Blister Beetles—Unexpected Wisconsin Connections

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.

Beetlejuice on the brain?

Elongate Hemlock Scale: The Grinch Trying to Ruin Christmas

Christmas has come and gone in 2019, but an uninvited Grinch may still be lurking to steal the holiday spirit. The Grinch in this case isn’t the green gremlinesque being of Dr. Suess, but a tiny invasive insect known as the elongate hemlock scale (EHS). The elongate hemlock scale (Fiorinia externa) is native to Japan and was first detected in the US in Queens, New York over a century ago. Since that time, EHS has spread to 15 states in the eastern US.

A heavy infestation of elongate hemlock scales.  Heavy infestations can have significant impacts on conifers.  Photo Credit: Eric R. Day, Virginia Polytechnic Institute and State University, Bugwood.org.
A heavy infestation of elongate hemlock scales. Heavy infestations can have significant impacts on conifers. Photo Credit: Eric R. Day, Virginia Polytechnic Institute and State University, Bugwood.org.

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.

The Blue Ridge Mountains near the border of North Carolina and Tennessee—the native habitat of Fraser firs. Photo Credit: PJ Liesch, UW Insect Diagnostic Lab.
The Blue Ridge Mountains near the border of North Carolina and Tennessee—the native habitat of Fraser firs. Photo Credit: PJ Liesch, UW Insect Diagnostic Lab.

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.

Two adult female elongate hemlock sales on the underside of a fir needle. Females are approximately 2 mm long. Photo Credit: Lorraine Graney, Bartlett Tree Experts, Bugwood.org

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.

Insects on the Move: Viburnum Leaf Beetle

A perk of being an entomologist is being able to better understand the world through the tiny creatures around us.  However, this can also be a bit disheartening at times.  While vacationing in Florida several years ago, I remember visiting the beach and the first three arthropods I encountered were out of place—a honey bee (originally arrived with Europeans), a millipede from Caribbean islands, and a weevil from Sri Lanka.  I doubt any other beachcombers recognized the international gathering amongst the dunes that day.

A honey bee (Apis mellifera) on a Florida beach.
A honey bee (Apis mellifera) on a Florida beach. Honey bees arrived in North America with Europeans and aren’t native to our area. Photo credit: PJ Liesch, UW Insect Diagnostic Lab

Seeing the world this way really reinforces the notion that humans play a critical role in the movement of species around the planet.  Scientists can make their best predictions about invasive species, but there are plenty of surprises in terms of when and where a given species will turn up.  For high priority invasives, designated surveys and inspections are conducted by government agencies to help monitor the situation.  The general public can also play an important role in documenting the presence and distribution of invasive plants, insects, and other organisms.  In Wisconsin, for example, the Wisconsin First Detector Network (WIFDN) uses a network of citizen scientists and a smartphone app to document invasive species.       

White-spotted caterpillar of the purple carrot seed moth (Depressaria depressana) found in Middleton, Wi in July, 2019. Photo credit: PJ Liesch, UW Insect Diagnostic Lab

In some cases, invasive species are simply stumbled upon.  Back in July, I bumped into the first case of the purple carrot seed moth in Dane county while riding some local mountain bike trails.  Along these lines, my wife and I were walking our dogs in early November when I spotted some suspicious damage on a row of viburnum shrubs.  A closer look revealed the distinctive feeding holes and egg pits of the invasive viburnum leaf beetlethe first evidence of an established infestation in Dane County

Egg pits of the viburnum leaf beetle on a viburnum twig.
Egg pits of the viburnum leaf beetle. Females chew small depressions in twigs of viburnum shrubs, lay several eggs, and cover the eggs with pits of chewed plant materials. Photo credit: PJ Liesch, UW Insect Diagnostic Lab.

The first established case of the viburnum leaf beetle in Wisconsin occurred in 2014 in northern Milwaukee county and a more detailed account of this species can be found in the original post on this blog.  Unfortunately, this invasive beetle has made some dramatic jumps on the map over the last few years—likely due to human movement of infested plant materials.  Back in 2017, VLB was detected in Oshkosh (Winnebago Co.). In June of 2019 viburnum leaf beetle was spotted in Hurley (Iron Co.) in far northern Wisconsin and was detected across the border in Ironwood, Michigan shortly thereafter. Other detections in 2019, include Racine and Walworth counties. 

Map of the the viburnum leaf beetle in Wisconsin.
Known distribution of the invasive viburnum leaf beetle in Wisconsin as of November 2019. Counties shaded in light blue had infestations known prior to 2019. VLB was detected in dark blue counties for the first time in 2019. Map: PJ Liesch, UW Insect Diagnostic Lab.

The viburnum leaf beetle can cause significant damage to viburnum shrubs and is already wreaking havoc in the greater Milwaukee area.  Viburnums, including American cranberrybush viburnum, arrowwood viburnum, and others are widely distributed in both urban and natural settings, meaning that Wisconsinites now need to keep an eye out for this damaging insect in new parts of the state.


To learn more about the appearance, damage, and biology of the viburnum leaf beetle, visit the original post and this factsheet.

Red Alert for the Lily Leaf Beetle

Author’s Note: Post updated in October, 2019 with the first confirmed report of lily leaf beetle in Pierce County, WI


It’s been a big year for the lily leaf beetle (Lilioceris lilii) in Wisconsin.  The lily leaf beetle (or scarlet lily beetle) is an invasive Eurasian species that made its first appearance in the state back in 2014.  This species originally showed up in North America around the time of World War II, arriving in eastern Canada with shipments of plant materials.  It eventually spread into New England in the 1990’s and has been moving westward ever since.  True to its name, this species has a fondness for lilies and can cause significant damage to true lilies (Lilium spp.), including both native lilies and cultivated types. Fritillaries (Fritillaria spp.) can also be attacked by the lily leaf beetle, as well as lily of the valley (Convallaria majalis) and Solomon’s seal (Polygonatum spp.) to lesser extents.  Daylilies (Hemerocallis spp.), canna lilies (Canna spp.), and calla lilies (Calla palustris) are not attacked.  The damage caused by lily leaf beetle can be severe.  Since its arrival roughly five years ago, some commercial flower growers in parts of Wisconsin have stopped growing and selling lilies altogether.

Severely damaged lily plants
A plant severely damaged by feeding activity of the lily leaf beetle. Photo credit: Leslie J. Mehrhoff, University of Connecticut, Bugwood.org

Adult lily leaf beetles are only about a quarter of an inch long but pack a punch when they chew irregular holes and notches in lily leaves, stems, and developing buds.  If there’s a redeeming quality of this invasive insect, at least the adults are a conspicuous bright red color.  However, when disturbed the beetles readily tumble from plants, and land upside down on the ground where they play dead.  Their dark-colored underside makes them much harder to spot when this occurs.

Lily leaf beetle adult
Adult lily leaf beetle (Lilioceris lilii) and damage. Photo Credit: Leslie J. Mehrhoff, University of Connecticut, Bugwood.org

If it weren’t for their destructive nature, one might even consider the vibrant red beetles rather pretty.  It’s hard to say the same of the larvae though.  Lily leaf beetle larvae are a pale yellowish color with a black head capsule and approach nearly half an inch long.  However, as a defensive behavior, the larvae typically camouflage themselves with their own excrement and look more like slimy greenish slugs or ooey-gooey animal droppings than insects.  Just like the adults, the larvae cause significant damage as they chew holes and notches in lilies.

Lily leaf beetle larva
A slimy, excrement-covered larva of the lily leaf beetle. The larvae can cause significant damage to true lilies. Photo credit: Richard A. Casagrande, University of Rhode Island, Bugwood.org

While pests like the Japanese beetle don’t make their appearance until well into summer, the lily leaf beetle can be a threat throughout the entire growing season.  This insect overwinters in the adult stage and the bright reddish beetles can emerge and start feeding early in the spring.  After mating, female lily leaf beetles lay tiny reddish eggs on the underside of leaves.  Eggs are often laid in batches of a dozen or fewer, but the long-lived females can lay hundreds of eggs in their lifetimes.  The emerging larvae start feeding and can be common during spring and early summer.  After gorging themselves for a few weeks, larvae eventually wander from plants to pupate in the soil.  The next batch of adults will be present through the summer and fall months.

Wisconsin map showing counties with known lily leaf beetle activity
Map of Wisconsin with confirmed detections of the lily leaf beetle. Counties that are dark blue had their first official confirmed detection in 2019.

If you haven’t encountered this insect yet in Wisconsin, it’s not too surprising.  The majority of the state has yet to see the lily leaf beetle—but that will likely change in the coming years.  When it was first detected in the Wausau area in 2014, lily leaf beetle was found nearly simultaneously in a number of spots around the county, suggesting that it may have been spread by the movement of infested plant materials.  Human movement of these insects remains an important factor today.  Since its introduction, the lily leaf beetle has steadily been spreading around central Wisconsin through both human and natural movement. Alarmingly, in the summer of 2019, the lily leaf beetle made some significant “jumps” and was detected in Dane and Door counties.  In early October, colleagues at DATCP confirmed the first detection of LLB from Pierce County.  This discontiguous pattern on the map points to human movement as a likely cause.  Unfortunately, these detections represent new footholds in Wisconsin and residents of those areas now need to be on alert for this invasive beetle.

Masked Hunter Bugs: Another Kissing Bug Look-Alike

“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 cruzia 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 (Triatoma sanguisuga)—ranges from Latin America as far north as southern Illinois.

Eastern conenose kissing bug adult.
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.
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.
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:

  1. Masked hunter bugs are entirely dark while eastern conenose kissing bugs have red on their body
  2. Masked hunter bugs lack the projecting “conenose” present on the head of kissing bugs
  3. Masked hunter bugs have a bulging, “muscular” appearance of their prothorax (trapezoidal region behind the head) when viewed under magnification
  4. 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.
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: labs.russell.wisc.edu/insectlab/visual-id-guides/

Is This a Kissing Bug?

Kissing” and “bugs”—two words you wouldn’t expect to be put together in the same sentence have been strung together rather frequently in the news lately.  No, this isn’t some poorly understood internet phenomenon amongst the youth of the country.  Rather, when you hear about “kissing bugs”, we’re really talking about a group of blood-feeding assassin bugs (Family Reduviidae, Triatoma species).

So what’s the story behind these insects and why the hype?
Kissing bugs are similar to bed bugs as they both feed on the blood of vertebrate hosts.  However, unlike bed bugs which have anthropophilic habits, kissing bugs are typically associated with animal nests in wooded areas.  Kissing bugs don’t go out of their way to sneak indoors, although if they do happen to wander in they can be attracted to the heat and carbon dioxide of a sleeping human.  When human bites do occur, it can often be on the exposed, softer skin of the face, hence the nickname of “kissing bugs”.  The biggest concern with kissing bugs is that under the right conditions they can serve as a vector of American trypanosomiasis (aka Chagas Disease), a serious disease that can lurk in the body and ultimately affect the heart and other organs.

What does the kissing bug story have to do with Wisconsin and the Great Lakes region?
In brief: not a whole lot.  While there are nearly a dozen species of kissing bugs in the western hemisphere, these insects are primarily found in rural Central and South America.  I recently spent some time amongst the Wisconsin Insect Research Collection’s  8 million+ specimens, and found no verified cases of kissing bugs in Wisconsin.  Technically, these insects have been found in some of the southern states, although they tend to be quite rare in the US and there isn’t any evidence to suggest that they’re expanding their range or increasing their numbers.  Unless you’ll be spending an extended amount of time in Central or South America, the threat posed by kissing bugs and Chagas disease is basically non-existent.  Overall, the hype about kissing bugs is more bark than. . .bite.

Think you’ve found a kissing bug in Wisconsin (or elsewhere)?
There are a few look-alikes that could potentially be confused with kissing bugs.  Boxelder bugs (Boisea trivittata) share the red and blackish coloration of certain kissing bugs, while the masked hunter assassin bug (Reduvius personatus) shares a similar body size and shape.  However, due to the slender body and similar “checkerboard-like” pattern around the abdomen , the insect getting confused the most with kissing bugs at the moment seems to be the western conifer seed bug (Leptoglossus occidentalis), which can be very common in Wisconsin and in many parts of the country.

Why the western conifer seed bug?  As described in an earlier post, western conifer seed bugs frequently try to sneak indoors in the fall to seek out a sheltered spot to spend the winter.  As a result, encounters with these harmless insects occur on a regular basis.  Want some peace of mind that the insect you’ve seen is a western conifer seed bug and not a kissing bug?  Check out this handy side-by-side guide comparing the eastern conenose kissing bug (Triatoma sanguisuga) with the western conifer seed bug:

Is this a kissing bug?
Distinguishing features of the Eastern Conenose Kissing Bug and Western Conifer Seed Bug; click for larger version. Photo Credit: PJ Liesch, UW-Entomology

Further reading:
Gwen Pearson recently covered the Kissing Bug story for Wired and included some excellent references.

5 Things to Know About Eastern Equine Encephalitis

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.

The mosquito Culiseta melanura
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.
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 over the last 50+ years.  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.

A Wandering Horde of…Millipedes

It’s a dark, overcast night as the horde emerges from the nearby woods. There’s no real coordination, but thousands of them—perhaps tens or even hundreds of thousands—seem to wander aimlessly through the yard.  Some approach the darkened farmhouse and a few even manage to make it inside…

If this were and episode of The Walking Dead, the protagonists would be in a tough spot, but we’re not talking about zombies in this case.  Instead, the topic is millipedes, which have been surprisingly abundant this summer in parts of the Upper Midwest.

Greenhouse millipede.
Greenhouse Millipede (Oxidus gracilis). Photo Credit: Joseph Berger, Bugwood.org

Most everyone is familiar with millipedes.  They technically aren’t insects, but they are related as demonstrated by their segmented legs and “crunchy” exoskeleton (both are types of arthropods).  These multi-segmented, worm-like creatures can be common in damp areas and are perhaps most recognizable by their slow walk and their habit of curling into a spiral when disturbed.

Unlike the zombies portrayed in on TV, millipedes are really quite harmless.  Some millipede species have been documented as minor crop pests, but in the grand scheme of things, I mostly think of millipedes as being beneficial detritivores.  Millipedes feed on decaying plant materials and they return nutrients to the soil.  Their feeding also breaks down plant materials into smaller pieces, allowing microbes to more easily assist in the decomposition process.  Millipedes can be especially common in damp locations with abundant plant materials: compost piles, rich soil with high organic content, mulch beds, wooded or prairie areas, CRP land, lawns with a heavy thatch layer, and similar.

Millipede curled up in a spiral
A millipede curled up in a classic defensive posture to protect its legs. Photo credit: Joseph O’Brien, USDA Forest Service, Bugwood.org

While mostly beneficial, millipedes can occur in very high numbers under the right conditions and can be a nuisance when they seem to suddenly appear in yards and homes.  Hopkin and Read’s The Biology of Millipedes (1992) describes situations where massive millipede hordes have covered acre after acre of farmland or stopped trains, quite literally, in their tracks.  The Midwest does see large masses of millipedes on occasion and it was a particularly busy year at the UW Insect Diagnostic Lab for calls about these creatures.

The reasons behind millipede mass migrations aren’t fully understood, but moisture is often noted as a common factor.  Other potential reasons range from general weather patterns to habitat disruption, competition, and reproduction.  When millipedes do move about, many species shun the sun and prefer to move at night or during very overcast days.  When they encounter a building, millipedes can sneak inside, although this is really accidental—it’s too dry for them to survive indoors and they typically die within a day or two.

Millipedes on a home's foundation
Thousands of millipedes along a resident’s home. From a case submitted to the UW Insect Diagnostic Lab this summer.

Millipedes can be frustrating when mass migrations occur as there’s not much that can be done to completely stop them.  It’s not uncommon to have cases where hundreds or thousands of of millipedes crawl onto the foundation or siding of a home every night.  If they mostly stay outside, that’s one thing, but this summer I’ve had multiple cases where large numbers of millipedes (hundreds) had snuck under a building’s siding and then rained down through ceiling light fixtures.  This sounds like something out of a sci-fi film, but if you were trying to sell your home it could be a real-life nightmare scenario.  In such cases, there simply isn’t any way to make the millipedes magically disappear.  Insecticides may be tempting but only help to a certain extent because more millipedes can simply show up the next day.

If you’re staring down a millipede horde, one of the most important approaches is physical exclusion.  Inspecting the exterior of a home and physically sealing up cracks, crevices, and other potential entrance points with caulk, expanding foam, or new weather stripping can be a chemical free, long-term solution to at least keep millipedes outdoors.  Because millipedes prefer damp areas with decaying plant material, keeping landscape pants, fallen leaves, and thick layers of mulch away from the foundation of a home could also help reduce hiding areas for millipedes.

Luckily, millipede mass migrations eventually run their course and quiet down on their own.   This year, I saw a spike in millipede reports starting in mid-June and running into early August before subsiding.

A Celebration of Insects

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

Black Flies: Out for Blood

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 want to scratch, 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.  The species, 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 2-3 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.

What’s Trending? Ticks and Lyme Disease

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…

Department of Entomology