While scorpions are common in southern parts of the US, they aren’t native to Wisconsin or the Upper Midwest. Occasionally, they show up in the state as hitchhikers from other locations. In the last decade, I’ve seen only a handful of cases where scorpions were spotted in the Badger state. Interestingly, I’ve now had three reports of live scorpions submitted to the UW Insect Diagnostic Lab this year—from Milwaukee, Madison, and recently from Prairie du Chien (as shown in the video clip below). In the rare cases that scorpions do make an appearance, they tend to be the striped bark scorpion (Centruroides vittatus) or a close relative.
The striped bark scorpion is one of the most commonly encountered scorpions in the United States. This arachnid can reach lengths of roughly 2½ inches. It typically has a beige or yellowish body with two dark stripes running down its back—hence the name. They also have a dark triangular pattern near the eyes at the front of the body, which can help distinguish them from other species.
The striped bark scorpion is primarily found in the south-central United States, with most sightings coming from Texas. Its range extends west to New Mexico and eastern Colorado, and as far northeast as the St. Louis area. The species is also present in Mexico. Occasional sightings have been reported outside this typical range. In their natural habitat, these scorpions prefer secluded spots such as under loose tree bark, logs, rocks, and woodpiles. They may also seek shelter near buildings and can inadvertently wander indoors.
A striped bark scorpion found in a home in Prairie du Chien. Photo credit: PJ Liesch, UW Insect Diagnostic Lab.
Like many other scorpions, striped bark scorpions are nocturnal and are mostly active after dark. These arachnids are generalist predators, hunting insects and other small arthropods. They use their pedipalps (“pincers”) and telson (“stinger”) to subdue prey. While technically venomous, the striped bark scorpion’s venom is relatively mild and not considered medically dangerous to humans. However, stings from this species can still be quite painful.
Do the three reports of live scorpions mean that these creatures are becoming more common in our area? No, not necessarily. While it’s hard to tell how the range of scorpions may push northwards with climate change, we’re still well north of the native range of species like the striped bark scorpion. The vast majority of Wisconsinites will never see one of these creatures in the state outside of captivity. If anything, the three cases this year may simply illustrate how scorpions can be moved around by humans under the right conditions.
If you’ve noticed all the lawn signs for mosquito treatments, you may be wondering if mosquito yard sprays harm other insects. If so, you’re not alone.As an Extension entomologist, this is a common question that I get from the public every year.To get to the bottom of this question, it helps to understand the different types of mosquito spraying that’s done.
One approach (Ultra Low Volume or ULV) is sometimes used by municipalities or abatement districts to control mosquitoes. These ULV applications generally involve using specialized equipment mounted on trucks or aircraft to apply extremely tiny droplets which kill adult mosquitoes by direct contact as the droplets float in the air. Such applications use very small volumes of insecticides either undiluted or with minimal dilution and are often applied after dark when mosquitoes are most active. The microscopic droplets from ULV treatments disperse relatively quickly and have little residual activity—think of them like a “one time strike” to knock down mosquito numbers.
The vast majority of research on mosquito sprays and non-target organisms has looked at these ULV-type treatments. Some good news is that these studies suggest that impacts to non-target insects are relatively small and short-lived.It turns out that the ULV treatments are most effective on insects with very small body mass, so insects larger than mosquitoes tend to be spared.A good summary of the impacts of ULV treatments on non-target organisms can be found in a 2012 review paper by J.A.S. Bonds in Medical and Veterinary Entomology.
Many mosquitoes like to rest on vegetation during the day, so some mosquito sprays specifically target these resting sites. Photo credit: Public Domain Image.
Case closed, right?—Not quite. Here in Wisconsin, we don’t really use ULV treatments a whole lot for mosquitoes.The common yard treatments are what we’d call “perimeter”, “barrier”, or “residual” treatments.Such treatments are applied via a backpack sprayer to create a coating or “barrier” on treated surfaces which affects mosquitoes that land on it.These treatments involve applying a residual insecticide (usually from the pyrethroid group) to vegetation in yards and around structures.The pyrethroid products are broad-spectrum and often last for a few weeks or longer depending on the formulation.These same ingredients (and sometimes the exact same products) can also be used to control a wide range of yard, garden, and structural pests (e.g., Japanese beetles, garden pests, household ants, etc.).
While the pyrethroids are very common and widely used for a range of purposes, there’s a knowledge gap when it comes to the impacts of mosquito “barrier” treatments on other insects.While this knowledge gap exists, a few studies raise concerns.One study by Dr. Karen Oberhauser and colleagues found that monarch caterpillars could be harmed or killed even 3 weeks after spraying.A more recent (2022) study by Qualls et al. found that honey bees were harmed 28 days after “barrier” treatments were applied.Thus, if a yard is being sprayed for mosquitoes monthly during the warm season, there are reasons for concern.More research is needed to help understand the effects of these “barrier” yard treatments on insects that often land on vegetation in yards, such as moths, butterflies, fireflies and other beetles, true flies, bees, wasps and other pollinators.
Fireflies can be very common on vegetation in a yard during the summer months. Scientists view pesticides as a concern for fireflies globally. Photo credit: RachelEllen via FLickr CC.
References:
Bonds, J.A.S. 2012. Ultra-low-volume space sprays in mosquito control: a critical review. Medical and Veterinary Entomology. 26: 121-130.
Oberhauser, K.S., Brinda, S.J., Weaver, S., Moon, R.D., Manweiler, S.A., and N. Read. 2006. Growth and Survival of Monarch Butterflies (Lepidoptera: Danaidae) After Exposure to Permethrin Barrier Treatments. Environ. Entomol. 35(6): 1626-1634.
Qualls, W.A., Moser, B.A., Periera, R.M., Xue, R-D, and P.G. Koehler. 2022. Impacts Of Barrier Insecticide Mixtures On Mosquito, Aedes Aegypti And Non-Target Honey Bee, Apis Mellifera. Journal of the Florida Mosquito Control Association 69: 34-42.
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.
Early 2021—The UW Insect Diagnostic Lab was still mostly closed to visitors at the time. Campus services were mostly back to normal by the start of the fall semester on campus. Photo credit: PJ Liesch, UW Insect Diagnostic Lab.
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].
Drought conditions in Wisconsin as of late December, 2021. It’s been an unusually dry year around the state. Map source: Drought Monitor, UNL.
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.
Insects like the pigeon horntail (Tremex columba) may be large (as far as insects go), but are completely harmless to humans. I saw plenty of cases where members of the public contacted me after killing such insects simply because they looked “big and scary”. When publishers such as the New York Times use sensationalized language (i.e., “murder hornet”) there are plenty of negative impacts. Photo credit: PJ Liesch, UW Insect Diagnostic Lab.
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.
Every year is a bit different here at the UW Insect Diagnostic Lab and 2021 was no exception. I’ll be curious to see what 2022 has in store for insects in Wisconsin!
—PJ Liesch
Director of the University of Wisconsin Insect Diagnostic Lab
As weather gets warmer and the outdoors beckons, people across Wisconsin are spending more time with the activities they wait for all winter long, including picnicking, hiking, camping, boating, fishing and more. While thoughts might be turning to filling the cooler with cold beverages and packing enough charcoal for the grill, there’s another aspect to the season that demands attention: tiny ticks and their potential to cause big problems this time of the year.
Wisconsin is home to only a few common tick species, but some pose significant medical concerns to both humans and pets, such as Lyme disease. However, following the ABCs of tick prevention can help ensure that outdoor activities remain fun and safe for family and friends.
Avoid: Given their small size, ticks have limited mobility. To find hosts, ticks often hang out on plants — such as tall, weedy grasses along the edges of trails and in wooded areas with dense vegetation — and they wait for a mammal to pass by. Steering clear of these areas can help reduce the chances of encountering ticks in the first place.
Be aware: Become familiar with common ticks and symptoms of tick-borne illnesses to know what to look for. Anybody bitten by a tick should get it properly identified and consult their health care provider about any potential medical concerns.
Clothing: Long-sleeved clothes provide a physical barrier to help prevent ticks from getting to skin. Wearing lighter-colored clothing such as khakis can also make it easier to spot darker-colored ticks. Tucking pants into socks can serve as an additional protection to make it harder for ticks to bite.
DEET and other repellents: A number of Environmental Protection Agency-approved repellents (such as DEET) can help keep ticks at bay when properly used. Always consult the product label for important usage instructions, such as application to skin versus clothing and how often to reapply. As another consideration, clothing can be treated with repellent products containing permethrin. These products designed for clothing treatments are often sold at outdoor and camping stores and can provide long-term protection from ticks when properly used. Some outdoor clothing brands even use fabrics impregnated with permethrin to provide protection for extended periods of time, even through repeated washings.
Examine: Tick checks can be an important precaution for both people and pets. To effectively transmit the bacteria that cause Lyme disease, deer ticks have to be attached and feeding for extended periods of time, usually at least 24 hours. This time requirement for infection means that daily checks can help find and remove ticks before they’ve had a chance to transmit the bacteria. If a tick is found biting a person or pet, the best removal method is to use tweezers to grab near the tick’s mouth parts and use a slow steady pull to remove it.
Family pets: Don’t forget about four-legged friends — pets that spend time outdoors can also be affected by tick-borne diseases. Veterinarians should be consulted to select appropriate preventative tick (and flea) products. Topical repellent sprays are also available for those times people take their pets hiking in prime tick habitat. Pay special attention when selecting products for pets, as there are important differences between products available for dogs and cats. Always check with the veterinarian with any questions. For longer term prevention, Lyme disease vaccines for dogs are also available through veterinarians.
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 5/27/20: 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. Update 12/20: No substantial changes by the end of 2020—in North America, AGHs are still only known from far northwestern Washington State and nearby parts of British Columbia. This insect has not been documented anywhere outside of that range.
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 full-size version.
Asian giant hornets and common look-alikes of the Midwest. Diagram organized by PJ Liesch, UW Insect Diagnostic Lab. Click for larger 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.
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.
Margined blister beetle (Epicauta funebris). Photo credit: Johnny N. Dell, Bugwood.org.
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.
An antique apothecary jar hints at the long medical history of cantharidin. Photo Credit: Hamburg Museum, via Wikipedia
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.
Robert “Fighting Bob” La Follette, governor of Wisconsin (1901-1906), was known for his progressive politics and impressive head of hair. Photo via Wikimedia Commons
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.
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.
“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.
Eastern conenose kissing bug adult. Photo credit: Robert Webster, via Wikipedia
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.
Juvenile masked hunter bug camouflaged with debris. Photo Credit: Chiswick Chap, via Wikipedia
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.
Masked Hunter Bug Adult. Photo credit: JP Hamon, via wikipedia
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
Side-by-side comparison of a kissing bug and a masked hunter bug. Photo Credit: Devon Pierret and PJ Liesch, UW Insect Diagnostic Lab. [Click for full sized version]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/
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.
Adult black fly taking a blood meal. Photo Credit: D. Sikes, via Flickr.
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.
Black fly larvae in a river. Photo credit: GlacierNPS via Flickr
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.
Adult female deer tick (Ixodes scapularis). Photo credit: Robert Webster / xpda.com / CC-BY-SA-4.0 via Wikipedia.
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.
Deer ticks are only one component of the Lyme disease equation. The spirochete bacterium Borrelia burgdorferi (or the closely-related B. mayonii) must be transmitted by these ticks to cause Lyme disease in humans. Similar to the deer tick situation, Lyme disease has had an interesting recent history. Research from the Yale School of Public Health suggests an ancient origin of Borrelia burgdorferi, but the first clinical cases of Lyme disease weren’t formally documented in the medical literature until the 1970’s. At that time, an unusual cluster of juvenile arthritis cases with an accompanying rash helped researchers characterize the disease near Lyme, Connecticut*. It wasn’t until the early 1980’s that the roles of deer ticks and Borrelia burgdorferi were recognized.
Skip ahead a few decades and the numbers for Lyme disease have increased steadily. Today Lyme disease is the most commonly reported arthropod-borne disease in the US with over 40,000 confirmed and probable cases in 2017 alone. Looking at Wisconsin’s statewide averages, approximately 20% of deer tick nymphs (juveniles) and 40% of adult deer ticks are carrying Lyme disease, which are alarmingly high percentages.
Deer tick nymphs (juveniles) next to chia seeds, sesame seeds, flax seeds and a penny for size reference. Photo Credit: Dr. Bieneke Bron, MCE-VBD.
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…
Wisconsin is home to only a 
