body
Masked hunter bugs lack the projecting “conenose” present on the head of kissing bugs
Masked hunter bugs have a bulging, “muscular” appearance of their prothorax (trapezoidal region behind the head) when viewed under magnification
Masked hunter bugs have stout beak-like mouthparts while kissing bugs have long, slender mouthparts when viewed under magnification
When it comes to kissing bugs, we simply don’t have these insects in the Upper Midwest, but we do have look-alikes. For side-by-side diagrams showing an eastern conenose kissing bug compared to common look-alikes, visit the ID Guide page on this website: insectlab.russell.wisc.edu/visual-id-guides/
It’s a funny world we live in. We hear regular reports of insect declines in the news and still get bombarded with constant ads for services pitching a mosquito free yard all summer and a grub free lawn. But what about simply appreciating insects and the critical roles they play in our everyday lives?
That’s a goal of the first ever Wisconsin Insect Fest being held at the Kemp Natural Resources Station in Woodruff, Wisconsin later this month. The two-day event—being held on Friday, July 26th and Saturday, July 27th—is a celebration of insects.
Wisconsin Insect Fest is free, open to the public, and will feature a wide range of activities for insect enthusiasts of all ages. Topics will range from how to observe and collect insects, to the role of insects in the ecosystem, entomophagy, and even forensic entomology. The Wisconsin Insect Fest will also feature The Great Wisconsin Bug Hunt—a 24-hour BioBlitz activity to see just how many arthropods can be spotted at the Kemp station in a 24-hour period (including a night time activity in conjunction with National Moth Week).
If you love insects, join in the festivities at the Wisconsin Insect Fest later this month or check out the event website for details: tinyurl.com/WisconsinInsectFest
Mosquito season has officially kicked off in Wisconsin, meaning the omnipresence of repellents for the foreseeable future. If mosquitoes have redeeming properties, it’s that they at least serve as food for a wide variety of animals and can even act as pollinators in some cases. When mosquitoes bite, they do so with surgical precision that would make a phlebotomist green with envy. Simply reading about mosquitoes might make you feel itchy, although on the spectrum of biting flies, things could be much more sinister…
Also very active at the moment in Wisconsin are black flies (Family Simuliidae) and our state is home to 30 species of these tiny sanguivores. Black flies—or “buffalo gnats” due to their hump-backed appearance—are deceptive creatures for their small size (~ 1/8″ long). You usually don’t notice them as much by sound like buzzing mosquitoes, but when they land to feed, these tiny flies are vicious. Rather than using needle-like mouthparts to delicately probe for blood vessel like mosquitoes, black fly mandibles resemble the jagged edge of Rambo’s survival knife which they use in a “slash-and-slurp” approach. These mouthparts slice into flesh to create a pool of blood which they then consume. If this sounds unpleasant—it is! Reactions to black fly bites can sometimes be severe, with fever and enlargement of nearby lymph nodes. In addition, their sheer numbers can take a psychological toll and can be a strong test of one’s fortitude if you must be outdoors during peak black fly season.
Of the 30 species in Wisconsin, only a handful actually bite humans. Other species are “picky eaters” with a strong preference for other animals. For example, Simulium annulus, specializes on common loons and in “bad” years the constant pestering can force adult loons to abandon their nests. Other birds, such as purple martins and bluebirds can face high rates of chick mortality when the black flies are bad. Pets, like dogs can commonly get bites and large pinkish welts on the soft skin of their belly. Dairy cows can be harassed to the extent that feeding and weight gain is greatly reduced and milk production all but ceases. In some cases, large animals including deer, cows, and horses have been killed outright by black flies.
With that said, if you’ve ever encountered an outbreak of black flies, you’d likely remember. If you haven’t bumped into black flies before, you’re perhaps in a good spot on the map. The larvae of many black fly species tend to be associated with streams and rivers, meaning that geography can play a role with outbreaks. Within the state, areas near the Wisconsin River and other large rivers and streams tend to see the most intense black fly activity. Black flies can be even worse to the north. These insects can be notoriously bad in the Boundary Waters Canoe Area in June, and in Canada black flies have even been enshrined in film and a surprisingly catchy folk song.
If there’s good news about black flies, it’s that the adults are short-lived. Wisconsin tends to see a blitz of activity spanning a few weeks in late spring. When black flies are active, the best approach is to layer up with long sleeves, break out the repellents like DEET, and use a head net if needed. If you’re in an area with intense black fly activity, cutting back on outdoor activities until these insects run their course for the year may be the simplest option.
This month’s post features contributions from Dr. Bieneke Bron
As stories about measles and vaccinations circulate in the news, it’s easy to lose track of other emerging health threats. May is Lyme Disease Awareness month, and if you want to look at an emerging health threat particularly relevant to the Midwest, look no further than deer ticks and Lyme disease.
A Brief History of Deer Ticks and Lyme Disease:
The Lyme disease story is surprisingly new to Wisconsin and deer ticks are something that our grandparents didn’t have to deal with while growing up. It wasn’t until the late 1960’s that our first deer ticks were documented in northern Wisconsin. At the time, this particular tick was known from more southern locations, so the first Wisconsin reports were noted as a curiosity in the scientific literature. In actuality, this marked an early foothold of deer ticks in the region, which have spread rapidly. Fast forward 50 years and deer ticks are widely distributed around Wisconsin and surrounding states.
Tracking Ticks with Mobile Technology:
With the changing tick and tick-borne disease situation over the last 50 years, understanding the factors that influence where and when ticks are encountered is more important than ever before. Researchers at the Midwest Center of Excellence for Vector-Borne Disease and the Northeast Regional Center for Excellence in Vector-Borne Diseases have teamed up to develop The Tick App—a mobile app to help gather critical clues to better understand human exposure to ticks. The app, available in iTunes and GooglePlay, not only allows the public to contribute valuable data to tick researchers, but the app provides helpful tips on tick identification, activity, and precautions to take. During the tick season, the researchers will also identify ticks from the images submitted in the app.
As we move into peak tick season, Midwesterners should be aware of ticks and take appropriate precautions to protect themselves [Recommended reading: the ABCs of Tick Season]. Learn more about The Tick App by visiting thetickapp.org or follow on Twitter @TickAppOnTour.
*Interestingly, a 57-year old physician from Medford, Wisconsin, was diagnosed with the hallmark rash of Lyme disease (erythema migrans) in 1969 [Scrimenti 1970, Arch Derm]. Just imagine, Lyme disease being known as Medford disease…
With daylight saving time beginning over the weekend and warmer temperatures knocking at our door, spring is finally crawling our way. Last winter is one we won’t soon forget—the season started out mild before temperatures plummeted with January’s polar vortex. During the coldest stretch, our coping strategy might have involved layers of blankets and reruns on Netflix, but what about the bugs? Questions regarding the winter impacts on insects have been some of the commonest at the UW Insect Diagnostic Lab this year. There will undoubtedly be some impacts of this year’s polar vortex, although many insect species are well-equipped to deal with the cold. Before we know it, overwintering insects will become active again in the Midwest and many species will simply shrug off the polar vortex as if it hadn’t happened. For insects that didn’t fare as well in the cold, high reproductive capacities will likely allow their numbers to bounce back relatively quickly.
Thus, 2019 isn’t going to be insect-free by any means and intuitively this makes sense. We know that every year insects make it through the winter months and become active as temperatures creep up in spring. Looking at an evolutionary time scale, this year’s cold snap wasn’t the first time that the species in our area have encountered frigid temperatures before, and many creatures are adapted to survive surprisingly cold conditions. We might have chosen to block it out of memory, but the Midwest experienced a very similar situation a mere five years ago. Weather patterns in January of 2014 saw temperatures dip to -20˚F and colder in some spots of the Midwest. The following summer, we still had plenty of insect activity in the region.
Since we don’t see insects bundling up with tiny mittens and scarves, how do they make it through the winter? It turns out that insects and other arthropods have a number of strategies to help them survive. For starters, insects typically have a particular life stage (e.g., egg or pupa) that is more tolerant of adverse environmental conditions, such as freezing or desiccation. Passing through the winter as a more resilient life stage is a good starting point.
Some of the other strategies are surprisingly similar to humans. Just like snowbirds heading to warmer states for the winter, certain insects like monarch butterflies and green darner dragonflies migrate southward to avoid the coldest temperatures. Our official state insect (the honey bee) doesn’t migrate, and instead chooses to remain active. Honey bee colonies shiver together as an insect version of central heating to keep the inside of their hive a constant temperature. Other insects simply seek shelter and overwinter in protected locations to avoid the worst of the cold. Insects like the multicolored Asian lady beetle, boxelder bugs, and the invasive brown marmorated stink bug are fond of sneaking into man-made structures to spend the winter. If insulation and central heating make homes warm enough for us, it’s plenty warm to prevent insects from freezing. In more natural settings, such insects might end up sheltering in rock piles or beneath the loose bark of a dead tree. Those locations might not be as toasty as a house, but they can still provide adequate respite from the cold—meaning that insects using this strategy should have been well protected from this year’s cold spell. Similarly, many insects and other arthropods spend the winter below ground or on the surface of the ground amongst a layer of insulating leaf litter. In addition, many parts of Wisconsin had a solid covering of snow by the time the polar vortex arrived, so creatures such as ticks had a thick layer of insulation from the coldest of the cold.
Another strategy utilized by insects is the production of natural antifreeze compounds (specific alcohols or proteins) which serve as cryoprotectants to help prevent freezing within their bodies. We know that a cup of water will turn to ice at 32˚F, but dissolve salts or other substances in that same water and it will require colder temperatures to freeze it. Insects producing high concentrations of these cryoprotectants can remains unfrozen at surprisingly low temperatures, similar to a bottle of high-proof spirits kept in a freezer. Taking it even further, the common black and brown woolly bear caterpillars seem to embrace the cold and actually allow ice to gradually form within their bodies. This may sound like a fatal mistake, but by regulating the formation of ice crystals on their own terms, woolly bear caterpillars are able to control where ice formation occurs and limit it to specific areas of their bodies to prevent damage. If the same caterpillars were unprepared and froze rapidly, their cells might burst like a can of soda put into a freezer.
And then the ash borer…
The insect I’ve gotten the most questions about lately has been the emerald ash borer. While not native to our area, this invasive pest comes from similar latitudes of eastern Asia and the cold-hardy larvae are fortified with cryoprotectants as they spend the winter beneath the bark of ash trees. These natural antifreeze compounds have their limitations though, and just like sidewalk salt failing to melt ice on a really cold day, the cryoprotectants only work down to certain temperatures before freezing (and death) occurs. For emerald ash borer, the point at which freezing spontaneously begins to occur (the supercooling point) is when temperatures dip into the range of -13˚F to -23˚F. This year’s polar vortex did see temperatures fall into and below that range, which would have killed plenty of emerald ash borer larvae, although the insulating effects of the tree bark likely provided some buffering.
Emerald ash borer populations will almost certainly take a hit from this year’s polar vortex, but it’s not going to be a knockout blow. Give it some time and the reproductive capacity of this invasive species will allow populations to rebound. The news reports of cold-induced EAB mortality in early February might have been encouraging, but scientific models from the US Forest Service suggest that to really knock down EAB in the long run, we’d have to experience arctic blasts on a regular basis—news that many Midwesterners aren’t likely to receive warmly.
Further Reading: For a great read on how wildlife survive the winter, check out Bernd Heinrich’s Winter World
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.