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.
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.
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.
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.
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”.
Does the COVID-19 situation have you cooped up at home? If so, you’re not alone during these unusual times. With the shift towards working from home, folks are spending more time in their own yards and gardens as well as nearby parks and nature trails. Spending time out in nature can have notable health benefits, but it also gives us a great opportunity to observe the creatures around us—including insects, such as butterflies.
In Wisconsin and the Upper Midwest, summer may be “peak” butterfly season, but a number of species can be active early in the year. These creatures might brighten your day during these tough times, and this guide will help you identify five of the commonest spring butterfly species in the Upper Midwest:
Mourning Cloak (Nymphalisantiopa):
This butterfly is often the first one seen in spring. It’s an easy species to identify given its large size (3-4 inch wingspan) and colors on the upper wing surface—dark wings bordered with a row of small blue spots and pale edges. Mourning cloaks overwinter as adult butterflies amongst leaf litter or in other sheltered spots, so as soon as it’s warm enough they can become active. This butterfly can catch people off guard if they fly while snow remains on the ground. In early spring when flowers haven’t bloomed yet, mourning cloak butterflies are fond of visiting the sap flows on trees caused by the activity of the yellow-bellied sapsucker.
Eastern Comma (Polygonia comma):
Like the mourning cloak, eastern commas overwinter as adult butterflies, so they’re ready to go as temperatures creep upwards. Eastern commas have a wingspan of approximately 2 inches. When spread, the wings are mostly orange with black spots and borders. The edges of the wings also have a “wavy” or “scalloped” appearance. The most distinguishing feature can be seen on the undersides of the wings when folded upwards: a small pale curved mark in the shape of a comma—hence the name. The closely-related question mark (Polygonia interrogationis) can also become active fairly early in the season and looks similar, but has a “?” shape on the underside of the hindwings.
Red Admiral (Vanessa atalanta):
The monarch butterfly (Danaus plexippus) is perhaps the best known migratory insect in our part of the world, but red admiral butterflies also migrate northwards in spring. The migratory behavior means that the arrival date and numbers can vary greatly from year to year, but red admirals can frequently be encountered in spring in the Upper Midwest. These butterflies have a wingspan of approximately 2 inches and have black wings with prominent white “!” marks near the tips of their forewings and a distinctive reddish-orange band cutting across the surface of their forewings.
Cabbage White (Pieris rapae):
Right around the start of the Civil War, the cabbage white made its first appearance in North America. Today, this European butterfly can be found widely distributed across much of the planet. Cabbage whites are indeed a whitish color with sooty black patches at the tips of their forewings. The forewings also possess black spots—1 spot for males, 2 for females. Their pale appearance and decent size (approximately 1 ¾ inch wingspan) make them easy to identify this time of the year.
Cabbage whites overwinter as chrysalises in the Upper Midwest, so they aren’t active quite as early as the mourning cloaks or eastern comma. However, the warmth of the sun can still lead to early spring sightings. Gardeners and vegetable farmers are well aware of this species since the caterpillars (“imported cabbageworms”) feed on plants from the mustard family—including broccoli, cabbage, and Brussels sprouts.
Spring Azure (Celastrina ladon ladon):
If you spot a cluster of small bluish butterflies around a puddle on a hiking trail in spring, there’s a good chance they’re spring azures. These butterflies are the smallest on this list, with a wingspan of only around 1 inch. The beautiful sky blue color of their wings can be seen in flight, but when they land, spring azures tend to keep their wings folded over their body, showing the grey undersides with an assortment of tiny black mark. There are many other species of small blue butterflies in our area throughout the year, but the spring azures are some of the earliest to fly and are wrapping things up for the year as June approaches.
The Upper Midwest is home to over 150 butterfly species—each unique in its appearance, biology, and distribution. If you’re looking for some additional resources to learn about our butterflies, some of my favorites include: Butterflies of the Northwoods by Larry Weber, A Swift Guide to Butterflies of North America by Jeffrey Glassberg, and the Wisconsin Butterflies website (wisconsinbutterflies.org) by photographer Mike Reese. The Wisconsin Butterflies website not only has wonderful photos and a wealth of information about each species, but users can view and submit butterfly sightings from around Wisconsin.
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.
It’s a funny world we live in. We hear regular reports of insect declines in the news and still get bombarded with constant ads for services pitching a mosquito free yard all summer and a grub free lawn. But what about simply appreciating insects and the critical roles they play in our everyday lives?
That’s a goal of the first ever Wisconsin Insect Fest being held at the Kemp Natural Resources Station in Woodruff, Wisconsin later this month. The two-day event—being held on Friday, July 26th and Saturday, July 27th—is a celebration of insects.
Wisconsin Insect Fest is free, open to the public, and will feature a wide range of activities for insect enthusiasts of all ages. Topics will range from how to observe and collect insects, to the role of insects in the ecosystem, entomophagy, and even forensic entomology. The Wisconsin Insect Fest will also feature The Great Wisconsin Bug Hunt—a 24-hour BioBlitz activity to see just how many arthropods can be spotted at the Kemp station in a 24-hour period (including a night time activity in conjunction with National Moth Week).
If you love insects, join in the festivities at the Wisconsin Insect Fest later this month or check out the event website for details: tinyurl.com/WisconsinInsectFest
Identifying ants by sight and smell
The tiny brownish odorous house ant measures in at only an eighth of an inch long, but a few features allow for quick identification. Ants are generally broken into two main groups depending on the numbers of bumps or “nodes” in their constricted waist. Odorous house ants are considered “one node” ants, although their single node is flattened and is hidden from view by the gaster (sometimes mistakenly referred to as the “abdomen” of ants). This is strikingly different than other ants, such as carpenter ants or field ants, where the single upright node can even be visible to the naked eye. This flattened node of odorous house ants is a key identifying feature but does require magnification to interpret this trait.
Interestingly, the easiest way to identify these ants isn’t by sight, but by smell. Identifying insects by smell may sound odd, but can be a quick and dirty way to confirm the identity of this ant species, and a few other ants like citronella ants. When squished, odorous house ants have an odor reminiscent of coconut, although some say rotting coconut or even blue cheese. This scent fades with older, dried-out specimens but is usually quite noticeable in fresh ants.
Country ant, city ant:
Odorous house ant colonies occur both indoors and outdoors in the Midwest, but the overall location of these ants in the landscape can have a drastic influence on colony structure and behavior. In natural areas (such as forests), odorous house ant colonies tend to be small (often <100 workers) and the ants are generally “well behaved”. In urban areas, these ants can produce much larger populations with multiple queens, tens of thousands of workers and many different nesting sites. They can behave like an invasive species in such situations.
When it comes to their nesting habits, odorous house ants don’t produce mounds like other common ants. Instead, these ants are fond of preexisting cavities—small hollow voids beneath rocks or man-made objects, amongst log piles, fallen leaves, mulch beds, or similar spots. I’ve even seen them take advantage of the cozy space inside of a fake rock “Hide-a-Key” on several occasions! Indoors, odorous house ants like to nest in hollow cavities such as wall voids, especially if a moisture source is nearby. These ants can also easily wander indoors when foraging, making them a common indoor nuisance invader.
In addition to their essence-of-coconut scent, odorous house ants are also known for having a notorious sweet tooth. Ant species vary quite a bit in their food preferences, with certain ants seeming to favor the “keto diet” with a strong preference for proteins or fats. In contrast, odorous house ants have a particular fondness for carbohydrate-rich materials, such as honeydew from aphids, nectar from plants, or sugary human foods. As a result, these ants routinely invite themselves to picnics and into kitchens. However, their sugar-loving ways can also be their Kryptonite and odorous house ants usually respond well to sugar-based baits when they do find their way indoors.
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.
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.
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 “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.
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.