Tag Archives: The Wonderful World of Insects

Large Milkweed Bugs: Featured Fall Insect

With the arrival of fall, we’re starting to see pumpkins, spooky yard decorations, and pumpkin spiced everything (*shudder*).  Not to be left out of the festivities, one insect can be quite noticeable this time of the year—the large milkweed bug (Oncopeltus fasciatus).

Large milkweed bug (Oncopeltus fasciatus) adult. Photo credit: PJ Liesch, UW Insect Diagnostic Lab.

If you’re wondering, we do also have a small milkweed bugs (Lygaeus kalmii), although it’s not usually as common as the ubiquitous, larger cousin.  Both juveniles (nymphs) and adults of the large milkweed bug are fittingly adorned for fall.  Adults reach lengths of nearly 3/4  inch long and are mostly orange with black patches on the wings and body.  Going through “simple metamorphosis” (technically, they’re paurometabolous), the juveniles or nymphs look similar in body shape to adults (although smaller) and are also orange with some black.  In more mature nymphs, the developing blackish wing pads are quite noticeable.  When you see a group of nymphs and adults hanging out on milkweed in the fall, it’s easy to recognize that they’re all the same species.

Large milkweed bugs specialize on milkweed plants and are one of the many creatures that can be found in and around milkweed patches.  When they feed, large milkweed bugs use their sucking-type mouthparts to sip fluids from plants; they’re especially fond of the developing seed pods and are often spotted on pods.  While home gardeners hoping to rear monarchs might be concerned about competition, these insects generally cause little harm to plants and are more of a curiosity than a pest.

Group of large milkweed bugs (Oncopeltus fasciatus) on milkweed at UW-Madison; both adults and nymphs are present. Photo credit: PJ Liesch, UW Insect Diagnostic Lab.

Large milkweed bugs have a very seasonal pattern in the upper Midwest.  They can’t survive the winter at more northern latitudes, so they must migrate northwards each year.  Here in Wisconsin, you’d be hard pressed to find large milkweed bugs in spring, but by July they’ve often arrived in low numbers.  Large milkweed bugs can become quite common by late summer and early fall as it typically takes 40+ days for a new generation of adults to appear from eggs laid in our area.

In much of Wisconsin, we’re just starting to see foliage change to reds, oranges, and yellows, but as you’re out enjoying the fall weather, keep an eye out for these festive-looking insects around milkweed patches.

UW-Madison and the Chamber of Flesh-Eating Beetles

Unbeknownst to most students, employees, and visitors at UW-Madison, there’s a room of flesh-eating beetles on campus.  An unmarked door on Bascom Hill leads to the chamber more formerly known a the Dermestarium, which serves a rather peculiar yet specific purpose.  No need to worry though—this isn’t 1999’s The Mummy.  Rather, these insects are actually quite helpful in the way that they’re used.

A fitting entryway to the chamber of flesh-eating beetles. Photo credit: PJ Liesch, UW Entomology.

Most insects are actually helpful in one way or another and provide ecosystem services as pollinators, predators, parasitoids, decomposers, or in other roles.  Humans have also figured out some pretty unique ways in which insects can help us out.  For example, mealworms can eat and break down certain types of plastics and are being looked at as a way to help reduce man-made waste materials.  In the legal realm, knowledge about insects is used to help solve crimes—a field known as forensic entomology, which dates back nearly 1,000 years.  In the case of UW-Madison and many other universities and museums, a specific type of beetle is used to help  clean skeletal remains for research, teaching, and display in zoological museums.  

The beetles in the UW Dermestarium are known as hide beetles (Dermestes maculatus) and they’re especially fond of dried-out, protein-rich materials such as remnants of muscles, sinew, fur, feathers, and similar materials.  Out in nature, such insects do play a role in the natural break down of animals remains—but not right away.  Rather, much of that initial work is left to the larvae (maggots) of blow flies (Family Calliphoridae) and flesh flies (Family Sarcophagidae).  Hide beetles and close relatives from the “carpet beetle” group (Family Dermestidae) show up days, weeks, or even months later once the remains are drier.  

Adult hide beetle (Dermestes maculatus). Photo credit: Udo Schmidt via Wikipedia.

In a museum setting, hide beetles can be helpful in the preparation of skeletal remains.  With their small size (roughly 1/4-inch long) , these insects use their mandibles to efficiently remove leftover bits of tissue from tiny nooks and crannies.  For a human trying to prepare remains, such a task would be tedious and may not be feasible for some structures (such as the inside of a skull).  However, a tank of these beetles can easily clean skeletal remains in a matter of days with relatively little effort required, other than maintaining correct ambient conditions for them. 

Skeletal remains in the UW Dermestarium; many larvae can be seen in the box in the photo. Photo credit: PJ Liesch, UW Entomology.

Interestingly, hide beetles and close relatives like the larder beetle (Dermestes lardarius) can be found in our own homes as well.  Their presence poses little risk to humans, but could indicate the presence of a dead rodent or bird in a structure.  Such insects can also develop on a range of protein-rich materials ranging from dead insects in a window sill to human and pet foods and they can occasionally be a pest in home pantries.  Historically, such insects were notable pests of dried meats and cheeses in storage. If you’re curious to know more about these and other insects associated with our homes and everyday lives, Richard Jones has an excellent book on the topic: House Guests, House Pests: A Natural Hisotry of Animals of the Home.

A more detailed history of UW-Madison’s Dermestarium can be found here.

   

Insects on the Snow

Despite the season, there’s a surprising number of insects and related arthropods that can be found on the snow during the winter months here in the Midwest.  Such creatures have fascinating life histories and special adaptations (such as natural “antifreeze”or cryoprotectants) that allow them to not only survive, but remain active at low temperatures.  Even these adaptations have limitations and winter insects generally aren’t active if temperatures are below ~20˚F (-7˚C).  Most activity occurs on mild winter days when temps close to or just above freezing.

If you’re curious to learn more about the stories behind these winter creatures and others, I’d encourage you to check out Bernd Heinrich’s Winter World: The Ingenuity of Animal Survival. Read on to learn about some of our commonest “winter” insects in Wisconsin and nearby states:

Snow FleasIf you follow this blog, you might recall the example of snow fleas from two winters ago.  These dark-colored springtails (Collembola) can sometimes be abundant enough to give large swaths of snow a sooty appearance.  Snow fleas can be common on mild winter days and if I’m out cross-country skiing in the Northwoods, I’m often more surprised if I don’t spot any.

Up-Close View of a Snow Flea. Photo Credit: Daniel Tompkins via Wikipedia

Snow FliesOne of the weirdest examples of a “winter” insect would be “snow flies” from the genus Chionea.  Despite their spider-like appearance, snow flies are actually a type of wingless Limoniid crane fly.  Being wingless and generally slow moving might sound like an easy target for predators, but by being active at cold temperatures these insects can actually avoid the many predators that feed upon related flies during the warmer months.  Interestingly, their physiology is so specialized, that these unusual insects can be active between about 20˚F (-7˚C) and 32˚F (0˚C), but if it’s a warm winter day with melting snow it can actually be too hot for them!  If you’d like a more detailed look at these insects, check out J.R. Schock’s article in The Kansas School Naturalist.

Snow fly (Chionea sp.) on the snow in northern Wisconsin. Photo credit: PJ Liesch, UW Insect Diagnostic Lab

Winter Crane FliesI occasionally get reports of “swarming mosquitoes” on winter days, and perhaps you’ve bumped into a cloud of tiny delicate flies out in the snowy woods or on a mild fall or spring day.  What you’ve likely encountered are winter crane flies (Family Trichoceridae).  These delicate flies are related to mosquitoes but have no interest in blood.  The adults are simply trying to mate and the larvae are scavengers.  

A winter crane fly (Family trichoceridae) that landed on the snow. These can be spotted flying on mild fall, winter, and early spring days. Photo credit: PJ Liesch, UW Insect Diagnostic Lab

Snow ScorpionfliesIn my mind, one of the more elusive winter insects is the snow scorpionfly.  Despite having “scorpion” in the name, these aren’t scorpions (or true flies for that matter).  Rather, they belong to a small order of insects (Mecoptera), which includes some bizarre examples, such as the common scorpionflies, hangingflies, and earwigflies.  Like the snow flies, the snow scorpionflies are also flightless and simply wander about on the snow when conditions are right.  In the Midwest, we only have two species from this group Boreus brumalis and Boreus nivoriundus, and both species are associated with mosses.

A snow scorpionfly. Elusive, but fascinating creatures. Photo credit: PJ Liesch, UW Insect Diagnostic Lab.

Aquatic insectsIf you’re near open streams or rivers during the winter months, certain aquatic insects can sometimes emerge and be found on the snow.  Caddisflies and stoneflies are two of the commonest examples.  I recall ice climbing one winter’s night at Governor Dodge State Park west of Madison and reaching the top of a frozen waterfall only to spot dozens of adult “aquatic” insects active on the snow.  The conditions must have been just right that evening, as I also saw hundreds of tiny Cynipid wasps (from oak galls) on the snow as I descended the access trail from the climb.

Caddisfly on the snow near a Northwoods stream. Photo credit: PJ Liesch, UW Insect Diagnostic Lab

SpidersHexapods aren’t the only arthropods getting in on the winter fun.  Species from at least a half-dozen families of spiders can occasionally be spotted on the snow on mild winter days.  They might be pretty lethargic, but it’s still interesting to see creatures like that out-and-about on the snow.  The video clip below shows a spider I spotted on the snow in Northern Wisconsin on New Year’s Eve a few years ago when the air temperature was right around 30˚F (-1˚C).

 

  

Looking back at 2021 at the UW Insect Diagnostic Lab

What a year it’s been. Things seemed like they were getting back to normal this past summer, only for the Omicron variant to pop up and say—not so fast. Despite all the ups-and-downs, services have carried on at the UW Insect Diagnostic Lab in one way or another through the second year of the COVID pandemic. Things have changed a bit and these days I’m on campus much more than a year ago. Throughout the pandemic, demand for services at the IDL has remained high with over 2,400 ID requests in 2021.

Early 2021—The UW Insect Diagnostic Lab was still mostly closed to visitors at the time. Campus services were mostly back to normal by the start of the fall semester on campus. Photo credit: PJ Liesch, UW Insect Diagnostic Lab.

Since COVID first popped up, there have been some subtle shifts in lab statistics—an increase in the percentage of samples solely involving digital images (vs physical specimens) and an overall increase in the proportion of cases coming from the public. Considering the pandemic, this makes sense. Over the last two years, campus buildings and the IDL have been closed to visitors at various points, meaning that clients couldn’t drop off samples. In other cases, it might have been tough to make it to a post office or the UPS store to ship a sample in. Likewise, with many folks working from home, it likely led to more time out in yards and gardens, or visiting local parks or hiking trails—and more time to notice insects.

Looking back at the cases from this last year, 2021 was a unique year due to our unusually hot and dry weather conditions in Wisconsin. Based on data from the Wisconsin State Climatology Office, Madison was quite warm and saw an extra ~500 growing degree days in 2021, but was down about 15 inches of precipitation for the year. Some parts of the state were even hotter and/or drier than Madison and most of the state was categorized as either unusually dry or in some stage of drought during the year [US Drought Monitor].

Drought conditions in Wisconsin as of late December, 2021. It’s been an unusually dry year around the state. Map source: Drought Monitor, UNL.

The weather conditions this year led to some shifts in the insects and related arthropods seen at the UW Insect Diagnostic Lab. A pest that had been relatively quiet the last decade, Lymantria dispar (formerly known as the “gypsy moth”), thrived with the dry conditions this past spring. In “rainy” years, a beneficial fungus (Entomophaga maimaiga) can “kick in” to help keep their numbers in check. If 2022 is another dry year, we could be in store for even more problems from this invasive species. Certain mites also thrived this year and I saw a large number of cases of eriophyid mites causing damage to plants ranging from coneflowers to garlic. Springtails weren’t necessarily more abundant (they feed on decaying plant matter and thrive under damp conditions), but I suspect the hot & dry conditions sent them looking for any place darker, damper, and cooler.  This led to lots of reports as they were trying to invade structures.

We’ll likely continue to see the impacts of the 2021 drought for some time.  Plants, including established trees and shrubs, also suffered from the drought and this will likely lead to an increase in reports of “secondary” insect pests in the next few years. Certain insects can be generally “well behaved” and leave healthy plants alone, only to attack stressed and weakened plants.  As an example, cases of the two-lined chestnut borer (a notable pest of oaks) often increase 1-3 years after a drought, and I’m expecting to see more cases in the coming years.

In the realm of medical entomology, it was a good year for ticks both in Wisconsin and other parts of the US. Black flies (Family Simuliidae) had another strong year in many parts of the state, although calls about these were shifted a bit earlier than in previous years (likely due to an “early” spring). If there’s a silver lining to the drought, it’s that mosquito pressure was down in Wisconsin for much of the summer. As we received a bit more rain in the latter half of summer we saw some late season activity, but disease pressure remained low (only three  West Nile Virus cases in Wisconsin, compared to 50+ in a “bad” year). As recreational and work-related travel increased a bit more in 2021 compared to 2020, I did see an uptick in reports of bed bugs.

With the Asian giant hornet garnering attention in the news for the second year in a row, I continued to see lots of reports of cicada killer wasps, pigeon horntails, great golden digger wasps, and other large insects.  Unfortunately, with the sensationalized hype about “murder hornets” (ahem—New York Times…) I had plenty of reports of other large harmless insects that were killed simply because they “looked big and scary” (one particular photo of a tomentose burying beetle comes to mind…).  Overall, the Asian giant hornet story was really pretty quiet this year, with a limited amount of activity in a small part of the Pacific Northwest.  As of December 2021, the Asian giant hornet has not been found in Wisconsin or anywhere close to us.

Insects like the pigeon horntail (Tremex columba) may be large (as far as insects go), but are completely harmless to humans. I saw plenty of cases where members of the public contacted me after killing such insects simply because they looked “big and scary”.  When publishers such as the New York Times use sensationalized language (i.e., “murder hornet”) there are plenty of negative impacts. Photo credit: PJ Liesch, UW Insect Diagnostic Lab.

I had plenty of reports of social wasps (yellowjackets, bald-faced hornets, and paper wasps) as well as bumble bees this year—including three reports of the endangered rusty-patched bumble bee in the same week in early August! We missed the Brood X “cicada craze” here in Wisconsin, but I still had plenty of questions about them from reporters. We will, however, see some periodical cicadas (Brood XIII) in 2024 in southern Wisconsin.

Some other IDL case highlights from 2021 include:
-An explosion of hackberry emperor butterflies in late spring in south central Wisconsin
-More black witch moths than I’ve ever seen before in a single year (over a dozen sightings!)
-First specimens of the invasive Asiatic garden beetle collected in Wisconsin
-An influx of fall armyworms in late summer, and finally
-Unexpected (live) European insect imported in a Jeep

Every year is a bit different here at the UW Insect Diagnostic Lab and 2021 was no exception.  I’ll be curious to see what 2022 has in store for insects in Wisconsin!

—PJ Liesch
Director of the University of Wisconsin Insect Diagnostic Lab

Hackberry Emperor Butterflies Take the Stage in Wisconsin

Wisconsin is home to roughly 150 species of butterflies. Some of these, like monarchs (Danaus plexippus), are well-known and easily recognizable. Other species can be more subtle in appearance (such as the “skippers”) or may not be particularly abundant. Nonetheless, we occasionally see localized “booms” of certain butterfly species from time to time. This year, the hackberry emperor butterfly (Asterocampa celtis) has taken the stage in some parts of the state.

Hackberry emperor butterfly with wings spread
Hackberry emperor butterfly. Photo credit, Richard Crook via Flickr.

In the last month, I’ve had more reports of hackberry emperor butterflies at the UW Insect Diagnostic Lab than any other butterfly species. These reports have primarily come in from southcentral and southwestern Wisconsin. In some cases, hackberry emperors have been spotted by the thousands as they covered rural roads or transformed backyards into temporary live butterfly exhibits.  Hackberry emperors primarily occur in southern parts of the state where the food plant of the caterpillars (hackberry trees) can be abundant; they’re also known from parts of central and west central Wisconsin.

Hackberry emperors are mid-to-large sized butterflies with a wingspan of approximately 2 inches. Their brownish-orange and black wings are somewhat similar to certain other butterflies (such as the “Satyrs”), which can make identifying them a bit more challenging to the uninitiated. Luckily, there’s a distinctive row of black spots on the wings—one distinctive spot on the topside of each forewing and seven slightly smaller spots on each hindwing. When the undersides of the wings are viewed (such as when the wings are folded upwards at rest), these black spots are bordered with a bit of yellow, giving them an “eyespot” appearance.  A close relative and look-alike, the tawny emperor (Asterocampa clyton), lacks the large black spot on each forewing.

Hackberry emperor butterfly with wings folded at rest
Hackberry emperor butterfly lapping salt. Photo Credit: Judy Gallagher via Wikipedia.

Adults butterflies often serve as pollinators when they visit flowers for nectar, but hackberry emperors have slightly different behaviors.  They prefer to head to oozing tree wounds for sap or decaying plant materials in compost piles. They’re also fond of salts and can readily be spotted at puddles (a phenomenon simply known as “puddling”), at dung or carrion, lapping sweat from humans, or on roadways.

Hackberry emperor butterflies on a rural road
Thousands of hackberry emperor butterflies were recently spotted on roadways in southwestern Wisconsin. Photo Credit: Jay Watson, WI-DNR. [Photo used with permission]
After overwintering as partially-grown caterpillars, hackberry emperors complete their development in late spring with two broods (batches of adults) in southern Wisconsin.  We see the first batch of adults in June, with the other in August, so we may see more of this species later this summer. If you’re located in southern Wisconsin, keep an eye out for these abundant butterflies in 2021.

In Defense of Ground Bees

“Ground bee” season is officially here, but before we get any further, let’s clear up a few things about these insects.  Ground-nesting bees get a lot of undeserved blame for stings that they simply aren’t responsible for.  Despite their claims, many folks have probably never been stung by an actual “ground bee”.  Every year I get plenty of calls about “angry stinging ground bees” in late summer, but these are almost always ground-nesting yellowjackets (Vespula spp.).  Undoubtedly, if you stumble into an in-ground yellowjacket nest, you’ll be forced to make a hasty retreat from the area as the colony defends itself.  But those aren’t bees

Entrance of a ground-nesting yellowjacket nest in late summer. These might be black and yellow, but they aren’t bees… Photo credit: Jeff Hahn, U. Minnesota.

While yellowjackets and bees are related (both belong to the insect order Hymenoptera along with the ants and sawflies), they belong to completely different families.  From a standpoint of taxonomic classification,  mixing up yellowjackets and bees would be like confusing dogs for cats, raccoons, or walruses (all belong to separate families within the mammalian order Carnivora).  We do technically have social, ground-nesting bees that can be ornery if disturbed (i.e., bumble bees), but folks generally recognize bumble bees by their large size and robust appearance.  

A solitary ground nesting bee guarding the entrance to its nest in a city park in Middleton, WI. Photo credit: PJ Liesch, UW Entomology.

So what about these other “ground bees”?  Most bees (about 2/3 of all bees) are actually ground-nesting species.  In the Midwest, we’ve got around 500 different bee species, meaning there are hundreds of ground-nesting species around us.  Our common ground-nesting bees include species of: cellophane bees, mining bees, squash bees, longhorned bees, sweat bees, and others. For the most part, these ground-nesting bees are solitary creatures that live alone, although many nests can occur in the same general area as shown in the video clip below.  They often prefer sunny, open areas with thin ground cover or bare, sandy soil and can be common in parks and home lawns.  

To a certain extent, solitary bees can be thought of as the insect equivalent of “preppers”.  Each bee digs her own nest—a small, bunker-like tunnel in the ground, which looks like an ant hill.  Not only do the females have to construct these shelters, but she has to gather all of the provisions needed for her young to survive inside—often in the matter of just a few weeks.  The female bees collect pollen and nectar from flowers to create a nutritious substance called bee bread, which they place into small chambers (cells) and lay an egg.  Once the eggs hatch, the young bees (larvae) have all the supplies they’ll need to grow and develop in their survival bunkers.  

Most of these ground bees have a single generation per year.  The adult bees are out and active for a short period of time (often a few weeks), before they’re done and gone for the year.  When they are active, our solitary bees can be excellent pollinators and can be more efficient than honey bees in some regards.  However, their pollination services often go unrecognized and unappreciated by the general public.  While news articles regularly sound the alarm about honey bee declines, we should really be much more concerned about the potential loss of our solitary bee species, as they’re more sensitive to disturbances, pesticides, and other stressors.

Post-jog entomologist next to five solitary bee nests. These bees are extremely gentle and unlikely to sting. This portion of a local park had thousands of solitary bees flying around. Photo credit: PJ Liesch, UW Entomology.

If you spot ground bees this time of the year, is there any reason for concern? No. Solitary ground-nesting bees are great to have around.  Being solitary nesters, these ground bees don’t have a large colony of  adult relatives to defend and they end up being surprisingly gentle and unlikely to sting.  Overall, they pose little risk to people or pets.  The best thing to do is to simply let them be and appreciate the pollination services they provide. 

If you’d like to learn more about Wisconsin’s bees, check on the Wisconsin Bee Identification Guide or the US Forest Service’s Bee Basics: An Introduction to Our Native Bees. If you have solitary ground-nesting bees in your yard and would like to teach others about these amazing pollinators,  click the image below to get a  sign to laminate and post:

A yard sign about wild bees

Brood X Cicadas in the Midwest?

Will we see Brood X cicadas in Wisconsin or the upper Midwest this year? Read on to find out: Cicadas—they’re all over the news and soon to be out by the billions. All this buzz is about periodical cicadas, a group of species from the genus Magicicada which emerge once every 17 years (or every 13 years in some cases). Periodical cicadas are only found in the eastern United States and vary by location and the timing of their activity. To help categorize these insects, entomologists refer to each cohort of cicadas as a “brood” and have numbered them with Roman numerals. This year’s cicadas are referred to as Brood X (i.e., Brood ten) and last emerged in 2004.

Two periodical cicadas on a rock
Brood XIII periodical cicadas in Lake Forest, IL in June of 2007. Photo Credit: Janet and Phil via Flickr (CC).

Periodical cicadas are amongst the longest lived insects and their long life span and massive emergences are believed to be a survival strategy—by overwhelming predators with sheer numbers, they simply can’t all be eaten. But the wait for their appearance is a long one.  Periodical cicadas spend 17 years below ground as juveniles (nymphs) feeding on the sap from tree roots, before making their way above ground. Their emergence is associated with soil temperatures, and when the soil has warmed to 64˚F, they emerge. This corresponds to parts of April, May, or June depending on the location on the map. Once they make their way above ground, the cicadas molt and transform into adults.  Shortly thereafter, a raucous mating free-for-all commences. After mating, the females cut small slits into twigs of trees to deposit their eggs. The eggs hatch and the juveniles head to the soil for their lengthy development. Periodical cicadas don’t live long as adults (a matter of weeks), so it’s a long build up to a noisy grand finale.

Ground covered by periodical cicadas
Ground covered by periodical cicadas. When these insects emerge, it can be by the billions! Photo credit: James St. John, via Wikipedia (CC).

With all the attention in the news, many Wisconsinites and other Midwesterners are wondering if they’ll be able to see or hear Brood X cicadas in their area this year. For Wisconsin, Minnesota, Iowa, and most of Michigan and Illinois the answer is noalthough they aren’t terribly far away either. Brood X cicadas can be found in over a dozen eastern states, but primarily emerge in three main pockets:

  1. Indiana, Ohio and nearby slivers of eastern Illinois and southern Michigan
  2. Southern Pennsylvania and parts of nearby Delaware, Maryland, Virginia, New Jersey, and New York
  3. Eastern Tennessee and nearby parts of North Carolina and Georgia
Periodical Cicada Brood Map from US Forest Service
Map of active periodical cicada broods of the United States. Map credit: USDA Forest Service. Click map for full size version and additional information.

While we won’t see Brood X cicadas here in Wisconsin, we will see other periodical cicadas in the not so distant future. Wisconsin is home to Brood XIII cicadas, which last emerged in 2007, meaning that the next big emergence in the Badger State is only a few years off in 2024. In the meantime, we’ll still see and hear plenty of our typical “dog day” cicadas during the warm days of summer.  To learn more about Brood XIII cicadas in Wisconsin, check out this post from last year.

Riding the Wind: Storms Transport Rare Moths to Midwest

The largest moths you’ll likely encounter in the northern United States are the giant silk moths (Family Saturniidae).  We have a handful of species in the Upper Midwest which can be encountered with some regularity during the summer months: cecropia moths, polyphemus moths, luna moths, promethea moths, and imperial moths.  True to their name, the giant silk moths don’t skimp on size—they generally have wingspans in the range of 3 – 6 inches, depending on the species.  These moths are native to our area and the impressively large caterpillars feed on the leaves of various hardwood trees.

An adult polyphemus moth (Antheraea polyphemus) resting on a tree trunk in northern Wisconsin. Photo credit: PJ Liesch, UW Insect Diagnostic Lab.

Finding an adult giant silk moth or one of the caterpillars is always a special occasion.  However, there’s an even more impressive large moth, which occasionally pops up in our area—the Black Witch (Ascalapha odorata).  The black witch has a wingspan of around 6 inches and can often be mistaken for a bat due to its dark colour.  This tropical species doesn’t natively occur in our area and originates in parts of South America and Central America.  However, the adult moths are somewhat regular “strays” and find their way as far north as parts of Canada.  Still, black witches aren’t common in Wisconsin (or the US in general), and I typically only hear of a few reports in the state each year.

An impressive cecropia moth caterpillar (Hyalophora cecropia). Photo Credit: Judy Gallagher via Wikipedia.

Wind plays an important role in the movement of black witches from their native habitat.  One report even documented an adult black witch traveling with a strong westerly wind to an island in the south Atlantic—a distance of over 2,000 miles from South America.  In the upper Midwest, dips in the jet stream and storm systems can play an important role.  Since starting at the UW Insect Diagnostic Lab in 2014, I’ve seen several cases where black witches are spotted in late summer after hurricanes have hit the Gulf Coast states.  Along these lines, hundreds of black witch moths arrived in Texas as Hurricane Claudette passed through in 2003.  Following such an intense journey, the moths are often damaged, with tattered wings or other injuries.  Surprisingly, some moths seem to arrive in nearly pristine condition, like this beautiful specimen spotted in Door County last month shortly after hurricane Sally made landfall.

An adult female black witch (Ascalapha odorata) moth, which was spotted in a warehouse in Door County, Wisconsin in September of 2020. The moth is in surprisingly good condition for having been transported several thousand miles in a short period of time. Credit: photo submitted to the UW Insect Diagnostic Lab.

If you do ever spot a black witch, consider yourself lucky.  If you’re extremely lucky, you might even spot one of the rarest moths that strays to the Midwest—the “owl moth” (Thysania zenobia)—another large moth which has only ever been spotted in Wisconsin a few times and is much rarer than the elusive black witch.

Great Golden Digger Wasp: Another Asian Giant Hornet Look-Alike

With the media craze about “murder hornets” this past spring, I’ve seen a definite increase in reports of Asian giant hornet look-alikes at the UW Insect Diagnostic Lab this summer.  Many folks recognize the commonest look-alike in the Midwest, the eastern cicada killer (Sphecius speciosus), which becomes active in July around the time that their prey (cicadas) start emerging.  Another look-alike is one that you might not have bumped into before—the great golden digger wasp (Sphex ichneumoneus).  Similar to Asian giant hornets, great golden digger wasps are large and nest in the ground, which are reasons why they may be mistaken for the former.

If you haven’t spotted one before, great golden digger wasps can be a bit intimidating in appearance as they can easily be over an inch long.  However, their anatomy and appearance are quite different compared to Asian giant hornets.  Great golden digger wasps are mostly black with a rusty-reddish color at the base of the gaster (“abdomen”).  Their legs are the same reddish color and the black thorax and head possess fine golden setae or “hairs” (hence “golden” in their name).  In contrast, Asian giant hornets have distinctive black and yellow stripes on their gaster and a vibrant yellowish-orange head.  Great golden digger wasps belong to the “thread-waisted” wasp family (Family Sphecidae) and have a long, slender petiole (“waist”).  This isn’t as thin and narrow as the “waist” of the related black and yellow mud dauber (Sceliphron caementarium), but still is quite noticeable when viewed from the side.

Great golden digger wasp
Great golden digger wasp (Sphex ichneumoneus); note the slender petiole or “waist”. Photo credit: Judy Gallagher, via Wikipedia.

In terms of their biology, both Asian giant hornets and great golden digger wasps do nest in the ground, but the similarities end there.  The Asian giant hornet is really quite similar to our ground-nesting yellowjackets in terms of their nesting behavior.  These are social creatures which start nests from scratch in spring and build up in size over the course of the warmer months.  Colonies ultimately die out in fall except for the “new” queens which overwinter.  With a large colony of relatives to defend, social wasps can be defensive, especially when colonies are at peak size.

In contrast, great golden digger wasps are solitary ground nesters.  Without a large colony of relatives to defend, they’re usually non-aggressive and very unlikely to sting.  Stings are only likely if one were to pick one up bare-handed—in which case you might be asking for it!  Similar to cicada killer wasps, each female great golden digger wasps excavates small tunnels in sandy soil and provisions them with prey for their young to feed on.  In the case of the great golden digger wasp, prey consists of katydids, crickets, and relatives from the “grasshopper” group (Order Orthoptera).  Rather than kill outright, the females inject their prey with a paralytic “cocktail” to keep them alive and fresh for their young to feed on—what a way to go!  In addition to hunting katydids, adult great golden digger wasps visit flowers and can be beneficial pollinators.

Great golden digger wasp on flower
Great golden digger wasp (Sphex ichneumoneus) drinking nectar from a flower. Photo credit: Roy Niswanger, via Flickr.

Because they’re unlikely to sting humans, controlling great golden digger wasps is rarely justified and these magnificent creatures can simply be admired.  Ultimately, these wasps are strongly associated with sandy soil, so if you see them in your yard every year and would prefer to not have them around, modifying the landscaping may be a long-term option to dissuade them from an area.


Author’s note: As of August 2020, Asian giant hornets have not been found in Wisconsin or anywhere in the Midwest.  In North America, these insects are only known from far northwestern Washington state and nearby parts of British Columbia. 

See this earlier post for additional details on the Asian giant hornet.

Some Insects Don’t Understand Social Distancing

In the grand scheme of things, most insects (and spiders) are loners.  Perhaps they set a good example for us in 2020 with their social distancing.

Of course, insects have to find a mate to reproduce at some point in their lives*, but out of the 1 million+ described insect species, being truly “social” isn’t the norm.  There certainly are some well-known examples of insects that are eusociali.e., they live together as a colony.  Examples include ants, certain types of wasps (such as yellowjackets and paper wasps), some bees, termites, and a few other interesting examples.  However, there are many insects that are much more solitary in their habits.  If you think of our bees in the Great Lakes region, we have roughly 500 species.  Other than honey bees, bumble bees and a few others, the vast majority of these species are solitary creatures with each female doing her own thing.

Two herds of Cerastipsocus venosus barklice. Photo submitted to UW Insect Diagnostic Lab.

Interestingly, there’s a quirky insect that can be commonly encountered this time of the year and it missed the memo on social distancing.  I’m referring to an interesting species of barklouse (Order Psocodea): Cerastipsocus venosusBarklice are relatives of true lice (e.g., head lice and pubic lice) but they’re really quite harmless to humans and tend to be scavengers.  Barklice make up an obscure group of insects and many entomology students simply identify them to “order” level as this group can be challenging to narrow down further to family, genus, or species.

Group of Cerastipsocus venosus juveniles. Note the striped abdomens which make them easy to identify. Photo submitted to UW Insect Diagnostic Lab.iny

If you haven’t encountered Cerastipsocus venosus (aka “tree cattle”) before, it might catch you off guard to find a group (formally known as a “herd”) of these small insects hanging out together on the bark of a tree or a rock in your yard.  The tiny juveniles are particularly striking with yellow stripes on their abdomens.  The adults are larger (up to 1/4″ long) and possess black wings.

A Cerastipsocus venosus adult. Note the black wings, which are only found in the adults. Photo submitted to UW Insect Diagnostic Lab.

Rest assured, these barklice pose no threat to trees or other plants in our yard and these native insects simply nibble on lichens, and pieces of dead tree bark.  Every year I get many reports of these insects in mid- and late- summer at the UW Insect Diagnostic Lab and there’s no need to spray or do anything about these if you spot them in your yard.  These barklice don’t seem to stay in the same place for very long, so perhaps their herds just move along looking for greener pastures.


*Some insects are able to reproduce asexually, and don’t technically have to find a mate…