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.
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.
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.
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.
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 eusocial—i.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.
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 venosus. Barklice 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.
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.
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…
Perhaps you’ve heard some buzz about periodical cicadas (Magicicada spp.) lately. These insects resemble our typical “dog day” cicadas, which we see in mid-to-late summer in Wisconsin, but they are orange and black with vibrant reddish eyes instead of a dull greenish color. Parts of the US are currently seeing mass emergences of periodical cicadas, which appear by the millions every 13 or 17 years depending on the species. I’ve had a number of questions this last month asking if this was “the year” for us to see them in Wisconsin, but it’s not time for the big show…yet.
Periodical cicadas are sorted into cohorts known as “broods”, which occur in particular geographic areas and emerge at specific points in time. For the most part, these insects are excellent timekeepers and some broods have been documented as far back as the 1600’s in the eastern US. There are entire websites and apps dedicated to these insects and their schedules, and scientists have labelled broods with Roman numerals to help differentiate the cohorts.
With all the broods out there, some parts of the US do see these cohorts overlap in space, but these can be separated by the years in which they emerge. In Wisconsin, the situation is fairly straightforward as we only see a single brood: Brood XIII. Brood XIII’s 17-year cicadas last emerged in 2007, meaning that we’ve got four more years to wait until their mass emergence in 2024.
Interestingly, I’ve received a number of photos and reports of periodical cicadas in Wisconsin over the last month or so. I’ve had several confirmed reports from the Lake Geneva area (Walworth County) a confirmed report from southeastern Dane County, and a suspected report from Sauk County. While most periodical cicadas stick to the schedule, occasionally some of these insects veer off course. These out-of-sync individuals are referred to as “stragglers” and it turns out that Brood XIII has a history of these stragglers. In the late 1960’s, large numbers of stragglers were documented in the Chicago area. Likewise, many of the Chicago suburbs are seeing a similar phenomenon this year. With that said, we did technically see some periodical cicadas this year, but we’ll have to wait a few more years before the real “fireworks”.
Fleas (Order Siphonaptera) can be an unwanted surprise—no one wants fleas on their pets or in their house. Our commonest flea on both cats and dogs in the Midwest is the “cat flea” (Ctenocephalidesfelis), and this same species can also live on a wide range of wild animals. Cat fleas may be annoying but can be controlled with a diligent multi-pronged approach: chatting with your veterinarian to pick a proper treatment for your pet and regular and thorough vacuuming. In heavy infestations, carpets and furniture may also need to be treated. While fleas could be encountered anytime of the year, I see the vast majority of flea cases at the UW Insect Diagnostic Lab in late spring and summer. In contrast, cases of fleas are few and far between during the winter months due to the dry conditions and lower temperatures which can be hard on these insects.
There is one type of “flea”, however, that I see regularly through the winter months—the “snow flea”. Snow fleas (Hypogastruranivicola and close relatives) aren’t actual fleas and rather than a pest, these harmless creatures are a beneficial curiosity. Their cold tolerance and ability to launch themselves into the air account for their nickname.
The snow fleas we’re talking about technically aren’t even insects and belong to a closely related group of arthropods known as springtails (Collembola). Springtails get their name from the furcula—an anatomical structure on the underside of their bodies, which springs downwards to catapult them up into the air. Springtails can’t “jump” very far by human standards given their tiny size (less than a tenth of an inch long), yet they can easily launch themselves many times their own body length in a mere blink of an eye (video).
The snow flea is unusual for springtails (and most arthropods) in the fact that these creatures can remain quite active during the winter months. As discussed in this post from last March, insects and other arthropods have a variety of strategies to make it through winter, ranging from migration to freezing solid in some cases. The vast majority of arthropods are inactive during winter, but some, like the snow flea, seem perfectly content wandering out on the snow. With their tiny size and dark grayish bodies, snow fleas can almost look as if someone had dumped out a pepper shaker on the snow.
Their ability to remain active at frigid temperatures is due to the concentration of specific proteins in their bodies, which serve as a cryoprotectant or natural “antifreeze”. During the rest of the year, these creatures simply blend in amongst fallen leaves where they scavenge upon decaying materials and help with nutrient recycling.
These creatures are truly a winter curiosity if you haven’t encountered them before. The next time you’re out snowshoeing or cross-country skiing, keep an eye out for these tiny acrobats on the snow.
Final Note: Overseas, our friends in the UK have different creatures they refer to as snowfleas—insects from the genus Boreus, which we’d call “snow scorpionflies” in our area.
Despite being winter, Wisconsin has recently been in the news because of insects—blister beetles—and their potentially deadly impacts on horses. In addition to their medical significance, these insects have a long and interesting story with some surprising twists.
Blister beetles comprise a diverse family of insects (Family Meloidae), with over 3,000 species known from around the globe. In the Unites States, we’ve got approximately 400 species, with the bulk of the diversity centered in the dry southwestern part of the country. However, this group is widely distributed across the lower 48 states, with nearly 30 species known from Wisconsin alone.
The common blister beetles species of the Upper Midwest are oblong and typically range from ½-inch to ¾-inch long, although other species can vary in size. Unlike the stereotypical “crunch” of most other beetles—think of accidentally stepping on a May/June beetle—blister beetles have softer bodies and are similar to fireflies in this regard. A few of our Midwestern species are striped or brightly colored, but many common species are dark-colored, being mostly black, grey, or a dark metallic green.
But don’t let their drab appearance fool you. Blister beetles wield a potent defensive toxin—cantharidin. In adult blister beetles, this compound is produced by males, which provide it to females during courtship. Females then use it to chemically protect their eggs.
The properties of cantharidin are well-known, and this chemical irritant and its coleopteran source have a surprising history dating back thousands of years. For example, Pliny the Elder knew of the toxic effects and mentioned blister beetles in his writings. Old medical reference books list a number of potential uses for cantharidin, ranging from the treatment of skin conditions to a supposed remedy for baldness. However, cantharidin might have harmed more than it helped. Dermal exposure has long been known to cause irritation and blistering—hence the common name of “blister beetles”. If ingested, symptoms can be much more serious: severe irritation of the gastrointestinal and urinary tracts, kidney and heart damage, and a cascade of other undesirable effects. Human deaths have been recorded in the medical literature and in a recent report, a soldier consumed a single blister beetle on a dare and ended up hospitalized with acute kidney injury.
Surprisingly, cantharidin was also historically deployed as an aphrodisiac—Spanish fly. In the days before the little blue pill, Spanish fly was known for its ability to irritate the urethral lining to produce a “stimulating” effect. In one historical report, French Legionnaires in North Africa complained of priapism after feasting upon frogs that had happened to eat blister beetles (frogs seem to be unaffected by cantharidin).
Humans aren’t the only creatures affected by blister beetles and horses are especially sensitive. Ingestion of only a few grams of cantharidin can potentially be lethal to an adult horse. Blister beetle poisoning is rare in equines, but can occur if the adult beetles happen to be in an alfalfa field feeding on blossoms at the time of harvest and are crushed by farm equipment. In an unfortunate situation, blister beetles have recently been reported in connection with the deaths of over a dozen horses in Mauston, Wisconsin.
Blister beetles have another noteworthy Wisconsin connection from the history books. The former governor of Wisconsin, Robert “Fighting Bob” La Follette, was well-known for his progressive politics as well as an impressive head of hair. His secret?—a hair tonic containing cologne, oils of English lavender and rosemary, and a cantharidin-containing tincture made from blister beetles.
Elongate hemlock scale attacks over 40 species of conifers—especially hemlocks which can be common throughout the Appalachian Mountains, and Fraser firs and balsam firs, which are commonly grown as Christmas trees. Certain types of spruces and pines can also be attacked. Established populations of elongate hemlock scale are not known from Wisconsin, but a recent detection of this pest in the state raises concerns for Christmas tree growers, the plant nursery industry, tree care professionals, and homeowners with conifer trees in their yards. Forested areas are also at risk, meaning the stakes are potentially high with this insect.
While insect activity is quiet in the Midwest this time of the year, we’re hearing about the elongate hemlock scale now due to its Christmas connection. Similar to 2018, the Wisconsin Department of Agriculture, Trade and Consumer Protection recently found that fir Christmas trees, wreaths, and other holiday decorations infested with EHS had been shipped to Wisconsin from North Carolina. The picturesque Blue Ridge Mountains of western North Carolina provide ideal habitat for Fraser firs—one of the most popular species of Christmas trees. North Carolina grows approximately a quarter of all the Christmas trees sold in the US each year and with elongate hemlock scale established in that state, it increases the risk of movement of this invasive insect around the country.
Elongate hemlock scales look unusual as far as insects go. These insects have traded mobility for defense—they hunker down on plants and produce a waxy coating which helps protect them from predators and parasites. As a result, elongate hemlock scales aren’t easily recognizable as insects since the usual signs of segmentation—body regions, legs, antennae—are not readily visible. Instead, these insects have a vague, oblong appearance. Adult females are small (just under 1/10th of an inch long) and are covered with a waxy brownish coating. They are typically found on the undersides of needles. Males are slightly smaller and develop beneath pale whitish coverings. Mature males do emerge with wings but are weak fliers and travel short distances to mate with the wingless, immobile females.
Under their protective coatings, these insects use needle-like mouthparts to suck fluids from plants. With their small size, damage occurs when large numbers of individuals infest plants. Their waxy coverings also limit the effectiveness of insecticides, making EHS a challenging pest to control if they become established.
Because elongate hemlock scale has been detected in Wisconsin this year in Christmas trees and other holiday decorations, a key objective at this point is to prevent this insect from getting a foothold in the state. By all means, continue to enjoy your holiday decorations, but when you’re ready to remove these materials, take the following steps to help prevent this insect from becoming established in Wisconsin:
1) If your Christmas tree or natural wreaths, garlands, or other decorations are from a local Christmas tree farm or elsewhere in Wisconsin, no special precautions are needed for elongate hemlock scale. Because EHS is not established in the state, these materials can be removed as usual at the end of the holiday season.
2) If your Christmas tree or natural wreaths, garlands, or other decorations are from a big box store, grocery store, or similar vendor, or if you are not sure of the origins of these materials, it is advised to check these materials for signs of elongate hemlock scale (i.e., brown spots on the undersides of needles). The Wisconsin Department of Agriculture, Trade, and Consumer Protection is advising that infested or suspect materials preferably be burned (check with the DNR for any burning restrictions in your area). Alternatively, such materials could be bagged and discarded as waste. Infested or suspect materials should not be composted or used for wildlife habitat in your yard.
For additional information on elongate hemlock scale, visit the WI-DATCP EHS page and the recent press release about the 2019 EHS detection.
“I think I’ve found a kissing bug and wanted to report it” is a surprisingly common line I get at the UW Insect Diagnostic Lab.
I’ve previously written about kissing bugs, but to quickly recap: these are blood-feeding assassin bugs found primarily in South and Central America. Kissing bugs tend to be associated with vertebrate nests outdoors but can bite humans and can also carry Trypanosoma cruzi—a parasite that causes Chagas disease. Due to this concern, I see a spike in website traffic and “reports” of suspected kissing bugs just about any time there’s national news coverage of these insects. While many kissing bug species exist, the vast majority are restricted to tropical and subtropical areas. The northernmost species—the eastern conenose kissing bug (Triatomasanguisuga)—ranges from Latin America as far north as southern Illinois.
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.
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.
Adult masked hunter bugs are slender, roughly ¾” long, and entirely dark coloured. They have long, thin legs & antennae and stout beak-like mouthparts which they use to feed on insects and other arthropod prey. Several key features help distinguish masked hunter bugs from eastern conenose kissing bugs:
Masked hunter bugs are entirely dark while eastern conenose kissing bugs have red on their body
Masked hunter bugs lack the projecting “conenose” present on the head of kissing bugs
Masked hunter bugs have a bulging, “muscular” appearance of their prothorax (trapezoidal region behind the head) when viewed under magnification
Masked hunter bugs have stout beak-like mouthparts while kissing bugs have long, slender mouthparts when viewed under magnification
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/
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 crimes—but 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.
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.
During the winter months, I often get reports of intimidating-looking, but harmless and quirky wasp-like creatures known as “wood wasps” (Family Xiphydriidae). What makes them quirky?—They’re basically the bobbleheads of the insect world, which always reminds me of going to baseball games as a kid.
Having “wasp” in the name can evoke a certain amount of anxiety, and you can already guess that wood wasps are related to the yellowjackets and paperwasps of late summer. However, the wood wasps belong to an early branch within ant/bee/wasp group (the Order Hymenoptera) and lack the anatomical structures and ability to sting.
Wood wasps have a distinct appearance, so once you’ve trained your eye, they’ll be hard to miss the next time around. These insects tend to be about an inch long with slender, dark-colored bodies and orange legs. There are often some pale stripes or patches on or just behind the head and in some cases the tips of the antennae can be pale as well. The most diagnostic feature gives wood wasps their bobblehead status in my book—the bulbous head of these insects is attached by a scrawny “neck” when viewed from the side. You can even imagine it bobbing back and forth, if only a tiny spring were attached.
You might ask yourself, how are these insect bobbleheads active in winter when most other insects are scarce? The answer boils down to firewood. The pale, grub-like larvae of wood wasps live in the wood of dead or dying trees. When these trees are chopped into firewood, we end up hand-carrying the insects into our cozy winter abode. If the wood isn’t used in the fireplace right away, the larvae take advantage of the spring-like conditions and transform into active adults indoors. To those unfamiliar with wood wasps, you can scratch your head for days trying to find the source, but once you recognize them and their origins, moving the firewood to a colder location is the simple fix.
We’re all familiar with phenology—that regular progression of plant and animal life through the seasons—to a certain extent. We might not stop to think about it in detail, but we recognize the crabapples blooming in spring, the fireflies lighting up the nighttime sky in June and July, and the southward flying geese and rutting deer in fall. When you think of the 25,000+ insects in the Great Lakes Region, there’s a rich diversity of seasonal patterns to pick up on. Some insect patterns, like cicadas, katydids, and tree crickets calling during the summer months, are hard to miss—although it can be challenging to decipher exactly who’s making that racket (Hint: here’s your translator). Others are much harder to pick up on unless you’ve been briefed on the subtle clues. For example, take the tiny foreign grain beetle (Ahasverus advena) which conspicuously pops up in unexpected places in August, September, and October.
To the naked eye, these tiny (1/16 inch long) brownish insects can be a bit tricky to see and it’s hard to tell if they’re beetles, ants, or something else. Even to budding entomology students pushing the boundaries of what they can interpret under the microscope, foreign grain beetles and relatives might be jokingly referred to as “little brown nothings” and passed over for easier-to-identify specimens.
Around the UW Insect Diagnostic Lab, foreign grain beetles are one of my favorite samples when they arrive in late summer and early fall as they give me the faintest sensation of what it must feel like to be Sherlock Holmes. Picture a client coming in with a Ziploc bag of tiny brown insects. After a cursory glance and before the specimens even make it under the microscope, I ask, “are you in a new home by any chance?” The standard reply is often along the lines of, “Well, yes—but how did you know?” A quick check under the microscope and the specimen’s identity is confirmed. It’s elementary, my dear Watson.
How is there such a reliable association with an unexpected source: newly constructed homes, where intuition wouldn’t have you expecting insects? The secret to this seasonal pattern lies in understanding the biology of the foreign grain beetle and its relatives. These insects love to feed on fungal spores—often in musty stored grains on farms. It turns out that during the construction of a new home, residual dampness in construction lumber, plaster, sawdust, and other materials can lead to the growth of a trivial amount of mold. Like vultures to carrion, these beetles fly in looking for a fungal smorgasbord. Eggs are laid and entire life cycles can be carried out in the wall void of a new home after the drywall, insulation, and siding are put up.
Fast-forward to late summer and just like clockwork the proud new homeowners suddenly have hundreds of tiny brown beetles crawling out through nooks and crannies, causing immediate dismay. While this can be alarming, these insects are harmless to people, pets, and the home, and are simply a temporary nuisance. As the construction materials lose that lingering moisture, conditions become unfavorable for the beetles and activity drops off over time. Pesticides often aren’t needed as the beetles already face an inevitable demise. Vacuuming or sweeping them up and running a dehumidifier are often the remedy in fall until the dryness of winter puts a final end to the beetle activity.