All posts by pliesch

2018’s Top Trends from the Diagnostic Lab (Part 2)

In this post, we’re continuing to count down the University of Wisconsin Insect Diagnostic Lab’s top arthropod trends of 2018. This is the second half of a two part series; the first half can be found here.


5) White-Lined and Other Sphinx Moths:
The white-lined sphinx moth (Hyles lineata) can be a common species, so encountering one of the 3 inch long hornworm caterpillars isn’t unusual. However, these caterpillars can also be encountered in massive road-traversing hordes if the conditions are just right. From midsummer onwards, large numbers of these caterpillars were observed around the state—in some cases by the tens of thousands. If you didn’t spot any of the caterpillars themselves, you might have encountered the large adult moths with their hummingbird-like behaviour in late summer. Several other sphinx moths species also had a strong presence in 2018, such as the clearwing hummingbird moths and the tobacco and tomato hornworm caterpillars which can regularly be encountered in gardens as they munch away on tomato and pepper plants.

Large, dark-colored hornworm caterpillar of the white-lined sphinx moth on a plant
Large, dark-colored hornworm caterpillar of the white-lined sphinx moth. Photo submitted by Ted Bay, UW-Extension

4) Sawflies:
Sawflies, the caterpillar copycats of the insect world, are a diverse group, so they’re always present to some extent. Last year saw an unexpected abundance of two particular types in Wisconsin—the dogwood sawfly and the non-native Monostegia abdominalis, which feeds on creeping Jenny and related plants from the loosestrife group (Lysimachia species). While sawflies are plant feeders, dogwood sawflies can also damage the soft wood of a home’s siding or trim when these insects excavate small chambers to pupate in. The UW Insect Diagnostic Lab saw a distinct bump in reports of wood damage from the dogwood sawfly last year.

Whitish larva of the dogwood sawfly curled up on a dogwood leaf
Larva of a dogwood sawfly showing the whitish, waxy coating. Photo Credit: PJ Liesch, UW Insect Diagnostic Lab

3) Armyworms:
True armyworms (Mythimna unipuncta) can be a dynamic and sporadic pest in the Midwest. This species doesn’t survive the cold winters of our area, so adult armyworm moths must invade from the south each spring. Depending on national weather patterns, the arrival of the adult moths can vary significantly from year to year. If an early mass arrival is followed by abundant food and ideal conditions for the ensuing caterpillars, large populations can result. Once they’ve arrived, true armyworms can go through 2-3 generations in the state and this second generation of caterpillars made an alarming appearance in mid-to-late July. Under the conditions last summer, massive hordes of these caterpillars decimated crop fields before marching across roads by the tens or hundreds of thousands to look for their next meal. In some cases, that next meal included turfgrass, meaning that some Wisconsinites came home from work to biblical hordes of caterpillars and half-eaten lawns in late July.

Striped caterpillar of the true armyworm
Caterpillar of the True Armyworm (Mythimna unipuncta). Photo Credit: Lyssa Seefeldt, University of Wisconsin-Madison Extension

2) Monarch Butterflies:
Much to the delight of fans and conservationists, the iconic monarch butterfly (Danaus plexippus) appeared to have a banner year in the Midwest in 2018. Reports and observations of high numbers of monarchs poured into the Insect Diagnostic Lab during the summer months. As comforting as these reports were, the butterflies still faced a perilous 2,000 mile journey to reach their overwintering grounds in Mexico.  The most consistent measurement of the eastern monarch population comes from estimating the area occupied by the densely-packed overwintering butterflies.  In late January the latest count was released with encouraging news—the eastern monarch population is up 144% over last year and is estimated to be the largest in over a decade.  In contrast, the western monarch population overwinters in southern California and has recently dipped to alarmingly low numbers. Regardless of the winter assessments, monarchs face tough challenges and Wisconsinites are encouraged to help conserve this iconic species.  The Wisconsin Monarch Collaborative recently launched a website with resources for those wishing to join the effort.

Seven monarch butterflies nectaring on a flower
Multiple monarch butterflies nectaring on a single plant in August. Photo Credit: PJ Liesch, UW Insect Diagnostic Lab

1) Floodwater Mosquitoes:
Mosquitoes snagged the top spot on 2018’s list for good reason. The upper Great Lakes region is home to over 60 different mosquito species, but one subset—the “floodwater” mosquitoes—drove the storyline last year and impacted outdoor activities through much of the spring and summer months. Mosquitoes in this group, such as the inland floodwater mosquito (Aedes vexans), flourish when heavy rains come. Last year’s mosquito season kicked off in force with a batch of pesky and persistent floodwater mosquitoes just before Memorial Day weekend. Mosquito monitoring traps in southern Wisconsin captured record numbers of mosquitoes shortly thereafter. Later in the year, the Midwest experienced an unprecedented series of severe rainstorms, setting the stage for an encore performance of these mosquitoes. It was this second explosion of mosquitoes that caught the attention of anyone trying to enjoy the outdoors in late summer—a time of the year when mosquitoes are typically winding down in the state.

Ephemeral pools of water created ideal conditions for floodwater mosquitoes in late summer. Photo Credit: PJ Liesch, UW Insect Diagnostic Lab

2018’s Top Trends from the Diagnostic Lab (Part 1)

Each year the University of Wisconsin’s Insect Diagnostic Lab receives thousands of arthropod samples and reports from around the state and region, providing a unique perspective into insect and arthropod trends in Wisconsin and beyond.  This post is the first half of a series counting down the top arthropod trends in our area last year.  The second part will be posted in early February and can be found here.


10) Dagger and Tussock Moths:
A few species of fuzzy caterpillars were surprisingly abundant last year and there’s a good chance you might have bumped into these in your own neighborhood.  Two similar-looking yellowish species, the American dagger moth and the white-marked tussock moth, were extremely common around Wisconsin and were two of the most widely reported caterpillars last summer. Another tussock moth associated with milkweed was also surprisingly common in 2018. With many Wisconsinites growing milkweed to attract monarch butterflies, the black and orange caterpillars of the milkweed tussock moth were also noted in abundance around the state last year.

Fuzzy black and orange Caterpillar of the milkweed tussock moth (Euchaetes egle)
Caterpillar of the milkweed tussock moth (Euchaetes egle). Photo Credit: Katja Schulz via Wikipedia

9) Fungus Gnats:
Pick any spot on a Wisconsin map and 2018 was most likely a soggy year. Understandably, rain encourages insects and other creatures that thrive under damp conditions. Last year’s rains created great conditions for fungus gnats, which became quite abundant by late summer. While fungus gnats are harmless to people and pets, they can be an annoyance if present in high numbers. Fungus gnats thrive in damp organic materials, meaning that rich soil, compost piles, and decaying plants can produce masses of these tiny, dark-colored flies. The larvae of these insects can also be common in the soil of houseplants.  As Wisconsinites brought their favorite potted plants indoors in autumn to avoid approaching frosts, reports of indoor fungus gnats were common.

Small dark coloured gnats captured on a yellow sticky card trap
Tiny (2mm long) fungus gnat adults captured on a sticky card trap near indoor plants in fall of 2018. Photo Credit: PJ Liesch, UW Insect Diagnostic Lab

8) Purple Carrot Seed Moth:
With several new, non-native insects showing up in Wisconsin every year, the impacts of each species can vary significantly. Some exotics, like the emerald ash borer make massive waves, while others cause merely a ripple. The impacts of one of our newest invasive insects, the purple carrot seed moth (Depressaria depressana), are not yet fully known. This European species was spotted in Wisconsin for the first time last summer and the tiny caterpillars love to feed on the flowers (umbels) of plants from the carrot family. Below-ground plant structures (e.g., the taproots of carrots) aren’t impacted, but notable damage to herbs like dill, fennel, and coriander can occur. As a result, this pest may be a concern for seed producers, commercial herb growers, or home gardeners with a fondness for dill and related herbs. The purple carrot seed moth has been reported in 8 Wisconsin counties thus far [Brown, Columbia, Dodge, Kewaunee, Milwaukee, Racine, Sheboygan and Washington Counties], so new county-level reports are encouraged at the UW Insect Diagnostic Lab.

Tiny (<1/4" long) spotted caterpillar of the purple carrot seed moth on dill.
Caterpillar of the purple carrot seed moth. Photo Credit: PJ Liesch, UW Insect Diagnostic Lab

7) Odorous House Ants
Imagine the stereotypical black ants zeroing in on sugary foods at a picnic and you’d have a fitting profile of the odorous house ant (Tapinoma sessile). Of the 100+ ant species in the Midwest, the odorous house ant stood out in spring and early summer last year with its sheer abundance. The UW Insect Diagnostic Lab was flooded with calls about these sugar-loving ants during 2018’s rainy spring, especially when these ants wandered indoors. The spring rains may have forced the ants from waterlogged colonies to seek out higher-and-drier locations, making odorous house ants the most commonly reported ant at the diagnostic lab last spring.

SMall black ant—an odorous house ant worker
Odorous House Ant (Tapinoma sessile) worker. Photo Credit: JJ Harrison via Wikipedia

6) Stink Bugs:
While the Midwest is home to over 50 species of stink bugs, one particular species—the invasive brown marmorated stink bug—stands out to give the rest a particularly bad reputation. If you live in a part of the state with the brown marmorated stink bug, you may have already encountered this species. With its habit of sneaking indoors in the fall, this insect replaced boxelder bugs in some areas as the top home-invading nuisance pest of 2018. This Asian species has made the diagnostic lab’s Top 10 list for several years now and unfortunately doesn’t show any signs of slowing down. In 2018 alone, BMSB was detected in 8 new Wisconsin counties, which hints at potential damage to fruit and other crops in those areas in the coming years.

Adult brown marmorated stink bug
Adult brown marmorated stink bug. Photo Credit: PJ Liesch, UW Insect Diagnostic Lab

To see the rest of Wisconsin’s top arthropod trends of 2018, check out part 2, available here in early February.

The Stories that Insects Tell

Imagine taking an American history class where many of the important events were reduced to mere footnotes or skimmed over entirely.  Anyone taking the class would be shocked at this notion—I mean, the Civil War was a big deal after all!  When you look at a different field of study—biology—such a trend has surprisingly occurred, with insects getting the short end of the stick.  Insects are the most diverse and abundant animals on the planet and make up roughly 70% of the 1,000,000+ described animal species.  Yet, many introductory biology textbooks skim over insects (and invertebrates in general) in favor of more charismatic megafauna—a trend that has only gotten worse over time.  Insects may be small, but they serve crucial roles in the world around us from pollinating plants to serving as the base of food webs.  Appropriately, E.O. Wilson referred to insects as “the little things that run the world” in his famous call for their conservation.  It’s difficult to conserve these little creatures that run the world when so few people really get to know them.  

With their sheer diversity and abundance,  knowing the insects also helps us better understand the world, and everyday life, around us.  Getting to know the many different insects is a bit like learning a foreign language.  Travel to an exotic country where you don’t speak the local tongue and you’d have a hard time understanding the everyday happenings around you.  As you picked up words and phrases of that foreign language, things will become easier to understand.  Along these lines, if you can recognize the insects around you, it helps interpret the stories they tell.  Truly knowing your insects is like possessing an all-powerful decoder ring to the untold stories that surround us.  

Let’s look to flies to illustrate this point.  To many folks, a small fly found in their home is assumed to be a fruit fly, and a large fly, a house fly.  But there are dozens of different flies that commonly show up indoors—each with their own story to tell.  Fungus gnats hint at overwatered houseplants, moth flies indicate build-up in a bathtub drain, and metallic blow flies can alert you to a mouse trap in need of checking.  Outdoors, other species of flies can provide clues that gauge water quality, indicate the presence of specific plants, or solve crimesbut only if one knows how to interpret their clues.  If a picture is worth a thousand words, I’d argue that a properly identified insect is worth even more.  

The unusual fly species, Asteia baeta. At only 2mm long, these flies can readily be mistaken for fruit flies to the naked eye. Photo Credit: PJ Liesch, UW Insect Diagnostic Lab

This holiday season, my own love of insects led to a scientific discovery that would have gone unrecognized in most households.  A day after setting up our “real” Christmas tree, I noticed several tiny flies at the windows of our home.  My curiosity was piqued and like any good detective, some sleuthing was needed.  I recall an undergraduate professor telling the class, “a biologist without a notebook is off duty” to which I’d add, “an entomologist without vials is off duty”.  So now I was off, vials in hand, on an insect hunt in my own house.  Once the specimens were examined under the microscope, I recognized the flies as a rare species (Asteia baeta) from the poorly-known family Asteiidae.  There isn’t much written about these flies, but they’re known to be associated with fungi, vegetation, and tree sap, which told me that the new Christmas tree was the source.  These flies have only been spotted in Wisconsin a few times and no preserved specimens exist for that family in the Wisconsin Insect Research Collection (I’ll be donating some soon).  Looks like our Christmas tree came with it’s own entomological story to tell this year—I’m glad I knew how to listen.

The source of the unusual flies—apparently our cat wanted to try and hunt for them as well. Photo Credit: PJ Liesch

2018 Update: Brown Marmorated Stink Bug in Wisconsin

Author’s Note: Original post updated in January, 2019 due to a confirmed report in Waupaca Co. and suspected report in Oneida Co.


One of the most concerning invasive insects to appear in Wisconsin in the last decade is the brown marmorated stink bug (Halyomorpha halys).  This Asian species delivers a double-whammy of not only damaging crops and other plants, but also being a significant nuisance when it sneaks into buildings in the fall. Since its initial detection in the state in 2010, populations of this insect have built up slowly but steadily. 

Brown marmorated stink bug adult on the side of a building in fall. This is becoming a common site in some parts of the Midwest. Photo Credit: PJ Liesch, UW Insect Diagnostic Lab.

What’s the current status of BMSB in Wisconsin?

As of late 2018, 28 counties have confirmed reports of the brown marmorated stink bug and a handful of other countries have suspected sightings.  This insect has a strong foothold in the state and was confirmed in eight new counties in 2018 alone—Eau Claire, Jackson, La Crosse, Marquette, Monroe, Richland, Trempealeau, and Waupaca counties. 

Distribution of the brown marmorated stink bug in Wisconsin—updated January 4th, 2019
Distribution of the brown marmorated stink bug in Wisconsin—updated January 4th, 2019. BMSB has been confirmed in 28 counties. Map Credit: PJ Liesch, UW Insect Diagnostic Lab.

Two core areas currently stand out for brown marmorated stink bug activity in Wisconsin: the Highway 41 corridor from Fond du Lac up to Green Bay and southern Wisconsin from Dane and Rock Counties east to the Milwaukee metro area.  These two areas have the longest history of BMSB in the state and account for the majority of reports thus far. 

Much of the state has yet to encounter this insect or truly experience its impacts.  When the brown marmorated stink bug is first detected in an area, there’s a proverbial “calm before the storm”.   The pattern observed in the state thus far has been a few “quiet” years where low initial populations of this insect result in only a few sightings annually.  However, after a few years in a given area, BMSB populations build up to the point where nuisance problems around structures are noted and reports of potential plant damage begin to trickle in.

What’s the Outlook for BMSB?

Unfortunately, Wisconsin has yet to see the full impact of this invasive insect.  Observations over the last few years have found that BMSB is able to survive our winters and reproduce in the state, so this adaptable pest will most likely continue to build its numbers in the coming years. 

Over time, the brown marmorated stink bug is likely to emerge as one of the top structure-invading pests in the state alongside the likes of boxelder bugs and multicolored Asian lady beetles.  In the eastern US, where BMSB has been established for over a decade in spots, problems can be significant.  In some cases these malodorous insects have been documented invading homes by the tens of thousands

Several brown marmorated stink bug juveniles on a dogwood shrub. Ornamental trees/shrubs, vegetables, and fruit crops can all be attacked by this insect. Photo Credit: PJ Liesch, UW Insect Diagnostic Lab.

While widespread crop damage has not yet been observed in Wisconsin, it may only be a matter of time as population of this insect continue to build in the state.  Agricultural problems have also been significant in the eastern US, giving us a glimpse into what could potentially happen in coming years.  For example, brown marmorated stink bug caused $37 million dollars in losses to apples in the mid-Atlantic states in 2010 alone.  

Having been detected in Portage County in 2017, brown marmorated stink bug may soon start to pose a threat to vegetable production in central Wisconsin.  Similarly, specimens confirmed from Door County in 2017 are forcing fruit growers in that part of the state to keep a close watch on their orchards and vineyards.  With the recent detection of BMSB in several western Wisconsin counties, we’ll likely see BMSB populations slowly build in that part of the state over the next few years as well. 

What should you do?

A Wood-Boring Insect Mystery

Imagine it’s August and as you wander in from your backyard, you notice a small pile of sawdust at the bottom of the door frame.  It might not be much sawdust, but you also find a few holes in the wood trim nearby.  It definitely seems to be insect damage, but who’s the culprit?

Unexpected insect damage to wood trim.

If you came up with a list of insects in the upper Midwest that can damage the wood of your home, it wouldn’t be terribly long.  For good reason, termites might be the first insect to come to mind, although our eastern subterranean termites are restricted to isolated pockets and are not commonly encountered in Wisconsin.  A close second on the list might be carpenter ants.  Interestingly, carpenter ants don’t technically eat (e.g., digest) wood and merely excavate soft, rotting wood to create a nesting site.  If anything, their presence in a home might be an indicator of a water damage.  Powderpost beetles can also attack wood and are commonly encountered in old barn beams and log cabins.  Carpenter bees help round out a list of the “usual suspects”.  These wood-boring bees can create good sized holes (a half inch across), although with their preference for unpainted softwoods used for trim, siding, and fence posts, their damage is mostly cosmetic in nature. 

Then another clue comes to mind—the nearby shrubs that had been eaten by some kind of worm-like insect over the past few weeks. 

Larva of a dogwood sawfly showing the whitish, waxy coating. Photo Credit: PJ Liesch, UW Insect Diagnostic Lab

When it comes to wood-damaging pests, sawflies generally don’t come to mind.  Sawfly larvae—Mother Nature’s caterpillar copycats—tend to feed on plant leaves.  Species like the European pine sawfly, dusky birch sawfly, rose slug sawfly, Columbine sawfly, pearslug sawfly, and birch leafminer sawfly can all be commonly encountered feeding on plants during the growing season.  One species that was common in 2018—the dogwood sawfly—is unique in that it not only causes plant damage but can also damage wood trim and siding of homes.  The dogwood sawfly is one of our commonest pests of native and landscape dogwoods (Cornus spp.).  When larvae are small,  they have a whitish waxy coating thought to mimic bird droppings and they can often be found curled up on the undersides of dogwood leaves.  As larvae mature, they lose the waxy coating and their black and yellow coloration becomes conspicuous.   

Mature dogwood sawfly larva with classic black and yellow appearance.

So how does this plant-feeding species end up damaging wood?  As is the case with any insect that undergoes complete metamorphosis, the larvae need to pass through the pupal stage to make it to adulthood. Insect pupae, however, are generally immobile can make an an easy meal for any predator that stumbles upon them.  Thus, many insects seek out tucked away spots to complete their pupal stage.  When ready to pupate, dogwood sawfly larvae typically create their own hideaway by chewing small chambers in rotting wood such as twigs, branches, or logs near the shrub they had been feeding on. 

Small chambers chewed into a fallen twig—a “typical” spot for dogwood sawfly to pupate.

If rotting wood is unavailable, the larvae may turn to other nearby wood materials—including wood trim and siding.  This typically occurs when larvae had been feeding on ornamental dogwood shrubs planted close to a home.  In the grand scheme of things, these insects don’t cause that much damage to wood, although homeowners won’t be thrilled if they’ve been caught off guard by this unexpected wood-damaging pest! 

September’s Mosquito “Madness”

While much of our insect activity in the Midwest slows down as summer draws to a close, some areas have seen an unusual increase in mosquito activity recently.  In Wisconsin, we generally expect mosquitoes to be “bad” from late spring through the summer months, but these pesky sanguivores typically fade away as autumn approaches.  September of 2018 has definitely bucked the trend, and mosquito pressure has been very high in many parts of the state and region this month.

As with other mosquito stories, the common denominator is water—in this case, the unprecedented rainfall events in late August and early September.  During this time, a series of storms dropped heavy rains across large swaths of Wisconsin and surrounding states.  Much of Wisconsin received several inches of rain, and some southern counties were bombarded with 10+ inches of rain in short periods of time.  Devastating flooding ensued, and it was only a matter of time before the mosquitoes responded as well.

Flooding caused over $200 million in damages in Wisconsin alone and set the stage for September’s unseasonably high numbers of floodwater mosquitoes. Photo Credit: PJ Liesch, UW Insect Diagnostic Lab

Surprisingly, not all mosquitoes can take advantage of floodwaters and some species have a strong preference for more permanent bodies of water, such as tree-holes, man-made objects, marshes, and other areas that can hold water for weeks or months on end.  Out of the 60+ mosquito species in the Midwest, it’s a much smaller subset that has flourished lately—a group appropriately called the “floodwater mosquitoes” for their ability to use temporary water sources to their advantage.  Members of this group, including the currently-abundant “inland floodwater mosquito” (Aedes vexans), tend to lay eggs in low-lying areas without water.  Laying eggs away from water may seem like a counterintuitive strategy, but the hardy eggs simply bide their time until heavy rains arrive—in some cases, years later.

Relying upon temporary resources can be a risky strategy; if the waters dissipate too quickly,  stranded larvae or pupae can be doomed.  Floodwater mosquitoes have evolved to race against the clock, with eggs that hatch shortly after exposure to water, followed by hasty growth and development.  Under the right conditions, it can take less than a week for these mosquitoes to make it to the adult stage.  This scenario is exactly what played out in our area—the rains came, followed shortly thereafter by hungry adult mosquitoes.

The “inland floodwater mosquito” (Aedes vexans) is currently abundant in the Midwest. Photo Credit: Sean McCann, via Flickr

With the unseasonably high mosquito pressure this September, one of the commonest questions has been, “when will it stop?!”  While the mosquitoes have undeniably been bad lately, we’re past the worst of the situation.  Mosquitoes and other insects are “cold-blooded” creatures, so there’s a general relationship between warmer temperatures and insect activity. Most of our insects in the Midwest become lethargic when temperatures dip into the 50s; below 50˚F mosquitoes are often too lethargic to fly, let alone pursue a blood meal.  We saw unusually high mosquito activity in early- and mid-September when temperatures remained in the 70s and 80s most days.  Looking at the weather for the near future, many parts of Wisconsin are expecting more seasonal temperatures, which will provide relief.  Mosquitoes might still be encountered on warm fall days, but evening temperatures may simply be too chilly for mosquitoes to go about their business and impending frosts will be the final “nail in the coffin” for September’s floodwater mosquitoes.

In the meantime, the best way to deal with the late season mosquitoes may be to embrace “flannel season” and put on some long-sleeved layers as a physical barrier to bites, and use  EPA-approved repellents as needed (such as on warm days).  Avoiding prime mosquito feeding times (dawn/dusk) and good mosquito habitat can help you avoid bites as well.  It may be sad to see summer go, but the changing leaves and cooler temperatures also signal the winding down of mosquito activity for the upper Midwest.

Sphinx Moths—Hovering at a Flower Near You

If you’ve watched the flowers in your yard or local park recently, you might have noticed some surprising visitors hovering at the flowers—the hummingbird-like sphinx moths.  Several species in the “sphinx” or “hawk” moth group (Family Sphingidae) are known for their day-flying, hummingbird-like behavior.  From a distance these moths can easily be mistaken for hummingbirds as they skillfully maneuver from flower-to-flower sipping nectar with their long mouthparts.

One of the commonest members of this group in Wisconsin is the white lined sphinx moth (Hyles lineata).  With a wingspan of nearly 4 inches, it’s easy to understand why this species can be mistaken for a hummingbird as it feeds.  The greyish adults are easy to pick out and a white stripe on each forewing helps identify them in the field.  The caterpillars (hornworms) of this species reach nearly 3 inches in length and can feed on a wide range of plants.  While this species is regularly encountered in the Midwest, this year has been especially good for white-lined sphinx moths in Wisconsin.  In mid-to-late July I received many reports of the caterpillars—sometimes in astounding numbers.  In several instances, “outbreaks” of tens of thousands of these large caterpillars were spotted as they migrated across roadways from agricultural fields.  The multitudes of caterpillars have since pupated and transformed into nectar-loving moths—leading to a recent spike of sightings.

White-lined sphinx moth (Hyles lineata). Photo Credit: Andy Reago & Chrissy McClarren; Wikipedia

In addition to the white-lined sphinx moth, several other hummingbird-like sphinx moths have been common this year—the “clearwing” hummingbird moths (Hemaris spp.) and the Nessus sphinx moth (Amphion floridensis).

The rusty-colored “clearwing” moths (Hemaris spp.) are smaller than the white-lined sphinx moth, and have a wingspan of approximately 2 inches.  Their shaggy appearance and patches of yellow coloration lend a resemblance to large bumble bees.  Characteristic transparent “windows” in the wings help identify these moths.  Several Hemaris species can be encountered in the Great Lakes region with subtle differences in appearance and biology.  Both the “hummingbird clearwing” (Hemaris thysbe) and the “snowberry clearwing” (Hemaris diffinis) can be common, while the “slender clearwing” (Hemaris gracilis) is associated with pine barrens and is rarely encountered.

The hummingbird clearwing moth (Hemaris thysbe) showing the transparent “windows” in the wings. Photo Credit: Andy Reago & Chrissy McClarren; Wikipedia

The “Nessus Sphinx” (Amphion floridensis) is another hummingbird mimic that was commonly reported earlier in the summer.  Although somewhat similar in size and coloration to the Hemaris clearwing species, the Nessus sphinx moth has opaque wings and two distinct yellow bands across the abdomen.

The Nessus sphinx moth (Amphion floridensis) in action. Photo Credit: PJ Liesch, UW Insect Diagnostic Lab

In addition to being a joy to observe, sphinx moths are a great example of “non-bee” pollinators.  Their unique behavior and anatomy allows them to form interesting relationships with some of the plants they pollinate.  In an extreme example, the Christmas Star Orchid (Angraecum sesquipedale) from Madagascar possess extremely long tube-like floral structures which contain the nectar.  Upon learning of the unique anatomy of this orchid, the famed naturalist Charles Darwin speculated that a moth with equally long mouthparts must exist to pollinate them.  It took over a century to document, but a sphinx moth wielding foot-long mouthparts was finally observed pollinating the Christmas Star Orchid.

Purple Carrot Seed Moth Appears in Wisconsin

In a given year at the UW Insect Diagnostic Lab, I typically document 2-3  new, non-native, potentially-invasive insects in Wisconsin. In some cases, these species make an appearance only to fade into the background with little impact, while other exotics become heavy-hitting invasive pests (e.g., emerald ash borer and gypsy moth). The latest non-native pest to make an appearance in the state is the tiny “purple carrot seed moth” (Depressaria depressana) and its impacts are not yet fully known. This species has a wide native range and can be found from western Europe through Russia to China.  It was first documented in North America in 2008 and is so new that few images exist and it’s not included in the common caterpillar and moth field guides on the market.

Purple carrot seed moth. Photo Credit: PJ Liesch, UW Insect Diagnostic Lab

In the last decade, the purple carrot seed moth has been documented in many locations in southern Canada and the northeastern US and has also been spotted in a few scattered locations in Michigan, Indiana, and Illinois. In mid-July of 2018, two reports came into the UW Insect Diagnostic Lab in rapid succession—Kewaunee and Dodge counties in Wisconsin. These cases were confirmed through images and caterpillar specimens that were reared to adult moths. After discussing the purple carrot seed moth on a recent episode of Wisconsin Public Radio’s The Larry Meiller Show, several additional suspected cases were reported in the state: Racine (Racine Co.), Random Lake (Sheboygan Co.), Burnett (Dodge Co.), and Franklin (Milwaukee Co.).

These insects get their name due to their association with flowers (umbels) of plants in the carrot family (Umbelliferae). The caterpillars of the purple carrot seed moth are small (3/8 inch long when mature), but dozens can feed on a single umbel. The caterpillars are dark green or reddish with many conspicuous white spots on their bodies. In addition to feeding on the flowers, the caterpillars tie together floral parts with silken webbing, which can make herbs like dill unusable. Eventually the caterpillars pupate within the webbing and emerge as adult moths a short time later. The adult moths are 3/8 inch long with a pale patch near the head; their purplish-grey wings are folded back along the body when not flying.

Caterpillar of the purple carrot seed moth, note the many conspicuous white spots on the body. Photo Credit: PJ Liesch, UW Insect Diagnostic Lab

The impacts of this non-native insect are not fully known for our area. The reports of plant damage in Wisconsin thus far have only been on dill. Due to the plant parts attacked (flowers), the impact on carrots, celery, and parsnip crops will likely be minor. The biggest impacts would be expected with umbelliferous crops commonly grown for seeds: dill, fennel, and coriander. Luckily, several organic control products may offer help on herbs: insecticidal soap and Neem oil are two low-impact products expected to help control this pest, if needed.  Cutting out and destroying infested flower heads may be another helpful tactic.

Damage from the purple carrot seed moth on dill. Photo Credit: PJ Liesch, UW Insect Diagnostic Lab

Because this pest is “new” in Wisconsin, if you believe you’ve found it on dill or other plants from the carrot family, please snap some pictures and contact me to help document this species in the state.

Chinch Bug: How a Tiny Insect Helped the Rise of Dairy in Wisconsin

It was over 170 years ago that Wisconsin was granted statehood.  While much has changed over the decades, some things haven’t—like the omnipresence of agriculture.  It’s hard not to notice agriculture in Wisconsin, be it crop fields, orchards and vineyards, or our famous dairy farms dotting the landscape.  To many, Wisconsin is practically synonymous with dairy, and America’s Dairyland is even enshrined on our license plates.  While Wisconsinites may take our dairy prominence for granted, it turns out we weren’t always the Dairy State—at one point in history, you might have even called us the Wheat State.

It’s easy to understand why Wisconsin has a long history of agriculture.  The region received an influx of rich soil with the last ice age which allowed us to become a top wheat producer in the early days of statehood.  To early farmers in Wisconsin, wheat was a profitable crop in high demand.  For a period in the 1800’s, Milwaukee was even the busiest wheat shipping port in the entire world1.  Fast forward to today and Wisconsin is best known for its dairy production, while states like Kansas, Nebraska, and the Dakotas are known for their bountiful grains.

Quote from J.G. Thompson’s The Rise and Decline of the Wheat Growing Industry in Wisconsin2

It was the mid-to-late 1800’s when the course of Wisconsin’s history was forever altered by a number of factors.  Fluctuating wheat prices and overworked soil might have been the primary drivers, but dry weather and a tiny insect also pulled on the reins of history.  Just as mosquitoes can thrive after heavy rains, other insects thrive under hot, dry conditions.  Droughts of the 1860s, 70s, and 80s set the stage for biblical outbreaks of some of these insects.  Farther to the west, fields in the Great Plains fell victim to swarms of Rocky Mountain locusts so massive that they darkened the sky for thousands of square miles.

Closer to home, the pest delivering a coup de grâce to wheat fields was the humble chinch bug, which thrived under the dry conditions at the time.  Chinch bugs aren’t much to write home about: at roughly an eighth of an inch long, most folks wouldn’t take the time to examine these tiny, black and white insects.  It was by their sheer abundance that these creatures decimated Wisconsin’s wheat fields in the 1800’s.  Using needle-like mouthparts, these insects sucked the life out of wheat plants, leaving behind wilted, yellowed stems.

The chinch bug (Blissus leucopterus). Photo Credit: David Shetlar, The Ohio State University, Bugwood.org.

When a pest outbreak occurs in a given year, a farmer might chalk it up to bad luck, bad weather, or other factors and hope things improve the next season.  With falling wheat prices and chinch bugs regularly devastating wheat crops in the late 1800’s, Wisconsin wheat farmers realized that their efforts yielded little profit.  Without an effective way to prevent the ravages of the chinch bugs, attentions shifted to more fruitful possibilities.

The first comprehensive report on the biology and habits of the chinch bug.

Understanding the biology of the chinch bug was crucial to discovering the limitations of that insect’s destruction.  It turns out that chinch bugs are picky eaters with a taste for grasses—wheat, corn, and similar.  Unrelated plants, including forage crops like alfalfa, weren’t affected by these insects and could be grown to feed livestock at the very time that the dairy industry was budding in Wisconsin.  Decades later our dairy prominence is featured on our license plates.  

When enjoying those Wisconsin cheese curds, ice cream, and other dairy treats during national dairy month, chances are you probably wouldn’t have thought about insects—but now you know how the tiny chinch bug helped make dairy a BIG deal in Wisconsin.


1Harbor and Marine Interests. History of Milwaukee City and County Vol I. Ed. W.G. Bruce. 1922. Print.

2J.G. Thompson. The Rise and Decline of the Wheat Growing Industry in Wisconsin. Bulletin of the University of Wisconsin No. 292. Economic and Political Science Series. Volume V(3): 295-544. 1909. Print.

Black Widows: The Hermits of Door County

Spider cases at the UW Insect Diagnostic Lab often boil down to clients wondering if they’ve found either a brown recluse or black widow spider.  Wisconsin is home to approximately 500 species of spiders, and essentially all of these are harmless, beneficial creatures that provide us with an astonishing amount of free pest control*.  While we’re outside the native range of the dreaded, but horribly misunderstood brown recluse spider (Loxosceles reclusa), Wisconsin is actually home to a native black widow species—the northern black widow (Latrodectus variolus).  In Wisconsin, these spiders are rare and have been documented in fewer than 10 counties.  Most Wisconsinites will go their entire lives without seeing a northern black widow out in nature and if you’re lucky enough to spot one of these elusive creatures, you’d almost certainly encounter a lone individual.  In contrast, there are several other widow spiders that can be much more common in other parts of the country.

The vast majority of black widow records in Wisconsin are from the east-central counties.  Door county historically stands out as having the most confirmed sightings and perhaps takes the place of Wisconsin’s black widow “capital”—although only a few sightings occur in most years.  The northern black widow doesn’t seem to occur farther north under natural conditions, which suggests an inability to the survive colder winters in the northern part of the state.  Along these lines, Door county’s unique geography and the moderating effects of Lake Michigan may explain why the majority of reports come from that part of Wisconsin.  Similarly, other confirmed reports of the northern black widow tend to be from nearby counties bordering Lake Michigan.  Away from the lake, northern black widows have also been documented in prairie areas in Crawford, Grant, and Sauk counties, where the microclimate on south-facing slopes may favor their survival.

“Scarlet”—the first Northern Black Widow documented in Sheboygan County. Photo Credit: PJ Liesch-UW Entomology

In a typical year, the UW Insect Diagnostic Lab might get a report or two of black widow spiders, but 2017 stood out in the sheer number of reports.  For spiders like the black widow, I keep in touch with Dr. Mike Draney, an arachnologist at UW-Green Bay.  During some stretches of 2017, Mike and I were emailing reports of black widows to each other once or twice a week!  These reports generally came from Door county and nearby areas.  In addition, these spiders were also documented in two additional Wisconsin counties for the first time last year: Brown county and Sheboygan county.

It’s possible that winter weather patterns might explain the distinct bump in northern black widow sightings last year.  Leading up to 2017, Wisconsin faced two consecutive mild winters, which might have favored insects, spiders, and other creatures that fare better in slightly warmer climates.  While the state did see an increase in reports last year, it’s not yet known if that trend will continue in 2018 as the state just emerged from a veritable winter season.


*A recent study estimated that spiders around the globe consume approximately 400 – 800 million tons of prey annually. Nyffeler, M. & Birkhofer, K. Sci Nat (2017) 104: 30. https://doi.org/10.1007/s00114-017-1440-1