Tag Archives: 2019 Lab Highlights

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.

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.

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: insectlab.russell.wisc.edu/visual-id-guides/