Tag Archives: 2020 Lab Highlights

Busy beetles: lady beetles take to the air and our homes

The spectacular fall weather this week has made it hard to work indoors. As Midwesterners, we know to appreciate the current warm spell as winter is just around the corner. If you’re like me, you’ve probably made it outside to take care of yard work, hike, grill out, or simply enjoy the fall colors. Speaking of colors, you’ve probably notices flashes of orange on the side of your home—multicolored Asian lady beetles (Harmonia axyridis). This fall, we’re seeing surprisingly high numbers of these lady beetles across Wisconsin.

An adult multicolored Asian lady beetle (Harmonia axyridis). Note the black “W” pattern just behind the head which helps identify this species. Photo credit: PJ Liesch, UW Insect Diagnostic Lab.

Just like us, the final warm days of autumn have worked these lady beetles into a frenzy of outdoor activity and our recent weather patterns are the key to this phenomenon. While not native to North America, the Asian lady beetle is an adaptable species and has a good feel for the seasons—it also knows that winter is coming. An important cue for lady beetle activity is the first frost or period of near-freezing temperatures in fall. This sets the stage and when the temperatures creep back up into the mid-60’s or 70’s, it initiates a massive game of hide-and-seek-shelter for these insects.

A group of overwintering Asian lady beetles beneath the loose bark of a dead tree. Photo credit: PJ Liesch, UW Insect Diagnostic Lab

But why our homes? It turns out that Asian lady beetles don’t necessarily want to invade our homes—they simply look for sheltered spots to spend the winter. In more natural settings, I’ve found dozens of these beetles beneath the loose bark of dead trees or in firewood piles during the winter months.

In their native range of eastern Asia, multicolored Asian lady beetles are cliff dwellers. These beetles use visual cues to actively seek out conspicuous, exposed rock faces with cracks to squeeze into. They’re particularly fond of south or west facing cliffs, which get warmed by the sun in the afternoon when they’re most active. The lady beetles fly to these rock outcrops and examine the cracks and crevices to see if a suitable overwintering site has been found.  To us, our homes don’t necessarily resemble cliffs, but to the Asian lady beetles, the basic formula is there: large contrasting objects that stand out in the landscape with an abundance of vertical and horizontal lines resulting from modern design and construction methods. To the beetles, this looks close enough that they’ll fly to structures and wander around seeking out nooks and crannies to slip into as shown in the video clip below from the UW-Madison campus.

From the lady beetle’s point of view, these insects would really prefer to slip into a sheltered crack or crevice, hunker down for the winter, and leave again in the spring. However, when these insects get beneath siding or into a soffit area of our homes, they can accidentally pop out in the living quarters of the home—much to the dismay of the human inhabitants. This isn’t ideal for the insects either, which can face death by desiccation in the dry winter air indoors.

Enjoy these final warm days of autumn, because we’ll all be bundled up inside soon enough—with or without a bunch of lady beetles.


My final two cents: One of the best, long-term approaches to prevent nuisance issues with multicolored Asian lady beetles and other insects (like boxelder bugs and brown marmorated stink bugs) is to have good physical exclusion. This refers to making sure that potential entrance points on structures are sealed up due to good construction methods, caulk, expanding insulation foam, weatherstripping, or similar means.

Given their small general size, multicolored Asian lady beetles can squeeze through cracks or gaps as small as ⅛ inch in size. For perspective, this is about the same height as two pennies stacked atop one another. With that said, if you can easily slide two stacked pennies into a crack or crevice on the side of your house—it’s a big enough opening for multicolored Asian lady beetles to potentially get in!

 

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…

Cicada Mania in Wisconsin?…Not ‘Til 2024

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.

Left: A common “dog day” cicada; photo credit: PJ Liesch, UW Insect Diagnostic Lab. Right: A peridoical cicada; photo credit: Jay Sturner, via Wikipedia

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.

Map of active periodical cicada broods of the United States. Map credit: USDA Forest Service. Click map for full size version and additional information.

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”.